Category Archives: Boat Electrical System

ABYC Electrical Standard Mapped to Sanctuary’s AC System

4/20/2020: Significant editorial updates to content.
5/27/2020: Added borders to images via HTML edits.

INTRODUCTION

All boaters at one time or another get involved in discussions about what boats “are required by standards and codes to have or to do.” This comes up every time the owner is faced with getting a boat survey. A boat survey report usually makes copious references to “ABYC Standards” and to “industry best practice.” But the vast majority of boat owners do not work in a world of industrial codes and standards and are not familiar with what they are, what they are intended to do, and how they are used throughout the marine and commercial business world (especially, the insurance risk world).

This article is in the form of a stand-up classroom presentation. Slides are presented along with text (“speaker notes”) that describes the slide’s content. This is a mix of “engineering” and “safety.” My hope is that this material will make sense in this format. What I do in this article is look at the “electrical system” of our own boat, and compare that to the requirements of the principle ABYC electrical standard, E11, “AC and DC Electrical Systems for Boats.”

Our trawler, Sanctuary, is a Monk36 Trawler fit with two 120V, 30A shore power service cords. In our case, the shore power cords are configured so that one feeds the house AC loads and the other feeds our heat pump AC loads. Many boats are configured in the same way, but other configurations are possible. Our house loads include a battery charger for our genset start battery, fridge, hot water heater, inverter/charger and several utility outlets. The heat pump loads include one 5kBTU self-contained unit and one 16kBTU self-contained unit and a raw water circulator pump.

While configurations of individual boat electrical systems may be different, the ABYC Electrical Standard E11, “AC and DC Electrical Systems on Boats,” applies equally to all electrical system configurations on all boats of all designs and hull forms. Boats that adhere to the ABYC electrical standard are highly likely to be safe and compatible with 2020 shore-side infrastructure (marinas, boatyards, community, condo, municipal and residential docks). These standards are intended to maximize the safety of the boat; safety from shock hazards, freedom from ground faults, freedom from accidental fire hazards and much worse. I strongly encourage boaters to bring their boats into compliance if that is not already done!

THE LAYOUT OF A BOAT ELECTRICAL PLATFORM

Figure 1 shows an “energy flow diagram” of the total electrical system of a typical cruising boat, comprised of three separate divisions. The central electrical system is the vessel’s DC division (shown in red). This is the division that starts the engine and powers navigation lights, pumps, windlass and miscellaneous navigation equipment. All engine-powered boats have DC systems, but AC divisions are optional. Sanctuary’s platform also has an AC division (shown in green) which allows captain and crew to enjoy the comforts of a shore-side residence. Interfacing between the DC and AC divisions is a means to charge the batteries, and optionally, also use the batteries to power all or part of the AC division.

2

Note: in this topology view, solar battery charging systems would be part of the DC Division.

Note: out-of-scope for this article is the Bonding System Division of the electrical system. Those interested are referred to my article “Bonding System Design and Evaluation.”

Figure 2 shows the interfacing division with an inverter/charger instead of a battery charger. The red highlighted lines show the Inverter/charger in “Invert” mode. For the inverter to be in “Invert” mode, no other AC power source is available to the vessel; ie, no shore power, and no onboard generator running. Absent a source of AC power, the inverter draws DC power from the batteries, converts it to AC, and provides AC power to a subset of AC circuits on the boat. This operating mode would be the typical operating mode for boats at anchor, or boats underway on a travel day. While at anchor or underway, power is available for an AC coffee maker, a microwave, a crockpot, AC space lighting and entertainment systems, and an AC charging source for computers, onboard routers, smart phones and tablet computers. At least, that’s what we do aboard Sanctuary.

3

In Figure 3, the red highlighted lines show the flow of AC power when the boat is connected to shore power via a dock-side pedestal. AC Power enters the boat at the SHORE POWER INLET, passes through a MAIN DISCONNECT BREAKER to, and through, the GENERATOR TRANSFER SWITCH and on to a DISTRIBUTION PANEL which supplies HOUSE LOADS. AC Shore Power passively “Passes Through” the INVERTER/CHARGER to power a subset of AC loads, and the inverter/charger device acts as a DC BATTERY CHARGER.

4
Note: in this topology view, the inverter/charger is fully integrated into the boat’s electrical system, and automatically switches between “Standby/Pass Through” mode and “Invert” mode as AC power from another source comes and goes. If a boater in a neighboring slip accidentally turns off Sanctuary’s pedestal breaker(s), our inverter/charger automatically transfers to “Invert” mode to maintain AC power to it’s attached loads. This configuration is the ONLY use case that ABYC supports for inverters or inverter/chargers installed aboard boats.

Figure 4 shows the above AC Electrical System components mapped to the actual wiring diagram detail of Sanctuary’s installed AC electrical system. The remainder of this article focuses on ABYC requirements of the E11 standard related to the AC Division of the boat platform.

5

Note: Sanctuary is not fit with an Isolation/Polarization transformer (shore power transformer). Shore power transformers have a number of unique ABYC requirements and considerations. Consult the E11 standard for the treatment of these devices.

Note: I occasionally hear that an isolation transformer has been recommended as a means of avoiding the need to “spend unnecessary money” in order to fix/correct conditions aboard a boat that cause dock-side ground fault sensors to trip AC shore power “off.” I strongly discourage that thinking. The conditions that cause ground fault sensors to trip are often serious, potentially dangerous electrical safety or fire hazards. Transformers do mask safety problems which can be a threat to the boat and its occupants, but they DO NOT CORRECT THE UNDERLYING ELECTRICAL FAULT-CAUSING CONDITIONS.

Figure 5 is a clear view of the wiring detail of our AC electrical system. Notice that the neutral buss for house circuits has been divided so that the circuits fed from the Inverter/charger are separated from the house circuits that are not. Further, except as necessary for explanation, AC safety ground wiring is not shown on this diagram; that is a conscious choice made in the interest of simplifying the diagram.

6

THE ABYC ELECTRICAL STANDARD, E11

The ABYC electrical standard is quite extensive and complex. This presentation only covers the major highlights that apply to the AC system division. Similar requirements apply to the DC division. Get these basics right and the boat will be well on its way to being safe. This presentation does not include a discussion of the requirements of onboard 120V load circuits; it focuses on the power distribution components of the AC division, to which we normally give little specific consideration.

L5-30

By far the most common 120V, 30A shore power connectors are National Electrical Manufacturers Association (NEMA) L5-30R and L5-30P pairs. These are found on the familiar 120V, 30A commercial cordsets. I do not like them because I feel they are not nearly robust enough for the repetitive removal and replacement to which shore power cords are subjected in normal use. NEMA L5-30 connectors were designed 80 years ago for light industrial applications where outlets were sometimes ceiling mounted and machinery cords hung from ceiling receptacles. They were plugged in and given a twist, and they were rarely touched again. They are not intended to be roughly handled by boat owners and dock assistants, dropped on docks, stepped-on, rained-on, snowed-in and otherwise abused in routine service.

Which brings up an important point about all ABYC standards. The “requirements” stated in ABYC E11 are MINIMUM PERFORMANCE REQUIREMENTS. They do not require a particular piece of equipment or a particular manufacturer’s product. They simply specify minimum compliance requirements. So, NEMA L5-30P/R connectors ARE NOT “required” by the standard. What is required is a “grounding plug that locks into place” so it can’t “fall apart.” Also realize, ABYC standards apply to boat manufacturers, marine equipment manufacturers, and service technicians. Only indirectly do they apply to boat owners. The standards DO NOT contemplate that DIY electrical work will be done by owners, but they do contemplate that all work done by anyone will comply with the requirements.

0DA35F75-5CF5-4F08-B340-40F94896936A_1_201_aI have personally chosen to replace the OEM NEMA L5-30P shore power inlet receptacles with those made by SmartPlug, LLC (http://www.smartplug.com/) (no personal financial interest; just a very happy customer). I personally feel SmartPlugs are much safer and more robust than L5-30 twistlocks, and they meet all NEC (UL, cUL, eTL) and ABYC requirements. That said, the SmartPlugs EXCEED the minimum performance requirements of the E11 standard.

The following slide shows requirements for the shore power CORDS and the shore power INLETS of the boat. The E11 standard refers to the “Type” of the wire. The cord’s “Type” descriptor is part of the information printed on (or molded into) the cord’s insulation, and should be easily readable on all marine-complaint cordsets. Don’t worry about the “Type” descriptor on Shore Power cables unless for some reason (I discourage this) doing a DIY shore power cord fabrication project. Simply buy products made by marine manufacturers and certified for marine use. The cordset manufacturers will have covered all that’s necessary for ABYC standards compliance.

7

The following slide illustrates a very important concept for shore power systems which all boaters should know; most especially, those who do DIY electrical projects!  At the head of the dock, in the facility’s electrical service infrastructure, the safety ground conductor is bonded (connected) to the neutral conductor. This is an NEC code requirement for all sources of AC power throughout North America, and results in a system referred to as a “Grounded Neutral System.” In a “Grounded Neutral System,” the neutral is intended to carry all of the current returning from the boat to the shore-side source. By design, the ground conductor IS NOT intended to carry current except to trip a circuit breaker in a fault situation. Thus, the neutral-to-ground bond is located in the facility’s infrastructure for both 120V and 240V systems.

8

The following slide emphasizes the boat-side of the shore power connection. The E11 standard requires that there be no neutral-to-ground bond(s) on the boat. At this point, for clarity, that firm statement can be modified to read, “there must be no neutral-to-ground bond(s) on the boat when operating on shore power.” The reason for this distinction now will become clear later, but for shore power, if there is a neutral-to-ground bond on the boat, that wrongly-placed bond creates a connection between the neutral conductor and the ground conductor that electrically parallels the two conductors all the way back to the dock-side infrastructure’s correct ground bond. Since the ground conductor on the boat is in direct contact with the sea water in which the boat is floating, this also parallels-in a ground path through the sea water. When all of these paths are in parallel, current that should flow only on the neutral will divide and flow in equal amounts on both conductors, and in some amount, through the water itself. By definition, this is a “ground fault,” and it will trip power “off” if there are ground fault sensors on the dock-side pedestal, but it can also kill people, pets and wildlife in the water. Incorrect neutral-to-ground bonds on boats are a primary cause for AC power leaking into the water, and can lead to incidents of ELECTRIC SHOCK DROWNING. For further information, readers are referred to my article on “Electric Shock Drowning.”

9

The following slide shows correct and incorrect wiring examples. In my article entitled “AC Electricity Fundamentals – Part 1,” I explain that a boat connected to a pedestal is intended to be wired like a sub-panel in a residential installation. Many residential electricians and DIY boat owners do not understand that technical detail, and so often connect neutrals and grounds together as they would in the main panel of a residence. On boats, as explained above, this is WRONG and DANGEROUS. Those who DIY must understand this natty technical detail.

10

The following slide shows the next major component in the flow of AC power into the boat: the Shore Power MAIN DISCONNECT BREAKER. This device is mainly for overload (and since 2012, ground fault) protection. Note that for 120V, 30A circuits, both the hot conductor and the neutral conductor must be switched, so this disconnect must be a 30A, “double-pole” circuit breaker with either a single operator handle or operator handles that are mechanically interconnected so if one side trips, the other side is also opened.

12

Boats built before 2012 will not have OEM ELCI (Equipment Leakage Circuit Interrupter) circuit breakers installed. That is OK. Although required since 2012 on new construction boats, ABYC states that boats that complied with the version of E11 that was in effect at the time the boat was built by the OEM manufacturer are “grandfathered” for compliance. Note that MANY MARINE SURVEYORS do not choose to adhere to/acknowledge the ABYC “grandfathering” policy. That can result in an inappropriate non-compliance finding in a boat survey.

The following slide shows the MAIN DISCONNECT SWITCH on a boat fit with 240V, 50A service.  The significant difference is that here, only the two hot conductors (L1 and L2) are switched. The neutral is not switched. Thus, a double-pole breaker rated at 50A is appropriate here. As before, this breaker must have either a single operator handle or operator handles that are mechanically interconnected so if one side trips, the other also opens.

13

Note that the neutral-to-ground bond is only correctly located in the shore power infrastructure, which is one of the National Electric Code (NEC) “rules” for residential and light commercial 120V/208V/240V electric services.

The following slide illustrates another very important wiring detail. Recall, Sanctuary is served by two 120V, 30A circuits. Earlier, we saw that neutrals and grounds MUST NOT be connected together aboard the boat. This is a similar case, and for the same reason. Here, it’s essential that the neutrals from Shore Power Circuit 1 and the neutrals from Shore Power Circuit 2 be SEPARATED aboard the boat. The reason is, both of the neutrals run back into the marina pedestal, or may run all the way back to the marina main service panel. If they are connected together on the boat, they become electrically paralleled all the way back to wherever they are ultimately joined together (pedestal junction, panel neutral buss, etc). All current returning from the boat will divide and flow equally on both neutrals. By definition, that is a “ground fault” at the pedestal circuit breakers, which will trip both breakers and interrupt power to the boat. But even more importantly, if one of the shore power cord neutral conductors were to fail open (due to, for example, a burned blade on a NEMA L5-30P twistlock plug), the other neutral circuit would become overloaded and could easily become a fire hazard aboard the boat. Preventing that fire hazard is why understanding and complying to these standards is important.

14

The following slide shows the “right” and “wrong” views described above.  Again, MANY, MANY  RESIDENTIAL ELECTRICIANS DO NOT UNDERSTAND THIS REQUIREMENT BECAUSE BOATS ARE NOT HANDLED IN THE SAME WAY AS THE MOST COMMON RESIDENTIAL INSTALLATIONS.

15

And by the way, the “wrong way” is a common way to find neutral wiring done on older boats.

Check your boat.

The following slide highlights the need for Equipment Leakage Circuit Interrupter (ELCI) devices for protecting against ground faults on the boat.

16

Those interested can read more about ELCI circuit breakers in my article entitled “ELCI Primer.”

The ELCI requirement was added to ABYC E11 in 2012 for new boats. ELCI devices are intended to both protect from overloads and detect ground faults. Ground faults on boats can result in dangerous levels of AC power being dumped into the water, which is a hazard that can lead to Electric Shock Drowning (ESD), as discussed previously.

An ELCI device on the boat is the same thing as a “ground fault sensor” on the dock-side pedestal (ground fault sensors on docks have many acronyms, including “EPD,” “GFD,” “GPD,” and “RCD;” don’t worry about what they’re called. By any name, they do the same thing.) ELCI devices also do the same thing as pedestal sensors, but the ELCI is physically installed aboard the boat. The value of having an ELCI on the boat is twofold. First, the simple act of installing an ELCI will flush out any silent, hidden wiring problems that currently exist on the boat. Second, ELCI will trip instantly upon the spontaneous emergence of a ground fault issue on the boat at some later date, so the boat owner will become aware of it, and be able to initiate repairs, as soon as it surfaces as a safety issue.

The following slide introduces the concept of a GALVANIC ISOLATOR. Galvanic Isolators are very important to controlling corrosion of underwater metals on any boat.

17

Galvanic Isolators are installed IN SERIES WITH the safety ground conductor AT THE POINT WHERE THE GROUND CONDUCTOR ENTERS/EXITS THE BOAT. Nothing – NOTHING – should be connected to the side of the isolator that leads to the shore power inlet connection except the actual safety ground conductor, itself.

18

The E11 standard considers Galvanic Isolators to be “optional” equipment, but if they are installed, the standard provides installation requirements.

If a Galvanic Isolator is NOT installed, the rest of the GROUNDING CONNECTIONS are still mandatory.

19

Earlier, above, the ABYC requirement that “there must be no neutral-to-ground bond on the boat when connected to shore power;” was mentioned with the proviso that it would “become clear later.” Now is the time to clarify as we look at the topic of POWER-SOURCE SWITCHING. The following slide shows the three possible sources of AC power on Sanctuary: 1) shore power, 2) genset, and 3) Inverter. The North American design standard for ALL AC power sources is, ALL power source neutrals are grounded at the source. Since shore power sources are grounded on land in the facility infrastructure and NOT aboard the boat, and since both the generator and the inverter are located aboard the boat, then how is it possible for them to be “grounded at the source” if neutral-to-ground connections are not allowed on the boat? Well, compliance is accomplished through appropriate source transfer switching.

20

Note the construction of the GENERATOR TRANSFER SWITCH shown on this slide.  That Generator Transfer Switch on Sanctuary is a three position rotary switch: “Shore,” “Off,” “Generator.” When the switch is in the “Shore” position, the generator’s neutral-to-ground bond is switched out of the circuit, thus meeting the shore power separation requirement. When the switch is in the “Generator” position, the shore power circuit is switched out of the boat’s electrical platform, thus permitting the onboard neutral-to-ground bond at the generator. The same type of logical switching is accomplished for the inverter by a relay located within the inverter.

Note: ABYC A31 requires that Inverters installed on boats be certified to UL458 (Power Converters/Inverters and Power Converter/Inverter Systems for Land Vehicles and Marine Crafts) to ensure this grounding management relay is present. ABYC E11 includes ABYC A31, amongst other boat electrical standards. BOAT OWNERS SHOULD ENSURE THAT ANY INVERTER INSTALLED ON A BOAT IS COMPLIANT WITH UL458. Especially, be aware that inverters from Harbor Freight and other discount sources will not be compliant to UL458 and are not suitable for use on mobile platforms like boats and RVs.

Following is a close-up of Sanctuary’s Generator Transfer Switch. This is a three-position rotary switch. There are other switching styles that use lockout slide mechanisms to accomplish the same thing. Here, the breaking of the neutral conductors is highlighted by the red ellipses.

21

The following slide is just a reminder of what we looked at earlier WITH RESPECT TO SHORE POWER SOURCES. For Shore Power, the neutral-to-ground bond is in the shore power infrastructure and NEVER on the boat.

22

And this slide shows the generator neutral-to-ground bond that is switched into the boat’s onboard AC system when the genset is running…

23

And this slide shows requirements specific to inverters…

24

The following slide moves to another very important safety issue. Rarely, it is possible to encounter a 120V dock power pedestal source in which the black (hot) and white (neutral) wires (or red and white) are physically reversed inside the pedestal or other location in the dock-side infrastructure. No, it should not happen. Yes, it should be found by the installing electrician before the circuit is put in service. But folks, it does happen (rarely, thankfully). I have seen it three times in 16 years of cruising.

25

What’s particularly bad about a “reverse polarity” situation is that it can be present and also be entirely symptomless on the boat. Electrical equipment aboard the boat will work normally. But, touch potential shock hazards are likely. Because this condition is largely symptomless, it’s important to detect it and warn the boat operator of the potential life-safety issue. The “RP” warning lights (and/or audible alarms) are connected between the Safety Ground (green) and the Neutral (white) conductors on the boat. There should never normally be more than a volt or two between those conductors. Anyone who sees a ”Reverse Polarity” warning light(s) illuminated on their boat should immediately DISCONNECT (physically unplug) the shore power cord from the pedestal and report the condition to facility management. This can be a potentially lethal condition in the right (wrong!) circumstances.

26

This slide shows “Reverse Polarity” warning lights wired between the safety ground and neutral conductors aboard Sanctuary.

Actually, Sanctuary has some duplication here. Our Generator Transfer Switch has Reverse Polarity indicators, as do both shore power distribution panels.
ABYC specifies the minimum impedance of RP detection devices must be ≥ 25kΩ. Since these devices are connected between the neutral and the safety ground, they are a possible path for small “ground fault” currents, and properly installed sensors on some boats can cause false trips of a dock-side or ELCI ground fault sensing device. This would be caused by either multiple sensors in combination or older incandescent sensors having too low an impedance, thus allowing too high a “ground fault leakage current.”
SUMMARY

The most current revision of the ABYC E11 Standard (July, 2018) as of this writing (April, 2020) is 67 pages of “shall” and “shall not” requirements, technical tables and example electrical drawings. Far more than I have covered here. Furthermore, there are several other ABYC Standards that apply to electrical subjects, such as A27, “Alternating Current Generators,” A28, “Galvanic Isolators,” A31, “Battery Chargers and Inverters,” E2, “Cathodic Protection” and E10, “Storage Batteries.”

These standards – and all ABYC Standards – make us all safer. They save property damage losses and they save lives. A marina fire is one of the most terrifying things any boater can ever experience, and there have been several this year alone (winter, 2019-20). When we aboard Sanctuary arrive at a marina, we must assume all of the boats that will be our new dock neighbors are safe. All of those boaters must also assume that we are safe. These standards are the reason we can all have some confidence in those forced assumptions. If there are condition(s) aboard your boat that you know need to come into compliance, please do so. The family you save may be your own!

For the record, I’m not much of a fan of covered slips, either. Those roofs help with UV damage and weather, but in a fire, heat arising from the fire’s origin is contained by the cover and spreads linearly along the dock until the cover finally burns through. This greatly foreshortens escape time; and, not a good thing for survivability of boats that were otherwise uninvolved in the first place. Always think fire safety and escape routes…

Electrical System Topology

Electrical System Schema:

The schema of Sanctuary’s vessel-wide electrical system contains three major divisions.  This diagram is specific to Sanctuary, showing two 30A shore power connections and a fully-integrated but modestly sized inverter/charger.  That said, the overall model generalizes very well to larger electrical systems based on voltage, inlet, inverter/charger and load capacities and configurations.

  1. AC electrical system division of the vessel includes:
      • 120V Shore Power inlet connections
      • AC Generator (Genset)
      • ABYC-compliant Generator Transfer Switch
      • AC Branch Circuit Distribution Panel(s) – (NewMar – House loads; Weems & Plathe – heat pumps, raw water circulator)
      • Galvanic Isolator
  2. DC electrical system division of the vessel includes:
      • Battery Bank
      • Propulsion engine alternator
      • DC Branch Circuit Distribution Panel(s)
      • Individual component attachments (Thrusters, Windlass, Autopilot, Entertainment, Inverter/charger, etc.)
  3. Interface, or Bridging, or Power Conversion division of the vessel includes:
      • Magnum MS2012 Pure Sine Wave Inverter/Charger

General Topology of the Vessel Electrical System:

topography

An Adobe Portable Document Facility (.pdf) version of this drawing is available by clicking this link: 20161019_electrical_system_topology.

Bonding System Design and Evaluation

2/9/2020: Significant edits to better connect concepts and include technique descriptions.

My previous post (Corrosion Article) discussed corrosion of underwater metals caused by various stray electric currents in the water.  In that post, I made passing reference to “bonding,” “bonding conductors,” and to underwater metals “being bonded together.”  This article looks specifically at the bonding system of a boat.  The objective is to provide a basic understanding of why bonding is installed, what it does, and consider the maintenance needs of the bonding system.

As boaters, we are constantly involved in discussions of the design, equipment, materials, techniques and components of the AC and DC divisions of a boat’s electrical system. When those systems fail, there are usually symptoms, anxieties and inconveniences that boaters notice. Although Internet boating discussion lists are filled with electrical topics, only rarely does one see discussion related to a boat’s “bonding system.”

As in other electrical technical areas, “bonding” is an area where there is a body of common concepts and terminology that apply across a wide range of AC and DC situations. Just as in the “Corrosion” topic, the concepts of bonding are consistently the same, but an understanding of context is essential to avoiding confusion.  Experienced electrical practitioners often take shortcuts with context. For the layman, the only way to get past that is to invest some time in understanding the concepts. After that, understanding context gets easier very quickly.

The terms “grounding” and “bonding” are often used interchangeably, but in fact, they are different. Following are definitions with which most experts would agree:

Ground” is the single-point of electrical connection between an electrical sub-system (like a boat) and the physical earth. This connection is made for the purposes of:

  1. providing a lightning discharge path,
  2. providing a path to bleed off static charge,
  3. sub-system voltage stabilization, and
  4. reducing RF interference.

Bonding” is an electrical connection (usually a network of electrical connections) which electrically interconnect metallic housings and device enclosure components. Bonding:

  1. provides a low-resistance path for ground-fault currents to ensure circuit protection devices (circuit breakers) trip,
  2. prevents dangerous “touch-voltages” from appearing on exposed metal surfaces, and
  3. provides a path for galvanic currents and AC and DC stray currents.

NOTE: there are two important reasons to have a bonding system on boats; 1) mitigation of galvanic currents and 2) AC electrical safety.  Sometimes, we hear and read that a bonding system is not needed or desirable, because it actually provides one of the conditions that are NECESSARY in order for corrosion to happen.  But, that is a very narrowly-framed point-of-view that ignores the importance of the bonding system to the safety of the AC Electrical System aboard a boat.

Figure 1 is a simplified topology overview of the three major divisions (AC division, DC division and Bonding division) of the electrical system of a typical cruising boat, whether sail or power, whether slow displacement hull or go-fast sport fish.  It is representative of the great majority of US-manufactured boats. This topology view is consistent with the “model” electrical system upon which the principal ABYC Electrical Standard, E-11, is based (“AC and DC Electrical Systems on Boats,” July, 2003 – 2018, Figure 10).

The ABYC E-11 standard treats a boat’s DC System as the “central-most” division of the electrical system of the boat, to which all other divisions are attached in a peer-to-peer relationship. This seems a reasonable assumption, since AC systems and bonding systems are neither required nor essential on a boat, but the DC system is always needed for engine starting and the operation of bilge pumps, navigation lighting and (usually) sound-signaling device requirements.

Total_System

Figure 1: The Bonding System on a Typical Fiberglass (FRP) Cruiser.

All of the conductors shown in green in Figure 1 are part of the boat’s “bonding system,” or “bonding network.” That entire network of conductors works together. In typical dockside conversation, the “bonding system” is often thought of as limited to the wiring shown on the right-had side of Figure 1. The usual term applied to the AC portion of the bonding system is the “AC safety ground.” Note, however, that the AC safety ground is an integral part of the overall bonding network of the boat.

In normal operation, all bonding systems are “silent” and “invisible.” When “everything is right,” the bonding system does nothing, and “everything works fine.” Bonding networks are so quiet and invisible that a boat owner might never know if a fault had appeared.

In fact, the primary purpose of the bonding system is to spring into action to protect us when an electrical fault does occur in either the AC or DC system. The only “normally active” purpose of the bonding system is to control corrosion due to DC galvanic currents.

Today we are very fortunate that the reliability of electrical components is very good.  The mathematical probability, confirmed by life experience, is that electrical faults are relatively infrequent. Given that the bonding system comes into play only when there is a fault, it probably won’t actually be needed very often. If the bonding system does have a defect, unless there is another, second fault, there will be no failure symptom or danger to people or pets. Yes, there may be an increased rate of corrosion, often interpreted as “electrical issues in the basin and nothing to worry about.” These are “handled” as a routine maintenance item, but the underlying cause is often not diagnosed or corrected. The bonding system adds complexity to the boat, but can save many headaches, much expense and even heartache for the boat owner if it is intact when needed. Some bonding system faults can create dangerous situations leading to fire, electric shock, loss of property and in the ectreme, loss of life.

The heart of the DC division of the boat electrical system is the battery/battery bank, including all B+ and B- wiring and all subordinate DC device attachment wiring. “B+” is the term for the DC positive feed (+12V, +24V) that originates at the positive post of the boat’s battery. “B-” is the term for the DC negative conductor that returns DC power to the negative post of the battery. In the common lexicon of conversation, the DC return circuit is often referenced as its “ground” conductor. However, the B- conductor in the DC system carries DC current back to the battery, so it is more properly analogous to the “neutral” conductor of the AC division.

Bonding circuits are intended to carry only galvanic and fault currents; never currents that power equipment or attachments. To avoid undesirable voltage drops in the bonding system, and problems with accelerated electrolytic corrosion, no B- connections should ever be made to any part of the bonding system. Such connections are analogous to a “code violation.”

ABYC E-11, Figure 10, shows the “DC Main Negative Buss” as the central collection point for all DC B- return circuits, as well as for the “AC Safety Ground” and the bonding network connections. The boat’s AC Safety Ground and the various branches of the DC bonding system are all connected together at one place, and at one place ONLY: the “DC Main Negative Buss.”

Neither ABYC nor NMMA “require” the installation of DC bonding systems. Bonding systems are “optional.” However, ABYC E-11 does specify requirements for the bonding system if one is installed. Among US boat manufacturers, bonding systems are the “normal” manufacturing practice.

The primary purposes of the bonding system are to:

  1. hold exposed metal parts at to “touch potential” that is safe for people and pets;
  2. provide a low resistance path for fault currents to trip “circuit breakers;”
  3. provide a single point-of-access to protect multiple structural metals of the boat from corrosion, via a sacrificial anode (zinc, aluminum or magnesium, depending on composition of minerals in local waters);
  4. provide a path for certain DC stray currents to safely exit the boat via the AC shore power safety ground;
  5. disperse static electricity formed in high winds and from nearby electrical storms, and
  6. reduce (attenuate) spurious RF electrical “noise” created by on-board equipment (battery chargers, inverters).

Many of the conductors of a “bonding system” are installed in the very hostile environment of the boat’s bilge. The various metal objects tied to the bonding system include:

  1. thruhulls, seachests, sea strainers and packing glands,
  2. rudder “stem iron,” rudders, rudder “shoes” (skegs), tillers and miscellaneous metal support structures of the steering system,
  3. various steering system components (quadrant, cables, metallic hydraulic lines, hydraulic pumps),
  4. trim tabs and thruster systems,
  5. anchoring system components, including all-chain rodes,
  6. exhaust system fittings and ports,
  7. radio counterpoise and static dissipation “ground plates,”
  8. fuel tanks, fuel filling ports and tank vents,
  9. potable water and black water tank access and vent ports,
  10. generator, battery charger and inverter chassis frames,
  11. solar panel and wind generator frames,
  12. handrail and bridge enclosure frames,
  13. heat pump and circulator pump frames,
  14. stove and water heater frames,
  15. refrigeration (compressor) frames,
  16. etc, etc, etc…

In short, lots ‘o stuff.

Figure 2 shows the hull penetrations on a typical trawler (Sanctuary) built with individual thruhulls (without a seachest).

Figure 2: Typical Hull Penetrations on a Boat with Thruhulls and Without a Seachest

The complete collection of all of these metal components are “bonded” – connected together into a single electrical network – as shown in Figure 3.

Figure 3: Typical Bonding System

Figure 3 is only one example of the construction of a bonding system. Other configurations are acceptable. Take particular note of the large gauge conductor shown in orange. That conductor is the “backbone” of the DC portion of the bonding system. That backbone conductor runs the length of the hull. To the backbone are attached all of the green stranded wire pigtails connecting the metal structures of the boat to the backbone. Also note the transom anode (zinc, aluminum or magnesium), which provides primary galvanic protection to all of the metals connected to the bonding system. When the boat is at anchor, away from shore power, it is the transom zinc that is the “ground” connection point. That is, the single point of electrical attachment to the earth, the primary dispersal point for static electricity and lightening and the electrical connection that establishes the “touch potential” for people and pets for the entire electrical system of the boat.

It would not be unusual if a boat’s owner did not know when the bonding network was last tested. It may have been quite some time; perhaps, never, even on older boats. It is possible that weakness(es) are present in the bonding system. I suggest full integrity testing of the bonding system should be done every three to five years.

Most if us have measured the terminal voltage of flashlight batteries many times. We have probably all measured our boat’s 12V (or 24V) lead/acid batteries at some time. Figure 4 reminds us of the very simple task of measuring the terminal voltage of a “AA” battery:

measure_battery

Figure 4: Measuring the Terminal Voltage of a Battery

This “typical” battery is a classic galvanic cell consisting of two “half-cells” (copper and zinc) located in an electrolyte. Since the battery is always seen as a packaged unit, the term “half-cell” is not commonly used except by engineers, battery manufacturers and technicians specializing in corrosion mitigation. The terminal voltage of a “AA” battery is measured with a digital voltmeter. When a load is connected across the battery terminals, current flows to illuminate a flashlight, for example, or power a radio or GPS.

Key concept: batteries are used to provide the voltage needed for circuits.  With batteries, their intended use means there should be a voltage between the positive and negative terminals.  A direct short circuit across a battery is never desirable, as it will dramatically accelerate the rate at which the battery becomes exhausted.  Inside a short circuited battery, the halfcells will become wasted (a form of corrosion) at an extremely fast rate, accompanied by the generation of heat and gasses.  However, in the case of the “accidental” battery created by the electrochemistry of dissimilar metals in seawater, the whole point of the bonding system is to create an electrical short circuit across the various exposed terminals of that “battery.”  Bonding creates a path for electrochemical galvanic currents to circulate.  Bonding holds all of the metal surfaces at the same, safe touch voltage, but in so doing, bonding also ensures the presence of the conditions needed for corrosion to occur.  That is the reason for the presence of the transom anode (zinc, aluminum or magnesium) in the bonding network.  The transom anode serves as a sacrificial metal (sacrificial anode) that protects all of the important, expensive, valuable more noble metals attached to the bonding backbone from corrosion.

For measuring and troubleshooting the bonding system of a boat, a reference “half-cell” is used. The reference cell is external to the bonding system.  The reference cell behaves in a known and predictable way when submerged in sea water. The reference cell becomes one of the halves of a “battery.” The metals attached to the bonding network of the boat become the other half-cell. In use, the reference half-cell is immersed in seawater outside the hull of the boat, and that seawater is the electrolyte of the “battery.”  Note here that “sea water” is a collective term.  The water in which a boat lots can be “fresh,” “brackish” or “ocean” in mineral concentrations.  It is minerals in the water (primarily salt) that affect conductivity of the water.  Since the water is the electrolyte of our corrosive galvanic cell, the voltage measured across the half-cell terminal will vary in different bodies of water and vary in different places on large bodies of water.

A Silver/Silver Chloride half-cell is the best reference cell with sea water (chemical symbol: Ag/AgCl) because it has known and stabile behavior characteristics in that application. That is, the voltage that other metals will produce against a silver/silver chloride half cell are very consistent across a wide range of temperature and electrolyte salinity.

Conceptually, measuring between the Ag/AgCl half-cell and the bonding network of the boat is the same as measuring between the terminals of a conventional “AA” battery. The bonding system and the Ag/AgCL half-cell immersed in sea water, become the “battery” being tested. The DVM measures the “terminal voltage” of that “battery.”

Figure 5 shows the measurement configuration described above:

measure_hull

Figure 5: Measuring the Bonding System with a Ag/AgCl Half-Cell

As a boat owner, there are two ways to proceed with the testing of the bonding system. One is to hire an ABYC-Certified Corrosion Specialist. This analysis is a form of “boat survey,” although is is highly specialized and not all surveyors offer it as a service. Two is for owners to “do it themselves.”  In the DIY case, one must obtain an Ag/AgCl half-cell, available from http://www.boatzincs.com and other Internet sources at a cost in the range of $140 – $150.  Or, a “Corrosion Meter,” such as is offered by Promariner.

DIYers will begin their testing by connecting the Ag/AgCl half-cell to the negative terminal of the DVM. Then lower the Ag/AgCl half-cell over the side into the water near the hull, to about the level of the boat’s running gear. The half-cell should not rest on the sea bed. The guiding principle here is, if the bonding system is fully intact and functional, all metals connected to the bonding system are expected to be at the same voltage. Probing any of the bonded metals with the DVM should produce the same voltage reading. If different voltages are noted, something is not right, and corrective action is advised.

The bonding system of a boat – whether connected to shore power or not – should produce a reading on the DVM of between -400mV and -1000mV, depending on the mineral composition of the water. Knowing that the bonding system has all of its metal structures tied together, we therefore know all of the readings must be found at the same voltage if the bonding system is intact.

So how does one figure out what a “nominal reading” for any particular locality should be?  There are two ways to get a good approximation of nominal “hull potential:”

  1. A friend who is an ABYC-Certified Corrosion Specialist offers this simple suggestion: “When starting a corrosion survey, I use a pencil zinc and check the potential between it and the Ag/AgCl reference cell.  This gives me an indication of the best reading that I will be able to get for any protected metals on the boat and it also tells me that the DMM is working and that the Ag/AgCl reference cell is behaving.”  This is completely independent of marina power distributions system, fast, easy and safe.
  2. Place the Ag/AgCl reference cell into the water of the boat basin, and probe the ground terminal (make sure to probe the “ground” terminal!) of any nearby pedestal 120V/240V power connector.  This works because the AC Safety Ground on the pedestal is electrically connected to the earth (grounded, earthed) at the service entrance panel of the dock.  Boats floating in the water of any boat basin are referenced to ground through the basin’s conductive water.  (A Galvanic Isolator interrupts this circuit.)  The basin water is the electrolyte through which galvanic currents flow.  Connected in this way, the Ag/AgCl reference cell is one half-cell of a “battery” and the earth connection acts as the other half-cell.  And when the boat’s shore power cord is connected to the pedestal, the bonding system on the boat is held at the level established by the  shore power service ground.  This method works well on docks with good electrical systems, but can be fooled by non-compliant boats.  If using this system, and reading look “suspicious,” revert to method one, above.

Once a good baseline voltage is established, start to evaluate the integrity of the bonding system and any point along the bonding network that is convenient.  Proceed to probe each of the various metal objects found all over the boat; that is, all the stuff previously mentioned [thruhulls, packing glands, sea chests, rudder posts and rudders, steering system components, exhaust fittings, main engine/transmission, Generator frame(s), battery charger/inverter chassis frames, solar panel and wind generator frames, handrail and enclosure frames, heat pump unit chassis frames, fuel tanks, fuel filling ports and tank vents, potable water tanks, thruster systems, black water tank, etc, etc, etc]. The voltage measured by the DVM should be the same as seen at the shore power connection everywhere. If it is not, something is “wrong!”  Note: from a purely “corrosion” point-of-view, only those components immersed in water are affected.  Other bonded metal equipment/components are checked for the purpose of verifying frame-to-frame touch potential safety and ability to trip the disconnect circuit breaker in an electrical fault event.

The last two steps in this analysis are to discover the cause of any inconsistent voltage reading, and then to make appropriate corrections. Some symptoms one might encounter include:

Symptom Possible Cause
Wide variation of voltages between different metal objects.
  1. Boat is not fit with a DC bonding network;
  2. Damage or corrosion to connections within the bonding system.
Most metal objects have consistent voltages except for one or two isolated objects, “here and there.” Loose, corroded, broken or missing bonding connections to the affected metal object(s).
A collection of several metal objects measure one voltage, but that entire collection is different from the baseline voltage. Broken bonding buss somewhere along the length of the backbone.
The baseline voltage is grossly different than expected (-400mV to -1000mV).
  1. Loose, corroded, broken or missing connections to the transom zinc or the shore power ground. Disconnect from shore power, looking for changes and to check the transom zinc by itself;
  2. Overly wasted transom zinc;
  3. Missing shore power ground connection;
  4. B- connection to the bonding system made in error;
  5. Stray DC electrolytic currents in the bonding system.
No reading occurs when the metal object is probed. Bonding connections absent.

(Note: this will only happen with metal objects above the waterline and not in contact with the water.)

AC Electrical System

AC System Overview:

Note: An electrical diagram of Sanctuary’s AC Power Distribution  System as described in this article is located here (Adobe Portable Document Facility (.pdf) file): 20161022_ac_electrical_distribution_system.

The ship is wired to operate from two single-phase, grounded-neutral, 120VAC, 30A shore circuits originating in a dockside shore power system.  Neither the shore grounded (white) neutral conductor (white) nor the ungrounded energized conductor (black) is connected to the safety ground (green) aboard the ship (ABYC E11, 11.17.1.2).

The ship’s AC safety ground (green) and DC negative buss (black) are connected together in the engine room (ABYC E11, 11.5.4.7.1 and subs).

The ship is fit with a ProMariner® Prosafe-1™ galvanic isolator.  AT the time of it’s installation, the device complied with the then requirements of ABYC A28, 28.13 (now obsolete). The diode pack of the device is installed in series with the ship’s incoming green safety ground wire. The isolator and its control module are located in the ship’s electrical closet. The enumerator/monitor is mounted at the ship’s electrical control center located stbd, in the companionway to the vee berth.

Note: the ProMariner® galvanic isolator control module was disconnected in May, 2016.  The design of the enumerator/control module places a ground fault on the incoming shore power circuit.  That ground fault is used by the device to test the ship’s safety ground wire for continuity.  That ground fault can trip shore power ground fault sensors.  Disconnecting the enumerator does not affect the purpose or operation of the diode pack itself, but it does defeat the self-checking feature of the OEM design of the enumerator/monitor.

The ship is fit with two 120VAC, 30 Amp SmartPlug® marine shore power inlet connections (ABYC E11, 11.6.3.1.2 and subs). “Shore 1” corresponds to a Newmar® ACDC-1™ “house” AC Load Center (identified with the numeral “1”). AC branch circuit breakers (ABYC E11, 11.10.1.5 and subs) serving the genset battery charger, refrigerator/freezer, 120VAC water heater, inverter/charger and several house utility outlet circuits are installed. “Shore 2” corresponds to a Weems and Plath® “heat pump” Load Center (identified with the numeral “2”). AC branch circuit breakers (ABYC E11, 11.10.1.5 and subs) serving two reverse cycle heat pumps and a raw water circulator pump (“air conditioner” units) are installed.  It is not necessary to connect both shore power circuits in order to use either one; each is completely independent of the other.

The ”AC Master Breaker” on the NewMar® “house” AC Load Center and the ”Master Breaker” on the Weems and Plath® “heat pump” Load Center function as shore power disconnect switches (ABYC E11, 11.10.2.6 and subs and 11.17.1.1 1). These double-pole breakers isolate their respective AC shore power circuits from the ship’s on-board AC distribution system. The 120V energized current-carrying (“hot”) buss on the AC side of the NewMar® Load Center has been modified from its OEM configuration. Breakers 1-4 on the NewMar® panel are fed by shore line-in or generator power. Breakers 5-8 on the NewMar® panel are fed by the onboard inverter/charger as described later in this document.

Footnotes:

  1. NoteThis section of E11 was upgraded to include ELCI in the July, 2012 release of the standard. Sanctuary complies with the July, 2009, release, E11, 11.7.2.2.1.1. Sanctuary is not fit with ELCI at this time.

The ship is fit with an ONAN® MDJE™ onboard generator. The generator is powered by aa Onan 2-cylinder, 4-cycle diesel engine. Diesel fuel for the generator engine is drawn from the ship’s onboard fuel tanks. The generator has a 2-stage (fresh water with heat exchanger) cooling system. The generator is rated for continuous operation at 7.5kW, 60Hz. Generator operation (glow plugs, start/stop) is controlled by two rocker switches mounted at the ship’s electrical control center.  The generator and its diesel engine are mechanical devices that require periodic preventive maintenance. Refer to the Onan manual for maintenance schedules.  The generator’s AC output is wired in a 240VAC configuration. The generator starter motor is fed through a BlueSea Systems ML-RBS remotely operated DC disconnect switch (ABYC E11, 11.6.1.2.1, 11.6.1.2.2).

The ship is fit with a Blue Systems® p/n 9093 manual Generator Transfer Switch. The GTS transfers the ship’s AC distribution load centers to either the shore power inlets or the onboard generator. When shore power is available, and the load center disconnect switches are set “on,” the corresponding green “Shore Power” LED on the GTS operator’s panel becomes illuminated. The GTS is of the break-before-make design. This prevents simultaneous cross-connection of incoming shore power source(s) and the ship’s generator (ABYC E11, 11.5.5.6). This allows the generator to be started and run for servicing while the ship is simultaneously connected to energized (live) shore power connections.

Shown following is the wiring layout of the GTS as installed. Shore power service cords feed “Source 1” and “Source 2.” The 240V onboard Generator feeds “Source 3.” The NewMar® AC Load Center for “house” loads is connected as “Load 1;” the Weems & Plath® Load Center for  heat pumps is connected as “Load 2.” The GTS is shown in the “Shore” position. If the generator is “running,” the green “Generator” LED on the GTS operator’s panel becomes illuminated. If both shore and generator power are available at the same time, both sets of LEDs will be illuminated.

gts

The ship is fit with a Magnum® MS2012™ Pure Sine Wave Inverter/Charger.

  1. When either shore or generator power is available, the device operates in “Passthru” mode to forward AC power to utility outlets via circuit breakers 5–8 on the NewMar® AC Load Center and to simultaneously charge the ship’s battery bank. When shore or generator power is not available, the device operates in “Invert” mode as the AC power source for circuits 5-8. The device automatically switches between its “passthru” and “invert” modes as availability of shore or generator power changes.
  2. The neutral buss for branch circuits powered by the inverter/charger is isolated from the neutral buss for branch circuits powered solely by shore or generator power. Magnum requires this separation, which they base on ABYC A31, 31.6.7.3.1. However, AC neutrals are defined to be “grounded conductors.” Therefore, this ABYC reference seems obscure, since it refers to separation of “ungrounded conductors.”
  3. Configuration of the operational status of the inverter/charger is manually selectable via the ME-RCtm Remote Control mounted at the ship’s electrical control center area.
  4. The “fault” lamp on the ME-RCtm Remote Control indicates a problem that prevents normal operation of the inverter/charger. The two most common faults are spike voltages and out-of-tolerance frequency deviations. These faults sometimes occur when the ship is operating on the generator as its AC power source and heavy loads cycle “on” and “off.” These “faults” can be manually cleared by recycling DC power via the inverter/charger battery disconnect switch in the engine room space.
  5. DC electrical energy to power the inverter/charger originates from either 1) the propulsion engine’s alternator (supplemented by the battery bank), if the ship’s propulsion engine is running, or 2) solely by the ship’s battery bank, if the ship’s propulsion engine is not running. In the absence of shore or generator power, the DC ampere-hour (aHr) capacity of the ship’s battery bank can be conserved by discontinuing use of the Inverter/Charger and its attached AC loads.

Finally, the ship is fit with a 700-watt Xantrex® Modified Sine Wave (MSW) utility Inverter. This inverter is an alternative AC power source that can feed a utility outlet power strip on the ship’s salon nav station. This inverter is a stand-alone device that is not integrated into the ship’s AC distribution system. It is available to power the satellite TV receiver/DVR and the TV. DC energy supply for this inverter is as described above. The device mounted on the aft bulkhead of the ship’s standing closet.

DEFINITION: “Secured State” of the Ship’s AC Electrical System

Aboard Sanctuary, a “secured state” for the AC Electrical System is defined to exist when all of the following conditions exist:

  1. All individual AC house circuit breakers on the NewMar® AC Load Center are in the “off” position,
  2. All individual heat pump circuit breakers on the Weems & Plath® Load Center are in the “off” position,
  3. The “AC Master Breaker” on the Newmar® AC Load Center and the “Master Breaker” on the Weems and Plath® Load Center are both in the “off” position,
  4. The generator transfer switch is in the “off” position,
  5. Shore power service cords are disconnected and stored aboard,
  6. The generator is not running,
  7. DC power to the Xantrex® MSW Inverter is discontinued via it’s disconnect breaker, located in the electrical closet,
  8. DC power to the Magnum® MS2012tm system-integrated Inverter/Charger is discontinue via the DC rotary disconnect switch located in the engine room, stbd bulkhead.

References to ABYC E11 contained in this document:

All references to ABYC E11, AC AND DC ELECTRICAL SYSTEMS ON BOATS, are to the July, 2012, release of the standard unless otherwise noted.

DC Electrical System

DC System Overview:

Note: An electrical diagram of Sanctuary’s DC System as described in this article is located here (Adobe Portable Document Facility (.pdf) file): 20161022_dc_electrical_distribution_system.

The ship’s DC electrical system is a “negative ground” system. (ABYC E11, 11.4.24 and 11.5.4.3)

The DC system is of the “ungrounded” system design (ABYC E11, 11.4 and E11, 11.5.4.3).

The ship’s AC safety ground (green) is bonded to the Ship’s DC negative buss (black) in the engine room. (ABYC E11, 11.5.4.7.1.2)

DC energy for the “house” and “engine start” services originates in a single battery bank comprised of six, 6 volt, flooded deep cycle “Golf Cart” batteries. Over-current protection (OCP) for the battery bank is provided by BlueSea Systems®, Type MRBF™, 200A fuses. (ABYC E11, 11.10.1.1.1 and 11.10.1.2 and subs).  Details of that design decision are discussed in my article, “Battery Bank: Separate vs Combined,” on this site.

A single Group 27 start-service battery is used to start the ship’s generator. A BlueSea Systems® model ML-RBS™ remotely operated disconnect switch, with p/n 2145 remote switch, is fit in the generator’s battery feed circuit.

The ship’s Main DC Disconnect Switch (ABYC E11, 11.6.1.2 and subs) for the DC feed to the NewMar® Load Center and other attached DC loads is located in the engine room, stbd bulkhead, above the ship’s battery bank.

The ship’s OEM NewMar® Model ACDC-1™ Branch Circuit Load Center/Distribution Panel is located to stbd in the forward companionway to the vee berth. Because there is a combined battery bank for house and start functions, the OEM Battery Selector Switch is discontinued and removed. The left half of the Newmar® Load Center serves as the DC Load Attachment Center for many DC attachments, including:

  • navigation, anchor lights and deck lights,
  • LPG safety shutoff valve,
  • refrigerator/freezer DC feed,
  • house drinking water pump,
  • raw water wash-down pump,
  • DC lighting,
  • salon VHF radio,
  • windshield wipers and horn,
  • toilet macerator, and
  • stereo.

This panel provides over-current protection for attached loads via circuit breakers. (ABYC E11, 11.10.1.5)

The ship is fit with a Blue Sea® System WeatherDeck™ DC Circuit Distribution Panel, located stbd on the flybridge. It is the primary load attachment center for the ship’s navigation instruments, including:

  • chart plotters (including Radar),
  • auto pilot controller,
  • VHF radio,
  • depth sounder,
  • under-console AIS receiver and wi-fi multiplexor, and
  • flybridge DC utility outlets.

This panel provides over-current protection for attached loads via circuit breakers. (ABYC E11, 11.10.1.5)

The ship is fit with a Magnum® MS2012™, Pure Sine Wave (PSW) Inverter/Charger. DC over-current protection is provided by a 300A Class “T” fuse (ABYC A31, 31.5.2.4.4 and subs; 31.6.4.1). The DC Disconnect Switch for the inverter/charger is located in the engine room, stbd bulkhead, above the ship’s battery bank. (ABYC E11, 11.6.1.2 and subs)

DC Power for some ship equipment attaches to the vessel’s DC Distribution System independently of the NewMar® load center. These attachments have individual over-current protection. These attachments include:

Attachment

Location of Attachment’s
Disconnect Switch
or OCP

(ABYC E11, 11.6.1.2 and subs, 11.10 and subs)

1 propulsion engine
a) starter motor feed and
b) control, instrumentation and instrument lighting circuits
fwd surface of galley drawer cabinet, floor level, aft of stbd salon door; switch is accessible without opening the engine room. This circuit is without OCP. (ABYC E11, 11.10.1.1.1, Exception 1)
2 Lewmar® H900 windlass tagged; on vessel’s electrical control center
3 Dickson® stern thruster Inline fuses, respective operator’s panel
4 Garmin® GHP10tm autopilot system tagged; engine room, stbd, mid-ships, above battery boxes
5 Magnum® MS2012tm, 2kW, PSW inverter/charger tagged; engine room, stbd, mid-ships, above battery boxes
6 ICOM® 706MKIIGtm Amateur Radio Transceiver Inline fuses, electrical closet, NewMar® B+ buss
7 bilge pump tagged; electrical closet aft bulkhead, eye level (tubular glass fuse)
8 high bilge alarm tagged; electrical closet aft bulkhead, eye level (tubular glass fuse)
9 shower sump pump tagged; electrical closet aft bulkhead, eye level (tubular glass fuse)
10 SirenMarine® Spritetm Boat Monitor inline fuse, electrical closet
11 salon +12VDC utility outlet. inline fuse, electrical closet

Battery State-of-Charge Status & Monitoring:

The ship is fit with six, Duracelltm, EGC-2, Golf Cart batteries.  These batteries have a 20-hour Ampere Hour (aHr) rating of 230 aHr and a Reserve Capacity rating of 448 minutes. These batteries are manufactured by East Penn Manufacturing® and are sourced from Sam’s Club. The batteries are combined in a series/parallel configuration to provide 12VDC.

The overall total rated ampere hour capacity of the ship’s battery bank is 690 aHr.

A Magnum® ME-RCtm Remote Control, and a Magnum® ME-BMKtm Battery Monitor Kit, are installed to monitor the ship’s DC electrical operating parameters and the state-of-charge status of the ship’s battery bank.

“Standard operating practice” aboard ship is to adhere to the “mid-capacity rule,” which states that lead-acid batteries (flooded wet cells, AGM or Gel) should not be discharged beyond 50% of their rated capacity and that discharging a lead-acid battery in excess of 50% of its capacity shortens its service life. Aboard ship, the ME-RCtm/ME-BMKtm Battery Monitor displays the “State-of-Charge” of the battery bank. Less overall depth-of-discharge is better.

The approximate eight-hour overnight (summer hours-of-daylight) DC system electrical consumption (refrigeration, anchor lighting, evening TV watching, computer use, etc.) aboard ship is 125 – 150 aHr. The approximate eleven-hour overnight (winter hours-of-daylight) DC electrical consumption is 150 – 200 aHr.

Battery Charging:

Shore Power/Onboard Generator:
When the ship is receiving AC power from either 1) shore power or 2) from the ship’s onboard generator, the ship’s battery bank is charged by the Magnum® MS2012tm 2kW Inverter/Charger 1.

Under way:
The ship’s engine alternator charging system consists of a single, 12-volt, 110 amp, Balmar® high-output alternator, model 712110, with a Balmar® MC-614tm external regulator. The external regulator receives its DC input power supply from the propulsion engine’s starter solenoid 2.

DC Distribution Wiring: 3

  1. Three attachments originate at the positive battery post of the ship’s battery bank:
    1. Attachment 1 is BlueSea Systems®, Type MRBFtm Fuse Block, p/n 2151, fit to the designated positive output terminal. (ABYC E-11, 11.12.1.2). This fuse block is fit with two, 200A, Type MRBF fuses.
      • Fuse 1 feeds the ship’s Main DC Power Disconnect Switch 4, a Blue Sea® Systems, p/n 6006, rotary switch, via a 2-0 AWG red wire. A 2-0 red wire continues from the disconnect switch to a BlueSea® Systems, 150A, Type ANL fuse block. The house DC feed is a 2-0 AWG red wire from the ANL fuse block to a 600 amp, 4-post terminal block. The terminal block is the ship’s Main DC Power Distribution Buss.
      • Fuse 2 connects the ship’s Balmar 110A alternator to the battery bank, via a #6 AWG red wire.
    2. Attachment 2 is a 2-0 AWG red wire that feeds the ship’s propulsion engine starter solenoid through a BlueSea System®, p/n 6006, disconnect switch located in the salon, stbd, beneath the fold-down table. This circuit is not overload protected (ref: ABYC E-11, 11.12.1.2).
      • The propulsion engine starter solenoid is the DC system attachment point of the engine’s DC sensors, controls, instrumentation and malfunction alarms, and the external Balmar® MC-614tm voltage regulator which energizes the on-engine Balmar® alternator unit.
    3. Attachment 3 is a 2-0 AWG red wire (ABYC, E-11, 11.12.1.1.1) that feeds the ship’s inverter/charger through a Class “T” fuse block fit with a 300 Amp, Class “T” fuse. A 2-0 AWG red wire continues from the Class “T” fuse block to a BlueSea Systems® p/n 6003e disconnect switch. From the disconnect switch, a 2-0 AWG red wire feeds the Inverter/Charger.
  2. House loads aboard ship are fed from the Main DC Power Distribution Buss.
    1. A 1-0 AWG red wire runs from the terminal block to a terminal block in the electrical closet. This is the DC attachment point for the ship’s bilge pump, high bilge alarm, NewMar® DC Load Center, BlueSea Systems® WeatherDecktm Load Center, Xantrex® Inverter and shower sump pump.
    2. A 1-0 AWG red wire from the terminal block feeds the vessel’s 70 amp windlass circuit breaker. From the circuit breaker, a 1-0 AWG red wire joins in the electrical locker with an OEM 38mm2 red wire to feed the vessel’s windlass contactor, located forward, in the chain locker overhead.
    3. A #8 AWG red wire feeds a 40 amp circuit breaker which feeds the Garmin® GHP10tm autopilot system.
    4. A fused attachment feeds the Magnum® ME-BMKtm battery monitor module.

Footnotes:

  1. Note: Setup options for the Magnum Inverter/Charger and ME-RC Remote Control are found in the MS-Word document entitled “Magnum_Remote_Control_Setup_Customization.doc.”
  2. Note: Setup options for the Balmar ARS-5 external regulator are found in the MS-Word document entitled: “Balmar_ARS-5_Setup_Customization.doc.”
  3. Note: the written description contained in this document is diagrammed in the document entitled ”DC_Electrical_Distribution_System.PDF.” Details of electrical system attachment points are documented in a table entitled “DC_Branch_Circuit_Functions.XLS.”
  4. WARNING: This  disconnect switch removes power from the bilge pump, sump pump and high-bilge alarm circuits. Therefore, it is to be used only for attended servicing of the electrical system. It is not intended for long-term disconnection of the battery bank while the boat is in the water!

Balmar® 110A High Output Alternator:

An alternator is a “self-limiting” device (ABYC E11, 11.4.26). That is, “a device whose maximum output is restricted to a specified value by its magnetic or electrical characteristics.” What that means is that an alternator can only produce just so much output current – in this case, 110A – regardless of how much drive is applied to its field winding. If the alternator fails, output generally stops. For self-limiting devices, a fuse is not “required” by ABYC E11, 11.10.1.1.2, but it is a reasonable precaution.

Aboard Sanctuary, the alternator connection to the ship’s DC system is protected by a 200A, Type MRBF, fuse. Two Hundred amps may seem too large a rating. The maximum rated output of the alternator is 110A. The ampacity of the #6 AWG conductor, derated because it’s in an engine space, operating in a 12V system with a 3% voltage drop and 105ºC insulation is 80A, and substantially higher for the 10% voltage drop case. So it may appear there is no scenario where the 200A fuse would protect the alternator connection wiring.

It’s very important to understand that we DO NOT want that fuse to open in the absence of a true, sustained over-current situation. If the fuse were to open while the alternator was operating in its designed power output range, the effect would be to instantly disconnect the electrical load (the battery bank) from the alternator. The magnetic field inside the machine would instantly collapse, creating a very high voltage “spike” inside the windings of the machine. That spike would almost certainly destroy the alternator’s internal diodes and render the device inoperable.

Alternators contain solid state full-wave rectifier diode pacs. Internal diodes prevent DC power from flowing backwards through the alternator when the engine is not in operation. If diodes fail in a welded-closed state – “shorted,” or “short circuited” – the result would create a direct path from the battery to ground via the alternator’s stator windings. The purpose of this fuse is to protect against that true over-current condition. In the case of a shorted diode, the 200A fuse protects the charging wire from becoming overloaded and, thus, a fire risk.

Magnum® MS2012tm Pure Sine Wave Inverter/Charger:

The positive and negative DC wires for the ship’s PSW Inverter/Charger are 2-0 AWG BC5W2 boat cable. Round-trip distance from battery-to-device and return is approximately 10′. The rated ampacity for 2-0 AWG primary wire inside an engine space is 280 Amps DC (ref: http://marinco.com/page/conductor-sizes). Magnum’s MS2012tm specs state that maximum battery charging current is 100 Amps DC, and maximum full load inverter draw at rated AC output load is 225 Amps DC. Optional configuration options are available via the ME-RCtm Remote Control to limit Inverter/Charger operating currents.

DC Return (DC “Ground”):

There are two terminal blocks in the ship’s engine room that comprise the ship’s DC return circuit to the main battery bank. The DC branch circuits and AC Safety Ground are all collected on a terminal block located fwd in the engine compartment, at deck level, starboard. This terminal block is connected to the main DC negative buss terminal block via a 1-0 AWG black wire.

The main DC negative buss is a Blue Sea® Systems 600A terminal block located amidships in the engine room, starboard, above the battery boxes. Joined at the main DC negative buss terminal block are:

  1. the consolidated branch circuit return terminal block, via a 1-0 AWG black wire,
  2. the Magnum® MS2012tm PSW Inverter/Charger, via a 2-0 AWG black wire,
  3. the propulsion engine block, via a 2-0 AWG black wire, (returns the Starter Motor circuit and the Propulsion Engine DC controls, instrumentation and instrument lighting), and
  4. attachment to the battery monitor’s 50mV, 500A measurement shunt, via a 2-0 AWG black wire.

The return connection to the negative terminal of the main battery bank is made from the battery monitor’s 50mV, 500A shunt, via a 2-0 AWG black wire.

Engine Wiring Diagram – Cummins 4B/6B

The wiring of the sensors and controls on a diesel engine in a boat involves several design variables, including:

  1. engine manufacturer preferences and choices,
  2. mechanically injected vs. electronically injected common rail technology platform,
  3. “normally-open” vs. “normally-closed” fuel shutoff solenoid,
  4. manufacturer and package options for gauges/sensors
  5. transmission neutral safety switch variables, and
  6. transmission oil pressure and temperature sensors/gauges, if installed.

The propulsion engine on Sanctuary is a Cummins 4BT-3.9 mechanically injected engine with a normally closed fuel solenoid that requires full-time DC power to keep it open.  The OEM sensor/gauge package is manufactured by VDO and includes tachometer, dual station oil pressure and temperature gauges and audible alarm sounders.  We installed dual station aftermarket high exhaust gas temperature sensors and alarms.

For those owners who perform DIY engine maintenance and repairs, I have included the wiring diagram I prepared for Sanctuary.  For simplicity, this diagram DOES NOT show gauge illumination wiring.  Click the following link to get a downloadable Adobe .pdf copy of Sanctuary’s engine wiring diagram: 20161022_engine_room_instrumentation_terminal_block.  This engine has two different kinds of oil pressure and temperature sensors.  The set that feeds the oil pressure and temperature gauges is analog.  The set that feeds the safety alarms is bi-modal (“on”/”off”).

Although this drawing is specific to the Cummins 4B, I would think it is “typical” of what would be found on many engines.  I encourage all boat owners or develop a wiring diagram of their propulsion engine.  If you ever need it, having it will save the skilled labor cost involved in figuring it out, diagnosing failures and making repairs.

AC and DC Motor Operation

In order for a motor to rotate, a torque must be applied to the rotor. The direction of that torque is what determines the direction of rotation; i.e., clockwise or counterclockwise. In both AC and DC motors, the torque is created by a magnetic field. Among the many styles of AC and DC motors, there are many techniques for creating and maintaining the rotational torque. In all cases, the magnetic field is created by an electric current flowing in coils in the motor. DC Motors are actually complex mechanical and electrical devices; generally, more complex than AC motors. This is because, since DC voltages do not have cyclic variation, DC voltages do not maintain a ongoing inductive coupling between the field and armature. Creating a consistent magnetic field in DC motors requires mechanical complexity that is not necessary in AC Motors.

The rotating part of a motor is called an “armature” in DC motors, and a “rotor” in AC motors. The terms both refer to the same thing, and are often used interchangeably. I mention it in case I lapse from one to the other in the descriptions that follow. Most motors are built with multiple independent field coils and multiple independent armature coils. These separate coils are electrically arranged in pairs or groups. In common discussion, these coils – or windings – are normally discussed for their electrical function, as if the collection of separate coils were a single entity. The distinction between the mechanical and electrical detail only matters when actually discussing actual motor construction. DC motor varieties in particular have complex schemes of the internal interconnection of the windings, depending on speed and starting torque design requirements.

DC Motors:
Series-wound DC motor types have their field coil(s) wired in series with the armature coils. Ordinary 12/24/32 volt gasoline and diesel engine starter motors are an example. DC series-wound motors are used in applications where the motor must spin-up against a significant mechanical pre-load. These motors must spin-up to operating speed while powering that mechanical load; operating speed can be highly variable. Series-wound DC motors that are not pre-loaded can and will reach “run-away” rotational speeds that can lead to physical self-destruction.

Parallel-wound DC motor types have their field coil(s) wired in parallel with the armature. These motor will not generally start against a pre-load. These motors are used in applications where load is applied after the motor is spinning at full speed, and/or where operating torque requirements are low. Starting torques are generally low-to-moderate. Fans and blowers might be a useful example.

A hybrid design of the series-wound and parallel-wound DC motor is one where some field coils are wired in series with the armature and others are wired in parallel with the armature in the same motor. This are known as series-parallel motors. These motors have the combined advantage of moderate-to-high starting torque and smooth running characteristics. They do not have the same speed range flexibility of the series-wound motor, and do not run away when unloaded.

In DC motors, a “commutator” is the internal mechanical means through which DC voltage is applied to the armature windings (coils of wire) of the motor. Multiple individual electric coils are assembled around the perimeter of the armature frame. The electrical connections to the individual coils emerge to terminals on the commutator assembly. As the armature rotates, the individual armature coils are sequentially connected and disconnected by carbon-brushes that ride on face of the commutator terminals. The more coils in an armature, the more evenly the motor will run. The torque of the armature is maintained by the offset of the magnetic field of the armature winding and the magnetic field of the field windings. That offset and the strength of the magnetic field determine total torque. On fractional and small horsepower DC Motors, these coils are generally arranged in groups of two. On large and very large HP motors, they are generally arranged in groups of four or more. Some large DC motors have brush racks that are adjustable, which allows torque to be adjustable through a limited range.

DC motors can often reverse rotational direction (run backwards) based on the offset of the magnetic field. DC Motors can also reverse rotational direction if the polarity of the applied voltage is reversed. Generally, reversing voltage polarity is simpler than designing and building an mechanically adjustable brush rack. Adjustable brush racks can be used to vary the speed of rotation of the motor itself; i.e., the more offset, the more torque, and the more torque, the greater the speed.

All motors have specification ratings for “start-current” and “run-current.” The reason is an interesting electrical phenomena that occurs withing the windings of the motor. When a DC motor starts, it accelerates from stand-still (also called “stall,” or “locked-rotor”) to it’s intended rotational speed. At the instant that power is applied, the amount of current that flows in the motor circuit is predicted by Ohm’s Law. However, during the period of armature acceleration, there is a progressively increasing DC voltage “generated” in the armature winding as a result of it’s rotation through the magnetic field of the field coils. This is the exact phenomenon that is desired in the case of a generator. The induced voltage is known as “back EMF.” Back-EMF voltages are opposite in polarity to the voltage that is applied to make the motor turn in the first place. As the rotational speed of the armature increases, the applied voltage and the back EMF voltage “cancel” one another to result in the net current flowing in the armature. That net current is what produces the motor’s operational output torque. This phenomenon explains why DC motors draw many hundreds of amps when starting, referred to as “locked-rotor.” As the armature accelerates in the magnetism of the field windings, and the back-EMF voltage rises, DC current flowing in the armature settles to much lower levels.

The carbon brushes that ride on commutator terminals, and the commutator terminals themselves, experience mechanical wear and electric arching.  Brushes require periodic replacement. The most common failure is that the motor will not start to rotate.  In gasoline and diesel engine starter motor applications, the starter solenoid will be heard to pick, or click, but the starter motor will not start to turn.  The larger symptom is, “the engine doesn’t crank.”  In this case, the starter motor brushes may be worn to the point that one or more is not quite in contact with the commutator.  An emergency action – worth trying – is to firmly tap the starter motor with a hammer or similar heavy object.  Don’t beat it to death, just give it a few firm taps.  Then, retry.  The taps may re-set the brushes in their rack, and allow the starter motor to spin-up.  Assuming the engine does start, make arrangements for immediate servicing of the starter motor.  This procedure, if it works, will only work a couple of times!

Carbon brushes are widely available as generic maintenance items at many hardware, auto parts and specialty shops.   Carbon brushes for small power tools can be obtained from the tool manufacturer, usually at premium pricing.  Commutator re-surfacing is sometimes required, although at much longer service intervals than brush replacement.  Commutator re-surfacing will require dis-assembly of the motor, and machine tooling.  This service is generally available at any alternator/generator specialty shop.

AC Motors:
All AC motors act like transformers. Compared to DC motors, AC motors are electrically and mechanically rather simple devices. Three-phase AC motors are by far the simplest of all. The very nature of three-phase AC creates a rotating magnetic field in a motor armature. The AC current in the armature induces a voltage in the rotating field. These motors will reverse rotational direction (clockwise or counterclockwise) if any two of the three-phases are reversed. This is usually accomplished with a controller, not physical re-wiring of the machine.

Small single-phase AC motors (split-phase) do not have/need commutators or slip rings, and depend entirely on this transformer-like induction to create the magnetic fields that result in torque and therefore, rotation. The field coil is built with a pre-set physical offset from the armature coil, and thus, the induced magnetic field causes rotational torque. These motors will not “run backwards.” The torque characteristic of a split phase AC Motor is determined by the mechanical offset the designer establishes between the armature coils and the rotor coils. Generally, these motors do not generate high starting torque. These motors start slowly, and bog down against load. These motors are cheap to build. They are a real workhorse when torque-matched to the correct applications. Mechanically overloading these motors simply stalls them.

Fractional and small horsepower motors that have to start against light to moderate pre-loads are made with a second field coil that is only connected during starting. When starting most shop tool motors under no-load, you can sometimes hear a centrifugal switch kick in (or out, when it’s spinning down). That switch connects and disconnects the start coil, which has a larger physical offset and will also draw more current than the steady-state running current draw.

A very common design for applications requiring moderate to high start and run torque in single-phase motors is the use of capacitors to electrically “adjust” the phase-offset timing of the current component flowing in the motor winding. This is advanced AC theory, but basically, Ohm’s law is slightly modified in all AC circuits. In Ohm’s Law, the resistive factor in AC circuits is really “impedance.” Impedance has both inductive and capacitive components. When a capacitor (or two, one for the start winding and one for the run winding) is added in series to a motor winding, that capacitor change the fundamentally inductive character of the motor winding. Capacitors change when, during the AC sine-wave cycle, the AC current flows with respect to the applied AC voltage. (AC current is *only* in-phase with the applied AC voltage in resistive loads, like light bulbs. This is the concept of “power factor.”) Suffice it to say, capacitors modify the otherwise mechanical offset of the magnetic field, and thus, the torque characteristics of the motor. This is particularly common in air conditioning compressors, where the AC motor must start against a moderate to high static pre-load back pressures. Capacitor-start, capacitor-run motors are used where high starting torques are needed.

The most common failure of fractional and small horsepower AC motors is seizing of the motor bearings.  This results in the motor overheating, and slow or no rotation.   The best prevention is to follow the manufacturer recommendation for lubricating the bearings.  Do not over-lubricate these bearings.  Use only lubricating oils recommended by the manufacturer.  Some oils get sticky as they age, and will only aggravate the problem.  These motors almost always can be refurbished by an AC motor repair specialty shop.  Such shops are widely available in most communities.  Replacement units can be ordered from manufacturers, assuming the OEM part is still available when you need it, but almost certainly at premium prices.  Generic replacement motors are also available, but can require custom mechanical fabrication at the job-site to install.

Universal Motors:
There is a special case of motor commonly called a “Universal” motor. These motors run on both AC and DC. They employ a commutator, and have very high starting torques for their size. They operate across a wide and variable speed range. The penalty they pay is they draw a lot of current proportional to their size, and generate a great deal of heat for their size in operation. They are rated for intermittent duty-cycle applications, not for continuous use. They are commonly used in household and kitchen appliance and hand-tool applications. Think blender, vacuum cleaner and electric drill applications.