Category Archives: Emerging AC Electrical Concern

Emerging AC Electrical Concern

Initial Post: 4/29/2015
Added “Isolation Transformers:” 6/16/2015

A significant AC electrical concern is emerging for some owners of older boats. For those who may be, or are affected, I urge you to investigate sooner rather than later.


Land-based building and construction codes are usually implemented through government rule-making and have the force of law.  In the United States, the National Fire Protection Association (NFPA) is a private fire safety association that creates and maintains the US National Electric Code (NEC).  In Canada, the Canadian Standards Association (CSA) maintains C22.1, and various other departments maintain industry specific Canadian Electric Codes.

In the US, the NEC is updated and published on a three-year cycle.  The most current version was published in 2014.  Across the United States, the 50 individual states, and many counties and municipalities, “adopt” the NEC as their construction and building standard.  Adoption occurs at random intervals and varies from locale-to-locale.  Code enforcement is through the permitting process, and designated local code enforcement officers called the “authority having jurisdiction;” the “AHJ.”  Today, some jurisdictions are operating on the 2008 NEC, some on 2011 and some on 2014.  People who own properties in multiple states may indeed be working with different versions of the NEC.

For boats and boat owners, there are no “permitting” processes for performing upgrades, and there are no official “authorities having jurisdiction.”  The only “codes” that apply to pleasure craft are very limited federal requirements (enforced by the United States Coast Guard) and a very broad set of voluntary standards developed by the American Boat and Yacht Council (ABYC).  Principally for pleasure craft, the standards of the ABYC take precedence.  The ABYC electrical standards align and integrate tightly with land-based codes, except that compliance is “voluntary.”  As boaters, the closest we come to any kind of formal “code enforcement” is through the business requirements of a lender or, more commonly, an insurance carrier.  To obtain hull insurance, boaters usually obtain a “survey.”  If a surveyor identifies a discrepancy or noncompliance to one of the provisions of the ABYC standards, the lender or marine insurance carrier may require the boat owner to implement corrective measures.  However, in practice, this process is flawed in significant ways.  Most surveyors are not expert in assessing AC electrical systems, and are unlikely to check for, or detect, AC ground fault or related current leakage issues.  Since compliance is voluntary for the boat owner, nothing is actually required for those owners who choose to self-insure.  Periodic surveys are not required by law.  ABYC compliance is not a legal requirement but rather, is loosely and inconsistently based on the business transaction between individual boat owners and the various marine insurers.

The Emerging Issue:

The scope statement of the National Electric Code, Article 555, is “… the installation of wiring and equipment for fixed or floating piers, wharfs, docks, and other areas in marinas, boatyards, boat basins, boathouses, and similar occupancies.  This article does not apply to docking facilities or boathouses used for the owners of single-family dwellings.”  The equivalent language in the scope statement of the National Fire Protection Association standard (303, Chapter 5, 5.1.1) is:  “This standard applies to the construction and operation of marinas, boatyards, yacht clubs, boat condominiums, multiple-docking facilities and multiple-family residences, and all associated piers, docks and floats.” In the NEC, the term “similar occupancies” include yacht clubs, condominium docks, restaurant docks, etc.  Because land-based codes are mandatory but boat codes are voluntary, there is an emerging issue (in 2015 and later) for boat owners, and definitely for owners of older boats, at all non-single family, residential docks.  These defined facilities are the point where the voluntary compliance requirements of cruising and transient boats interface through the shore power code with the mandatory requirements of the land-based NEC.  We as boat owners are squarely in the middle.

The average age of one fleet with which I am familiar is 27 years.  Across that span of years, electrical standards, materials and best-practices have all evolved significantly.  Across those years, many “previous owner modifications” may have been made to a boat’s AC electrical system, and perhaps not always implemented “in the right way.”  Furthermore, some boats built new, offshore, contain equipment choices selected for cost and do not comply, new, out-of-the-box, with ABYC requirements.  And finally, across the years, systems and components can deteriorate and fail, sometimes in obscure and non-symptomatic ways, invisible to and hidden from the boat owner.

The issue to which older boats in particular are exposed, then, is that they may have one or more true ground faults and/or leakage faults aboard.  Simply put, boats that are not compliant with the 2012 and 2015 versions of ABYC E11 will be INCOMPATIBLE – by definition and in fact – with the shore-side requirements of the 2011/2014 National Electric Code for ground fault protection on docks.

Requirements placed on land facilities:

The National Electric Code, Article 555.3 (entitled: Ground Fault Protection) says:  The main over-current protective device (OPD) that feeds the marina shall have ground fault protection not exceeding 100mA.   Ground-fault protection of each individual branch or feeder circuit shall be permitted as a suitable alternative.

In the case of a complying facility, then, the statement, “The main over-current protective device (OPD) that feeds the marina…” would refer to the AC feeder to EACH individual dock.   So EACH dock would have to be GFP-protected to no more than 100mA.  Also, the statement, “Ground-fault protection of each individual branch or feeder circuit shall be permitted as a  suitable alternative” means there are three practical choices for a facility operator to achieve compliance with 2011/2014 NEC 555.3:

1. The ENTIRE DOCK would share a single feeder with 100mA GFP, or
2. A CLUSTER OF SLIPS (two, four, six, etc) would share a feeder protected at no more than 100mA, or
3. EACH PEDESTAL would have a “home run” to the mains distribution panel, and EACH INDIVIDUAL PEDESTAL would be protected at no more than 100mA.

As to the capital costs faced by a facility operator in order to comply with Article 555.3:

1. Item 1 is the least capital intensive for the facility to install, but it is also the most troublesome.
2. Item 2 is middle-of-the-road from the perspective of capital cost to install, and middle-of-the-road for being troublesome.
3. Item 3 is the most capital intensive and the least troublesome.

When I use the word “troublesome” above, I am referring to the fact any boat with a ground fault will trip the feeder to which it connects.  So in case 1, a single boat with a ground fault will take down the entire dock.  In case 2, a single  boat with a ground fault will take down a cluster of slips.  In case 3, a single  boat with a ground fault will only affect one pedestal, but NOT its neighbors.

Obviously, for a large marina intending to support a largely transient customer base, case three would be the conservative, preferred option to ensure uninterrupted electrical service to its customers.  In a private club or condo dock, where there is virtually no transient traffic, a less conservative approach may be acceptable.  Obviously, the least risk of service disruption is associated with the greatest capital maintenance costs.

What It All Means to Boats and Boat Owners:

In light of the above, consider a cruising boat with a hidden ground fault that arrives at a newly upgraded, NEC-compliant marina or boatyard.  If that boat has a ground fault aboard, it is possible for that transient boat to bring down an entire dock, or a cluster of neighboring slips. In that case, some number of “innocent” neighboring boats will be negatively affected; that is, they will all lose power.

A boat wired in compliance with the 2012 ABYC E11 standard will not have undetected ground faults. New production boats manufactured after 2012 must have ELCI devices installed.  New boats and those retrofit with ELCI devices aboard will not have hidden ground fault problems.  However, many older boats do not – maybe never did – meet the ABYC E11 standard, and there is no legal requirement that they be retrofit to comply.  Therefore, ALL FACILITIES that comply with the 2011/2014 NEC for Article 555.3 WILL ENCOUNTER ground fault issues with some number of transient boats.   What that also means is the owner of a boat with a ground fault condition will be more and more often exposed to not having power in newer, more modern facilities.  And obviously, the owner of the boat that is the cause of a loss of power on a dock will not be a very popular or welcome guest.

I would guesstimate at least 10% to 20% of older boats could have true ground faults, either by wiring performed by the previous owner(s) or by now-obsolete OEM equipment installed years ago at time of manufacture.   Some argue for a much higher number, but whatever the real number, it is significant.  Just yesterday (end June, 2015), I walked a dock at my home yacht club with a clamp-on ammeter.  I found at least one boat with two 120V shore power cords and co-mingled neutrals.  I found at least 6 boats leaking more than 100mA into the water.  All of those boats would cause a GFP device with a 100mA set point to trip and disconnect power to their boat.  Finally, for the individual owner of an older boat who happens NOT to be an electrical geek, there may be significant time and expense in hiring a marine-certified electrical technician capable of correcting ground fault problems on boats!

Looking ahead to the future:

The development of the National Electric Code is a methodical and disciplined process.  Change proposals require many months or years of study and consideration before they are adopted.  The next release of the NEC (NFPA 70) is scheduled for 2017.  On November 5, 2014, ABYC submitted a proposal entitled “Assessment of Hazardous Voltage/Current in Marinas, Boatyard and Floating Buildings” to NFPA which recommends requiring GFCI outlets on all marine pedestals.  Pedestal outlets under this proposal would be spec’ed at 30mA for 100mS.  Assuming this is adopted by NFPA (Section 303, Chapter 5) and incorporated into the NEC (Articles 553 and 555), it would probably speed the overall rollout of GFP on docks, as it is much easier and less expensive than the whole dock solutions discussed above as provided in today’s standards.

Isolation Transformers:

With an isolation transformer, the shore power ground stops at the transformer, where it connects to an internal shield that is electrically isolated from the transformer’s case.  The case of the physical transformer is connected to the boat’s onboard AC safety ground.  ABYC E11 treats the secondary (output side) of an isolation transformer as an on-board power source, like a genset or an inverter.  The primary (Input side) of the isolation transformer is fed from the dock pedestal. The secondary (output side of the transformer) has its neutral and ground conductors bonded (connected together) at the transformer.  With an isolation transformer, there is no through electrical connection between the shore power ground and the boat’s on-board grounding system.

From a GFP-on-the-dock perspective, by design, there is no ground fault path (unless the transformer itself has a physical flaw).  Boats with isolation transformers will not have GFP issues on 2011/2014 NEC GFP-compliant docks.  (That said, it is possible to have wiring errors aboard that would constitute ground faults if configured for direct attachment to shore power instead of an isolation transformer.)

There is one significant “EXCEPT” to the isolation transformer story.  If a wired telephone, wired Ethernet or shielded TV cable is ever brought onto the boat, the ground conductors in those cables create an electrical path between the shore power ground and the boat’s on-board electrical grounding system; that is, they bridge the gap that was deliberately created by the design of the isolation transformer.  So, first, boat owners MUST ALSO have galvanic isolator devices installed in ALL OF THOSE CABLES in order to create the physical separation gap in the ground path. These isolators can be of the magnetic or optical coupling design.  The Cable TV galvanic isolator is easy; $10 off the Internet.  Isolators are made for the other cables, but may be pricey.  Second, if a boat with an isolation transformer does have a ground fault in its on-board wiring, the boat will trip a GFP at the time one of those (telephone/Ethernet/Cable TV) “bypassing shore ground paths” is connected.  The risk of this is low, but not zero.  Third, because the wires in telephone and Ethernet circuits are physically small, if there are hidden ground fault wiring errors on the boat, those physically small wires may act like fuses, and open.  There is also the potential of damage to attached electronics.  Again, the risk is low, but not absolute zero.

Word to the wise:

Investigate the status of your older boat now!  If you have this problem, it is only a matter of time before it bites you!