My Admiral and I live full-time aboard Sanctuary. We cruise in the warmer months. At least twice each year, we stay at the same marina facility for several weeks at a time. We stay at our home yacht club in the spring and mid-to-late fall to stage our departure and return from summer cruises. We migrate south and enjoy our winter season in warmer climes.
For long-duration marina stays, it is common for marina facilities to measure electricity consumption with an electric meter. The marina then invoices the slip holder for actual electricity used, measured in “kilowatt hours,” or KwH. This is also, of course, residential practice everywhere in North America.
We have observed that rates for electric power vary widely from region-to-region and place-to-place. It is not entirely uncommon to find that the electric meters fit into slip-side pedestals are either not working at all or produce incorrect readings. When this situation is known, the marina typically bills a flat-fee that is equivalent to some “average” for boats our size. When it is not previously known, it can result in interesting conversation with marina office personnel. All of this has caused us to wonder – often – about the actual magnitude of Sanctuary’s “average” electric use.
With the above as background, I recently learned of a company called Energy, Inc., of 648 Marina Dr., Charleston, SC 29492, d/b/a “The Energy Detective,” http://www.theenergydetective.com/. This company makes a line of energy monitors, one of which is intended for use in premisis wiring systems in the residential market, and is quite suitable for use aboard Sanctuary.
Sanctuary is fit with two 30A shore power inlets. One feeds the “house” circuits and the other feeds the heat pumps and associated raw water circulator pump and pump controller.
I purchased a TED5000G. This model is meant to monitor power use in one single phase, center-tapped, 240V, conventional on-premises electric service. This is equivalent to boats with a single 50A shore power service or two 30A shore power services. The TED5000G comes with 1) two clamp-on current transformers, 2) a unit that monitors incoming power and relays status information to 3) a control unit the company refers to as a “Gateway.” This makes for an easy DIY installation. Because the current transformers clamp over the incoming hot conductor of each 30A shore power inlet; that means no fiddling with the inlet wiring is required of the installer.
The TED5000 Gateway box has a wired Ethernet interface that plugs into any 802.11b/g/n capable Ethernet router. Sanctuary is fit with a Cradlepoint MBR95. The TED Gateway has internal firmware (Linux, perhaps?) with a web server front-end and a data base back end. Data collected by the monitoring unit (MTU) is fed to the Gateway unit as a digital signal over the existing power lines in the boat. The transmission protocol is “Power Line Carrier.” Digital data packets are imposed on the premises (boat) power wiring at a carrier frequency of 132 kHz, and transmitted during the zero-crossing of the 60 Hz AC sine wave.
The TED5000 monitors line voltage in real-time, and collects power usage data. The web server allows access to a real-time display of data from any browser (Firefox, Chrome, Safari, IE) on any computer/PC/tablet/smart phone. The web server has configuration capability, and can be be set up with time/date, electric rate you pay to your electricity provider, billing cycle, local weather, and it allows for differences in prime-time, off-time and seasonal billing rates.
This system is not exactly sophisticated by today’s computer technology. It needs a wired Ethernet connection to a router rather than having an internal Wi-Fi adapter. The internal web server is a tad slow. However, at a $200 price point, it seems utilitarian. Here’s a screenshot of the real-time “Dashboard:”
This view shows I’m configured for a flat-rate electric billing plan at $0.21/kWh (expensive). The current time is 16h04, and I have 11 days to go in the billing cycle. I’m currently consuming 0.372 Kw of power, and have used 10.5 KwH since midnight last. The current line voltage is 121.5VAC (good), and my average daily usage in this billing cycle has been 14.0 KwH. I don’t have enough experience with this system yet to know if the projections are valid.
Here’s a screenshot of the “History” page. This page shows actual power usage:
The “Day History” shows my cost at $0.21/kWh; a low of $1.03 and a high of $6.08. The “low” day was dry, clear, mid-70s, boat wide open for 24-hours. The high day was hazy, hot, humid, high 80s, running A/C all day and night. The “Hour History” shows the heat cycling on in the overnight last night; 52ºF this morning. So, the data all correlate and make sense.
Now for those that think the story is over, stay with me for a minute. There’s more than just power usage and cost tracking for the boat owner here!
I was most impressed to discover this little monitoring system could also tell me a lot about the health of my shore power connections. Following is a screenshot of the “Graphing” tab. The blue line shows power usage, and the red line shows incoming AC line voltage. The settings for this graph reflect a data sampling interval of once-a-second (“Second Live View”) and the total time duration of this graph is 30 minutes. This screen shot was taken during dinner preparation a couple of days ago. The admiral was doing pasta in the microwave. Here’s the raw data:
And here’s what was happening:
There are several noteworthy observations reflected in this graph:
- as the power stair-steps up, the line voltage stair-steps down. Why? Is that OK, or not OK? Well, er, ummm… not!
- the battery charger decided it needed to be heard from; who knew? Yes, that is a pattern with our inverter/charger; It does come on when line voltage dips, although there is no DC load that appears to correlate with the charger activation.
- the line voltage is sampled from the 30A AC inlet that feeds the “house” power panel, which powers the microwave and the battery charger. The heat pump is on a 2nd 30A AC shore power inlet. Since the heat pump cycling “on” did not result in a corresponding dip of the line voltage, doesn’t that suggest the voltage drop implicates the boat’s “house” AC shore power service, and not the marina’s dock feeder cable to the pedestal? Hmmm…
Investigation of item 3 ensued forthwith. I “shot” the pedestal 30A shore power breakers with an infrared (IR) thermometer, and they were getting warm with load. Faced with this graph, it’d be hard for the marina to conclude that a boat owner doesn’t know what he’s talking about. The marina promptly changed-out the pedestal circuit breakers. Some improvement, but not enough. So, we’ll next change out the pedestal 30A sockets.
Now here’s the pearl at the end of this story. It’s obvious the line voltage measured at the “house” shore power panel on the boat is dropping. I was unaware of it. There were/are no symptoms of that voltage dip that I could observe without this graphing function. It may have been noticeable with a digital voltmeter, but I have an analog meter on my “house” panel. Even if I could have seen it, it would have been much harder to convinced the marina to take action
One final note on “Power Line Carrier” technology. From the TED troubleshooting guide: “Today’s homes usually contain numerous devices capable of producing noise on the power line. These include fluorescent lights and ballasts, halogen lights, UPS back-up power supplies, unfiltered dimmer switches and fan speed controls and A/C–D/C power supplies for fax machines, computers, televisions, printers, WiFi devices, and numerous other electronic products.”
Aboard Sanctuary, the only interference we experience is related to 120V dimmers that control 120V halogen lightbars located in the galley and salon. When those lightbars are “on,” data transmission between the MTU and the Gateway is interrupted. Sanctuary’s inverter/charger (Magnum MS2012), in passthru mode, does not interfere with TED5000G data transmission.
So, yes, I like my TED5000.