Shore power voltage & Tripped Breaker w/ Hot Water & A/C

[Mike Vaccaro]

I'm a fan of monitoring both DC and AC systems with some type of multimeter.  We use a Link 10 for the DC system on our boat and a Blue Sea Systems AC multimeter for the AC side.  Neither one of these components are inexpensive; but they provide a great deal of flexibility for energy management.  We do have air conditioning on board, and as other posts have noted, you can't run all AC appliances simultaneously if the total amperage draw is greater than 30 amps (or the maximum amperage that the shore power circuit is capable of delivering, e.g., 15 or 20 amps).  It's also not a tremendous idea to run any circuit at 100% rated capacity for extended periods of time. 

With the ability to monitor actual system draw, you can make a rapid assessment about whether or not you need to turn off the coffee pot to run the vacuum.  The DC meter may also allow you to monitor the health of your battery and charging systems as well. 

The air conditioner is likely to be the highest drawing component installed, but depending on the unit, it may still be practical to run it on a 20 amp circuit.  Amperage draw will be highest when the compressor is first switched on, but then taper off rapidly.  On the old (circa early 90's) King Air unit we have on our boat, this amperage spike averages 10 amps.  With "background" AC draw (usually 1.3-2.0 amps) created by the battery charger powering DC systems, peak amperage will be around 24-25 when the compressor kicks in.  It will then rapidly drop to 13-14 amps as the motor stabilizes.  Depending on the configuration of the shore power circuit, this may or may not trip the circuit breaker--it shouldn't trip the breaker in your boat, but the breaker at the dock.  If the dock breaker does not trip, your system will run fine; but not if add much else to the load! 

With some models of air conditioner, there is a simple check you can perform if you want to be sure that your on-board system wiring is good: you can run the compressor unit without cooling water.  If the system is working normally, it will overheat fairly quickly and shut itself down by tripping the dedicated on-board air conditioning circuit breaker.  Check with the manufacturer before you try this, however, as 1) it may not work with all units; or 2) you may damage your air conditioner in the process.  By the way, you may encounter this exact set of circumstances if you attempt to run the air conditioner with the cooling sea-cock closed!     

Hot water heaters and coffee pots are also appliances that are relatively high-draw that cycle on and off regularly.  This will become very apparent if you monitor system amperage when you've got appliances on.  After a while, you will develop a good feel for energy requirements and become adept at turning components off and on to maximize efficiency and minimize problems.  Hence the reason many newer boats have multiple AC circuits and/or 50 amp service vs. 30!

Your nose is generally the best detector for the initial phase of an electrical malfunction that is a potential fire hazard, is is monitoring the physical temperature of a circuit breaker or wire (i.e., touch).  Any abnormal odor probably is (abnormal!) and should be investigated immediately.  If in doubt, de-power and carefully re-power one circuit at a time to avoid problems. 

In an emergency, beer can always be cooled by ice and the boat sails just fine without electricity or an engine!

Cheers,

Mike

[Jim Price]

Bob K, another point on the hot water heater.  Don't know if you have ever replaced the heating element but your boat is older like mine and I replaced mine a couple of years ago (buy element from Home Depot) and it made a BIG difference in heating up.  If yours is original, it is probably covered with scale; thus you will use more "juice" to heat the water and bingo, there goes the breaker.   

[Stu Jackson]

Another trick on hot water heaters:  if you get in the habit of using the hot water faucet, even when there is no hot water, you'll keep gunk moving through the heater and perhaps reduce the amount of scale buildup on the coil; it also reduces any chance of rotten egg smells from the hot water side.