AC and Hot water on at same time - Breaker burned up

[Bob K]

A few weeks ago I had the AC running (Mermaid 16000 BTU), and turned on the hot water heater.  I hadn't done this in the past for fear of popping the main (30A)breaker.  Well, the breaker did not pop, but after a while we started smelling burning plastic.  Quickly shut down everything and went looking for the source.  The breaker panel was quite warm to the touch, and the main breaker was hot.  It was the source of the smell.  I replaced it, inspected and tested the panel, and things seem to be running OK.   I will no longer attempt to run AC and HW heater together, but am curious how many amps I was drawing.  The Mermaid website says the AC draws about 12A.  Maybe mine draws a few more (may be an older modeL).  Does anybody know how many amps the stock (1992) hot water heater draws?  My paperwork has no specs.  Has anybody else had the burning breaker experience?

[jmnpe]

Hi Bob,

I had a 1991 C34 with the 16K Mermaid, and it drew about 14 amps. The water pump draws about 2 amps or a little more if it is the Marsh pump. The 6 gallon water heater draws 12.5 amps, which gives a near maximum load of 28.5 amps. On our previous 1991, I had problems with all of the high amperage breakers, but it wasn't the breaker's fault. The culprit was the push-on spade terminals and bare copper wire used to hook into the breakers. Once the spade terminal connections got hot from a full load, they got a little looser on the CB terminal, and the next time they got hot again it became a vicious circle of looser connections and higher contact temperatures. The water heater feed spade terminal and wire from the breaker finally got hot enough that everything started to melt and smoke. The main 30 amp CB also looked pretty bad. I finally had to replace wires and terminals on both breakers with good quality terminals ( Anchor Marine ) crimped with a good ratcheting crimper, and of course cleaned up the mating spades on the associated CBS to reduce the contact resistance. I never had any trouble for the remaining several years we had the boat.

Hope this answers your questions.

John

[Jim Price]

Bob,

I have a 1991 that I replaced the entire panel about 2 1/2 years ago (used current Seward model) because of problems with the old style push / reset breakers.  With the current date breakers I frequently run the Mermaid, battery charger (TrueCharge 20), hot water heater, AC interior lights with absolutely no problems.  The ONLY time I have experienced any breaker "trips" is when running all and the Admiral runs the microwave (600W) on a long (several minutes) cooking cycle.  However, using all including the microwave on short 1 minute cycles has never tripped any breakers.  When she needs to run the microwave for an extended cycle, we simply turn the water heater breaker off while doing that task.  I am betting the overload comes when the Mermaid cycles on and you have the initial compressor surge with every thing else going on.

I am not an electrician but this certainly suggests the modern breakers can "manage" amprage and heat better than the old panel breakers but still not when everything is cycling on with initial surges.