a cautionary note about Seaward Water heaters

[BobH260]

While living on our boat last January we had quite a scare. Suddenly the cabin filled with smoke. We were in a slip on shore power. Sherry and the dog got on the dock right away, I pulled the shore power plug, turned batteries off. Then opened the hatches and ports. The smoke was coming from under the aft berth where our Seaward water heater was installed. Fortunately it is quite accessible, I had it out of the boat and onto the dock quite quickly. It was still smoking. The smoke quickly cleared in the cabin and fortunately did not leave any residual smell. We were lucky that we were on the boat when this occurred. We now only turn the hot water tank on when it is needed, and never leave it on when we are not on the boat.

I opened the heater to investigate the problem and photographed what I found. It appears the black wire got red hot, melted all the insulation off of it and burned all the insulating paper. Had I not been on board to turn the power off I don't know how much further this may have progressed. The thermostat and high temp did not open because the water did not over heat and the heater did not exceed the breaker trip current. I think maybe the black wire was corroded and turned into a high resistance. The water heater was built in 2003. The tank was installed in a very dry location, showed no corrosion on the outer case or inner aluminum tank.

The heater was factory installed running on a 15 A breaker, 14/3 marine wire from the panel. The black wire began to melt the plastic after it passed into the insulated area of the heater. It terminated with crimped ring terminals at the high temp shut off, then the thermostat and finally at the heating element. The white return wire going up from the heating element appears to only have been damaged by the heat generated by the black wire. The element is rated at 1500W and measured about 10 ohms, I did not measure any leakage to ground in the element.

I contacted Seaward, reported the problem, sent them the photographs and also the electrical components. They promised to submit the parts to a lab for analysis of the fault, and let me know the results. So far I've heard nothing more. I don't know why this happened. I'm not trying to say Seaward did anything wrong or it is a bad design. We replaced it with another Seaward water heater. I do want to advise others about the potential hazard of leaving the water heater on when you are away from the vessel or asleep.

Bob

(I also posted this here )

[hellosailor]

Bob-
From what I can find, the allowable ampacity of a 14AWG wire should be 15A indefinitely, and 20A for short periods. So your 15A breaker should have tripped well before the wire could get hot enough to slag down.
I'd test the breaker with a known 15A+ load, and perhaps simply replace it in any case rather than trust it not to fail again.
The other thing that sounds familiar, is that I had recently bought an ATC/ATO type fuse holder from Littelfuse, a company that has a pretty good name. Fuse came in, and I looked at the wire, and said to myself, this doesn't look right. Sure enough, the color of the wire was wrong (compared to the catalogue description) and the wire was clearly marked one gauge size smaller than the catalogue description. Which might have carried the intended load, but would have messed up my crimping.(G)
When I brought this to the attention of Littelfuse, they came back with 'the manufacturer [contractor in Mexico] changed the wire size without telling us'. That's kind of frightening. But if someone at Seaward, or supplying Seaward, was screwing around with wire sizes and types...that could explain why a wire would slag down, without exceeding the breaker's trip current.
Possibly least likely, the shore power was terribly over or under voltage? Which I don't think would still excuse the breaker. There have been recalls on breakers too, fwiw.


Glad you caught it before the fire marshals had to come and poke over the bones of a boat! Might want to file a report to the consumer safety people in any case, though.

[Tayana42]

Bob, wow, were you lucky! Thanks for alerting us to this issue. I'll look at my water heater differently after reading this.


S/V B'Shert

[Journeyman]

Bob, contact resistance is possible. Circuit breakers offer no help for this type of fault. Are the crimped rings and the high temperature shut off material all copper? If the copper wire terminates on a brass temperature shut off connection, alloying can occur exacerbating the contact heating. Were the connections tight? Are they now on your new unit? Red hot wires at loose connections between dissimilar metals can start fires at currents way below circuit breaker thresholds. -J