a cautionary note on Seaward water heaters

[Bob 04 H260]

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 now 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 at all.

I contacted Seaward, reported the problem, sent them the photographs and 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 so I decided to post this as a warning to others about the possible danger of leaving the water heater on when no one is aboard.

Bob

 

[Rich Stidger]

Glad that you had the good fortune to be able to prevent a disaster.

We also have a Seaward HW tank and it is the 6 gallon galvanized model. It may be 7-8 years old, not sure.

We are almost never on a dock with shore power and we only turn it on with our generator when needed. But I do not consistently turn it off after it is hot and satisfied unless I am running other heavy loads and I don't want it to turn back on inadvertently.

Thanks for giving us a heads-up.

 

[Gunni]

I frequently leave my seaward HW heater on when I am about the slip, or nearby. It is switched off when we leave shut off the water supply and head to the house. And oh by the way, who turns off their home HW heater when they leave the house? Yeah, nobody. Seaward has some 'splaining to do as to how this could happen. I find it really hard to believe that the current necessary to burn insulation off of the wiring was not enough to kick the breaker. What is the breaker rated at?

 

[Bob 04 H260]

I frequently leave my seaward HW heater on when I am about the slip, or nearby. It is switched off when we leave shut off the water supply and head to the house. And oh by the way, who turns off their home HW heater when they leave the house? Yeah, nobody. Seaward has some 'splaining to do as to how this could happen. I find it really hard to believe that the current necessary to burn insulation off of the wiring was not enough to kick the breaker. What is the breaker rated at?

The heater element is rated at 1500 W. I measured the resistance at 10.2 Ohms. The breaker is rated at 15 Amps. Obviously the heater should not draw more than about 12.5 Amps. The heater was factory installed from panel to heater using 14/3 marine wire. The only wire that melted was the black hot wire inside the water heater. Where the white wire inside the case is melted it appears to be from the heat generated by the black wire. The only explanation I can come up with is that black wire suffered corrosion and it turned into a heating element, it was in series with the 10 ohm element so the breaker could not blow. The white wire did not melt because it was not corroded. Any other theories ?
Bob

 

[All U Get]

Can you tell if it was wired 110V or 220V? (I heard that some time ago so can't remember it all) If you had a schematic of the wire scheme can you follow it. Any chance of reverse polarity? We were at a dock and my shore power cord had been burnt. Three slips away two other boats also got fried. Never found the culprit.

All U Get

 

[woodster]

could it have been that the thermostat switch malfunctioned ...that would be my guess looking at the pics you posted ...it looks like the bulk of the damage is in that area but i could be all wrong in my assessment

 

[Doug4bass]

Man.....this hits close to home.

http://forums.sbo.sailboatowners.com/showthread.php?t=172707

 

[mitiempo]

Can you tell if it was wired 110V or 220V? (I heard that some time ago so can't remember it all) If you had a schematic of the wire scheme can you follow it. Any chance of reverse polarity? We were at a dock and my shore power cord had been burnt. Three slips away two other boats also got fried. Never found the culprit.

All U Get

It would be 110 volts on a Hunter 356. Reverse polarity shouldn't have caused this either. My guess is a poor connection causing resistance. It is 12 years old so not a design problem. I wouldn't blame Seaward.

 

[Bob 04 H260]

It would be 110 volts on a Hunter 356. Reverse polarity shouldn't have caused this either. My guess is a poor connection causing resistance. It is 12 years old so not a design problem. I wouldn't blame Seaward.

Looking at the pictures the black wire came down going through the high temp cut out (2 connections there) to the thermostat (another 2 connections there) and then terminates at the input to the heater element (1 connection there).

Coming out of the heating element is the return white wire, it goes straight back to the white power input wire at the top of the heater.

Only the black wire is burnt, the white wire only appears to have damage from the heat generated by the red hot black wire.

If the heat was caused by one of the 5 connections in the black wire I can see how that could melt the wire back from that connection, maybe between those two connections.

Is it logical all five connections went bad together ? None of the screw terminals were loose on those 5 connections. None of the screw connections showed any corrosion.

If the heating element caused the problem then the white wire should have melted as well, it carried the return current but did not melt. I think this indicates the black wire had resistance that caused the heat generation along the whole wire between each connection.

Is it possible the black wire and white were not the same construction ? This difference cause the black wire to corrode ?

The outer case on this heater is galvanized and painted, it did not have any rust or corrosion, the aluminum water tank did not have any leaks or visible corrosion.

I think the real take away here is, don't leave the hot water tank on when you are not on the boat or sleeping. I think Seaward should tell the owners that. I don't think this is a common problem or it would be well known. Who knows maybe this post will generate some others who had similar problems but never reported it.

Bob

 

[mitiempo]

There is one connection of the black (hot) wire not shown - its connection to the boat's wiring from the breaker. That connection would have been done by the builder, not Seaward. Could that connection be the cause of the resistance?

 

[Bob 04 H260]

There is one connection of the black (hot) wire not shown - its connection to the boat's wiring from the breaker. That connection would have been done by the builder, not Seaward. Could that connection be the cause of the resistance?

The pictures were taken after I removed the water heater from the boat, so I don't have any pictures of those connections. The power input connection was made using crimp connectors on the black and white wires, the green ground wire had a crimped ring terminal that was under the bolt with the green wire from the heater. I cut the two power wires just behind the crimp connectors leaving them on the boat.
If you look at the last picture in my post it is a closeup of the water heater wires where the power comes into the heater. That was where the black and white wires were cut, the bolt was removed to release the green ground wire. The black wire is not melted. This area of the heater is where the electrical connections are made, the wires are in the air without the fibreglass insulation around them. The three heater wires (black, white and green) go through a wire tie and into the fibreglass insulation after that the black wire starts to heat up. You can see it melted just after the wire tie. I took that picture because Seaward said there had been some problems with heaters where the installer had removed their wire tie at this position and the wires had chafed. They asked if my heater still had the wire tie there.
If there was one bad connection on the black wire that caused the heat I don't see how it would cause the wire to melt 2 connections away, they are completely thermally isolated. Each piece of black wire has a component between the two bolted connections. It looks like each piece of black wire had resistance. Perhaps the black wire ahead of the wire tie has resistance too but because it was in the air it did not heat up enough to melt the plastic insulation ?
Bob

 

[All U Get]

,,,,,,and the heater element is OK?

All U Get

Sorry I totally missed it. Where were you in January? It wasn't in Canada was it?

 

[Bob 04 H260]

,,,,,,and the heater element is OK?

All U Get

Sorry I totally missed it. Where were you in January? It wasn't in Canada was it?

No not in Canada in January at a dock !

We were in Florida. The heating element measured about 10 ohms so about right for a 1500 W element.

Bob

 

[pfaffk]

I have the same water heater on my 2001 Hunter 290, but I only turn it on when I will need hot water and turn it off when I am done. But thanks for the warning

 

[walt]

It is odd that only the black wire is burned up - as you said, there must be two conductors involved in the current flow so why only the black wire. Normally the white wire would have identical current to the black wire.

If you take an ohm meter and measure the resistance between the green wire and the white or black wires, what do you get? You should measure an open between the green wire to both the black and white. Sounds like you have the unit with you so this should be easy?

If for example you measured a low resistance between the white and the green, you could have had a fault that resulted in the current in the black wire returning through both the white and the green wires - twice the wire so they don’t show the burn. Note, the green wire should show a low resistance to the metal chassis - but that should be the only connection.

Second thing is you said there is a 15 amp fuse in the line. Is this the fuse on your boat or is the fuse in the marina? Not that it matters.. but just curious.

It’s also somewhat odd that the air conditioner case also looks like it was the black wire that mainly was involved in burning up. Even though normally the black and the white wires carry equal current (for 110 VAC in the US), the white wire is normally always very close to the earth potential - very close to the green wire potential. It is the black wire that has the voltage on it with respect to the earth potential. Try measuring this at a 110 VAC socket (carefully) with an AC volt meter from green to white (measures near zero) and green to black (measures 110 VAC). Maybe because the black wire has a potential on it with respect to earth potential, it and its connections are more susceptible to corrosion just from being in that marine environment - but that is a complete speculation on my part..

 

[Bob 04 H260]

It is odd that only the black wire is burned up - as you said, there must be two conductors involved in the current flow so why only the black wire. Normally the white wire would have identical current to the black wire.

If you take an ohm meter and measure the resistance between the green wire and the white or black wires, what do you get? You should measure an open between the green wire to both the black and white. Sounds like you have the unit with you so this should be easy?

If for example you measured a low resistance between the white and the green, you could have had a fault that resulted in the current in the black wire returning through both the white and the green wires - twice the wire so they don’t show the burn. Note, the green wire should show a low resistance to the metal chassis - but that should be the only connection.

Second thing is you said there is a 15 amp fuse in the line. Is this the fuse on your boat or is the fuse in the marina? Not that it matters.. but just curious.

It’s also somewhat odd that the air conditioner case also looks like it was the black wire that mainly was involved in burning up. Even though normally the black and the white wires carry equal current (for 110 VAC in the US), the white wire is normally always very close to the earth potential - very close to the green wire potential. It is the black wire that has the voltage on it with respect to the earth potential. Try measuring this (carefully) with an AC volt meter from green to white (measures near zero) and green to black (measures 110 VAC). Maybe because the black wire has a potential on it with respect to earth potential, it and its connections are more susceptible to corrosion just from being in that marine environment - but that is a complete speculation on my part..

Hi Walt !
I don't have the electrical parts any longer, Seaward asked me to send them in so they could have a lab analyze them and figure out what happened.
The water heater was powered off a 15 A breaker in the boats shore power panel. We have two 30 A lines coming into the vessel. Each circuit runs on a separate breaker same as your house circuits. I did measure from the heater terminals to ground with my ohm meter and saw no connection. I had wondered if there was say 10 ohms to ground then the black wire would see two 10 ohm resistors in parallel, so 5 ohms. Therefore the white wire would carry half the current, green wire the other half. So the black wire would burn up but white and green would be ok. However that would have tripped the 15 A breaker anyway. I could not find any connection like that with my meter.

Seaward did not want the water heater intact only the electrical parts. I removed them put them all, placed them in a plastic bag and shipped them in. The water heater carcass went into the dumpster.

Seaward suggested I rebuild the water heater and even sent me the new parts to do that, but it smelled so bad of burnt wire we did not want it back on the boat. And without an explanation of the fault were nervous about reusing it even if the smell could have been removed.

Bob

 

[walt]

could it have been that the thermostat switch malfunctioned

It looks like there are two thermosats each with two connections (four total). It would also be interesting to measure the resistance from each of those four connections to the metal chassis. All four of those should show an open between the terminal and the chassis.

 

[walt]

woops.. no hardware to measure.. you sure would think the fuse would blow before that wire burned up..

 

[Gunni]

My guess is a poor connection causing resistance. It is 12 years old so not a design problem. I wouldn't blame Seaward.

I am not savvy on electrical engineering design safety protocols, but I would expect a manufacturer of an electrical appliance to anticipate a malfunction as simple as a loose connection or resistant corrosion leading to electric overload and fire. And I would expect that a burned up conductor would have radically raised the resistance in the system and quickly sent the current beyond 15 amps - tripping the breaker. So, where was this situation going to terminate by design protection? Filling the boat with smoke and deactivating the HW heater is one thing - setting the boat on fire is another.

My Seaward HW heater is 12 years old too - should I proactively replace it because it is a Seaward, and this sort of thing happens? I'm really not wanting to treat my HW heater like ordinance, locking and safety tagging and that sort of thing.

 

[Maine Sail]

I am not savvy on electrical engineering design safety protocols, but I would expect a manufacturer of an electrical appliance to anticipate a malfunction as simple as a loose connection or resistant corrosion leading to electric overload and fire. And I would expect that a burned up conductor would have radically raised the resistance in the system and quickly sent the current beyond 15 amps - tripping the breaker. So, where was this situation going to terminate by design protection? Filling the boat with smoke and deactivating the HW heater is one thing - setting the boat on fire is another.

My Seaward HW heater is 12 years old too - should I proactively replace it because it is a Seaward, and this sort of thing happens? I'm really not wanting to treat my HW heater like ordinance, locking and safety tagging and that sort of thing.

Take a look at all the boat fires caused by twist-lock shore power cordsets where no breaker ever trips. I have piles of melted twist locks that came damn close to starting boat fires yet no breaker trips. High resistance creates heat and can easily start fires at well below circuit breaker trip points. Probably happens a few times per week on boats here in the US alone.......