Water heater high limit reset switch tripping

[scottdube]

Interesting issue, I found the water heater high limit reset switch tripped. Reset it, made hot water via AC power just fine. Fired up engine got to destination, next morning ran the genset to charge and make hot water via AC. Ran it for a while, wife was not pleased with cold shower after my assurances the water should be hot. I have now seen this several times where after the engine runs for a while the high limit switch is tripped. Never trips on just AC I assume because the thermostat on the water heater is shutting it off at a lower temp than the water temp is reaching via the engine coolant loop. Water heater is a Seaward 6 gallon.

Has anyone seen this?

Thanks!

 

[Gunni]

That reset triggers at 190 degrees. Your engine coolant should not be running that hot. Maybe 170. Sounds like your HW heater gave you a warning regarding your engine condition.

 

[Don S/V ILLusion]

It's unlikely the thermal switch is working properly. If it was hot enough to trip a properly functioning switch, the more likely symptom would be the pressure relief valve would release. Plus you would see abnormally hot water by looking at the engine temp readout.

Replace the switch.

 

[scottdube]

That reset triggers at 190 degrees. Your engine coolant should not be running that hot. Maybe 170. Sounds like your HW heater gave you a warning regarding your engine condition.

Not so sure about that... It's been running at 180 for as long as I've had it (15 years) except earlier this season when the belt snapped and it got hotter and the warning light illuminated. The light is set to come on at 199... I've read in Mainesail's posts about coolant temps reaching 210 degrees. I've stumbled on to some posts where the poster suggests a "weak" reset switch which sounds weird to me...

 

[Benny17441]

My experience with a high limit temperature switch is limited to a hot tub but I found out that once they start giving problems it is best to replace them. They are not that expensive anyways.

 

[Gunni]

Yes, the 2 ltr. Yanmar temp alarms at 200 degrees. Why would you assume 210 degrees was acceptable? Having taken coolant temps above 200 d you would have also heated your HW water that hot, well above the control design limit.

 

[Don S/V ILLusion]

Also keep in mind that engine (coolant) temp can never equal that of the coolant which actually reaches your water heater. Depending on the 'run', it will lose some heat in its travel. Consequently, 190 degree water at the engine will be less at the water heater.

Change the thermal reset switch.

 

[scottdube]

Yes, the 2 ltr. Yanmar temp alarms at 200 degrees. Why would you assume 210 degrees was acceptable? Having taken coolant temps above 200 d you would have also heated your HW water that hot, well above the control design limit.

Why would you assume that I assumed it was acceptable? I'm simply passing along information from a reputable source. I'm not saying he said it was normal in all cases either... He was speaking about the need for ABYC to require a thermostatic mixing valve to prevent scalding. In the course of making his argument he was talking about coolant temps reaching that high.

Don, I ordered a new thermal switch from defender.... I'll post an update when I get it tested out.

 

[Gunni]

Why would you assume that I assumed it was acceptable? I'm simply passing along information from a reputable source. I'm not saying he said it was normal in all cases either...

You overheat your engine, set off the 200 degree high temp alarm, and then somehow find your way to maybe 210 degrees is normal? Read of the manufacturer's engine specs and know, overheating can have dreadful consequences.

 

[scottdube]

You overheat your engine, set off the 200 degree high temp alarm, and then somehow find your way to maybe 210 degrees is normal? Read of the manufacturer's engine specs and know, overheating can have dreadful consequences.

Gunni, somehow we are not communicating... I never said 210 normal! I am well aware of the limitations and the consequences. ONCE MORE the engine is operating at 180 which it has for the past 15 years except for one incident of a belt failing. This has nothing at all to do with that. Thank you for your thoughts on this.

 

[jssailem]

Scott spud slime you are on the right course. Let us know what happens with the new switch. It's not nice to give the wife the cold shower.

 

[jssailem]

Scott spud slime

I just read the spell checker-editor response to your name "scottdube". Sorry. Usually can catch those. Must have been asleep.

 

[scottdube]

I thought that was just a saying over there in Salem...

 

[jssailem]

Only when discussing the State politicians named Scott.

 

[CarlN]

I think you were on the right track. The engine temp gauge hasn't changed so the problem isn't there. Whether the engine temp is really 175, 180, or 185 when the gauge reads 180 doesn't matter. It hasn't changed.

The limit switch was probably always quite close to the coolant temperature. The difference between 180 and 190 is only about 5%. These switches aren't designed to land the space shuttle. I think they are just a little bi-metal strip and a relay. Your overheating episode may have damaged the strip a bit changing the set point. A new one costs $28.

I once had the same problem. I "fixed it" by turing off the water heater A/C breaker when I started the engine and leavomg it off for about 3 hours after I shut down to let things cool a bit. My limit switch wouldn't trip if it had no power.