Water Heater T-stat

[Stmar]

4500 watt electric water heater thermostat tripped. Any chance this is just a one time deal or am I looking at replacing the stat? I reset it and am testing to see if it holds, may have had a power outage yesterday so could that have caused it to trip?

 

[NHSleddog]

4500 watt electric water heater thermostat tripped. Any chance this is just a one time deal or am I looking at replacing the stat? I reset it and am testing to see if it holds, may have had a power outage yesterday so could that have caused it to trip?

Brand and model would help. In my experience it is usually the element failing that causes the thermostat to trip. Depending on the unit, they could be together in one assembly, or two different components.

 

[Stmar]

It is a 240 volt A.O. Smith ProMax. It burned wires to the T-stat after I reset it so I definitely have to replace the stat. The elements read the correct ohms so can I assume it is a bad stat? See picture, it is the upper stat.

 

[Michael In Tennessee]

It is a 240 volt A.O. Smith ProMax. It burned wires to the T-stat after I reset it so I definitely have to replace the stat. The elements read the correct ohms so can I assume it is a bad stat? See picture, it is the upper stat.

I think that is the wire to the element. I'd just get the kit with two elements and 2 tstats for $30 and replace both upper parts. Get the element wrench too. 1 trip. Done.

 

[Stmar]

I think that is the wire to the element. I'd just get the kit with two elements and 2 tstats for $30 and replace both upper parts. Get the element wrench too. 1 trip. Done.

No such kit in our little ACE, went ahead and got a t-stat and it was almost that much, the price we pay for living in such a small town. Wired it in and waiting to see what happens. If the elements read the correct ohms then how could you tell if one is bad? Since the t-stat did not trip a second time and melted the wires would that be a clue, bad stat?
You are correct those are the wires to the live side of the elements.

 

[Stmar]

New stat, 2 days, so far so good. Bugs me that the old one got the wires so hot, must have shorted somehow but panel breaker did not trip. Tore the old one apart and heat was concentrated at the constant hot side terminal, where one wire from each element attaches. No sign of heat at any other points. Anybody ever see a t-stat malfunction this way? ***8361;

 

[SidecarFlip]

High resistance connection, possibly caused by dissolved minerals in your water.

 

[Stmar]

Could that happen even though the elements showed the correct resistance/ohms?

 

[SidecarFlip]

I don't mean internally, I mean externally from minerals that get in the air. Here we have a little bit of sulfur dioxide in the well water and when the water is pumped from the well, the dioxide liberates from the water (because the atmospheric pressure is less above ground than it is below ground) and it becomes a gas and it's corrosive so we get high resistance connections from it. Copper especially is very susceptible to oxidation and it causes a high resistance connection over time if, the connections aren't pre treated with di-eletctric grease, something that is sop with me. Every connection I make in the house or on my vehicles and tractors has a coating of di-electric grease on it.

Don't know the make up or mineral content of your water, but if you have any sulfur dioxide in the water, your connections can be compromised.

 

[Stmar]

So you are saying there could have build up on the copper wire causing too much resistance resulting in over heating at the terminal? When I looked at the wires they did have a scale on them that I rubbed off, thought it was because of the heat. Good idea about grease or deox.

 

[SidecarFlip]

When copper wire oxidizes (tarnishes), the oxidation is high resistance.

 

[GreensvilleJay]

add this to your 'yearly MUST do ' list...

kill power to heater
remove covers
tighten all screw connections.

There's a LOT of amps running through them , on and off, that generates heat and can 'loosen' the actual connections.

And SO2 is bad stuff. I had to replace all the photocell sensors in my remote energy control systems in the 'industrial area' of Hamilton due to SO2 ....
ended up using a phototransistor with glass window.

 

[B737]

unrelated water heater story...
I figured it was time to replace the 25 year old, 80 gallon electric hot water heater in my home. I had my plumber install a (provided) 65 gallon Rheem Electric Hybrid Water Heater. My plumber had never seen one before, and he advised against it for the record. Was around $2000 just for the heater. My electric bill went down $50-$65 a month immediately. I absolutely loved this thing. It uses a heat pump to heat the water, its recovery time is slow but we never ran out of hot water (only two of us here). It absolutely sips electricity. Was super high tech, whats not to love!

One random night after 9 months, it started smoking and died. I was pretty bummed. Home depot took the unit back for a full refund, and rheem actually refunded me cash for all the labor. So I have hand it to both companies for their support.

I ended up installing a natural gas unit with power vent after that. Not as fancy or "cool" but it works, makes lots of hot water and has not burned my house down.

If I did not have NG available I would almost consider giving the hybrid unit another chance. I couldnt believe the savings it was providing.

 

[Stmar]

Tightened all connections and put deox on. Thanks for the responce. Water heater is over 15 years old but still working. Looking at Marathon as a replacement when the time comes, supposed to be impervious to corrosion, non metal tank. Anybody have any experience with that brand/type? Friends put one in their new house but they moved after a couple of years so I did not get a chance to see how it worked over long term.

 

[SidecarFlip]

At least 15 on mine too. I drain the sediment monthly. Original elements too.

 

[SidecarFlip]

unrelated water heater story...
I figured it was time to replace the 25 year old, 80 gallon electric hot water heater in my home. I had my plumber install a (provided) 65 gallon Rheem Electric Hybrid Water Heater. My plumber had never seen one before, and he advised against it for the record. Was around $2000 just for the heater. My electric bill went down $50-$65 a month immediately. I absolutely loved this thing. It uses a heat pump to heat the water, its recovery time is slow but we never ran out of hot water (only two of us here). It absolutely sips electricity. Was super high tech, whats not to love!

One random night after 9 months, it started smoking and died. I was pretty bummed. Home depot took the unit back for a full refund, and rheem actually refunded me cash for all the labor. So I have hand it to both companies for their support.

I ended up installing a natural gas unit with power vent after that. Not as fancy or "cool" but it works, makes lots of hot water and has not burned my house down.

If I did not have NG available I would almost consider giving the hybrid unit another chance. I couldnt believe the savings it was providing.

Our HWH is on a separate meter and we get a low ball rate. I believe a month for the 2 of us is about 20 bucks. Cheaper than propane.

 

[Michael In Tennessee]

New stat, 2 days, so far so good. Bugs me that the old one got the wires so hot, must have shorted somehow but panel breaker did not trip. Tore the old one apart and heat was concentrated at the constant hot side terminal, where one wire from each element attaches. No sign of heat at any other points. Anybody ever see a t-stat malfunction this way? ***8361;

No. Glad its working. To get high enough current to burn insulation, you must have had a short to ground. Your element can show proper ohms across leads and still show short to ground. You didn't say you checked to ground. You might still need an element in the future.

 

[Stmar]

Yes I did check each element to ground but I will keep an eye on it. Would it not trip the breaker if short and not just the t-stat reset?

 

[Michael In Tennessee]

No clue how the T-stat reset works. I thought it was thermal only, not current. Current is handled by the disconnect and/or fuse panel.

 

[Stmar]

No clue how the T-stat reset works. I thought it was thermal only, not current. Current is handled by the disconnect and/or fuse panel.

That's what I thought and am puzzled about the wires getting so hot as to melt the insulation and plastic on the t-stat. High resistance seems to be the issue and I have checked for shorts and ohms/resistance on the elements. I will keep checking and see if it happens again.