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Discussion Starter #1
Hi everyone.

The other day I started hearing loud pops from my 40 gallon electric hot water heater.
I immediately pulled it's plug, left the room, closed the door and went far, far away.

The next day the upper thermostat was replaced (it's set to 150 for the over temp). Plugged it back in and within 20 minutes the water was scalding after less than a minute of flow. Unplugged it again.

This morning, four days later, the water has finally cooled down. Breaker off, plug out, I replaced the bottom thermostat. Set it to warm.
Plugged it in and within 20 minutes we're back to scalding. Unplug. Turn off breaker. Utter expletives.

I've never had water this hot come out of this unit because I keep it set to warm or a bit hotter. It's about 18 years old. Elements were replaced about a year ago. Tank was completely flushed about 5 years ago. Anode rod has never been replaced.

Any idea what the heck is going on?

Thank you.
 

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If your setting your bottom thermostat at 150 your water is going to be a lot hotter then 150 degrees. Try setting top thermostat at 140 and bottom at 130. When the bottom thermostat is heating your water to 150 the hot water rises as it heats which is why it will be hotter then 150. That should take care of it but your going to have to use the hot water in the tank before you can check it again. Every once in a while an element will fail and draw current even with the thermostats satisfied and the water will keep getting hotter until the pressure relief valve trips. But this is rare. Easy to check with an amp meter if you have one


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ive seen 15 years old tank completely filled with crap so the thermostat were not able to sense water temp, you should remove the elements to see if it is clean inside
 

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The elements don't sense the water temp. The T-,stat is held against the outside of the tank senses the temp.

150 is way to high, set both t-,stats at 120.

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I agree with rjniles.

The thermostats do not sense the water temperature. They sense the temperature of the outside of the tank (upper and lower). The electricity coming to your water heater first goes through the safety cut off switch, that red button thing. I could be wrong but I believe it is set at 150 degrees and is not adjustable. The electricity then goes to the upper thermostat. The safety cut off and the upper thermostat are all part of the same device. If the upper thermostat is not satisfied (the water is not hot enough) the electricity goes to the upper heating element. When you adjust the temperature setting on the upper thermostat you are not adjusting the temperature of cut off device. You are adjusting the cut off temperature of the upper heating element. When the upper thermostat is satisfied (the water is hot enough) the electricity is transferred to the lower thermostat. If the lower thermostat is not satisfied (water is not hot enough), the electricity goes to the lower heating element. When the lower thermostat is satisfied (water in the bottom of the tank is hot enough) every thing stops.



Sounds like you had a defective thermostat, probably the upper one. When you replaced it you set the upper thermostat to 150 degrees in error, thinking you were setting the emergency cut off.

Reset to 120 degrees.
 

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Discussion Starter #6
Attached are the pics of the upper & lower thermometer settings.
I did a temp test of the water before I plugged it in and after.

It just feels like my skin is being boiled off but at 125 degrees that's not possible.

The joys of being a wimp.

Thank you, all, for your comments and suggestions.
 

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Appears to be some inaccuracy in the upper thermostat. Perfectly alright to lower to lower setting.
The joys of being a wimp.
To be more sensitive does not make one a wimp.
It is 70 degrees outside and I have on two heavy cotton shirts. Does that make me a wimp?
 

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We would all be better off if you measured the temperatures you are talking about.

"scalding" is a description, not a data point.

Do you have the make/model/age of the water heater - just a bonus for those trying to help... (perhaps I missed them?).

I've had many water heaters that pop and crackle at client homes.
 

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Discussion Starter #10
The unit is a Reliance Sta-Kleen 805 with dual 5500 watt elements. (Yup, it's THAT old).

Yesterday I drained the tank and replaced both elements (I replaced the thermostats back in May).

Attached are pics of what the elements I removed look like. Has anyone seen this kind of damage to elements before? One of them is fused together and the other exploded.

And as an added bonus, the water reached 160 degrees F before I noticed. I immediately turned the dial down to warm but I was too late.

I ran an electrical tester near the wires and the unit has power.

The breakers didn't trip. Yet.

I haven't pushed the reset button yet, either. I don't think that will solve the problem of why the water keeps getting so hot that it trips in the first place.

Any ideas?

TYIA
 

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-Remove the new upper and lower thermostats you just bought.
-Remover the upper and lower new elements you bought.
-Disconnect old WH and dispose of.
-Install new WH.
-Save new parts for future replacements.
 

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Discussion Starter #12
Hi Lawnguy...

Just curious why I would need to replace the tank. It isn't leaking and all it does is hold the water.
 

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Discussion Starter #14
sure I can replace the whole unit. but my question is why would the lower element explode? It isn't covered in scale nor buried in sediment.

And what would make the upper element fuse together at the tip?
 

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your element was grounded through it casing so it was always heating water even if thermostat was not calling for heat (thermostat only cuts one side of the 240v, so when it is off the heater still gets 120v if it is grounded). a gfi breaker would have tripped, but not a standard one
 
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