Ongoing upper thermostat issues


Old 12-09-19, 09:08 AM
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Ongoing upper thermostat issues

About 2 years ago, my then 12 year old water heater failed and I replaced it with a new Rheem Performance Plus 50 gallon model purchased from Home Depot. My neighbor, who is a commercial plumber installed it. It turned out to be a lemon and after much effort to repair it, Rheem replaced it under warranty and even paid for Home Depot to install the replacement. Initially things were fine, but when cold weather set in I started to notice very inconsistent results with my available hot water. Sometimes the first shower of the morning would be piping hot, but other times it would be lukewarm. In the warm months things seem to be fine. After some troubleshooting on the phone with a multi-meter, Rheem sent a replacement upper thermostat. I should note that my water heater has indicator lights on the outside so you can see when a given element is running, and we had noted that the upper element NEVER seemed to run, and even when I turned the upper all the way to 150 and the bottom all the way down, it would not send power to the upper element. The replacment helped for a short while, but then the problems returned. . I tested the new thermostat with a meter and it had started exhibiting the same problem - would not engage upper element. I ended up just turning the lower thermostat to 150 and lived with it like that as we could get by that way. Spring came and again things were fine so I forgot about it.

Now cold weather has set in again and I started having problems again. I went and purchased a new thermostat and installed it. Immediately the upper light came on and the upper element engaged. That night the water was nice and hot. But then the next day the problem returned, and now once again there seems to be no way to get the upper thermostat to engage the upper element.

I'm totally at a loss, and talking to Rheem (I do still have warranty) is a mixed bag. Sometimes I can get someone who will work with me to have me run tests with a multi-meter. Sometimes they just want me to hire someone to come out and will reimburse. I'd really like to figure this out myself before getting another professional involved. I live in a very rural area so it's tough to get help sometimes.

Any thoughts anyone can offer? I do have a multimeter and am comfortable checking whatever. I have confirmed I have 240 coming in on the top 2 screws of the upper element. I can check voltage or Ohms resistance and/or measure temp of water. Currently I once again have the lower set to 150 just so we can get by.

Thanks all!

Last edited by ADS66; 12-09-19 at 09:23 AM.
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Old 12-09-19, 09:44 PM
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You'll need a meter to check for 240vAC.
Measure L1 to L3. Should be 240vAC incoming.
Measure top element. Should be 240vAC when tank is cold.
L4 is a common terminal. T2 is live when the top is active and T4 is live when the bottom is active.

When tank heats up to upper thermostat set point...... the top element shuts off and the lower element is live. Measure for 240vAC on lower element AFTER the top of the tank has heated.

Also... be sure the high heat limit (red button) is locked in on upper thermostat..
Old 12-10-19, 09:32 AM
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Thank you for the diagram - I will do some more testing with my meter. However posting my message yesterday I discovered that I am getting hot water at my sinks - It's just the showers that are the problem. I read some more on this forum about the mixing / anti-scald settings in one-handled faucets and suspect that might be where my real problem lies. Problem I have now is trying to get the handle off - It looks like the screw is stripped out - I think it was originally a alan wrench screw (Price Pfister), but I can' really tell at the moment.

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