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Rick
Rick, Construction Supervisor
Category: Plumbing
Satisfied Customers: 19512
Experience:  Licensed Master plumber with 40+ yrs. experience.
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My water heater has a lower thermostat that will not come on.

Customer Question

My water heater has a lower thermostat that will not come on. It only comes one if I turn the heater off for a few hours and turn it back on. Then it will go off and not come on again unless I repeat the shut off process. The upper thermostat stays on constantly. I replaced the upper thermostat and had the same problem. My question is,if I replace the lower thermostat will this solve the problem, or do I have to replace an element.
Submitted: 7 months ago.
Category: Plumbing
Expert:  Rick replied 7 months ago.
Is this a standard electric water heater? What is the brand and model number?
Customer: replied 7 months ago.
Rheem XE50M0L55U0
Expert:  Rick replied 7 months ago.
Does this model have the electronic control?
Customer: replied 7 months ago.
No
Expert:  Rick replied 7 months ago.
Ok, then how do you know the lower thermostat works sometimes but not others? BTW the upper should not stay powered constantly. Once the upper is satisfied it should switch power to the lower.
Customer: replied 7 months ago.
If I turn the water heater off at the service entry and then on again the thermostat comes on. Then it will go off. I don't know when it will go off but it will after a time and will not come back on. I have lights on a panel that tell me that the upper thermostat is on and that the power is on. The upper thermostat stays on constantly unless I turn it off at the service entry.
Expert:  Rick replied 7 months ago.
Since I didn't have any luck finding specs for your model number before I'm relying on your description. So you have a conventional thermostat with no electronic controls just an LED that comes on when an element is active? I'm going to do some more digging in the mean time
Customer: replied 7 months ago.
Should I stay on line.
Expert:  Rick replied 7 months ago.
Is this what your unit looks like? http://www.rheem.com/docs/FetchDocument.aspx?ID=d028a690-f06a-4e4f-851c-c0cbf0f7f11b
Expert:  Rick replied 7 months ago.
Do you have a multi-meter?
Expert:  Rick replied 7 months ago.
Also, do you have any hot water?
Customer: replied 7 months ago.
Yes, except it has led's on the top thermostat panel that indicate if the power is on, which thermostat is on, upper or lower, one for each thermostat.
Expert:  Rick replied 7 months ago.
Ok, please answer my other questionsDo you have a multi meter? Do you have any hot water?
Customer: replied 7 months ago.
Yes, I have a multimeter.
Expert:  Rick replied 7 months ago.
What about hot water? any? none? a little?
Customer: replied 7 months ago.
I have hot water. I have to turn off the water over night so that the thermostat will not have to be reset.
Customer: replied 7 months ago.
As a matter of fact the water will get too hot.
Expert:  Rick replied 7 months ago.
Ok, what you're telling me doesn't add up so I suspect there's something wrong with those LED indicators. The way this unit is supposed to work is that the upper thermostat is energized first. Once it's satisfied it sends power to the lower. It's a simple double pole switch. Nothing that a reset should effect. If the water is too hot then turn down the thermostats. Both should be set the same and 120 to 130 max is typical.
Expert:  Rick replied 7 months ago.
You could check for 220/240 volts to the lower stat and element when the LED says the upper is working but the water is (too) hot. If you have 240 to the lower then disregard the LED's. They aren't worth fixing.
Expert:  Rick replied 7 months ago.
Most electric water heaters don't have them
Customer: replied 7 months ago.
I have both thermostats set to 120. I will try to see if there is power going to the lower heater. I will get back to you later.
Expert:  Rick replied 7 months ago.
Ok, is your new thermostat making good contact with the tank?
Customer: replied 7 months ago.
yes
Expert:  Rick replied 7 months ago.
Ok, let me know what you find