Electric hot water heater 100 degrees

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Rich Smith

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Rheem 50 Gallon only 4.5 years old. Both thermostats and elements replaced still same issues. Output temp is barely over 100 degree even though both thermostats are set for 150 degrees. If I drain tank then refill and turn on heater top element turns on and seems to heat to 150 and then the
Lower comes on and does the same. I can then turn on hot water faucet and run it until lower comes back on but upper never does. Almost seems like upper thermostat is stuck on 150 degrees however if I remove the thermostat after a few minutes I hear it click telling me the temp has dropped below 150. The side of the tank in upper panel is extremely hot. Is it possible the side of tank is heating up more than the water temp making it seem that it is 150 degrees? If so, what would cause that? Thank you in advance!
Rich
 

WorthFlorida

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Bad thermostats. They are very easy to replace and cost is low, $25 for upper and lower. Obviously turn off the breaker before changing them. They clip on to the tank because they sit on the exterior of the steel tank. Without me being able to check voltages I can't say for sure which one is bad. When the upper thermostat is satisfied it switches power to the lower thermostat. If there is voltage at the lower thermostat then the lower thermostat is not switching on if there is no voltage at the heating element. On top of the tank there is usually a wiring diagram of the thermostats.

Just be careful when you're checking voltages, only one side is switched to the heating element. The other side are tied together. Below is typical but alway try to find your model wiring.

This shows how each element gets its power. Ignore the 110v scheme.
https://i2.wp.com/411plumb.com/wp-c...lectric-Water-Heater.jpg?resize=600,327&ssl=1
 
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WorthFlorida

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upload_2020-12-12_7-27-23.jpeg
 

Rich Smith

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Bad thermostats. They are very easy to replace and cost is low, $25 for upper and lower. Obviously turn off the breaker before changing them. They clip on to the tank because they sit on the exterior of the steel tank. Without me being able to check voltages I can't say for sure which one is bad. When the upper thermostat is satisfied it switches power to the lower thermostat. If there is voltage at the lower thermostat then the lower thermostat is not switching on if there is no voltage at the heating element. On top of the tank there is usually a wiring diagram of the thermostats.

Just be careful when you're checking voltages, only one side is switched to the heating element. The other side are tied together. Below is typical but alway try to find your model wiring.

This shows how each element gets its power. Ignore the 110v scheme.
https://i2.wp.com/411plumb.com/wp-content/uploads/2009/09/Electric-Current-Paths-Electric-Water-Heater.jpg?resize=600,327&ssl=1
 

Reach4

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Almost seems like upper thermostat is stuck on 150 degrees however if I remove the thermostat after a few minutes I hear it click telling me the temp has dropped below 150. The side of the tank in upper panel is extremely hot. Is it possible the side of tank is heating up more than the water temp making it seem that it is 150 degrees?
Does the side of the WH being extremely hot co-exist with the 100 degree water? If so, I don't have an explanation compatible with a bad thermostat, unless the thermostat is generating the heat itself.
 

Rich Smith

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The problem I have tried 3 new thermostats (upper & lower). The lower is working properly got sure. The uppers seem to be working fine as well because when you remove them from the side of the tank within 2~3 minutes you hear them click indicating they are dropping below the set temp. If you touch the side of the tank through the upper access panel extremely hot but water coming out is not extremely hot.
 

Reach4

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The problem I have tried 3 new thermostats (upper & lower). The lower is working properly got sure. The uppers seem to be working fine as well because when you remove them from the side of the tank within 2~3 minutes you hear them click indicating they are dropping below the set temp. If you touch the side of the tank through the upper access panel extremely hot but water coming out is not extremely hot.
Sounds like a bad upper element or a high-resistance connection between the thermostat and the upper element. This would be a weird failure mode for an element itself, so I am suspecting a connection.
 

Rich Smith

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Does the side of the WH being extremely hot co-exist with the 100 degree water? If so, I don't have an explanation compatible with a bad thermostat, unless the thermostat is generating the heat itself.
Yes, side of the tank is much hotter if touched inside of the access panel than the water itself.
 

WorthFlorida

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It's possible the cold water dip tube broke off. Cold water enters at the bottom of the tank. If it broke off, cold water mixing at the top of the tank where the hot water is drawn from and mixing with it and cooling it down. Just yesterday I was at Home Depot and they have replacement dip tubes.

upload_2020-12-12_12-18-29.jpeg
 

Rich Smith

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It's possible the cold water dip tube broke off. Cold water enters at the bottom of the tank. If it broke off, cold water mixing at the top of the tank where the hot water is drawn from and mixing with it and cooling it down. Just yesterday I was at Home Depot and they have replacement dip tubes.

View attachment 68777
I keep coming back to the dip tube as well just seems so unlikely in 4.5 years but I guess that will be the next thing I look at. My only concern is you would think if dip tube broke then the element would be on all the time trying to keep up with the cold water being introduced into the tank.

Rich
 

Bannerman

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Hot water is less dense than cold water so the hot water will rise to the top of the tank to flow out the tank's outlet connection. Because hot water rises, the upper element will be mainly utilized when there is little hot water remaining in the tank.

As Worth stated, if the cold water connection is at the top of your tank, it is likely the dip tube has broken off inside the inlet fitting. Although the majority of water within the tank may be at full temperature, without a dip tube, the inflowing cold water will mix with the hot water at the top of the tank, reducing the temperature of water flowing out to fixtures. To install a replacement dip tube, the cold water feed connection will usually need to be temporarily disconnected from the tank.
 

WorthFlorida

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If the tube broke off at the inlet itself, and as you draw hot water, the cold water inlet is at a higher pressure and the hot water flow is at a lower pressure. The cold water flow maybe going directly out the hot side. Before opening up the plumbing, it might be possible to drain the tank and remove the heating elements to get a peek inside the tank.
 

Phog

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If you have the ability to disconnect the hot water outlet from the top of the tank without too much difficulty, you could shut off the water supply, disconnect the hot, and then take a temperature measurement down inside the tank. Using something like a narrow meat thermometer (just has to be long enough to reach down and touch the top of the water level).
 
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