Water Heater T&P Valve Opneing


  #1  
Old 01-15-03, 12:44 PM
hcrisler
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Water Heater T&P Valve Opneing

Yesterday, I noticed that my water heater had discharged hot water from the T&P valve. Also, it smelled like an electrical burn in my garage. I removed the covers over the heating elements and the upper thermostat had damage from overheating. I could not keep my hands under the kitchen faucet when the water was turned to full hot (I could the day before) so I replaced the upper thermostat, figuring it stuck in the on position and the T&P valve opened due to high water temp. I turned the breaker back on and 1-1/2 to 2 hours later the T&P valve discharged again. I measured the temperature of the water in the kitchen (full hot) to be 137F. Should the T&P valve open at such a low temp? When the heater is not on electrically, the T&P valve does not open.

Thanks in advance for your help.
 
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Old 01-15-03, 01:05 PM
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I believe that those T & P's are set to blow at 125 deg. I would try replacing the lower thermostat as well.
 
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Old 01-15-03, 02:02 PM
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T&P opens at 210 degress and 150 psi, replace the lower stat at the same time you replace the upper stat, then see if the proble is solved.



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Old 01-15-03, 07:01 PM
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The lower thermostat is a very likely cause. You could disconnect one of the wires to the lower element and see if things get back to almost normal. You will have only about 1/2 the normal quantity of hot water but you won't have the T&P going off either.
 
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Old 01-16-03, 05:43 AM
hcrisler
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Last night I replaced the lower thermostat and the T&P valve discharged again. I measured the water exiting the valve to be 110F this time. I replaced the T&P valve and everything is back to normal. The original valve did not have a discharge line running to within 6" of the floor, so I think the original valve failed and the discharged water contacted the upper thermostat causing a short circuit. The short circuit overheated the thermostat, causing the melting of the tstat case. This unit was built in April of 98. While the tank was drained and flushed, no sediment was seen exiting the hose.

Thanks for the advice. Now I need to get a new heat pump installed in my house. My 17 year old compressor is shorted. This has not been a great start to a new year.
 
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Old 01-16-03, 05:51 AM
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With temperature not a factor the only other possibility is pressure. But there is no reason it would just start happening. Did you have a new pressure regulator put on your water supply? Or any plumbing work at all just before this started happening?
 
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Old 01-16-03, 05:59 AM
hcrisler
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No work of any kind done recently. To recap, the upper thermostat had a melted case and the T&P valve was opening prematurely. After replacing both thermostats and the T&P valve, the water heater is working properly.
 
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Old 01-21-03, 01:50 PM
hcrisler
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Update to previous problem.

My water heater tank was leaking where the T&P valve boss was attached to the tank. This unit was built in April of 1998 and had an 8 year tank warranty. It was installed in the house when I purchased it 3 years ago. Sears gave me a new water heater under warranty even though I was not the original purchaser. I am very impressed with Sears' warranty service.
 
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Old 01-21-03, 03:11 PM
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Thats great. It is only a copout anyway when manufacturers play that game. Honestly 8 years is 8 years, but if they can get out of giving a replacement, they surely will.
 
 

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