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Old 03-21-2011, 12:13 PM   #1
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T&P Valve Gushing Hot Water.


Hello everyone, I have a Utica Boiler with a 30gallon Utica Hotline Hot water Holding tank Model:HL30.

I dont know if this has anything to do with my problem but about a month ago I had some troubles with my boiler so I had a guy come in who told me the aquastat on the boiler had gone bad. So I had no choice but to have him replace that. The old one he took off was set at 160 degrees and the new one that he put on only goes down to 180 degrees so thats the lowest I can keep it on.

Ever since then I have had nothing but problems with my hot water tank. Every now and then it will blow off water through the T&P valve. I contacted him he said it was nothing really to worry about it might happen once or twice since he just replaced the aquastat.

Now a month later it is starting to get bad. So I got ahold of another guy who sold me a new thermostat for the holding tank itself. I do believe this had something to do with it because the old one looked very corroded and we think the wires may have had a short because I could jsut touch the wires and the circulator would turn on sending hotter water into the tank. We changed that and yesterday it blew off twice. Last night it blew off and this morning it has once. I called the guy back he has me going to get a new T&P valve and replacing that. Says with all the releases it might have gotten weak.

I have checked the expansion tank, it has 15psi in it and no water. Boiler seems to be running fine. the hot water at the faucet and shower, etc. seems normal no scalding hot water and still seem to have the same amount of hot water.

The temp on the boiler says 175 degrees and about 15psi.

I'm hoping that changing the T&P valve will solve my problem but I wanted to post something so that hopefully when and if it does blow off again I can check and see what other people have posted. Thanks a lot for your time reading my post and for the help.

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Old 03-21-2011, 02:30 PM   #2
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T&P Valve Gushing Hot Water.


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Originally Posted by Conde54 View Post
I have checked the expansion tank, it has 15psi in it and no water.
I'm not familiar with a boiler system like you have but check the installation instructions for your expansion tank. It will probably say to pump air in it without it being connected to the water system, so that the static pressure in the tank is equal to the normal water pressure in your system. (Which should normally be about 60 psi. Maybe less depending on your city water pressure. But 15 psi sounds way too low.)

HRG

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Old 03-21-2011, 02:57 PM   #3
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T&P Valve Gushing Hot Water.


The T&P valve trips on either high pressure or high temperature (hence its name). Do you know what the temperature threshold is? (May be on a label on the valve.) Since your new aquastat has a higher temperature setting, the domestic water is now ending up heated to a higher temperature and perhaps exceeding the T&P valve threshold.

If you did change out the T&P valve for a 190 degree one then with the furnace set to 180 degrees you won't have the blow off problem.

150 degrees is a little too hot for comfort when it comes to domestic hot water. YOu may want to, as a separate future project, install a tempering valve system just above the hot water tank so water going to the hot faucets isn't so hot to cause burn injuries in a matter of seconds.

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Old 03-21-2011, 06:42 PM   #4
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T&P Valve Gushing Hot Water.


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Originally Posted by Homerepairguy View Post
I'm not familiar with a boiler system like you have but check the installation instructions for your expansion tank. It will probably say to pump air in it without it being connected to the water system, so that the static pressure in the tank is equal to the normal water pressure in your system. (Which should normally be about 60 psi. Maybe less depending on your city water pressure. But 15 psi sounds way too low.)

HRG
I was told by both people that I talked to that the expansion tank should be around 12psi. and i recall that one of them said that the towns water pressure is around 40psi. I do not have the instructions for the expansion tank as i just bought this house less than 5 months ago. the expansion tanks says its an Amtrol, Extrol model 60 and the pre charge measurement is 12psi do not exceed 100psi
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Old 03-21-2011, 06:51 PM   #5
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T&P Valve Gushing Hot Water.


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Originally Posted by AllanJ View Post
The T&P valve trips on either high pressure or high temperature (hence its name). Do you know what the temperature threshold is? (May be on a label on the valve.) Since your new aquastat has a higher temperature setting, the domestic water is now ending up heated to a higher temperature and perhaps exceeding the T&P valve threshold.

If you did change out the T&P valve for a 190 degree one then with the furnace set to 180 degrees you won't have the blow off problem.

150 degrees is a little too hot for comfort when it comes to domestic hot water. YOu may want to, as a separate future project, install a tempering valve system just above the hot water tank so water going to the hot faucets isn't so hot to cause burn injuries in a matter of seconds.

(some other text deleted)

I did change the valve today.Both the old T&P valve and the new one are rated for 150psi and 210 degrees. The guy who put the aquastat in told me that the temp of the water going through the boiler has no barring on the temp of the holding tank because it has its own thermostat. From what I understand the holding tank fills with cold water and then the thermostat says it needs to be warmer (Right now my hot water is set around 120 degrees) so it kicks the circulator on and fills with hot water from the boiler until the thermostat tells it its hot enough; which is why we changed the thermostat first. He tells me that the aquastat on the boiler could be set at 240 degrees and will not effect the T&P valve, reason being that water is only used to re-heat the water in the tank. Never the less I set it to 180 degrees (As low as it goes).
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Old 03-21-2011, 09:38 PM   #6
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T&P Valve Gushing Hot Water.


Quote:
Originally Posted by Conde54 View Post
I was told by both people that I talked to that the expansion tank should be around 12psi. and i recall that one of them said that the towns water pressure is around 40psi. I do not have the instructions for the expansion tank as i just bought this house less than 5 months ago. the expansion tanks says its an Amtrol, Extrol model 60 and the pre charge measurement is 12psi do not exceed 100psi
All new expansion tanks come with just a "token" pre-charge of about 15 to 20 psi. Instructions for residential expansion tanks and tutorials on the internet say to use a bicycle pump or other slow controllable air pump to increase the pressure to match the normal house water pressure without connecting the tank to the house plumbing. Don't use a service station air hose to charge the tank as the air could go in too fast and over pressurize the tank and damage it.

Here's a link to an expansion tank installation tutorial on youtube:


If the city water pressure can exceed 80 psi, then a pressure regulator must be installed in the main water line. In your case the static water pressure is 40 psi so I believe your expansion tank should be pre-charged to 40 psi. I think it will be worth your while to find the instructions for your expansion tank on the internet and see what the charging instructions are to obtain the full benefit of your expansion tank.

Best regards,
HRG
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Old 03-21-2011, 11:34 PM   #7
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T&P Valve Gushing Hot Water.


Quote:
Originally Posted by Conde54 View Post
I was told by both people that I talked to that the expansion tank should be around 12psi. and i recall that one of them said that the towns water pressure is around 40psi. I do not have the instructions for the expansion tank as i just bought this house less than 5 months ago. the expansion tanks says its an Amtrol, Extrol model 60 and the pre charge measurement is 12psi do not exceed 100psi
The pre-charge in the tank is a MSDS deal. Lower ship rates for low pressure. Anything high pressure is a safety concern and it cost more to ship.

Same principle as a well/pump system. 2PSI below cut-on pressure, or in your case, pressure from the city.

Having it set 2PSI below is allowing more air in that tank to do the work, compress, and absorb the excess water pressure during expansion. If you have it too low, the air is doing no work, and the rubber diaphragm is doing too much work, and it will wear out more quickly.

Another note on your T&P valve : Some people believe in replacing them regularly. If it isn't leaking constantly, and it's popping off occasionally, then it is working and it is doing it's job. Now you need to track down whether it is a temperature overload, or pressure overload.

I didn't read the whole thread, but did you check the air valve in the top of the expansion tank to see if water comes out of it? If it does, then that's your issue.

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