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High domestic side pressure??

DIYmark
DIYmark Member Posts: 5
in Radiant Heating
I’m not sure what’s wrong. I have a HTP light duty water heater separated from the heating loop by a heat exchanger. When I was running my system before connecting the thermostat and relay the pressure stayed fine. Now when it get up to temp , the presses rising by nearly 90 psi. Enough to open the t&p valve and have water trickling out. Any advice would be greatly appreciated 

Comments

  • DIYmark
    DIYmark Member Posts: 5
    Do I need an air vent in the side with the water heater or should I be adding an expansion tank ? Is airlock a thing?
  • Big Ed_4
    Big Ed_4 Member Posts: 3,304
    You need a domestic thermal expansion tank....

    There was an error rendering this rich post.

    DIYmarkGroundUp
  • Jamie Hall
    Jamie Hall Member Posts: 26,542
    Is this the pressure in the domestic hot water? If there is any form of check or pressure reducing valve on your domestic water supply, you absolutely have to have a domestic water rated expansion tank on the domestic hot water. If you are on a private well, you already have one (the pump control expansion tank).
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    Big Ed_4DIYmarkSuperTech
  • DIYmark
    DIYmark Member Posts: 5
    Jamie Hall said:

    Is this the pressure in the domestic hot water? If there is any form of check or pressure reducing valve on your domestic water supply, you absolutely have to have a domestic water rated expansion tank on the domestic hot water. If you are on a private well, you already have one (the pump control expansion tank).

    Yes, there is a check valve and this is on the domestic supply side and I have city water. Thank you for confirming what I need to do. I have an expansion tank that I just need to plumb in. Can you tell me what pressure i should charge the tank to? the water pressure that comes into my house at about 53 psi.
  • DIYmark
    DIYmark Member Posts: 5
    Also, does the tank need to be on the cold side of the water heater ? Or can I add it to the hot side where I have more room ?
  • Jamie Hall
    Jamie Hall Member Posts: 26,542
    The expansion tank can be on either side of the water heater -- doesn't matter. It should be precharged in your situation to about 50 psi.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    DIYmark
  • DIYmark
    DIYmark Member Posts: 5
    Thanks everybody for your help. I installed a 2 gallon domestic expansion tank to my 50 gallon water heater yesterday. I charged the tank to 55 PSI which is the pressure that comes into my house from the city. Watching my pressure gauge as my system operated i noticed the PSI rise only slightly to around 60 PSI. Is this a normal increase?
  • Jamie Hall
    Jamie Hall Member Posts: 26,542
    Yes. Good show!
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    DIYmark

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