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1930 AS HW furnace hi temp/press

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scott92
scott92 Member Posts: 1
in Oil Heating

After a cold night with thermostat set for 63, the furnace showed 22 psi and 200 deg F. Tap HW measured at 180! Furnace cycled to maintain temp of house thru night. Why is HW so hot?

Comments

  • BDR529
    BDR529 Member Posts: 371

    Faulty tempering valve.

  • HydronicMike
    HydronicMike Member Posts: 227
    https://forum.heatinghelp.com/discussion/comment/1875863#Comment_1875863

    Or no tempering (mixing) valve. The 22 psi could be from undersized and/or failing diaphragm expansion tank, or water logged expansion tank…or the boiler feed…or air.
    The 200° is just where your hi limit is set.

  • mattmia2
    mattmia2 Member Posts: 15,335

    What is the pressure normally when hot? 22 psig hot is fine on a 30 psi boiler if the expansion tank is smallish for the size of the system or the system is tall. If it isnt creeping up over time when it is hot it is fine.

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