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Oil fired hot water coil

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Syats27
Syats27 Member Posts: 1
in Oil Heating

Quick question. Oil fired boiler with a heating coil. It’s currently June so the boiler is only in use to make hot water for faucets. Pressure was at 0 in boiler which locked out boiler (thank you LWCO!)…I lifted the handle on the water feeder (bell looking one) and the feeder filled boiler to 15 psi and stopped…my question is, if the boiler is only on for a call to make hot water will the pressure drop to 0 if the water feeder is faulty and not refilling the coil? Or does the coil have nothing to do with the actual boiler pressure.

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  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 18,217

    The boiler pressure is set for about 15 psi when cold. As the boiler water is heated (weather you running for heat or hot water) the pressure will rise as heated water expands. The pressure in the boiler when the water is heated to its highest normal temp (usually 180-190) should not exceed 25 psi. 20 is better and will vary with the amount of water in your system and the size of the expansion tank. Most boilers have a 30 psi relief valve. But the boiler should stay at 15 or above at all times

    If you pressure went to "0" I would suspect your water feeder (PRV) was stuck closed which is fairly common. Possible expansion tank issue.

    I would keep my eye on it and look for leaks for now.

  • Jamie Hall
    Jamie Hall Member Posts: 26,169

    To add — there is, or should be, no connection between the domestic hot water coil and the heating system water in the boiler.

    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England

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