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how to heat the boiler only when the thermostat calls for heat

nonutin Member Posts: 2
I have a Hydrotherm hc-145 natural gas boiler. I want to heat the boiler only when the circulating pumps turn on. Is there a control or a method to do this? Now it stays heated so that it is ready when I need heat. I think I waste a lot of gas this way.


  • JohnNY
    JohnNY Member Posts: 3,230
    Maintaining temperature is not cool.

    There's probably an aquastat set in the boiler somewhere that you could disconnect. Pics would help.
    Contact John "JohnNY" Cataneo, NYC Master Plumber, Lic 1784
    Consulting & Troubleshooting
    Heating in NYC or NJ.
  • Xray
    Xray Member Posts: 24
    All kindsa ways...

    If the circ pump switching relays have end switches (like the RA832A), you could wire them in parallel with the boiler high-limit aquastat.  if not, you could go cheap with current-sensing relays.  OR...does the boiler aquastat have T1 and T2 terminals?
  • Alan (California Radiant) Forbes
    Alan (California Radiant) Forbes Member Posts: 4,002
    edited November 2013

    Your Hydrotherm boiler has a Honeywell H8148J 1009 (or a close relative) aquastat controller on the front of the boiler. If you remove the cover with the power off and tell us how it is wired, maybe we can help. If there are any peripheral controls, it could complicate things. The best bet is to hire a pro to figure it out.
    8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour

    Two btu per sq ft for degree difference for a slab
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