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Hot water furnace reaches upper limit and cycles off and on.

drdave Member Posts: 1
I have a Weil-McLain GV boiler series 2 (23 years old) that cycles on and off while the thermostat still calling for heat. From a cold start if runs however long it take to reach the upper limit around 220-230 degrees, shuts off, cools down to around 180, after 1-2 minutes, turns back on for 1-2 minutes to reach the upper limit, shuts off again, And keeps doing this. I drained some water off the bottom spigot of the boiler and 2 other places in the system. The 1st gallon is black then the rest is clear, Some dust streaks settles out in the 1st gallon. No air in the bleeders. I'm wondering if the circulator can slowly wear out. Most radiators get warm to hot, 3 barely give off heat. The fins are clean. Shouldn't the pump keep running when the upper limit switch cuts the gas off? Can I turn down the gas in the burner so it doesn't reach the upper limit? Is this normal? I haven't noticed it before. MIght I need a new pump or upgrade to a stronger pump. It's a Bell & Bossett NRF-22.


  • Jamie Hall
    Jamie Hall Member Posts: 23,442
    Well, let's go step by step here.

    First. NO you cannot turn down the gas. It is possible to down fire some -- but not all -- gas boilers, but to do so you do not turn down the gas. You change the orifice and adjust everything with test instruments.

    Second, what does the pressure gauge on your boiler say? You mention you removed over a gallon of water from the system. Did you replace all that water, either manually or with the automatic feeder? If not, you are going to have a pressure problem.

    Third, that upper limit -- it it's real -- is dangerously high. It should be no more than 190 or so.

    Now. Having covered those issues... you do have a flow issue. And pumps do wear out, or more often simply fail. But -- if there are filters on the system they may have become clogged, or if there aren't clogs may have formed in some of the piping.

    Do you have a competent heating person who would come and check the system out?
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    JUGHNE Member Posts: 11,076
    That boiler may have bypass piping with a valve for adjustment.
    Can you post pictures of it showing all the piping around it?