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Help with heating outage in gas-fired hydronic baseboard system

Hi all,

We're in the midst of a cold snap here in Boston and my girlfriend's heat suddenly went out. She has a gas-fired hydronic baseboard system with a Burnham boiler and Taco circulators. The system has two zones, and one zone is working fine. The other has no heat. The local heating service folks have been out twice and say it is fixed, but the heat doesn't come on. They replaced the pump and purged the system and told us it's probably a frozen pipe.

The boiler is firing, the lights for both zones are on and the pipes right at the furnace are hot for both zones. Both the outgoing and return pipes become abruptly cold at the first elbow in the pipe as it leaves the furnace to cross the basement, and all the baseboards are ice cold.

We've spent the afternoon warming up pipes with a hairdryer and space heaters to no avail.

Suggestions? Tips for what I should say when I call the service tech back?

Thank you !



  • Jamie Hall
    Jamie Hall Member Posts: 22,942
    Ask them if they were able to get any flow through the misbehaving zone when they purged. The system should be purged zone by zone, individually, to check that.

    Are any of the pipes -- even short stretches -- along an outside wall? If they are, they might well be frozen. Been pretty chilly up your way.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    EBEBRATT-Ed Member Posts: 15,344
    If they replaced the pump it may be air bound. Are there any bleeders or air vents you can let some air out and see if it starts to heat? Take the baseboard covers off and check for coin vents. Usually on the end of the baseboard with a screwdriver slot.

    Otherwise get em back their and don't pay for the pump till they get the heat on
  • sparkleworker
    sparkleworker Member Posts: 7
    Thank you!
  • Ironman
    Ironman Member Posts: 7,352
    edited March 2017
    Two basic areas to look at:
    1. Are the controls sending power to the circulator upon a call for heat from the thermostat? If yes, then:
    2. Then there's an obstruction in the loop restricting flow. As already mentioned, here are the possibilities:
    A. The loop is air bound. Purge the air out. The circulator cannot do this. It must be done manually at the means that's provided on the system. TEMPORARILY increase the static fill pressure to 25 psi while purging, then return to 15 psi cold.
    B. The pipes are frozen somewhere and must be thawed out. If so, look for splits in the pipe where it was frozen and repair them as necessary before attempting to refill the loop.
    C. There's debris somewhere in the loop. This is the least likely, but also the hardest to locate.

    P.S. If your fill valve is NOT maintaing 12 -15 psi cold pressure on the system, then that might be the culprit that's causing the loop to be air bound.

    After considering your description, I would lean towards one or two possibilities: either the loop was frozen and the tech discovered it after he replaced the circ; or, he failed to purge the air out after replacing the circ.
    Bob Boan
    You can choose to do what you want, but you cannot choose the consequences.