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radiator not hot after circulator replacement

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steamedchicago
steamedchicago Member Posts: 72
in Radiant Heating
I have a Peerless cast iron boiler, feeding what was once a gravity system. Single zone, circulator pumping into the boiler. There was a Bell and Gosset NRF-22, which failed a week ago. I replaced it with a Grondfos UPS15-58. Now, I have a basement radiator that won't get hot.

My near boiler piping is a bit of mess. Coming out of the boiler, the supply Y's off into two 1 1/4 trunks, one serving the front of the house, the other the back. Coming off the branch for the front, there's a tee splitting off a 3/4 line that feeds the not hot radiator. The return for that radiator is hooked into the return for the radiator on the first floor directly above it. The 3/4 supply pipe is not hot past a foot or two from the split.

I assume the problem is that the B&G moved a bit more water, and could get flow into the small pipe. I have the grondfos on high. Is the best alternative to cut into the pipe, and put another circulator to drive water to our cold radiator?

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  • DZoro
    DZoro Member Posts: 1,048
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    Can you bleed the air out of that radiator/ line.
    D
  • steamedchicago
    steamedchicago Member Posts: 72
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    DZoro said:

    Can you bleed the air out of that radiator/ line.
    D

    There's no air. I get cold water as soon as open the bleeder on the radiator, and at the bleed fitting at the tee.
  • HomerJSmith
    HomerJSmith Member Posts: 2,441
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    Pictures, please. The Grundfos circulator on speed 3 is a good replacement for the Bell & Gosset.

    Something else is going on. If it was working before and not now, I would suspect trapped air somewhere in that circuit.
  • steamedchicago
    steamedchicago Member Posts: 72
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    HomerJSmith said:

    Pictures, please. The Grundfos circulator on speed 3 is a good replacement for the Bell & Gosset.

    Something else is going on. If it was working before and not now, I would suspect trapped air somewhere in that circuit.

    So, I closed the isolation valve on the return from the radiator (which I know was wet, because the stem leaks when its anything but full open or closed) and hooked a hose up to the boiler drain on the radiator (it's the lowest point in the piping, even lower than the boiler). I drained about five gallons of the nastiest looking and smelling water, which sounded like it had a bunch of air in it. The radiator is now heating up. I'll have to check in the next boiler cycle, too, but I suspect that's solved the problem. The air must have been trapped in the vertical pipe between the radiator, and the supply on the ceiling.

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