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Heat stopped working, weird noises, buzzing/slurping pump

zsawan Member Posts: 2
My furnace recently started having troubles (see title for symptoms) and I’m trying to diagnose. I’m pretty sure the furnace is original to the house (built 2005) so it’s had a good run. Yesterday I heard a pretty loud buzzing and pinpointed the noise to the pump/cartridge circulator. I also smelled a bit of a burning odor. Hard for me as a normie to know what’s going on but based off intuition and what I’ve read I’d guess either the pump’s going out or there’s air in the system that needs to be purged. I’ve turned the system off/on a couple times - the first time it got the heat working again, the second time it didn’t. I’ve also lightly tapped the pump with a rubber mallet, to no avail. If purging sounds like the next step in figuring this out then I’d really appreciate some instructions (as if written for a 2 year old haha) Thanks!


  • Zman
    Zman Member Posts: 7,569
    What does the pressure gauge read?
    "If you can't explain it simply, you don't understand it well enough"
    Albert Einstein
  • zsawan
    zsawan Member Posts: 2
    Zman said:
    What does the pressure gauge read?
    20psi. I cut electricity off to the furnace about 45 minutes ago if that matters
  • HomerJSmith
    HomerJSmith Member Posts: 2,440
    edited March 25
    The direction of flow thru that pump is down. Feel the input pipe to the pump and the output pipe of the pump. Does the temp seem the same? The cartridge in the pump may be bound up with debris, such as magnetite and not be revolving the impeller. If that is the case you need a new pump although the cartridge can be replace in the pump. The cost difference is very little, so I would replace the pump. Are you getting heat in the house? Is the output supply pipe out of the boiler hot? That would be beyond the expansion tank. By the way you are pumping into the expansion tank, a no, no. I would recommend a Grundfos UPS15-58FC pump.
  • Intplm.
    Intplm. Member Posts: 1,962
    Seems you are on the right track. The smell may have indeed been the circulator over heating. Was it extremely hot.
    Did the breaker trip? Is the damper making?