Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.
If our community has helped you, please consider making a contribution to support this website. Thanks!

One boiler zone not heating - is the pump the culprit?

Options
varska
varska Member Posts: 3
in THE MAIN WALL

Bell and Gosset circ pump installed about 25 years ago. Pipe above pump (intake) is 105 degrees, temp of pipe below pump (outlet) is 122 degrees. Pump housing is a whopping 240 degrees.

Pump is drawing .98 amps (rated for .8). I opened the air-bleed screws on the baseboard radiators and got cool water coming out.

Do you think I'm looking at a seized impeller, an airlock somewhere, a bad capacitor? Any other diagnostics I can do to determine the problem before I jump in and swap out the pump?
Thanks for any guidance.

PXL_20251219_204257794.jpg

Comments

  • hot_rod
    hot_rod Member Posts: 26,548

    Looks like a shut off valve below, is there one above also? That would make it easy to remove and check.

    Let it cool down before you attempt any work.

    Another trick is to loosen the 4 allen bolts to see is any air burps out.

    Next step is to remove the allen bolts an pull the motor out and check for stuck impeller.

    How much pressure in the boiler?

    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    varska
  • mattmia2
    mattmia2 Member Posts: 15,484

    you can take the 4 allen screws out and see if the impeller is free. you will need to isolate it or drain the system to do that.

    varska
  • varska
    varska Member Posts: 3

    Thanks for taking the time to reply. Not sure the pressure gauge can be trusted, but it shows about 18 psi. Sounds like the next move is to let it cool, cut the power, close the valves above and below and drain the zone. Then loosen the 4 allens to inspect the impeller.

    PXL_20251219_212616465.jpg
  • mattmia2
    mattmia2 Member Posts: 15,484
    edited December 19

    you have isolation valves, you can take that circulator out without draining the system if you close the valve above and below it, assuming both valves are holding. i thought i saw a valve above. it is just a boiler drain.

    you likely will need new washers for the flanges if you take it apart there or a new o ring for the body if you take it apart there.

    that zone could be airbound somewhere other than at the bleeder too

    varska
  • EBEBRATT-Ed
    EBEBRATT-Ed Member Posts: 19,466

    Shut the pump off now. The impeller is probably spinning because the pump temp is is 240 and the inlet and outlet temps are relatively cool.

    The spinning impeller is overheating the water because you are not pumping for some reason

  • varska
    varska Member Posts: 3

    "Shut the pump off now"

    Done.

    One other weird thing - there was about a 30 degree delta in the pipe temps on either side of the B&G Flo-Control valve. I'm reluctant to mess with that thing (also 25 years old) it loke like a royal PITA to replace.

    PXL_20251219_140424066.jpg
  • mattmia2
    mattmia2 Member Posts: 15,484

    the flow control is rebuildable. there should generally be no heating in that circuit with the circulator off if it is closed although you can still sometimes get gravity flow through the return. you probably have to manually open that when bleeding the circuit.

    varska

Categories