My MIL has an exterior wood boiler with two TACO circulators that provide heat to the house. She says that she's been replacing the circulators aprox every year because they burn out. Of course this is spectacularly bad performance - these usually last much longer, and it's worse given that they're only running when heating. When operating, they are reportedly so hot you cannot touch them. The water temp does not ever get hotter than its rating. I'm trying to figure out what would cause this so I can try to troubleshoot. What would cause a circulator to burn out?

  • Having the pump work too hard? What would cause that? Back pressure or something?
  • Would this be electrical? Inadequate voltage or amperage? It's only a 110v, but I don't know.
  • There are warnings about not running it dry (which it's not), but could air bubbles be causing an issue?

Mostly grasping at straws; she's had multiple people look at it and no one can offer an explanation.

EDIT: Despite the precise model number listed in the comments, and the fact that this was an open-end question, the moderators have decided to close this. Apparently there is no path to dispute this action.

  • 1
    for reference, this is a taco 007-hbf5-j
    – end-user
    Commented Jan 1, 2023 at 21:57
  • Would take one apart and see if there is anything(dirt/sediment/stuff not water) blocking it.
    – crip659
    Commented Jan 1, 2023 at 22:05
  • She says she has had a friend who works on these things do just that. He was unable to find any fault or cause, other than to confirm that it had siezed/frozen/died. Which, to me, suggests that the thing was over-exerting itself.
    – end-user
    Commented Jan 1, 2023 at 22:26
  • Have a couple similar(not taco) myself. If nothing found in the pump, then there might be blockage/kink somewhere in the pipes. If the wood boiler about the same as mine, then it is just a tank and any air bubbles should pass though. Pipes/radiators might need a flush or at least check that the water has a clear pass.
    – crip659
    Commented Jan 1, 2023 at 22:40
  • You have the major possibilities listed The air bubbles sound like a problem. There should be a air bleeder system of some type check that out. That should get rid of the air in the system and the bubbles. Air or air bubbles can cause the pump to cavitate causing a lot of damage damage to the pump.
    – Gil
    Commented Jan 2, 2023 at 16:59

1 Answer 1


A picture of the setup would help.

Generally you install the circulators low and on the return side so that water running through them is as cool as possible. You also install an expansion tank and air separator on the high supply side so that no air ever makes it to the circulators. So hot you can not touch them doesn't sound right.

Do you have a Y sediment trap before the circulators?

How many zones does she have? Generally a single circulator should be able to handle a standard house. Do you have zone valves?

  • So, that may be one factor - the circulators are definitely on the sending side. The circulators are on the boiler itself, and plugged in there. This seems odd to me because it implies the boiler controls them. I don't know if there's a Y trap or tank or air separator - if those are on the system they may be inside the house somewhere.
    – end-user
    Commented Jan 2, 2023 at 14:22
  • I won't be able to fully troubleshoot this myself because I'm only visiting. Additionally, she's had multiple professionals look at it and come up empty so I don't really expect to fix it. I was primarily hoping to understand what conditions would cause a circulator to have a ridiculously short life, like continually under powered, or "clogged arteries" somewhere in the system, or something.
    – end-user
    Commented Jan 2, 2023 at 14:25
  • 2
    I find a lot of plumbers don't really know what they are doing when it comes to hydronics. They have a vague idea and can replace failed components or bleed the system but re-design or making something better/optimal is likely to require a hydronic pro who installs the systems - not a service plumber. Commented Jan 2, 2023 at 17:28

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