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High Efficiency Boiler Fan Test

rbeck Member Posts: 56
What is your process to test the fan on a high-efficiency boiler to determine a fan or control problem? I know to remove the 4 wire connector and the fan should ramp to 100% providing there is 120vac to the fan.


  • Robert O'Brien
    Robert O'Brien Member Posts: 3,512
    That's the only method I know. Most often the bad blower is running 100% when you get there
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    delta T
  • hot_rod
    hot_rod Member Posts: 19,927
    I think those table top simulators that reps have can modulate the fan. They are used for control training classes
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • ratio
    ratio Member Posts: 3,509
    I know you can get controls to exercise furnace ECM blowers, if they interface the same way one of those might work, possibly with a harness adapter. If not, they're probably vendor-specific & would need a tool from the mfgr (or possibly the motor mfgr).
  • GBart
    GBart Member Posts: 746
    Assuming we mean furnace not boiler.
  • ratio
    ratio Member Posts: 3,509
    I was thinking that the inducer motor might be a cousin of the ECM blower motors, but the more I think about it, that's probably not the case. My guess now is that it's a custom integrated motor control so no bets outside the mfgr; but an analog control signal (PWM, 2-10V, 4-20 mA in order of my guess at probability) isn't outside the realm of possibilities. A multimeter and study of the schematics might tell us more.

    Which boiler? A service manual might be Googleable.