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Pressure switches

Bob C._2
Bob C._2 Member Posts: 33
What is best procedure to test pressure switches hi and lo fire

also best way to check to see if secondary heat exchanger is clean and ok?


  • furnacefigher15
    furnacefigher15 Member Posts: 514
    Test procedure

    When on furnace:

    Run the inducer, and check the pressure with a manometer, or magnehelic gauge. If the vacuum is more then rating on the switch, it should electrically change position.

    If outside of unit, you can create a vacuum with a hand vacuum pump. like the ones they use in the automotive world. Check the amount of vacuum in the same method as outlined above.

    Note if the pressure switch has 2 ports, like on a 90% furnace, then the only accurate way to test is with a 2 port manometer connected to the same points as the pressure switch.

    Secondary HX

    Visual inspection. Remove collector box to inspect inside.
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