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Thread: Replaced EWC-ST-2E with NCM-300, now system hums/vibrates

  1. #1
    Junior Member

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    Replaced EWC-ST-2E with NCM-300, now system hums/vibrates

    I replaced my zone control board EWC-ST-2E with an upgraded NCM-300 so i could run nest thermostats in a new house i just bought. thermostats run great, heating runs great, but now when Zone 2 calls for heat the wall vibrates. Any thoughts? the Nest diagnostics say that the wiring is working and i havent had any battery issues, but one troubleshooting website said that it could be the 24vac transformer. the ST-2E control board had labeled "1" and "2", but the new board has R and C. is it possible i have those swapped on the new board? everything seems to work other than the vibration noise.

  2. #2

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    You can swap R and C (as long as they only go to the transformer) but shouldn't matter. Could be a damper isn't opening or closing fully?

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