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Clicking thermostat

Bill H.
Bill H. Member Posts: 30
I had a 9 yr old Honeywell thermostat to control my hydronic heating system and central A/C. It quit on me last week. It worked well, made no noises, and as far as I know contained no mercury. It was programmable, battery operated, had an LCD display, etc. The only model info was a sticker reading TB8112D1005 which may have been a contractor special model.

 I have replaced it with a Honeywell RTH 6350D unit which works ok but makes a muted double clicking sound whenever it operates. I had tried a LUX thermostat first, and returned it because of the same sound. I've contacted Honeywell tech support, and was told all their units make that sound, and is caused by a relay. I asked why my original did not make that sound, and no one knew unless it was a mercury type ( which I doubt it was, what with the electronics inside ).

 If I must, I can live with this sound, but it seems that with tech advances it should be quiet. Has anyone experienced this or know of a modern silent thermostat?


  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    I have two Honeywell digital thermostats.

    Both have a little relay that clicks when it calls for heat and when the call is satisfied.

    The newest one is from 2009, a PRO TH 4000 Series, model TH4110D

    The other one is a CT-3600. I do not remember how old it is, but I am pretty sure it is less than 10 years old.
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