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Honeywell RCHT8612WF2005/U Room Thermostat - Mystery Terminals

contrawise Member Posts: 5
Isn't it great when you're installing a new model thermostat for the first time and the manual is short on details? It comes with a "Quick Install Guide" that is more of a tutorial about not getting the wires mixed up when you take 'em off the old thermostat. Necessary - but oh so shallow. Couldn't find a "real" manual on the honeywell web site.

The new stat's sub-base has 16 terminals. Only about half have their functions explained. Several I can figure out from years of experience: heat pump terminals. Real puzzles are:
* Two terminals labeled U & U (U-midity control?) .
* Two labeled S & S (outdoor or remote indoor sensor?). Honeywell often uses T & T for those functions.
(Service lights like clogged filter or compressor lock-out?)
* A terminal labeled A (usually outside air / occupied mode in commercial 'stats).
Not a peep in the manual about any of those. Non functional in this model?

Thanks in advance for any wisdom anyone can pass along ... !


  • ratio
    ratio Member Posts: 2,763
    U are the universal output terminals, programmable for de/humidity, & on at least some other models an extra stage of heat/cool; S are remote sensor terminals, programmable for outdoor control (i.e. heat pump changeover) or display only, or indoor control or averaging.
  • ratio
    ratio Member Posts: 2,763
    Oh, and A is IIRC occupied or possibly programmable to heat pump fault. Not too sure about this terminal, I've never used it.
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