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HVAC question regarding wiring new thermostat

bczoom

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Any HVAC techs out there?
I'm working on replacing my thermostat and ran into this wiring snag on the new t-stat. (I have a heat pump coupled with interior electric furnace/air handler.)
I do have the Y1, W1 & W2 wires in my existing thermostat. These directions tell me to stop and contact a pro.
Does the whole thing need rewired or can I attach these 3 wires somewhere?
Pics of existing wiring and the new t-stat instructions below.
Here's a link to the full instructions. I'm on pages 22 & 23.
 

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bczoom

Super Moderator
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A couple other notes.
I'm replacing a White Rodgers with a Honeywell RTH7600.

Here's how far I got on wiring the old to new:
E to E – White

C to C – Dark blue

C black wire goes to? W2?

R to R – Both wires – smaller gauge red
Alternately, R to R, jumper R to RC on new unit
Or do I put one existing red wire in R, the other in RC

W2 to Aux – blue thicker wire

W1 to W white ????????

Y1 to Y - yellow

Note in new t-stat instructions: If E and Aux terminals on new do not each have a wire connected, jumper them together

O to O – Thick red wire

G to G – Green wire
 

Melensdad

Jerk in a Hawaiian Shirt & SNOWCAT Moderator
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Sorry. No clue. I’ve hooked up dozens of thermostats but never to a heat pump.
 

Backyardski

BackyardskiLima
GOLD Site Supporter
Not sure if this will help at all, our white-Rodgers is wired to a hydron module heat pump. I was staring at schematics as I was wiring in a power feed today and don’t think my eyes could take looking at any more diagrams, hope the pic is useful
38A805D9-397D-43E8-AE07-C37D72FAFA99.jpeg
I’m not a hvac guy either
 
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workinsilence

New member
Dude, I have no idea how to help you. When I had problems with HVAC, I always found specialists who did everything for me, and I didn't even want to go there. Moreover, in the summer, I was doing HVAC installation, and I had to spend a lot of money first to find normal specialists who would do their job efficiently and then pay for the service itself. Everything about HVAC scares me, haha. I hope you fix your problem, friend. And I suggest you don't do wiring yourself. Good luck! If you need help, write to me in private chat, and I will send you the contacts of a HVAC service I like.
 

bczoom

Super Moderator
Staff member
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My fix was to replace the entire furnace, heat pump and thermostat. ;) The new one is much better.
 

chowderman

Well-known member
heat pump systems with resistance backup:

the resistance heating is designed to "kick in" under one (for sure) and two (that's a mebbe) reasons.

heat pumps are not economical below certain outside / ambient temperature. the exact degree number of outside temp depends on the manufacturer (efficiency of compressor and outside coil) - and that sensor/signal comes from the outside unit.
when the outside temp is too low, the compressor should stop, and the resistance heating should take over.
that situation is handled by the normal thermostat wiring - i.e. call for heat, or call for cooling.

the second case is where the inside temp drops below the set level and a differential degree amount.
if thermostat was set for 62'F (away from home, example...) but is re-set for 78'F (heh, we're home!) and inside is below 75'F (example) then the thermostat tells the system to run both heat pump and resistance heating.
less common, the heat pump compressor is running but cannot maintain the inside set point - thermostat signals resistance heating to kick in, in addition to the heat pump (i.e. heat pump still cost effective, but inadequate)

those situations require a different thermostat (set temp and x-degrees less) than set temp, and more wires.
super newer units can use frequency signals to use "same" wires with "more" messages....
 
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