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HVAC Guys, Did I Wire My New T-Stat Correctly...

Grnd93

The Dude
Joined
May 19, 2020
Member Number
236
Messages
738
Loc
Michigan
Or am I going to burn my house down?

came home to a blank screen on my thermostat. Changed batteries, still blank.

have been wanting a smart thermostat for awhile so checked all the box stores and decided on a Honeywell RTH9585WF.

after doing some reading learned that I needed a common wire on the “c” terminal. No big deal, there was an extra conductor not hooked to anything.

swapped wires from old to new one by one until I got down to a white and blue wire. White went to W on the old t-stat, blue went to 0/B.

problem is, those are both the same terminal on the new t-stat. I checked the labeling on the furnace control board connections and saw white was on W1 and blue on W2

so my connections are as follows :
Furnace-Color-Tstat
Y-yellow-Y
W1-white-W/OB
W2-blue-W2
R-red-R
G-green-G
C-Orange-C

photo is the connection at the furnace. There is an extra red/white for a humidifier.

furnace seems to be working. Hopefully when it’s time to turn on the AC I don’t blow anything up.
 

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Gas or electric heat? There is probably a few settings in the stat you will need to set up to make it work right.
 
the internets said:
  • G: The G terminal controls the fan relay and is responsible for turning the blower fan on and off automatically or manually via the thermostat.
  • RC: The RC terminal is the 24-volt cooling power supply.
  • RH: The RH terminal is the 24-volt heating power supply. (Note: The RC and RH terminals are jumpered together in a four-wire heat/cool system and a single-stage heat pump system, but not in a five-wire heating/cooling system.)
  • Y/O: The Y/O terminal is used to control the cooling condenser. When the thermostat calls for cooling, signals are sent to power up the condenser and the blower fan, cooling your home.
  • W/B: The W/B terminal controls the heat relay or valve. When the thermostat calls for heat, a signal is sent to power up the furnace and the blower fan or the boiler, heating your home.
  • Y1: The Y1 terminal is used for the compressor contact in a single-stage heat pump installation.
compare to terminal definitions for thermostat. make match.
 
Gas or electric heat? There is probably a few settings in the stat you will need to set up to make it work right.
Gas, forced air with split AC system.

the W and W2 are what’s confusing me. If I understand correctly this means I have 2-stage heating, whatever that is.
 
Shooting from the hip...I am not an HVAC guy. I think the new "smart" thermostats need a constant 24V to operate. You might need to jumper in that spare wire over to the transformer in the HVAC. Your lucky in that you have a spare wire, otherwise you would give up fan control. Post up HVAC information i.e. model numbers.
 
Shooting from the hip...I am not an HVAC guy. I think the new "smart" thermostats need a constant 24V to operate. You might need to jumper in that spare wire over to the transformer in the HVAC. Your lucky in that you have a spare wire, otherwise you would give up fan control. Post up HVAC information i.e. model numbers.
I’ve got the 24VAC covered. You are correct in that being required.

House is up to the temp it is set at and it hasn’t shut itself off. This is mildly concerning
 
Don't assume the original HVAC peeps wired your thermostat to any so called standard. It is sort of a trailer park thingy...
 
House didn’t burn down overnight. Seems to be heating per the programming...except waking up at 3 am and it’s set to heat to 60 degrees when I set it lower.

maybe the dogs turned it up? I’ll have to go over the programming again today.
 
Don't assume the original HVAC peeps wired your thermostat to any so called standard. It is sort of a trailer park thingy...
I used to install (briefly) HVAC in trailers. I should know what I’m doing but those systems were generally much simpler. And I have forgotten most of it.

I think I’m ok, just a little unsure of the W and W2 wires. I did what seemed logical, W1 to the W terminal and W2 to W2.
 
O/B is for heat pump reversing valves. W2 is for gas or heat strips depending on what kind of system you have. Fire up the A/C and see if it works. if it does you're good. Or lucky.
 
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