Changing Thermostat (substitute G for C?)

[DigitalCancer]

Pretty sure the OP doesn't still have the problem after 3 years.
admin allisolm

Sorry if there's a lot of info here guys...I tried to make it detailed to see if I could get some assistance on what the issue may be.

- Fan stays on
- Thermostat doesn't control the unit (heating...can't test cooling)
- Condenser kicked on

Ok, so I've been having some heating issues as of late and I have to turn the thermostat up to like 80 for it to even get a decent temp in the house and even then, sometimes it'll say its 75 when it's clearly closer to 60 so...I thought I'd try a new thermostat before calling in a pro.

I bought a Honeywell RTH8580WF (WiFi, touch-screen) to replace the aging digital thermostat (I don't recall the brand/name), but I ran into an issue.

The old one is a 4-wire setup but the furnace does have a 'C' jumper.

After I set this up (with the Green = C configuration outlined below), The unit fired right up, but...once I turned it off at the Thermostat it didn't actually turn off.

After awhile it did kick-off (not sure why) and then my condenser kicked on (luckily I was sitting very close to the 'kill switch' for the furnace as it was like 12 F outside. ^_^

So for now, I've given up and placed the original Thermostat back on and switch my wiring back to the original.


So I had it hooked up like so:

Red = R (RC jumpered to R (there is no RH on this one but was on the old one)

White = W

Blue = Y

Empty = G

Green = C

From what I've found, I can:

1. Move 'G' wire to 'C' slot on Thermostat

2. Move 'G' wire to 'C' slot on Furnace

3. Add jumper from 'G' to 'Y'

In doing this, you lose the ability to run JUST the fan (so it'll be Auto at all times and kicks on with the unit).


OLD Thermostat Wires

Red = RC/RH (bridged)

White = W

Blue = Y

Green = G

Furnace Board Wires

Red = R

W = White

Y = Blue (Red to AC)

G = Green

C = (White to AC)

 

[MixMasterTang]

RH - This wire comes from the 24VAC transformer on the heating system.
RC - This wire comes from the 24VAC transformer on the air-conditioning system.
W - This wire comes from the relay that turns on the heating system.
Y - This wire comes from the relay that turns on the cooling system.
G - This wire comes from the relay that turns on the fan

Have you tried just touching the RH, W and G wires together as a test and see if that heats up your house? I'm not sure you have a thermostat issue.

Edit: Also your furnace won't shutoff immediately when the thermostat is turned off, it may take a minute or so for it to cycle down.

 

[Mixolydian]

I did this same technique when I had a Honeywell Wifi thermostat that required a C-wire, which my system obviously didn't have. Of course, my furnace is way too old to have any kind of electronic circuits in it, and just a bunch of unmarked wires. I did get it to work. However, I recently upgraded to a Nest Thermostat (which does NOT require a C-wire) and I switched it back to the original wiring setup. However, I still cannot control the fan independently, and whenever you turn on the fan manually, the condenser activates as well. Ugh.

 

[DigitalCancer]

So...any other recommendations/suggestions? I've had no trouble with it since changing it back to its original configuration...I changed the filter (which actually seemed to help a bit as far as keeping the place warm). I did find some air seepage from under the living room door which I've now clogged with a towel (b/c it's been in the negatives here lately) as the living room does stay cooler it seems but that's probably b/c of the stupidly placed vents (2 of them...and they're behind out love-seat) and they're the stupid vents that come out of the wall umm, can't think of the name off-hand but they blow the air up against the wall and upwards.

btw...this is a 1500sq ft ranch so definitely not overly big.

 

[Vdubchaos]

OP, I suggest you find another forum that is more focused on these sort of things.

Here you will just get bunch of hipster nest responses.

 

[nickbits]

Make sure the thermostat is setup right for your config. Maybe it setup for heat pump or 2 state heat/cool.

I'd shut off your A/C breaker while you play with it. I assume the stat isn't calling for cooling?
stat / wire / furnace
R/Rh/Rc = Red = R
W = White = W
Y = Blue = Y
C = Green = C
G = not connected = G
should work.

You will lose independent fan control doing this.. Fan will always be auto.

can you post a pic of of the new stat and furnace board wired the new way?

 

[DigitalCancer]

Make sure the thermostat is setup right for your config. Maybe it setup for heat pump or 2 state heat/cool.

I'd shut off your A/C breaker while you play with it. I assume the stat isn't calling for cooling?
stat / wire / furnace
R/Rh/Rc = Red = R
W = White = W
Y = Blue = Y
C = Green = C
G = not connected = G
should work.

You will lose independent fan control doing this.. Fan will always be auto.

can you post a pic of of the new stat and furnace board wired the new way?

Yea, I never use the fan on it's own anyway (never have) so that's not really an issue for me.

It'll probably be later this weekend before I tear it all down and try again. The Stat does have a setup for the heat pump/2-stage, but...it defaults to the 2-stage and so I couldn't even go into the settings for it b/c it 'detected' the proper config I guess? I followed the instructions at first thinking that I had to set it but it said if you have a 2-stage then it's ready to go.

 

[nickbits]

Yea, I never use the fan on it's own anyway (never have) so that's not really an issue for me.

It'll probably be later this weekend before I tear it all down and try again. The Stat does have a setup for the heat pump/2-stage, but...it defaults to the 2-stage and so I couldn't even go into the settings for it b/c it 'detected' the proper config I guess? I followed the instructions at first thinking that I had to set it but it said if you have a 2-stage then it's ready to go.

Based on your furnace board, you do not have 2 stage heat/cool or you would have Y2 and W2 terminals. You have single stage heat/cool. You should be able to get into settings and verify function 0170 is set to 1.

But my best guess is you had the wires hooked up right but one of them was shorting.

 

[DigitalCancer]

Based on your furnace board, you do not have 2 stage heat/cool or you would have Y2 and W2 terminals. You have single stage heat/cool. You should be able to get into settings and verify function 0170 is set to 1.

But my best guess is you had the wires hooked up right but one of them was shorting.

Oops...that's what I meant....Single Stage...anyway...yea, from everything I could find online, it seemed right but as I said, my house wiring certainly isn't the best. Seems that the previous tenants wanted to do EVERYTHING themselves.

Btw...is there another way to get into the settings w/o hooking the unit up?? Just so I could verify the settings that are currently on it?

 

[Red Squirrel]

Make sure the AC is not kicking on at this time of year, it could be bad on the compressor, the oil will be really thick, if frozen. I would turn the breaker off at the unit, and you can use a volt meter to determine if it's being "turned on" or not (for troubleshooting) by testing at a point before the outside breaker.

I don't know if this will help but here is my configuration:

Thermostat side:


From right to left:
Relay 1: Furnace
Relay 2: Blower
Relay 3: Future A/C (don't have A/C, so those wires don't actually go anywhere yet)

Your thermostat may have a relay diagram you can use to compare.

Furnace side:


Ignore the wire that goes to the common and Hum terminal, that's for the humidifier motor.

Basically as far as I can tell: (been a while since I wired this)
red + white = heat
red + green = blower
red + Yellow = A/C

You can jumper those terminals at the furnace to confirm, as the terminal names seem to differ between furnaces.

Hope this helps.


Edit: NM, it was right, but I provided a better pic.

 

[nickbits]

Oops...that's what I meant....Single Stage...anyway...yea, from everything I could find online, it seemed right but as I said, my house wiring certainly isn't the best. Seems that the previous tenants wanted to do EVERYTHING themselves.

Btw...is there another way to get into the settings w/o hooking the unit up?? Just so I could verify the settings that are currently on it?

Hook up only COM and R and it should power the stat but it won't be able to control anything. If something kicks on then you have a short with the wires or they are labelled wrong.

 

[Dallbright]

I recently installed a goodman air handler and outside condensing unit it came with a 10kw heater kit I was wondering if i changed it out to a 15 kW heater kit will i need to do anything with the thermostat since I'm going to a bigger heater

 

[spacejamz]

hope you figure it out...I installed two of those honeywell thermostats two weeks ago and love them...

my home was built in 2003..the wires (aside from the standard Y/W/G/R wires that were connected, it also had Blue, Orange,Brown and Black which were not being used) were already run from the furnace zone controller (I have two zones) to the thermostats but the blue 'C' wire wasn't connected at the zone controller...took a minute to connect them there for both zones and then a had a live 'C' wire...

I just got them because they are directly compatible with alexa and voice control over the temps is awesome....and they look pretty spiffy on the wall....