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[Critrgitr]

 I know there are alot of these posts, but it seems that there are so many different variables regarding wiring thermostats correctly. I think mine is fairly simple, but I haven't been able to figure it out yet.

Just installed my OWB and exchanger in the existing plenum of my LP furnace. I need the fan to run based off my temperature setting on my thermostat without the LP furnace trying to start up itself.

The wiring block in my furnace is R, W, Y, G, C, from left to right.
The four wires from my thermostat are Red to R, White to W, Yellow to Y, and Blue to G.
There are also two lines running from the Y and C blocks out to my A/C unit. Those colors are White to Y, and Red to C.

Once again, sorry for a post that the information is probably listed somewhere in this forum....I just can't find it.
Thanks ladies and gents.

[Ridgekid]

Forced air gas heat?  You'll need aquastat. 

Once your OWB has reached the aquastat set point, your thermostat will only turn on the house fan. Not the gas furnace.

[RSI]

DO you want to use a second thermostat or just have the existing one control it?

I prefer adding a second thermostat because you can go a long time before the house cools down that much. If you have an aquastat on the pipe to switch over it starts burning gas right away.

Here is how you would wire a second thermostat. If you want to use an aguastat and not add another thermostat I will post that.

G is the fan relay
R is the 24v. This is all you need to the new thermostat.
W is the terminal you need to use on the new thermostat.

So, remove the blue wire from the G terminal and run it to the W on the new thermostat. (leave the G empty on the old thermostat)
Add another wire to the R on the old thermostat and run it to the R on the new one.

If your new thermostat has a C connection you might need to run a wire between them in the two thermostats. (not usually needed if the thermostat uses batteries or isn't digital)

[Ridgekid]

Does a second thermosat still allow his gas furnace to be his backup automatically or does he manually have to switch? 

[RSI]

Does a second thermosat still allow his gas furnace to be his backup automatically or does he manually have to switch?

Yeah, the gas will come at whatever it is set at. I have mine set at 60 and the second thermostat at 72.

The gas has never come on but if for some reason it was needed I just have to turn it up to whatever temperature I want the house at. If no one is home the house won't go under 60.

Another way to do it would be to use a 2 stage thermostat but the backup heat is usually a fixed differential so if you turn up the temperature too much it will fire the furnace.

To wire up a 2 stage thermostat, just move over all the wires but put the white (W on old tstat)on the W2 and the blue (G on old tstat) on the W1.

[jerkash]

I agree with RSI - Just add a second thermostat to control the fan only and your gas furnace will still come on if the temp drops to the setting you have it set on

[Critrgitr]

Ok, here's what I did. I ran a new two wire lead from the new thermostat down to the furnace. I hooked the R on the thermostat to the R on the furnace block. I then hooked the second wire from the W on the thermostat to the G on the furnace block. Fan came on as expected, but my A/C compressor started up. I disconnected the blue wire on my old thermostat that was attached to the G block on my furnace and the compressor stopped. Not sure why my A/C kicked on? My old thermostat was set to heat. For now I'll leave the blue wire off until I or any of you can correct what I did. Thanks for all the help guys, I really appreciate it.

[RSI]

Yes, you need to leave that wire off. The original thermostat backfeeds to the Y connection for some reason when you leave it connected.

[Critrgitr]

Yes, you need to leave that wire off. The original thermostat backfeeds to the Y connection for some reason when you leave it connected.

Ok.....thanks RSI for the help. Everything seems to be working great now.

[ffbare]