Outdoor Wood Furnace Info

All-Purpose OWF Discussions => Electronics => Topic started by: WoodMOJoe on January 08, 2014, 05:33:47 PM

Title: Using 2nd thermostat to control blower only?
Post by: WoodMOJoe on January 08, 2014, 05:33:47 PM
I know this has been discussed here before but my searching brought up nothing that made sense for my specific situation, so...

My system...propane upflow furnace w/AC, homemade outdoor boiler (online soon I hope!).

I am wanting to use a second thermostat to control the blower when the OWB is producing heat, and my existing thermostat to fire up the propane unit if the OWB fails to hold the heat up.   I was planning on using a cheap programmable t-stat (probably a Honeywell) for the 2nd t-stat, but would be glad to hear any recommendations.

***Here are pics of my existing wiring at the back of the t-stat and where that wiring connects to the propane furnace.  I guess the extra red and white wire at the furnace go out to the A/C compressor.***  Let me know if you need any more info, thanks.

***The upload folder is full. Please try a smaller file and/or contact an administrator.***

Can't get the 2-75K pics to post, keep getting this message:

The upload folder is full. Please try a smaller file and/or contact an administrator.




Title: Re: Using 2nd thermostat to control blower only?
Post by: RSI on January 08, 2014, 10:00:52 PM
All you should have to do is remove the wire from the G terminal on your thermostat and run it to the W on the new thermostat. Then put a jumper wire from the RH on the original thermostat to the RH on the new thermostat. If you have a wire on the C terminal, you can also run a jumper to the C on the new thermostat.

The C connection is needed if your thermostat doesn't use batteries. If it does use batteries and you connect the C it most likely will only use them as backup so they won't go dead.
Title: Re: Using 2nd thermostat to control blower only?
Post by: WoodMOJoe on January 09, 2014, 08:00:37 AM
Thanks RSI.  I had found a post of yours that was similar to what you just said here but the other poster had introduced wire colors into the mix and they just confused me (don't take much to confuse me  ;) ).

I do have a wire on the C terminal at the furnace (think it's one of the ones going out to the A/C compressor), so if it won't hurt anything I will go ahead and run a jumper from C old to C new on the stats.  Both of my thermostats will have batteries in them.
Title: Re: Using 2nd thermostat to control blower only?
Post by: RSI on January 09, 2014, 05:23:07 PM
C is a direct connection to the transformer. The A/C compressor may use it too.
The wire that controls the A/C compressor from your thermostat is the Y connection.
Title: Re: Using 2nd thermostat to control blower only?
Post by: WoodMOJoe on January 10, 2014, 02:49:20 PM
C is a direct connection to the transformer. The A/C compressor may use it too.
The wire that controls the A/C compressor from your thermostat is the Y connection.

Got it, thanks.  Looking forward to getting things all hooked up and the first fire.  Looks like we should have some decent weather to work on it soon.
Title: Re: Using 2nd thermostat to control blower only?
Post by: WoodMOJoe on February 03, 2014, 08:19:31 AM
Looking ahead (aka dreaming) to cooling season and was wondering...

Can I just turn the new thermostat to Off and operate my cooling system with my old thermostat...or do I need to return the wiring to the original setup...or...?
Title: Re: Using 2nd thermostat to control blower only?
Post by: RSI on February 03, 2014, 08:28:17 AM
Yes, it should work fine.
If you want to run fan only in the summer, just turn the 2nd thermostat up and then the auto/off (on 2nd tstat) will do the same thing the fan switch used to before you moved the wires.
Title: Re: Using 2nd thermostat to control blower only?
Post by: WoodMOJoe on February 03, 2014, 08:34:05 AM
Perfect, thanks for the info RSI.   :thumbup:
Title: Re: Using 2nd thermostat to control blower only?
Post by: sizmo on February 04, 2014, 07:40:09 AM
I know this has been discussed here before but my searching brought up nothing that made sense for my specific situation, so...

My system...propane upflow furnace w/AC, homemade outdoor boiler (online soon I hope!).

I am wanting to use a second thermostat to control the blower when the OWB is producing heat, and my existing thermostat to fire up the propane unit if the OWB fails to hold the heat up.   I was planning on using a cheap programmable t-stat (probably a Honeywell) for the 2nd t-stat, but would be glad to hear any recommendations.

***Here are pics of my existing wiring at the back of the t-stat and where that wiring connects to the propane furnace.  I guess the extra red and white wire at the furnace go out to the A/C compressor.***  Let me know if you need any more info, thanks.

***The upload folder is full. Please try a smaller file and/or contact an administrator.***

Can't get the 2-75K pics to post, keep getting this message:

The upload folder is full. Please try a smaller file and/or contact an administrator.

WoodMOJoe:

I have the same furnace/AC/Wood boiler setup as you do. Another option is to use one thermostat for everything. I bought a touchscreen LUX thermostat. It will support two stages of heat. Your green wire for the fan only goes to the first stage of heat (wood boiler) the propane burner wire goes to the second stage of heat. You can then set the differencial on the thermostat. So when the wood furnace isn't heating enough, it will kick on the propane burner to bring the heat to where you have it set. Was real easy to do.

Let me know if you have any questions.
Title: Re: Using 2nd thermostat to control blower only?
Post by: WoodMOJoe on February 04, 2014, 08:10:09 AM
Thanks for that info sizmo. 

I already have the 2-stat setup installed, but if one of them shoots craps in the future I would consider going with a single-stat setup.
Title: Re: Using 2nd thermostat to control blower only?
Post by: WoodMOJoe on February 05, 2014, 02:04:22 PM
Last night I went to redo the new thermostat wiring (to change it from surface-mounted to hidden in the wall) and after re-reading RSI's great instructions I noticed something I missed the first attempt.

My new thermosat does not have a "RH" terminal, just "R" and "RC".  It also has a (removable) factory installed metal jumper from R to RC.

What terminal on the new stat can I use and do I need that jumper in place?  Or, do I need to get a stat with an "RH" terminal?

Title: Re: Using 2nd thermostat to control blower only?
Post by: RSI on February 05, 2014, 10:29:21 PM
R is the same as RH. Some just label them different.
RH is for heat and RC is for cooling. You only take the jumper out if the heating and cooling systems are completely separate.
Title: Re: Using 2nd thermostat to control blower only?
Post by: WoodMOJoe on February 06, 2014, 04:46:09 AM
Good deal, that is the way I had it hooked up before attempting the redo.   One of these days  ::)  I will get some water in the system and try it out, think I am ready now.

Appreciate all the help RSI.  If you ever need any tips on putting up a satellite dish system I'm your guy.   ;)

Title: Re: Using 2nd thermostat to control blower only?
Post by: Farmer616 on February 09, 2014, 06:26:01 PM
im trying to do this exact same thing ive run the G from the old thermostat over to the W on my new one and ran a jumper from RH to RH, now my old thermostat is ran on batteries and my new one is not but neither of them have a C terminal, any help?? been fighting this for a while
Title: Re: Using 2nd thermostat to control blower only?
Post by: WoodMOJoe on November 29, 2018, 04:33:26 PM
I have been burning for a couple of days now but am unable to get my "2nd" thermostat to control the system.

It's always worked before and I don't think I have changed anything.

It won't even run the furnace fan when you switch the fan to On position.

We have just been manually turning the fan on and off with the switch on the "1st" thermostat.

Have checked the wiring, even bought a new "2nd" thermostat and replaced it...no dice.

Hoping it's something simple I am overlooking but was wondering if anyone had any troubleshooting suggestions?


Title: Re: Using 2nd thermostat to control blower only?
Post by: RSI on November 29, 2018, 09:12:47 PM
You left the wire on the G terminal in the original thermostat? If so, do you have a/c? A lot of thermostat will backfeed if you do that and run the a/c in the winter. You can isolate it with a relay if you want to keep the fan switch operational.
As for the 2nd thermostat not working, check that the wires are connected properly at both ends. If it still doesn't work, you can temporarily jumper the wires together that are on the RH and the W terminal in the 2nd thermostat. If that does not make the blower run then it is a wiring problem somewhere.
Title: Re: Using 2nd thermostat to control blower only?
Post by: WoodMOJoe on November 30, 2018, 07:44:09 AM
You left the wire on the G terminal in the original thermostat? If so, do you have a/c? A lot of thermostat will backfeed if you do that and run the a/c in the winter. You can isolate it with a relay if you want to keep the fan switch operational.
As for the 2nd thermostat not working, check that the wires are connected properly at both ends. If it still doesn't work, you can temporarily jumper the wires together that are on the RH and the W terminal in the 2nd thermostat. If that does not make the blower run then it is a wiring problem somewhere.

The G wire is running to the W terminal on the 2nd thermostat.

I will try jumpering the W to RH and see if that gets the fan to operate.

It's odd that it has worked for 4 years but not now, I must have changed something or have a bad connection.

Will report back, thanks for your help!
Title: Re: Using 2nd thermostat to control blower only?
Post by: WoodMOJoe on November 30, 2018, 08:32:53 AM
Jumpering from W to R/RC on the 2nd thermostat did operate the fan.

I have posted a new pic of the existing wiring, the G terminal wire (green) is tied into the W terminal of the 2nd thermostat (black) and the R terminals in both stats are connected (red).



Title: Re: Using 2nd thermostat to control blower only?
Post by: WoodMOJoe on November 30, 2018, 03:04:32 PM
Since the fan runs when I jumper the W to RH terminal on the 2nd stat does that indicate a bad 2nd stat?

I tried 2 identical stats (one of them brand new) and still can't get the 2nd stat to run the fan, even when I turn the fan to On and I think all me connections are good.

Is there a way to test the pins on the back of the stat to see if it is working correctly?

Title: Re: Using 2nd thermostat to control blower only?
Post by: RSI on November 30, 2018, 11:26:31 PM
Are you using the same backing plate for both thermostats you tried? If so, that may be the problem. If not, I would check the thermostats to see if there are settings for the type of system it is set for. You will want it setup for gas furnace.

Also, make sure the thermostat is set to heat mode.
Title: Re: Using 2nd thermostat to control blower only?
Post by: WoodMOJoe on December 01, 2018, 06:57:58 AM
Are you using the same backing plate for both thermostats you tried? If so, that may be the problem. If not, I would check the thermostats to see if there are settings for the type of system it is set for. You will want it setup for gas furnace.

Also, make sure the thermostat is set to heat mode.

I did try using the old backing plate at first but changed it out to the new one immediately when it wouldn't work.

There is a slide switch on the back of the thermostat for "Gas or Oil" and "Electric or Heat Pump"...and it has been set to Gas.

I have the 1st stat set to Heat/Auto (fan) and the setpoints are lowered so the propane unit will kick in only if the temp in the house drops to 64.
 
The 2nd stat is set to Heat/Auto also but won't operate the blower even when I switch it to Fan.


And to clarify...the only way we can get the blower to work is to run the green wire to the G terminal on the 1st stat, taking the 2nd stat out of the system entirely, and turn it to Fan.

I think you asked that earlier and I didn't really answer it.





Title: Re: Using 2nd thermostat to control blower only?
Post by: RSI on December 01, 2018, 07:09:33 AM
It sounds like there is something wrong with the thermostats,
Try putting the wire in the Y instead of the W on the 2nd thermostat and flip the switch to heatpump.
Title: Re: Using 2nd thermostat to control blower only?
Post by: WoodMOJoe on December 01, 2018, 07:28:35 AM
It sounds like there is something wrong with the thermostats,
Try putting the wire in the Y instead of the W on the 2nd thermostat and flip the switch to heatpump.

That didn't do it either. I tried it with my new and old 2nd stat.

I think I may have another stat I can try if I can find it, will see how that works out.

Thanks for your help  :thumbup:
Title: Re: Using 2nd thermostat to control blower only?
Post by: RSI on December 01, 2018, 10:47:36 PM
Seems weird that 2 thermostats would be bad. Try using the G connection and setting it to heatpump.
Title: Re: Using 2nd thermostat to control blower only?
Post by: WoodMOJoe on December 02, 2018, 06:54:49 AM
Seems weird that 2 thermostats would be bad. Try using the G connection and setting it to heatpump.

Weird for sure but that must have been it, I installed another stat and I am back in business, working great.

I even stuck the first 2 "2nd" stats back on to see if they would work after I got it going with the 3rd one, no dice.

Thanks again for your help, you are one of the guys that helped me get my system going when I built this beast.

 :thumbup: :thumbup: