# Pellet Stove using an existing thermostat



## enroberts (Oct 2, 2009)

Hello. I posted this same post in an HVAC forum and was blown off because I am not an HVAC professional, so hopefully someone here can help.  I have recently purchased a wood pellet stove that has a 2-wire thermostat connection on the back. I currently have a thermostat in my kitchen that controls the natural gas heater in the basement. We have been running the pellet stove for the last few nights and manually turning on the thermostat to use the returns in the house to move the warm pellet stove air and heat the house. It's working great. So great that it's actually too warm in the morning! My question is can I run a wire to the current thermostat and use it to run the pellet stove and still automatically kick on and off the fan when the pellet stove runs? I know its a low voltage stat and so it the pellet stove. I also know that the stove needs to use the R and W terminals on the stat to work, but when I disconnect the current R and W wires the fan obviously does not turn on when I throw the switch to "Fan On." Can I run the stove and heater in parallel and leave the heat/ac switch in the off position and the fan in the auto position? Thanks very much for your help and let me know if you need more information. -Neal


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## dac122 (Oct 2, 2009)

Pretty sure I know the forum you're talking about, and yes, they aren't too tolerant of DIYers - which is pretty much what these forums are all about.  Sorry you got blown off but that won't happen here.

Ideally you'd want a two stage thermostat such as one that controls a heat pump, but that's probably way over kill for this application, and too complicated for you to wire and configure.  I'm thinking of a second thermostat tying into the existing control wires.

To make a full recommendation can you tell me whether your current thermostat is battery powered or powered by your furnace's transformer?  

I'm still mulling over some simple ideas so let me know so I don't go down a blind path.


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## enroberts (Oct 2, 2009)

dac122 said:
			
		

> To make a full recommendation can you tell me whether your current thermostat is battery powered or powered by your furnace's transformer?



I should really know the answer to this one but I want to wait until I get home from work to answer for sure.  I didn't install the current thermostat, it was in place when we bought the house.  Chances are that it's powered by the system transformer as I have never replaced a battery in it in the two years we have lived here.  I'll double check and repost tonight.  Thanks very much for you response.  I feel much more welcome here already!  -Neal


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## imacman (Oct 2, 2009)

enroberts said:
			
		

> ......I feel much more welcome here already!  -Neal


Welcome Neal

Lots of nice people here, and most all are willing to help.


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## hossthehermit (Oct 2, 2009)

I'm not an HVAC pro, but my first thought is that an existing t'stat would work better than a non-existing one.


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## enroberts (Oct 3, 2009)

Ok glad I checked, the current stat runs on batteries. Does that help, Dac122?  Thanks, Neal


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## dac122 (Oct 3, 2009)

enroberts said:
			
		

> Ok glad I checked, the current stat runs on batteries. Does that help, Dac122?  Thanks, Neal



Okay that's good.  A few more questions:  just to verify you have R, W and G on your tstat hooked up right now, and going to your furnace.  Correct?  Do you have A/C?  Also, how does your pellet stove work on thermostat:  idle up/down or stop/start.

These answers will help provide a more comprehensive solution.   As I see it there are two ways you could go with solutions:  one is a two heat thermostat (heat pump with backup/aux), or a second independent thermostat.  I'm going back on my original recommendation as I beleive a two stage thermostat will be less complicated to hook up, but maybe less flexible.  Prices for two stage thermostat turn out to be about the same as regular thermostats.


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## enroberts (Oct 3, 2009)

dac122 said:
			
		

> enroberts said:
> 
> 
> 
> ...



Yes, I have G,RC,Y, and W going to the furnace now.  I do in fact have A/C and the RC is jumpered to the RH as well.  In terms of how the stove works, I'm not exactly sure but it's a Whitfield Profile 20 if that helps.  I'll look into it in the mean time.  I am currently running a temporary 2nd thermostat but That doesnt allow me to leave the fan on auto for the furnace's air mover, which is how I would like the system to work.  I'd be happy to run a two heat thermostat as long as the furnace can be the back up and the stove as the main. Thanks for your help so far, Neal


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## enroberts (Oct 3, 2009)

The stove just simply shuts off when the stat tells it to as opposed to just slowing down.  it's got an igniter to restart it. -Neal


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## dac122 (Oct 3, 2009)

K Neal, since you already have a pellet thermostat lets work with that.  

I think this is what you want to do: run wires from RC (or RH) and G from the furnace thermostat on to the pellet thermostat, and then run a wire from the pellet thermostat's R and G (or W if G not energized in heating) onto the pellet stove.  Does that make sense?

When working you'll want the furnace thermostat at a lower set point than the pellet thermostat, depending on how long you want before the furnace kicks on as backup.


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## charles u farley (Oct 3, 2009)

A second thermostat and a 2 pole relay would be the best way I can safely think of doing this.  Only low voltage connections need to be made and nothing would be modified on either appliance.

Mount a second thermostat for the pellet stove, put it near the existing one or anywhere else that might be a better place to control the pellet stove heat.
Set the pellet stove stat for a comfortable temperature, set the furnace stat for backup temperatures, somewhere about 5-10 lower. 

Run a 2 wire stat cable from stove to furnace, and another 2 wire from the pellet thermostat location to the furnace.
R from furnace transformer goes to R on pellet thermostat.
W from pellet stat goes to A1 (coil) on a relay (mounted near furnace).
A2 on relay goes to C or common on furnace transformer.
Relay pole 1 Common goes to R on furnace.
Relay pole 1 Normally Open goes to G on furnace.
Relay pole 2 Common and pole 2 Normally Open goes to stat wires on pellet stove.

Caution: Mixup any wires on the relay and possibly fry your stove board or furnace board.
This is why pro forums will be unlikely to help and you got the brush off.   They get paid to do this stuff and don't want to assist amateurs coming in without at least a starting knowledge of the materials and methods of the trade.  They have no idea of your experience level and might end up suggesting something which you follow (to the best of your ability) and doesn't work or worse, wrecks something.  Knowing exactly what you are telling a person to do based on a forum post for help and having what you typed to them performed correctly is risking misinterpretation, made much more likely if the two people don't have have the same experience or background.

HTH and willing to answer questions.


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## charles u farley (Oct 3, 2009)

dac122 said:
			
		

> Pretty sure I know the forum you're talking about, and yes, they aren't too tolerant of DIYers - which is pretty much what these forums are all about.  Sorry you got blown off but that won't happen here.
> 
> Ideally you'd want a two stage thermostat such as one that controls a heat pump, but that's probably way over kill for this application, and too complicated for you to wire and configure.  I'm thinking of a second thermostat tying into the existing control wires.
> 
> ...



Just to butt in, make sure to consider isolation of the control voltages.  The pellet stove is expecting a dry contact and so is the furnace.   Apologies if this is already taken into account in what you might propose.


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## enroberts (Oct 4, 2009)

Ok, I've got R and G from the furnace's stat looped to the stove stat.  Then I connected R and W to the stove from the stove stat.  The stat turns on the stove and I can manually turn on the furnace's fan using either stat, but the fan will not come on when the stove stat is on auto fan.  any ideas?  thanks, Neal


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## enroberts (Oct 4, 2009)

Charles- where might I find a relay like you are suggesting?  any links or specifiactions?  thanks, neal


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## enroberts (Oct 4, 2009)

ALL IS WELL IN DUAL TSTAT LAND!  As I was putting the stove stat back together I noticed that there was a jumper on the back for gas or electric.  It was on gas so I moved it to electric and voila!  When I turned up the heat, the stove switched on and the fan in the basement also switched on. When I moved the heat back down, everything cycled down.  Thanks very much for your help dac122!  I know now where I'll come for answers to my stove questions!  -Neal


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## dac122 (Oct 5, 2009)

Thanks for letting us know how it turned out.  I suspect in gas mode that tstat only energizes W in heat mode; but energizes both W and G in electric mode.  I believe you could have gotten the same affect by putting a jumper between the W and G on the stove thermostat.

No thanks needed.  Simply pay it forward to the next person that needs help.


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