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Can I use a multistage tstat on a 2 stage furnace that does not have AC?

Can I use a multistage tstat on a 2 stage furnace that does not have AC?

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  #1  
Old 04-28-09, 09:45 AM
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Question Can I use a multistage tstat on a 2 stage furnace that does not have AC?

Hello, I’m trying to figure out which wiring process I would use for the following setup and which system type I would define in the thermostat. A bit long….

I have a Lennox G61 2 stage furnace. I do NOT have a heat pump or AC installed.

I am looking in to using the Honeywell TH8320U_1008 thermostat.

I want to use the 2 stages of the furnace as well as be able to use and program the fan for regular air circulation.

I know it’s a bit more of a thermostat then I need right now but in a couple of years I do plan on having AC installed so figured I would go with a tstat that could do it all now and be set for the future, as much as one can be anyway.

I see there are the following wiring hookups on the furnace:
W1 – Heat Demand from 1st Stage tstat
W2 – Heat Demand from 2nd Stage tstat
G – Manual Fan from TSTAT
Y2 – Tstat 2nd Stage Cooling signal
Y1 – Tstat 1st Stage Cooling Signal
C – Thermostat Signal Ground connected to transformer and chasis ground
R – Class 2 Voltage to tstat
1 – Error Code recall
H – 24V Humidifier Output
L – Lennox System Operation Monitor
0 – Tstat signal to Heat Pump reversing valve

The Thermostat has the above with similar labels/designations and adds the following:
RC – Cooling Transformer hookup jumpered with R by factory
E – Emergency Heat Relay
Aux – Auxiliary heat Realy
L – Heat pump reset / System monitor
O/B Changeover valve for heatpumps
S1 - Optional Outdoor/Remote sensor
S2 - Optional Outdoor/Remote sensor


My concern is that I see several tstat options like 1h/1c 2h/2c 2h/1c etc as I do not have AC I am looking for something along the lines of 2h/0c what option on the thermostat do I use? Or do I have to basically just wire it up as heat only tstat?

Tstat Options available:
1. 1 heat/1 cool conventional
2. 1 heat/1 cool heat pump (no aux heat)
3. Heat only 2 wire
4. Heat only with Fan
5. Hot Water Series
6. 6 Cool only
7. 2 heat/1 cool heat pump (with aux heat)
8. 2 heat/2 cool multistage conventional
9. 2 heat/1 cool multistage conventional
10. 1 heat/2 cool multistage conventional
11. 2 heat/2 cool heat pump(no aux heat)
12. 3 heat/2 cool heat pump(with aux heat)

Do I wire the tstat & furnace up as
1. Heat only with fan(an use the furnace jumpers to run in a handicapped 2 stage mode), (tstat option 4)
2. 2 heat/1 cool (tstat option 9)

I thought of adding the outdoor sensor as well. Would I gain anything with it or no? Even though I don’t have a heat pump or AC installed would having it help the tstat configure proper heating/blower use?
 
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Old 04-28-09, 09:59 AM
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I think all you have to do is set it up for 1c/2h, just don't ever set it to "cool."

As for wiring, W1, W2, R, G, & C should be all you need.

Originally Posted by surfsatwork View Post

I thought of adding the outdoor sensor as well. Would I gain anything with it or no? Even though I don’t have a heat pump or AC installed would having it help the tstat configure proper heating/blower use?
That would only be useful if you had a heat pump.
 
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Old 04-28-09, 12:04 PM
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Originally Posted by badtlc View Post

That would only be useful if you had a heat pump.
Would having the outdoor sensor hurt anything? Would I still get the display on my tstat even though it wasn't really doing anything for me? Only 20 bucks more, figure if I'm buying the tstat why not get this too since I don't have an outdoor thermostat.
 
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Old 04-28-09, 01:08 PM
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yeah, your t-stat will then show the outside temp. That would be about it.
 
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Old 04-28-09, 08:51 PM
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Yeah, you are fine to use this t-stat, and outdoor sensor for your system.

Do you have window/wall A/C?
 
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Old 04-29-09, 04:02 AM
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Yeah we have a couple of window A/C units. I just ordered the tstat and sensor last night should have it today or tomorrow already. Ordered from Pexsupply.
 
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Old 04-29-09, 09:49 AM
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I don't know how your house is laid out, and what areas you want to cool with your windows units.

I've done this in the past in an apt I had window unit, and I set my t-stat to cool, and set the temp of what I was trying to shoot for with my A/C, and the fan will come on when it gets too warm and help moved the air around the apt.

I've had a few of my customer in the past done this and had good results with it..
 
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Old 04-29-09, 10:13 AM
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Yeah thats kind of my plan, use the furnace fan to circulate the air around the house and get some upstairs. I will have 2 room air conditioners downstairs so I should be able to get some pretty good cool air circulation I hope.

Even though I don't have A/C installed in the funrace would I still set my tstat to cool? That won't hurt anything will it?
 
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Old 04-29-09, 11:45 AM
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If you run the fan ON, the blower speed is a bit slower.

If you set to cool, and the room temp gets above set point, it will turn the blower on a higher speed to move the air. And, no it won't hurt anything at all.
 
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Old 04-29-09, 11:53 AM
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Well thats just cool. haha little pun there Now I just need to find some 18 gauge 5 or 8 stranded wire...
 
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Old 04-29-09, 01:04 PM
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One caveat, if your ductwork is not insulated, or if like mine your furnace is located in the garage with an uninsulated section of return air duct, then using the furnace blower to circulate the air may result in losing the A/C benefit. I know that is true in my house.

So before the cooling season arrives in my area I'm going to insulate my return air duct in the garage.
 
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Old 04-30-09, 07:22 AM
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My furnace is in my basement, which is cooler year round then I keep my house at anyway so I don't imagine the loss of cooling through my duct work will be much, but I imagine I do lose some heat through the duct work in the winter. Basement isn't heated, and on those cold days when it was zero degrees out my basement was about 45 - 50 degress.
 
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Old 04-30-09, 07:30 AM
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Do you have any vents in the basement? Also you use the basement or jsut a big open unfinished area?

I would suggest open a couple of vents in the basement in the winter months to make the floors feel warmer.
 
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Old 04-30-09, 07:44 AM
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we don't use it for much of anything yet not even that much stored down there currently. If it was organized a little more would be mostly all open. We do plan to finish off half of the basement at some time.

I will probably put in electric baseboard heating. We are on whats called municipal electric, really cheap electric. Its a contract between the village and a somewhat local powerplant. I can run 3 window AC units all day, pool pump, electric dryer, computers, TV's. electric stove for hours a day if I wanted to and only pay like 60 - 70 bucks a month for electric. I figure since it is so much cooler down there that it may need to heat differently then the rest of the house. And since my electirc is so cheap, would be cheaper for me to heat with electric then zone my furnace.

I have thought of adding a register to the air return to take advantage of the cool air from the basement to help aid in cooling the rest of the house. But the basement smells a little, damp and musty, need a dehumidifier down there.
 
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Old 04-30-09, 09:49 AM
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Yeah, you'll need to get some air moving and dried out there, then it won't be the musty dead air smell.
 
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Old 05-04-09, 06:03 AM
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Good News! I wired in my the thermostat this weekend, works like a charm. No problems or hickups along the way, installed/programmed just fine.

Thanks for your help and input everyone.

Now to move on to some of the outside projects.
 
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Old 05-04-09, 07:33 AM
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Glad to hear it worked out.

Did you set all the CPH (Cycles per hour) to 3?
 
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Old 05-04-09, 07:40 AM
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Originally Posted by Jay11J View Post
Did you set all the CPH (Cycles per hour) to 3?
HHmmm, nope I didn't. I see that I fall in to function 240 and 250 for 2 stage. I don't have 3 stage or emergency should I bother changing the setting for function 260 and 270 to 3?

What will that do anyway? Not quite sure I understand it.
 
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Old 05-04-09, 10:36 AM
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Originally Posted by surfsatwork View Post
I don't have 3 stage or emergency should I bother changing the setting for function 260 and 270 to 3?
No, that won't show up on your t-stat setting if you set the t-stat to two stage gas heat.

What will that do anyway? Not quite sure I understand it.
That will control how much the furnace runs.. If it set to 5, it will cycle about 5 times an hour at 50% load, that will cycle on and off too often.

Where, set to 3, it will give you a longer run time and better comfort.

Here are the settings I'd suggest.

170-9
180-0
220-3
240-3
250-3
280-1 (if you have C hooked up, makes a great night light)


Any other settings you have questions on, please feel free to contact me.
 
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Old 05-04-09, 11:31 AM
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Originally Posted by Jay11J View Post
Here are the settings I'd suggest.

170-9
180-0
220-3
240-3
250-3
280-1 (if you have C hooked up, makes a great night light)
Cool, thanks. If memory serves me right the only 2 functions I will need to change then are 240 and 250.

I turned on the night light too (280-1).
 
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