Two Stage Heat


Old 12-05-05, 07:47 PM
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Two Stage Heat

I have a Lennox G32 Series two stage gas furnace. I have a Honeywell T8400 single stage thermostat. The furnace seems to run in both modes... I assume it is smart enough to figure out high and low speeds on its own. What would I gain by upgrading to a two stage thermostat?
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Old 12-05-05, 08:51 PM
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... You get COMFORT!

Right now your furnace only runs on time to go from 1st stage to 2nd.. It dose not learn or know.

Most equipement is set up to run low for about 10 minutes, then goes into high stage.. Some time the equiepment may only run in high fire for 2 min, then shut off.

Downfall of single stage.

-System may short cycle.
-System will not fire 2nd stage right away from night set back, or if a door/window been left open from company comming and going.
-Extra heat that is really not needed on mild days.
-House temp may not be equal.

Good thing of a single stage.

-No extra is needed
-For area where you may not be able to pull new wires to work with a two stage stat.


Now with a two stage t-stat, you get comfort!

The stat will tell what the furnace should run to meet the temp demand.

Good thing about two stage stat.

-System will go into 2nd stage if you use set back or starting it on a cold house.
-System will run longer... Longer run time means much more even temp in all rooms in the home... The air has more chance to "change" in the rooms to balance out. Also, with the long run time, the air is going over the air filter more for cleaner home.
-No short cycling.
-System will last longer with longer cycle(run time) than the stop and go.
-Did I say comfort?

Downfall of 2 stage stat.

-Cost of t-stat maybe higher
-Extra wire may be needed.


I have a Honeywell Vision Pro two stage stat on my furnace, and right now we are -11 degrees.. Forcast for -14 tonight. The furnace has been running steady pretty much all evening in low stage.. No drafty air flow. I think it kicked into 2nd stage this evening.. didn't paid much attention to it.

With the longer run time you are getting most of your gas.. Like driving your car.... You going to get a better gas milage on a steady cruise speed vs the stop and go at stop light?
Old 12-06-05, 08:39 AM
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How many wires will I need for a two stage thermostat?
Old 12-06-05, 09:27 AM
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You will need 5 wires.. some time 6.. Mine can use both.. I got the 6th wire hooked up so it don't have to depend on the battery on the t-stat, and also, I have back light on all times.

R - Power
W1 - 1st Stage heating
W2- 2nd Stage heating
Y - Cooling
G- Fan
C- Common

If you do upgrade your t-stat to two stage, make sure you read your install manual on how to set up your furnace to two stage. Most ofo them has a jumper or pin that needs to be removed.
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