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Judoplayer
Mar 9, 2008, 04:56 PM
Company installed a GMV95 gas furnace, using my old Honywell thermostat, single stage.
I believe that the 2-stage furnace needs a 2 stage thermostat. As of now the old thermostat is connected with 4 wires. If i upgrade the thermostat to a Honeywell visionpro RTH8500, won't i need an addit. 2 wires for the 2nd stage heat and A/C? Y2 and W2?
The company says no, i need only 4 wires. Don't have to run new wiring.
I am confused and want the new furnace to run as anticipated.
T-Top
Mar 9, 2008, 05:23 PM
Your system can be set up to use just a single stage thermostat, the logic in the furnace control board will control high and low fire from time, not time and temp swing.
Judoplayer
Mar 9, 2008, 05:34 PM
Thank you T-Top.
Is it better to use the 2 stage thermostat? Will the system run more efficiently?
T-Top
Mar 9, 2008, 05:58 PM
If it was me I would use the two stage thermostat so I could have a quicker response to load demand.(comfort level)
hvac1000
Mar 9, 2008, 08:06 PM
Go for the Honeywell 8000 series t-stat. There are a few different models so I would read up on them first.

Catalog (http://customer.honeywell.com/honeywell/UI/Pages/Catalog/ApplicationCategory.aspx?Catalog=Homes&Category=Thermostats_102&ChannelID=%7b2EB2F178-20ED-44E0-97FB-CCFB4218DD64%7d)