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Old 12-13-2010, 09:28 PM   #1
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HVAC Thermostat Issue


We have 2 HVAC units with 2 thermostats (unit for front and back of house). The thermostats are located only about 8 feet apart and their sensitivity apparently varies by about 1/2 degree. If I set them both for 68, the one in the back always comes on to heat the house and the front one never comes on. If I set the front to 69 it will come on and the back one never will. I need to adjust one of them about half a degree if that is possible. They are Honeywell digitals (TH5220Ds).


Last edited by almapman; 12-13-2010 at 10:06 PM.
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Old 12-14-2010, 02:35 AM   #2
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HVAC Thermostat Issue


Those are two stage non programmable. The y are accurate to only +/- one degree farenfart. The proximity the stats have to one another is a problem.

Is you heating system two stage heating?

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Old 12-14-2010, 08:08 AM   #3
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HVAC Thermostat Issue


Yes, they are 2-stage. I realize they are too close together but that's the way they were when I bought the house. I don't guess it's possible for both units to be connected (by a serviceman) to the same t-stat is it? Or, could the t-stats be replaced by t-stats that can be adjusted to exactly matching temps?
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Old 12-14-2010, 01:09 PM   #4
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I don't think the location of the stats are good but if you trying to overcome

a half degree difference I think you are fighting for a lost cause.

If the home stays with half a degree from front to rear I think that is as good
as you are going to get it.

If you have two furnaces than the contractor who designed and installed the system had his stuff together.

The benefit is that you have better heating than a lot of homes that have only one furnace to serve a large area. Single furnace installs in larger homes are subject to heating some parts on the home well and shutting off too soon before the furthest living areas have a chance to catch up leaving them much cooler than the rest of the house.

My home is a good example. The north side of the home is cooler than the south side by 4*F in 30*F weather.
Today it is in the teens and I am measuring almost 8*F diff. (windward side and we have been getting a lot of wind)

So correct me if I am missing the point: You want both stats in synch because they disagree with on another by 1*F. Is that correct?[IMG]file:///C:/DOCUME%7E1/John/LOCALS%7E1/Temp/moz-screenshot-1.png[/IMG][IMG]file:///C:/DOCUME%7E1/John/LOCALS%7E1/Temp/moz-screenshot.png[/IMG]
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