Thermostat location? - InspectionNews

BARRY ADAIR · #1 (**permalink**) 05-21-2007, 08:14 AM

How will this location, within 3' of the thermostat, in relation to the return air affect the equipment function?

Brian E Kelly · #2 (**permalink**) 05-21-2007, 08:18 AM

The thermostat will get a false reading as the air moves across the stat to the return air grill.

Scott Dana · #3 (**permalink**) 05-21-2007, 09:22 AM

Maybe I misunderstood an HVAC technician who is very reputable in this area, but I swear he said to me it was good to have the thermostat "near" one of the return vents. In my house that is the case with both my HVAC systems.

Bob Mayer · #4 (**permalink**) 05-21-2007, 10:04 AM

Quote:

Originally Posted by BARRY ADAIR

How will this location, within 3' of the thermostat, in relation to the return air affect the equipment function?

It should make the temperature reading more representative of the actual air temperature in the house. The thermostat is not sitting in a dead-air pocket.

Quote:

Originally Posted by Brian E Kelly

The thermostat will get a false reading as the air moves across the stat to the return air grill.

Why? There is a misconception that airflow cools objects. This is true if either the object is warmer than the air or if it is moist. If the object is dry, airflow tends to bring the object to air temperature, which, for a thermostat, is a good thing. (Of course, if the air is moving really fast, the object will be heated, think of reentry from outer space.)

Quote:

Originally Posted by Scott Dana

Maybe I misunderstood an HVAC technician who is very reputable in this area, but I swear he said to me it was good to have the thermostat "near" one of the return vents. In my house that is the case with both my HVAC systems.

I would agree.

- BOB

Jim Luttrall · #5 (**permalink**) 05-21-2007, 10:35 AM

Ditto, Bob.

You don't want the SUPPLY air to blow across the stat, but a stat mounted on the wall near a return grill is a good thing.

Bob Mayer · #6 (**permalink**) 05-21-2007, 11:37 AM

Quote:

Originally Posted by Jim Luttrall

Ditto, Bob.

You don't want the SUPPLY air to blow across the stat, but a stat mounted on the wall near a return grill is a good thing.

Right. The temperature of the air going into the return register is (likely) representative of the temperature of the air in the house. The temperature of the air coming out of a supply register is more representative of .. well.. the temperature of the heat exchanger. (Of course there is some temperature drop in the supply ducts.)

- BOB

Brian E Kelly · #7 (**permalink**) 05-21-2007, 12:46 PM

All I can say is when I took the Manual D duct school we were told not to place the thermostat near either the sully and or return air registers as it would possiable give it a false reading. I have never put a stat near either.

Scott Patterson · #8 (**permalink**) 05-21-2007, 12:57 PM

Not a thing wrong with that location, in fact it is a good location. As for a false reading, it is reading the air temp. The air at the return will be more representative of the air in the home, as the air is being pulled to the area from around the home.

Thom Walker · #9 (**permalink**) 05-21-2007, 02:39 PM

I may be nit picking, but I'd be more concrned about the location of the return that close to the access hatch. How was it sealed? Did it have much insulation?

DavidR · #10 (**permalink**) 05-21-2007, 03:27 PM

Returns have almost no effect on room air patterns so I would say it is fine.

James Duffin · #11 (**permalink**) 05-21-2007, 05:46 PM

Some HVAC systems have a return air sensor located in the return air duct. This is used to control a chilled or hot water valve. This type of sysetm works fine so a room stat located near a a ruturn should work as well.

Joseph Rago · #12 (**permalink**) 06-01-2007, 10:45 AM

Perfectly OK in or around the return air location. This location will give a general indication of "mixed air temperature" within the home if air is properly returned from other spaces. (Undercuts, transfer grilles etc.)

Thom Walker · #13 (**permalink**) 06-01-2007, 03:04 PM

So, should the location of the return right next to the attic hatch be of concern?