Best location for the thermostat

[Vector]

I remember when I moved into the house the old thermostat was installed right next to the air handler closet. A FPL(power company) energy survey guy said something to the effect that installers do that out of the ease of installation. Another words rather than running the electrical wiring through the attic at a decent distance or centrally located area(better in his view), they ran it close to the handler for less work and convenience.
So based on this advice, when my old thermostat gave up the ghost I bought a fancy Honeywell programmable one and had the A/C guy run it about 30 feet away from the air handler and not near a overhead vent. Everything has been fine as I really did not notice a difference.

The reason for my inquiry is that this new system that I am having installed apparently requires it's own thermostat, and may actually need a additional wire to be run for it to function properly. The contractor did not say anything about an extra charge to run the wire, but if the existing wires cannot be used, it might be an issue if they cannot snake the new wire/s while pulling the old one(i.e. crawling through the attic).

So does the thermostat placement make a difference as to it's placement, and if so, is it better to be closer or farther away from the air handler?
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[ball a/c]

I have always installed the stat as close to the return air as possible, if there is just one return. My reason is because it reads an average of all the rooms as the air passes through the return.

[bill88]

I have always installed the stat as close to the return air as possible, if there is just one return. My reason is because it reads an average of all the rooms as the air passes through the return.

I would have to agree

[Kevin O'Neill]

I also agree. Away from direct sun and where no supply blows on it and as near as possible to the main return.

[gevans]

Yup.
The original installer placed it "close to the airhandler". If the return is right there at that airhandler, that's the proper location.
Central location (not in a separate room)
over a return
Interior wall (no heat gain/loss false reading)
Out of the sun

[pstu]

Please allow me to ask a question which *might* help the OP, and would help me. Is there conventional advice on thermostats, when a master bedroom has temperatures well different from the part of the house with the thermostat? The thermostat location near the main return sometimes reads 6-9 degrees different from the master bathroom. Any ideas appreciated.

Thank you -- Pstu

[wahoo]

If you have certain areas of your home that you need, or want more precise temperatures, you might want to consider a wireless thermostat. That way you can set it in the area you want to more closely control!! I've found these very helpful for nursuries (sp?) or bedroom areas far from the existing thermostat! Numerous suppliers have added these stats, and most are about the size of a pack of cigerettes, and can set on a dresser, or shelve in the area you want more temp. control of. Just have to replace the batteries about once a year, and install a receiving unit where the old stat was. Pretty simple, and not too expensive. Check it out!

[Vector]

Please allow me to ask a question which *might* help the OP, and would help me. Is there conventional advice on thermostats, when a master bedroom has temperatures well different from the part of the house with the thermostat? The thermostat location near the main return sometimes reads 6-9 degrees different from the master bathroom. Any ideas appreciated.

Thank you -- Pstu

The guy also said that according to local code he must install the thermostat within 5 feet of the air handler.
I don't know if codes have changed or the FPL guy didn't know what he was talking about, but apparently they will need to bring the thermostat closer to the air handler closet.

As to a temperature difference in the house, my are handler is on one side of the house and the bedrooms on the other. I never noticed a need to lower the temperature gauge real low to get the bedrooms colder, but they do not get as cold as the area where the air handler is. I just always assumed this was normal as the cold air has to travel a decent distance to reach the far end of the house.
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[Jack2007]

My house was built in 1988. The mercury thermostat was placed directly below "one" of the returns in a room with one entrance.

The problem was it measured ONLY the temperature of that room. Once the T-stat called for heat, the cold air from the rest of the house immediately sent the T-stat to auxiliary heat bypassing the heat pump.

When my new system was installed, I insisted the T-stat be placed in the center of the house within 8 feet of a second return. My house is much more comfortable AND the new heat pump does the job that was intended.

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[Cold Feet]

The guy also said that according to local code he must install the thermostat within 5 feet of the air handler.

Sounds a bit fishy to me. Ask the guy to cite the specific code clause and then look it up yourself.

[HVAC PE]

I am not aware of any requirement within the Florida Building Code requiring thermostat placement within 5 feet from the AHU. If so, I had better change the way I draw my plans...

[Vector]

You never know, it could be a Miami-Dade county code. They are coming up with all sorts of new restrictions. Not in the best interest of the public mind you, but as a means of generating extra revenue when they fail the job and require a new permit fee to come back out. I know that sounds cynical, but things have gotten pretty bad down here in the last few years.

The good new is that they will run the wire regardless and the price is included.

[HVAC PE]

What if the thermostat is controlling a packaged roof top unit?

I agree - I do not enjoy designing projects in the Miami area... endless review process.