[echochicago]

I have a honeywell RTH7600 thermostat. The inside temperature on the termostat says it is 4 degrees higher than the room actually is. It says it is 78 degrees and it is actually 74 degrees. Is there a way to calibrate the thermostat to show the true temperature?

[hvac1000]

Did you ever think the thermostat was correct and your other device defective OR that it is 78 degrees exactly where the thermostat is mounted. Usually Honeywell thermostats are accurate.

Here is your operating manual so you can check and see if it is adjustable.

http://customer.honeywell.com/techli.../69-2207EF.pdf

OR this one.

http://customer.honeywell.com/techli.../69-2206EF.pdf

[echochicago]

I have 3 other divices giving me a temperature readout. One is a mercury thermometer, and 2 other (expensive) digital thermometers. All 3 read 74 degrees and the thermostat reads 78, I think the honeywell is defective, or I hooked it up wrong.

[hvac1000]

Did you caulk or plug the wall where the wires come through so as to block any air flow?

[echochicago]

Yes, I stuffed it with insulation. I keep thinking that a draft behind the thermostat is influencing the reading, but it is sealed well. Since it runs on batteries, I guess I could kill the power to the furnace; and remove the thermostat from the wall. Put the thermostat and my other thermometers in another room for awhile. If they all read the same, then there is an air infiltration at the wall mount affecting the thermostat. If the thermostat is still different than the other 3 devices, then the thermostat must be faulty.

[echochicago]

I really appreciate you taking the time to help people on this message board, not many people with knowledge do that. Thanks

[echochicago]

I read your profile, and you have an impressive background in HVAC. My father was a sheet metal worker in Chicago, he passed away 30 years ago. When I was younger, I was on the list to go through an apprentice program, by the time I finally got the call I had already started a different career. I have knowledge in pretty much everything... carpentry, plumbing, electrical, concrete, and a little HVAC. I am not afraid to get my hands dirty, and can usually figure out anything. This electronic thermostat has me stumped. I wrote to honeywell, but have not received a response yet. I appreciate your time, believe me. It is freezing in my 2 story home mainly because I am trying to have faith in this thermostat. There is a 4 degree difference from the top floor to the first floor where the thermostat is located. I have damper controls on all the trunk lines, and have opened the top floor fully, and cut the first floor damper to 50%. My theory is I am forcing more air flow to the top floor, and starving the first floor to fool the thermostat into running longer... thus letting the furnace run longer in hopes of heating the top floor more. I also realize I have to keep the entire system in balance so as not to cut in/out flow to the furnace itself. I am not running around closing supply registers in hopes of increasing flow to the ones I leave open, because I know that is improper and will throw effenciency way off. I only closed the supply register closest to the thermostat (5 feet away) because it was too close and would affect accuracy.

[hvac1000]

A 4 degree difference from the first floor to the second floor is not that unusual since many homes have that and even greater temperature differential. I would not worry about the temperature as much as the comfort level. Set it where you feel comfortable or save a few buck up and buy a different one unless the one you have is new then take it back for an exchange.

There is no need to drive yourself nuts over 4 degrees as long as you can be comfortable and if you are going to try and fix the temp spread from the bottom floor to the top floor good luck since heat rises and you will have to throttle down some of the supply air to the first floor.

[echochicago]

Thanks, I agree. This is kind of funny because I have to set my thermostat (on the 1st floor) to 80 degrees to get it to be 76 degrees on the 1st floor and 72 degrees on the 2nd floor... because the thermostat is also off by 4 degrees. Just getting harder to keep focused. But you are absolutey right to tell me to think about comfort and not the actual numbers, because it will have you thinking it is costing you more money because you see 80 on the thermostat. It all comes down to the rate at which the rooms cool off through heat loss and cold infiltration. If the home is tight, with good humidity; it doesn't really matter what number is on the thermostat. The heating system is going to cycle at the same frequencey unless you can improve on heat loss. Thanks for prodding me into thinking about comfort rather than the numbers.

[hvac1000]

Looking at temperatures is like watching the clock when you were a kid in school. It never seemed the clock moved fast enough so the school day would be over sooner.

[echochicago]

Another oddity... my 2nd floor temp is 4 degrees "colder" than the 1st floor. I know heat rises, but I have a 12" x 24" cold air return at the top of the stairs which must be grabbing the warm rising air and sending it back to the furnace; very little warm air makes it to the 2nd floor. I only have 2 returns in the whole house, not the best way to install the ductwork in a home with windows and doors. Supply registers should be under windows and near exterior doors because of heat loss, and returns should be on the opposite walls to pull the circulation across the room. No way to redo all of this, just have to live with it.

[echochicago]

Looking at temperatures is like watching the clock when you were a kid in school. It never seemed the clock moved fast enough so the school day would be over sooner.

LOL... very true.