Actual Temp 5+ degrees from Thermostat Setting before turning on

[brogers]

Essentially the problem I’m having in my home is that my programmable Honeywell thermostat is set to 67, and the heat does not come on from my Trane unit until the temperature is well below 67 (sometimes it does not come on at all without manual intervention & the actual temp has gotten as low as 55). This problem is intermittent and sometimes works fine for days without this problem occurring.

When I notice that it is getting too cold in the house & it is 5 or more degrees lower than the 67 setting, I manually turn the power to “Off”, wait 30 seconds and turn the power back to “Heat”. If the heat does not come on within 1 minute, I’ll repeat the process & it usually comes on. Sometimes after turning it to “Heat”, I’ll increase the setting to 68 degrees, which usually seems to help (and it makes the “Energy Save” light turn off. I’m not sure the purpose of this light).

I’ve had it serviced & the technician indicated that when he opened up the HVAC unit to evaluate & test it, everything worked fine, but when he arrived he could see that the thermostat was well below the 67 setting. He thought it was likely due to the Limit having some rust on it, and thought it was not a thermostat problem. $200 to replace the Limit (parts, $120; labor, $80) & the problem still exists.

Any thoughts on what could be causing this?

How much should the temperature drop before the unit turns on, 1 or 2 degrees?

[mdossey]

The first question is which Honeywell t-stat do you have? (How old is it) The new Honeywell t-stats operate on a plus or minus 1 degree, while the older stats and most all of the digitals on the market will have a tempature swing of 6-9 degrees. The use averageing to hit the temp setting, thus causing the large swing. In the older days service techs would call that over shooting or under which ever the case.

[t527ed]

sounds like the heater is locking out on a safety, by turning thermostat off annd back on you are resetting it. should call for service, maybe try another company.

[fix_it_dude]

get yourseft a new stat

i-know, i-know, i-know,

it's OK

[chillerout1]

next time it happens go to unit to see if tstat is made or if you are notcomfortable/knowledgable to use a meter make sure that the service tech checks tstat first to isolate problem to unit or stat.If its an old honeywell digital it may be an internal relay on stat.

[beenthere]

As t527ed said, sounds like a problem with the furnace locking out.

Call a service company, before it doesn't reset, and you have to pay that over time in the middle of the night.

[4l530]

Changed batteries in the thermostat lately??

[brogers]

Thanks for the responses.

The Thermostat model is a "Chronotherm III" and is at least 6 years old as I've been in the house that long without changing it. It is a digital model & the batteris are less than 1 year old in it.

Based on your collective responses, it sounds as if the problem could still be with either the Thermostat or the Unit itself. If the Thermostat, any input on how much it should cost to have it replaced w/ a basic unit? If the Unit, I'll suggest to the tech it could be locking out on a safety.

Chillerout1, what do you mean by, "...go to unit to see if tstat is made"?

[sskzekeman]

I would say that the tech took a bad guess and changed parts unnecessarily. You should DEMAND repayment of the $200 dollars. At a minimum, the tech should have opened the thermostat and checked the voltage on the w terminal or gone to the furnace control box and found the w wire there to verify if it was calling for heat. That would have isolated the problem.