continues blowing when temp is reached

[kvnjhnsn]

I have a programmable thermostat set to 72 degrees. It shows that the temp in the room is at the programmed 72 degrees but the unit continues to run and occasionally indicates that the emergency heat is on as well. The thermostat is in the living room were I have vaulted ceilings. I noticed that if I turn on the ceiling fan to circulate the heat that the unit will become satisfied and shut off, but this does not work at night when it is cold outside. Last night I introduced a heater to the living room to supplement the heat in the room and it seemed to keep the unit from running all night but this is obviously not an acceptable solution to the problem. Would you have any suggestions as to what could be going on with my unit?

[Scottpat]

Sounds like you might have a bad thermostat, although it could be something else. I would start at the thermostat. An HVAC contractor should be able to run it down fairly quickly.

[Eric B]

You mentioned "emergency heat" which means heat pump. Is it possible that it's too cold outside for the heat pump to maintain the 72 degrees. If so, put the thermostat in emergency heat mode and just run your secondary system.

Scott will be familiar with your current outside temps.

As a general rule, once the outside temp gets down to 30 degrees or so the heat pump begins to have trouble keeping up with the heating requirements thereby causing the secondary (emergency) heat to come on. The secondary system will bring the room temp up to a certain point then shut down and let the heat pump finish the last degree or two of heating - if it can.

Sorry if I told you something that you already knew.

[inspector57]

From what you decribed, it sounds like the unit is running normally... but maybe I missed something.

Eric is right on the mark about the emergency heat.

Just in case...

Check the hole in the wall behind the stat and caulk it up to prevent drafts from tricking the stat.

Don't fret over what the exact temp is when the unit is running or not, concentrate on the results. If you set the stat on 72 and it maintains the temp within 2 degrees, it is doing its job. Some stats will intentionally run the blower longer to scavenge residual heat, some have a little delay or lag built in.

Does the unit maintain the right temp. or does it over shoot and continue to raise the temp. in the room?

Don't forget when the outdoor temp is cold there will be a defrost cycle that will keep the unit running once the cycle has begun in spite of the thermostat setting.

[Jim Katen]

Originally posted by kvnjhnsn

I have a programmable thermostat set to 72 degrees. It shows that the temp in the room is at the programmed 72 degrees but the unit continues to run and occasionally indicates that the emergency heat is on as well. The thermostat is in the living room were I have vaulted ceilings. I noticed that if I turn on the ceiling fan to circulate the heat that the unit will become satisfied and shut off, but this does not work at night when it is cold outside. Last night I introduced a heater to the living room to supplement the heat in the room and it seemed to keep the unit from running all night but this is obviously not an acceptable solution to the problem. Would you have any suggestions as to what could be going on with my unit?

If it's an older style stat with mercury-filled switches, it might not be mounted level. If it's electronic, then I have no idea.

- Jim Katen, Oregon

[Phillip]

If it only does this in the heat mode not the cooling mode, the fan is running until the heat strips cool down.