Thermostat does not stop heat pump unit

if you have it set at 60 F and it is working at 65 to 68 F then that would be about right
as the air is cooled the cold air falls to the floor and out under the door, open window or anywhere else it can escape
the unit has to be at 80% room height so if it is set in a window then when the cold air gets up to the thermostat or ac level in the window then it will stop cooling
So if the ac unit is say 4ft from the floor and the ceiling height is 8 ft then the ac will only cool the bottom 4 ft
cold air does not rise but falls down
if you are using a ceiling fan then the cold air is stirred up and the 65F sounds about right
remember that the setting temp ( what you set it at) is the lowest temp that it will go down to before it stops cooling and if that is not reached it will keep working to attain that temp and if the room is too big, air leaks under door . around the fit in the window , no insulated walls , hot exterior wall,etc then maybe 65 F is the best you will get

Hi Demetrio
Furnaces turn on and off based on what they're told by your thermostat. The thermostat, in turn, will control the furnace based on:

1. The temperature AT the thermostat.
2. What the internal heat sensor thinks the temperature of the air is.

So, if your idea of 68 degrees is what the thermostat thinks is 71 degrees (thermostat reads three degrees high), then when the air by the thermostat gets to about 65 degrees (by your account), it'll think it's 68 degrees and shut the furnace off.

Also, if the thermostat is, say, near a source of local heat, like a lamp, a big piece of electronics, a fireplace, or that place that you habitually set down your coffee, then the air right next to the thermostat may be warmer than the rest of the room, and fool it into thinking it's at it's target.

The sensor is usually inside the housing for the thermostat. If it hasn't been dusted in a while, then it can be hard for air to get inside to affect the sensor, though this would generally cause it to lag on readouts and run the temperature higher than you wanted.

If you have a digital readout, and the system is saying , hey, target is 68, and the readout gets to 66 and the system cuts off the furnace.... my only other guess is that the unit may have features that are trying to prevent overshoot - i.e. by the time the temp at the thermostat actually gets to 68, most of the room is more like 73. That'd depend on your particular thermostat. At that point, you may want to call customer service with the manufacturer and tell them the issue. There may be ways to adjust the unit to get behavior closer to what you seek.

Good Luck!

DH

I assume that you have a heat pump system. If this is the case, the outside temperature is probably lower than the heat pump is sized for and it is using the auxiliary heating system to keep up. The auxiliary heating system usually is an electric coil in the heat pump unit which supplements the heat being produced by the heat pump. This is normal operations and does not indicate a problem with the heat pump, it is just really cold outside. If it is not colder than usual outside, there may be a problem with the heat pump and you should call a heating contractor to check it out.

did you change the batteries ?

You didn't include a model number, so it's hard to know for sure - but I'll take a stab at this one. Many of these t-stats have a programmable offset to reduce "hunting". This can be as little as 1 degree or more than 2 degrees.

This means if you set the offset to 1 degree and the room temperature to about 65 degrees, the furnace will heat the room until the t-stat registers a rising temperature of 66 degrees. The furnace shuts off and will not turn on again until the t-stat registers a falling temperature of 64 degrees. The average is 65 degrees, and prevents the furnace from starting and stopping numerous times instead of just once with the 1 degree offset.

You can further reduce the number of furnace start and stops by increasing the offset to 2 degrees. This would work like this when the t-stat is set to 65 degrees and the room is cool:

Room Temp Furnace
63 On
64 On
65 On
66 On
67 On
68 Off

The room is now warm and heat or furnace is off. The room begins to cool like below:

67 Off
66 Off
65 Off
64 Off
63 Off
62 On

With a 1 degree offset, the room temperature varies +/-1 degree (about 2 degrees total). With a 2 degree offset, the temperature about varies +/ -2 degrees (about 4 degrees total).

Also, when the thermostat shut the heat off, the heat that was made is delivered to the space instead of wasted by sending outdoors - so the room will get a little warmer even though no fuel is being burned. The same holds true at the other end. When the t-stat turn heat on, fuel is burned, but there's little heat until the source has reached the optimum temperature and then the heat is delivered to the space.

I hope this helps & good luck! Pleas rate my reply - thanks!

What type of system do you have, Heat pumps have an AUX setting if that not comming on depending on where you live it may not keep up on its own. A gas furnace should give no trobble check you normal stuff like the filter and it is not on a program and changing over around the time you check it.

Could be under sized unit or fan relay on unit.

You did not make it clear if the thermostat is a programmable unit or not. I am wondering if the thermostat is not set on the correct heat anticipation setting. A heat anticipater is a small heater that helps the thermostat turn off before it over shoots the desired temperature setting. If the thermostat is set for a 5 degree setting, it will turn off at 63 degrees if set at 68. If the anticipater was set at 1 or 2 degrees, it will shut off the heater at 66 or 67. Newer thermostats will only allow the thermostat to cycle 6 times per hour so if you never reach the desired temp, you have to wait 10 minutes before it will allow a call for heat. Check the installation instructions to see if there is a setting where you can get the anticipator temperature closer to your set temp. Good luck.

This is the problem you have when you rely on "modern electronics". Suggest you buy a manual 'stat and just turn down the temp at bedtime. Make it cold and use a blanket, that is what we did in the " good 'ole days".

make sure it is not telling you room temp, some of the Honeywells, will display room temp over desired temp. check that, if it wont let you switch temp than buy a new one, if you dont have a heat pump a new cheap stat is around 20.00.