No matter what you do the thermostat will not keep the correct temperature in your home. You set it for 72 degrees and an hour later it shuts off at 78 degrees. The next day it shuts off at 65 degrees. You have problem that needs to be resolved. We can help.
If this is an older thermostat (analog) and it has been tracking the indoor temperature correctly for years you should just replace the thermostat. Chances are the heat anticipator in the thermostat is faulty and this is causing the problems. The heat anticipator turns the furnace off just before the thermostat reaches its setting. It uses the amount of electricity the furnace consumes to generator a small amount of heat in the spring assembly in the thermostat. You can reset this anticipator, but if it’s faulty…it is faulty.
If you just changed out the thermostat with a new one and it is doing this you probably installed a 24 volt thermostat instead of a millivolt thermostat. This will work occasionally but will never track the temperature correctly. This thermostat usually doesn’t always the furnace to turn on. Floor and wall furnaces use millivolts (thousandths of a volt) of DC current while forced air furnaces typically use 24 volts AC. They are not compatible.
If this is an older thermostat an you haven’t had this problem before you most likely have millivolt generating or delivery problem. A corroded wire connection or broken wire commonly can cause intermittent action on floor and wall furnaces. The thermostat wire should not be longer than 20 feet. If the wire is longer than this you can experience intermittent problems with the controls. The length of the wire consumes the voltage generated by the pilot assembly and doesn’t always leave enough to pull in the gas valve.
Vent register blowing on the thermostat. This occurs quite often. The vent is opened up and now blows on the thermostat causing the thermostat to heat up too quickly (before the air in the home) and shut the system down. The thermostat will then turns back on rapidly and starts the furnace back up. After performing this for several times the thermostat actually reaches the temperature of the room and the short cycling of the furnace stops. This will wear out a thermostat prematurely.
Skylight or sunshine shining on the thermostat. The thermostat heats up according the level of sunlight touching it. This is radiant heat transfer. The air does not heat up, but the thermostat and the wall behind it heat up independently of the temperature in the home. Thermostats should never be installed where sunlight can shine upon them.
The thermostat installed on an exterior wall. This creates a penetration through the interior surface of the wall. This means that air from in the wall can enter the thermostat affecting the temperature reading. A thermostat on an outside wall is subject to the gaps and penetrations of the insulation. Never install an interior thermostat on an outside wall.
The thermostat installed to close to a window or exterior door that opens up. Windows and doors leak air. Every time the door is opened up to the outside a burst of air from outside can wash over the thermostat causing the thermostat to either turn on or turn off the furnace.
A breeze in the wall heating or cooling the thermostat. This most often occurs after a new system in installed in a house that once had a floor furnace or wall furnace. The bay in the wall where the floor furnace or wall furnace was installed is usually the bay where the electrical to attic and the gas line is installed. It is also a convenient place to put the thermostat. If the penetrations in the floor leading to under the home and the penetrations leading to the attic are not sealed properly a draft up through the wall from the crawl space to the attic can occur depending upon weather conditions. The wall where the thermostat is mounted can become a different temperature than the rest of the home. If the wires leading to the thermostat are not sealed through the wall the draft can actually push into the home right through the thermostat. This can cause radical temperature shifts in the home.
A defective thermostat. Thermostats do break, but bear in mind that blaming your thermostat for your furnace not working properly is like blaming your light switch for the light bulb burning out. Sure, it can happen, but normally it doesn’t happen. The majority of new thermostats that we install, over 90%, are for new or replacement installations to bring older non-compliant forced air heating systems up too current code requirements.
An ignition problem in the furnace. If the furnace fails to ignite occasionally or the burners goes out because a defect the temperatures in the home can vary even though the thermostat is doing its job correctly.
