This sounds like a common problem that we run into many times during the heating season. It is especially common for people with heat pump systems. A heat pump system typically has two different heat sources, the primary heat and the secondary heat. The primary heat is supplied by the heat pump which is just an air conditioner in reverse gear. The secondary heat is usually electric heat strips similar to the plug in space heaters you find in many retail stores. This type of secondary heat is what is called radiant heat and is very inefficient. You can tell how frequently your system uses radiant heat by how high your electric utility bill gets in the winter.
This secondary heat is sometimes referred to as emergency heat or AUX heat on your thermostat. It usually will have an indicator light or some other indication on touch screen thermostats. It can also be the primary source of heat if the thermostat is manually set to AUX HEAT or EM HEAT. Setting this mode will turn off the heat pump and only use the secondary heat. But this is very expensive so only use this if your heat pump is not working and until the service technician can get it back up and working properly.
In our case, what is happening is that the heat pump is not working and the system is relying only on the secondary heat. With a properly matched thermostat, the internal program recognizes when the heat pump is struggling to heat the house in cold temperatures and initiates the secondary heat to help the heat pump. The program also limits this help to when the actual house temperature is 2 or more degrees below the set temperature. This restriction, which is built into the thermostat program, is why the house will never get all the way up to the set temperature with the malfunctioning heat pump and the thermostat on the normal settings.
The situation does require further investigation as to why the heat pump is not working, but the information provided here is not enough to make a proper diagnosis. That will require someone to put their test equipment on the unit. The home owner can switch the thermostat to AUX HEAT in the meantime and it will keep the house at the set temperature, but it will be very expensive to leave it that way for too long.
So you notice your house is too cold or too hot. You glide over to your thermostat to adjust the temperature and notice it is blank.
As you start to panic, your mind immediately jumps into action and thinks about what to do next. Then the fear sets in. Who can I call? who can I trust? Can I do this myself? Will I end up on NBC’s Dateline?
Well, don’t panic just yet. There are several good reasons the power has gone out to your thermostat and several of them are warning signs of something major. But there are also some very minor reasons as well. Lets start from the easy fixes first and move up to the major fixes.
- A wire has come loose from the thermostat. The thermostat runs off of 24 volts supplied by the furnace or air handler. If the thermostat wire has come loose behind the thermostat, just remove the front panel and inspect the wires in the connections to the back panel.
- Now given that those connections are all good, lets move on to a loose connection at the furnace or air handler. You may see some loose wires or a wire has fallen out of the wire nut at the furnace. That can cut the power to the thermostat since the furnace or air handler supplies the power for the thermostat.
- If those wires are good, then look to see if the power to the furnace has been turned off or a breaker has been tripped. Do not reset a breaker as there is a danger if the system has shorted out. But a light switch can be turned on for furnaces without worry.
- Maybe the switch and/or breakers all look good. Then the next possibility is a bad light switch for furnaces only (not heat pumps) This will require someone with experience to check and replace. But is relatively inexpensive. This point and the next two will require a trained technician and goes beyond the DIY stage.
- By now after all other possibilities have been exhausted, we get to the more serious repairs. Check to see if there is water in the drain pan under the AC coil or air handler. If so, you have a leak in the refrigerant and need it fixed. Topping off with refrigerant only delays the repair that is really needed and in harmful to the environment. This is where you need to call a reputable company with good reviews and highly recommended to come out and determine if it is a leak, where the leak is, and what is required to FIX the leak.
- If it isn’t a leak, then there are so many other possibilities that the technician you called for #5 will be helpful to identify the real reason the screen is blank.
Is the location of your thermostat causing your heating or air conditioning problem? Did you know that the thermostat should be located on a wall away from windows, doors, and direct sunlight? That’s right, away from all those areas that can directly affect the operation and true reading of the average room temperature.
The proper location of the thermostat is on an inner wall, about 5′ off the floor, away from heat sources, and close to the return grill. This will put the thermostat in an area unaffected by spot heat sources and around the correct height for most standing people’s comfort.
Don’t forget to visit our website. We service Raleigh North Carolina, Durham North Carolina, Cary North Carolina, Apex North Carolina, Holly Springs North Carolina, Morrisville North Carolina, Fuquay-Varina North Carolina, and Research Triangle Park.
I’m trying to decide what smart thermostat to get for a new system, and the Nest and the ecobee are the most appealing products I’ve found so far. Most of the problems I’ve read about with Nest systems are in cases where there’s no C wire providing power and so the battery runs down; however, in a new system I can just make sure I do run a C wire so I shouldn’t have any of that type of problem.
So what other considerations should lead me one way or the other?
View Question on Quora
WHOA! Just because you run a C wire doesn’t mean the thermostat is capable of using that C wire. Note that the batteries (if only two) are only about 3 volts. The R/C combo is 24 volts and may fry your thermostat. The function of the thermostat is just to turn on and off a switch at the appropriate temperature. So all the bells and whistles are the sales tools to get you to buy their brand. My recommendation is a good quality programmable thermostat so you can adjust temperature while at work or at night and save a few bucks each month. If you’re a tech gadget kinda guy, like me, then the Nest is pretty cool from a gadget perspective. The main function is no different than the old mercury switches of long ago; It opens and closes a circuit. – Frank Alexander