Capacitors are very similar to batteries. They get charged up, hold this charge, then release it. The only difference between a capacitor and a battery is the amount of time it takes to charge and discharge. Batteries are slow to charge and slow to discharge. Capacitors charge and discharge nearly instantaneous.
Several other properties are similar too. For example, they wear out over time, they have a shelf life, they lose their power capacity when exposed to extreme heat, and they can fail internally and leak. The one thing that makes them different also makes them dangerous. Since they can discharge in an instant, this means the current and voltage they hold can severely injure or even kill someone who does not know how to handle them.
The quality of a capacitor is dependent on the materials used to manufacture the capacitor. Some materials are better than others. There are capacitors that have 5 year warranties and cost more due to the materials. There are others that are made from cheap less suitable materials and the capacitors can fail within months.
HVAC technicians have a wide variety of choices from their distributors and sometime just go for the cheap brand so they can make lots of profit. Not to mention they get more frequent return visits. Most consumers are not educated on the brands or what to ask their technician. Check with your technician if he/she offers any kind of part warranty for your piece of mind.
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 Freon 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.