Watching Those Filters

Supplemental Heat Vs. Emergency Heat

Ever wonder why your heat pump needs supplemental heat or why your thermostat has an "emergency heat" setting? Most heat pumps come equipped with alternative heat sources that make use of these modes. The following explains the difference between the supplemental and emergency heat functions on your heat pump.

Different Names, Same Purpose

Whether it's "supplemental heat," "emergency heat" or "auxiliary heat," the underlying purpose remains the same. These heating modes all rely on the use of your heat pump's alternative heat source whenever it has trouble keeping up with heating demand. Supplemental heat sources are also commonly referred to as "second-stage heat" sources, whereas "first-stage heat" represents the sole use of your heat pump.

Supplemental heat sources usually come in the form of an electric resistance heater installed within the indoor air handler portion of the heat pump system. Despite supplying heat at 100-percent efficiency, it's still not as efficient as your heat pump, which offers an energy efficiency of 200 to 300 percent.

How Supplemental Heat Works

The average heat pump works by extracting latent heat from outdoor air and transferring that heat indoors - essentially the opposite process of how an air conditioner works. At temperatures below 40 degrees Fahrenheit, however, most heat pumps aren't able to extract enough latent heat to keep up with a home's heating demands. This is where the supplemental heat comes in.

Your heat pump's supplemental heat source kicks in whenever the heat pump itself has trouble keeping up with your home's heating needs. This source usually runs in tandem with the heat pump, providing it with a well-needed boost when outdoor temperatures drop to near or below freezing.

Supplemental heat is also used when the heat pump is in defrost mode. This prevents cold air from coming into your home while the heat pump defrosts its outdoor coil.

How Emergency Heat Works

When compared to supplemental heat, the "emergency heat" setting on your heat pump's thermostat works a bit differently. Whereas the supplemental heat function activates automatically and runs in conjunction with your heat pump, the emergency heat setting is a manually-activated function that forces your heating system to run solely on its supplemental heating source. Depending on the type of supplemental heat your home uses, this could prove a very expensive and energy-consuming feat.

The only time you should use the emergency heat setting on your heat pump thermostat is, of course, during an emergency. If the heat pump stops working for any reason, for instance, that would be the time to rely on emergency heat until an HVAC technician can take a look at your heat pump.

Contact a company like Brian's Heat and Air for more information and assistance.