This Little-Used Thermostat Setting Could Save Your HVAC In A Freeze

With frigid weather firmly settling in throughout the lands, most folks are going above and beyond in their efforts to stay warm. While bundling up in hats, gloves, and other cold-weather wear is a must for many when they're headed out for the day, most would no doubt prefer not to keep so bundled up when they're in the confines of their own home. And if you want to ensure you are cozy and warm inside your house, you'd be wise to check that your HVAC system is primed and ready for the cold. 

But even if you have prepped that heating system ahead of a deep freeze and are ignoring potentially damaging old-school HVAC advice, it is still possible that the frigid temps will test it to the edge of its warming limits. In some cases of prolonged freezing temps, it can even lead to a system malfunction, leaving you to brave the dangerous temps both inside your home and out.

Your system may, however, have a little-used feature that can help you keep the heat on amid a dangerous deep freeze, and you should be able to engage it with a quick trip to your home's thermostat. That feature is called emergency heat, and it is designed to keep the warm air pumping through your vents even if your HVAC unit has failed. It can also be activated manually from your thermostat's settings menu if you're worried about your heating system during a cold snap.   

Before we go any further, we should tell you that not every HVAC system is equipped with emergency heat. In fact, the feature is largely relegated to units that operate using a heat pump, and it has to be turned on and off manually at your thermostat if you opt to use it during a freeze. Likewise, those heat pump systems may instead be equipped with what's called auxiliary heat, which provides a similar function but is designed to kick on automatically and utilize electric coils built into the system when there's insufficient warmth to heat your home or a sudden drop in temperatures outside.

The latter system, of course, also turns off automatically when there's enough exterior heat to draw into your home. It's also meant to function whether or not you are in an emergency weather situation. That is not the case with emergency heat, which, as its name clearly implies, should only be used in the case of an emergency.

Like the auxiliary option, emergency heat utilizes electric heating coils in its operation. Unlike auxiliary, some HVAC professionals recommend that you only use emergency heat when temperatures have dropped below 30 degrees and only if your heat pump has failed. Just in case there's any question, neither system will be functional in a power outage unless you've got them connected to one of the market's top-rated generators. And yes, the fact that both systems require electricity to function means that they are sure to drive up your energy bill when you use them.  

To be clear, neither emergency heat nor auxiliary heat should be viewed as an alternative to your normal heating system. They are, instead, primarily designed as backup measures for heat-pump-driven HVAC systems. To understand why they're so important to those specific systems, you'll need to know a little about how the heat pump actually works. In essence, heat pumps draw in warm air from outside the home and use it to bolster the temperature of the home's interior. And yes, that task becomes increasingly more difficult during extended cold snaps.

Thus, an electrically powered feature like auxiliary heat, which uses electric strips and heating coils inside the home to generate heat, could be vital in preventing heat pump failure. That's because the feature's rapid manufacture of heat is meant to lessen the heat pump's workload in heating your home and potentially keep it from straining its components to the point of failure in the process. It should also kick on automatically if your heat pump freezes up or temporarily turns off to go into defrost mode.

Given those last facts alone, if you were looking to retrofit your HVAC system with either emergency heat or auxiliary heat, it may be preferable to go with the latter option, as the similarly-designed emergency heat is primarily intended to keep your home warm after your heat pump has already failed. Either way, if your HVAC system does utilize a heat pump, you'd be wise to ensure some sort of backup system is functional ahead of extreme cold events.