How NOT to Use Your Heat Pump Thermostat
Recently I've learned of two people running their heat pump in a way that costs them a lot of extra money. With heat pumps, there's an extra setting on the thermostat. In addition to heat, cool, and off, there's a setting for emergency heat. You should never put your heat pump in that mode unless your heat pump is not keeping the house warm.
A heat pump, as I wrote before, pulls heat from the outside air (unless you have a ground source heat pump, which pulls heat from the ground or a body of water). As it gets colder outside, your heat pump is able to pull less heat inside. Eventually it can't pull enough to meet the heating load of the house. That's where supplemental heat kicks.
For most heat pumps, the supplemental heat is electric resistance (strip) heat, which is 100% efficient. The heat pump, by that same measure, is 200 to 300 percent efficient, so when you switch your heat pump from heat to emergency, you're going to spend a lot more money to heat your house.
For some reason, a lot of people overlook that the thermostat says 'emergency,' not 'supplemental,' and think that when it gets cold outside they have to switch over to emergency heat. Now, here's the kicker. Evidently they have good reason to think that, because in both of the two cases I've heard about recently, their HVAC tech told them to switch over when it's 'in the thirties' in one case and 'below freezing' in the other.
How are people supposed to learn the correct way to use their thermostat for a heat pump when they're getting such bad advice from the guy who's supposed to know!? If you switch to emergency heat, you're going to pay a lot more, probably hundreds of dollars more, to heat your house.
Another interesting thing about one of these cases is that the owner had just had his electric furnace, which is all strip heat, replaced with a heat pump. He spent thousands of dollars to get a more efficient heating system, and the HVAC installer told him to bypass that extra efficiency and just run it the way his old electric furnace ran.
By the way, electric furnaces have now been banned here with the adoption of our new Georgia energy code. Hooray! Now we just have to teach owners - and installers - on the proper use of heat pumps.
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