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HVAC School - For Techs, By Techs

Mar 26, 2024

In this short podcast episode, Bryan talks about when to switch to emergency heat. He talks about coefficient of performance (COP) and how it's a deciding factor when to run emergency heat, which is when a system ONLY runs the backup heat; it doesn't use it as supplementary heat.

When we have a heat pump with backup electric heat, we shouldn't ever rely just on emergency heat; we want the heat pump to run. Electric heat is just designed to supplement the heat pump's heating because it's inefficient. Hybrid or dual-fuel systems can use gas or hydronic fuel-based heat, and they work well on their own (such as if the heat pump is broken). You can't usually run the fuel-based emergency heat at the same time as your heat pump, so it makes sense to run just the emergency heat if it is fuel-based.

The thermal balance point is the point at which the heat pump can no longer keep up with the heating load by itself; the temperature in the space will start to drop, but the heat pump will still produce heat. The thermal balance point can give us a clue about client comfort, not efficiency. COP is a measure of efficiency, and an electric heater has a COP of 1. A heat pump with a COP above 1 saves energy (compared to using just electric heat). COP is the heat delivered in BTUs divided by the energy supplied; it's a ratio.


You can read the "Good COP - Bad COP" tech tip at

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