Advantage of first stage heat with 2 stage heat pump
Good morning. I have a Trane 4twx8036c1000ea heat pump and TEM6A0C36H31SBA air handler. I was trying to do due diligence in setting my thermostat up for best efficiency to see how it worked. I changed all of the stage change thresholds from comfort to 4.5f and put the heat strips at 9f. So far, since then, my heat pump has rarely been out of stage 1.
I understand this is an energy efficient step to take with cooling, but I was surprised to read that the COP on at least some heat pumps in heat mode is better in second stage than first. Trane is famously reticent with their equipment information if you’re just a lowly customer, so I don’t know if that’s the case with my setup.
I know the biggest thing I can do for energy efficiency is to avoid using the backup heat strips as much as possible, but I’d like to know the pros and cons of first stage vs second in heat. I believe I have read that running longer with lower cfm mixes the air better for a more consistent temperature around the house? I know there is also better air filtration with longer run time. Is there any other advantage? Should I run second stage in heat?
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Replies
Generally compressors operate more efficiently at lower outputs. So for the same amount of heating or cooling, it's more efficient to have long runs at lower output than short runs at higher output.
It's also easier on the equipment, turning on and off is harder on electric motors than running continuously.