The question for all makers of ASHPs is how do you best defrost for the shortest amount of time without taking heat from the conditioned space. Most older traditional HPs would have a relay that would turn on every 30-60 minutes for a set period of time and/or measure the suction temp which should be well above freezing. With forced air HPs, the interior air often got too cold as the heat from indoors was used to defrost the coil, so finding ways to minimize it is important. At least with water heating there is a large source of heat and with a reversing valve, the heat comes from tank which was produced at a good COP. What you do depends on your goal.....if you will be defrosting every 1/2 hour, 5min of straight electricity is a lot of power, 2 steps forward and 1 back.
What is a cxr? I haven't seen that term.
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