Do these frost stripes on the heat pump mean anything? I have not observed this before.
There are many reasons for this to happen. Google it.
Looks normal for a heat pump in heat mode, it has a built-in defrost cycle to melt built-up frost. As long as it’s heating and does not ice up entirely, you’re fine.
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Thank you!
It’s low on refrigerant charge.
Defrost sensor does not get cold enough to allow defrost. Eventually it will totally freeze up.
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What was the ambient outdoor temperature and humidity?