Hello - I'm hoping someone can provide some help with my heat pump issue. I'll try to explain it as best as I can.

This past summer we had a new 2-stage SEER 16 Heat Pump installed (not geothermal). We used to have a single zone in our townhouse but we had a second zone upstairs added. It has been working great till we switched over to heating now that the weather has turned colder. The heat pump heats both zones great and seems to be working well overall. The only problem is whenever it kicks on the unit outside is very noisy. It rattles rather loudly
then after a minute or two it quiets down and you really don't hear it running then. I had a contractor look at it and he explained from what I understand that the refrigerant is having to heat up quickly to get the heat pump running and that is very common. What's puzzling to me is since our heat pump is running fairly often with the cold weather I would think the refrigerant would keep warm and not have to heat up per se each time therefore causing the rattle. I had him check the unit's balance and that is fine too.

Can anyone give some feedback on this? Is this common? Can it be quieted? Any help would be greatly appreciated.