Why isn't the hot gas discharge lin on air to air heat pumps insulated

[Cassie]

Haven't been able to get a good answer as to why you wouldn't insulate the vapor line coming off the compressor in heating mode. Most replies just say if it were significant the manufacturers would have done it. But I'm having trouble believing that its energy efficient to blow refrigerated air across two feet of exposed copper (most units have mufflers which act as a pretty good heat sink) for 15 to 20 minutes (typical cycle in heating). If nothing else it would seem that you are clearly desuperheating and maybe even condensing some to bring these components up to temp. What am I missing?

[gtojohn]

Insulating the larger suction line can be good, it would help losses during both heating and cooling modes. If you use you heat pump for cooling I wouldn't insulate the liquid line because during cooling mode you want to lose as much of the compressor's heat as possible to assist in subcooling the refrigerant. If you use it for heat only I would insulate the line set and all piping you can to prevent heat loss.

[marx290]

I would agree with that assessment, Cassie. As long as these machines are designed to be reversible, they will not be optimized very well for either function. From what I've seen of air to air systems, they seem optimized more for cooling than heating, but that's just my view. Anytime I come across a multi-tool, I find it convenient, but rarely as good as a box full of individual tools.

My preference is to focus on the application I desire the most (usually heat), and build from there. I'd prefer to leave the reversing valve BS to Trane and Carrier. If I want AC, I'll build a special system made specifically for that.