I've owned a place for about a year now and was just having some work done on my heat pump.

I've got a contractor, I really like and trust, though I don't have much history with him. I'd like to run what he's told me past some proffesionals, not so much to get a second opinion as to get a supplement to what he's told me.

Initially he replaced the compressor in the heat exchanger and repaired a leak in the return piping to the compressor.

In doing so he noticed the pressures on the return line were much higher than they should have been. Looking for the source of this problem, he's found two issues.

First, the heat exchanger is too large for the furnace. The heat pump is a Trane HP26-036-7P and the furnace is a CB29M-41-1P which don't match up according to ARI tables in Trane's engineering handbooks.

The other problem is that he doesn't think the installer filled the copper lines with an inert gas when soldering them together and the interior of the pipe is flaking off and plugging up the expansion valve.

He'll be replacing the expansion valve this week and will try to clean out that line.

My question is how poorly will the mis-sized units function together? He says it will do better in cooling than heating? Are we talking 80% efficient or 40% efficient?

Also has anyone else had similar problems with copper lines not being installed right and then plugging up the expansion valve?