"Steve Kraus" wrote in message

The foam rubber insulation on the bigger (cold one) copper line from
the compressor to the house, has deteriorated

Not that it matters in the slightest but the larger cold line is actually
the suction from house to compressor.

Yes. I'm not sure that exposing a couple of feet of suction line will
affect the efficiency so much, but it's normally insulated. Perhaps to keep
it protected from the elements and reduce oxidation.

I can see that inside the house, the reason to insulate may be mostly to
avoid dripping all over the place. Any heat absorbed by that line (inside
the house) just adds to cooling and does not lower efficiency.

Regards,

RichK