Capacity loss with line size

Einride

I came across the table below in the Service Manual for Goodman heatpumps. I have a new 5 ton unit awaiting a lineset install. I have a 7/8" set with a 20-25 foot effective run. My reading from the table is that all units from 42000 BTUH and up really need a 1 1/8" suction line to avoid a substantial loss in capacity. Especially mine which--extrapolated out--would have its capacity reduced to 95% with a 7/8" line.

The 36000 BTUH systems fall off the most if a 3/4" line is used.

The spec sheet for my particular unit indicates use of a 7/8" line up to 50' effective run. The installation manual says to definitely add a 7/8" to 1 1/8" adapter at the compressor end, without mentioning the specs.

My system is rated at 16 SEER. I suppose a reduction in capacity might also mean a reduction in SEER to 15, if the same electric power draw applies.

Anyone have any comments on this?

sktn77a

You will get better than a 95% multiplier for the 7/8" vapor line with a 25 foot lineset (the extrapolation is not linear). So your "16" SEER may only be reduced to 15.5 SEER. You're going to have more losses elsewhere in a typical system (coil matching, air handler matching, ductwork, filters, etc). If you can change out the lineset, by all means so so, but I wouldn't lose any sleep over it if you can't.