I'm replacing one dead mini-split system with a different model. The original unit called for a 5/8" suction line, and the replacement specifies a 3/8" suction line.

Will using the existing over-sized suction line with reducers cause a problem?

Thanks!
Paul

Use the proper suction line size for the new unit.

Yep,, you can ,might ,probably , will void the warranty by improper installation

Got it, thanks!