So far the aircon is cold.It got 4 ticks.I change back to copper as i research info that i MIGHT get an issue after some time later.No charge $$ was made.I was relieve that the contractor who install my aircon also now just is using Aluminium afew months to review himself but he got no idea if it is going to cause a problem.So my opinion is stick to copper as i might not use their service in future for servicing.FYI,M'sia is popular on this YORK brand.