The lines from my outside a/c unit has frost build up, what cause that?

Question

The lines from my outside a/c unit has frost build up, what cause that?

Answer 1

humidity condenses on the cold vapor line and the water freezes. it should be insulated to prevent this. especially in attics as the ice will melt and leak into the drywall. the other line is the liquid line and does not require insulation.

Answer 2

Lack of insulation around your copper.

Answer 3

several things causes the lines to freeze, one is low on freon, another is air filter needs replacing,you will always have one line cold when the unit is running, but not frozen,good luck.

Answer 4

I agree with pomohub vapor line should not frost even with no insulation sweat but no frost. sounds like dirty filter or evaporator coil. Possibly too slow fan speed or overcharge.