Can I use the old line set even though the new one is 1/8" larger. don't know if I can get it inside the wall

Question

It will be difficult to get the new line down through the wall. Can I splice the new into the old?

Answer 1

What are you talking about what kind of line set????

Answer 2

You can cut the old line set where it comes out of the wall and solder the new line to it at both the condenser and evap coil.  the smaller line going thru the wall will not cause a big enough pressure drop that would affect the operation.

Answer 3

You run the new line set on the outside of the wall and put a metal line set cover over it to cover the new line set up. You should put foam fill in the cover at the bottom to keep things from crawling up inside it. You want to use the right size that the equipment calls for so that you get the performance out the system. If you short the sizing of the line set you will need to adjust the charge of the system to compensate for the change. This is because the condenser is pre-charged with refrigerant at the factory. You should only check the charge once the house is down to normal room temp with normal humidity levels, then check the pressure and temps of the lines and look the charts to make sure they are where the factory wants them.