I live on the second floor of a three story condo buildingin Fairfax, VA. Its about 20 feet from my evaporator/indoor-coil/air-handler Unit to the chase which runs another 20 feet down to the outside condensing Unit. I had a contract to replace my broken 10 Seer Unit but they couldn't use the existing refrigerant tubing (5/16 rather than the 3/8 required. They were going to run all new refrigerant and return tubes but couldn't. They tried to snake down through the existing chase so as to thread a new 3/8 refrigerant line but got stuck between between floors.

Although my downstairs neighbor will allow me access to the chase from her unit, the vendor wouldn't go that route because of liability issues.

I have found a contractor that is willing to attempt to run a new refrigerant line by using my neighbors unit for access but I have some questions concerning the 20 foot run above my ceiling.

Can the 3/8 tubing lie free on the ceiling studs and/or insulation with no clamping except possibly at the ends. The things I'm worried about are 1) is the heat from the refrigerant tube capable of starting a fire 2) are there building codes requiring clamping and 3) vibration problems or potential damage to tubing.

I've been told the free run of refrigerant tubing is not a problem by the contractor wiiling to do the work (and sell me a new heat pump), its not a problem. I'm looking for a second opinion.