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return line insulation, does it help?

joeynenj on Tue July 01, 2008 1:03 AM User is offline

Year: 2001
Make: subaru
Model: outback
Engine Size: 2.5-4cyl
Refrigerant Type: 134a
Ambient Temp: 80
Country of Origin: United States

hi, i have a general question. Does insulating the return line going back to the compressor in a HOT engine compartment do any good or any harm, or nothing at all when the system is running? Thanx

mk378 on Tue July 01, 2008 9:05 AM User is offline

Theoretically, it helps. The refrigerant gas expands as it warms up. The compressor can't compress as much (mass flow) warm gas because it is less dense.

Also of course any heat picked up in the line will ultimately have to be removed by the condenser.

Not clear whether the effect is enough to actually notice a difference though. Many manufacturers do insulate at least part of the line.

Edited: Tue July 01, 2008 at 9:08 AM by mk378

bearing01 on Tue July 01, 2008 11:16 AM User is offline

A suction tube in the engine bay is fine but it helps to insulate or go with hose when running along near an exhaust manifold. Also because the hose is flexible and the tube will be mounted to the fender while the compressor is mounted on a vibrating engine. FWD cars (transverse mounted engines) have the exhaust next to the firewall so this may not be obvious, but on RWD cars with an exhaust manifold next to the fender and next to the compressor, hoses like to be insulated. Insulation will also help the hoses live a longer life without degrading & leaking in the heat. If the suction line does excessively heat up say from 33'F to 63'F near the exhaust manifold then that extra 30' will heat the compressor crankcase and also appear as a 30'F rise in temperature at the compressor outlet. Hotter compressor head temperature can help degrade seals and reduce oil viscosity. It's also extra superheat that has to be removed by the condenser, as mk378 said.

Edited: Tue July 01, 2008 at 11:17 AM by bearing01

CCWKen on Tue July 01, 2008 7:12 PM User is offlineView users profile

I would check the temperature of the suction line before you insulate it. A warm line helps to finish the job the evaporator is supposed to do--Turn the liquid back to gas. If the line is ice cold, it could mean liquid is still present in the line after the evaporator. If the compressor is fed liquid, you won't be doing it any favors. I'm sure it would help to reduce the temperature at the compressor but you want to make sure it's getting gas and not liquid.

-------------------------
Ken Kopsky

Custom Car Works
"Rules are for the guidance of wise men and the obedience of fools."

mk378 on Tue July 01, 2008 7:25 PM User is offline

That's what the TXV does. It restricts the refrigerant flow until the evaporator outlet is warm enough to ensure that superheated conditions exist at the outlet of the evaporator.

CCWKen on Tue July 01, 2008 8:33 PM User is offlineView users profile

LOL... Of course it does. When it works correctly.

-------------------------
Ken Kopsky

Custom Car Works
"Rules are for the guidance of wise men and the obedience of fools."

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