Insulating cold a/c lines?
 

I run without the a/c when I can, but here in New Orleans it can get terribly hot in traffic. Would insulating the cold a/c lines inprove a/c efficiency? Why isn't this done from the factory?

CHEGAI -

Welcome to EM! I think insulating the lines would help. I think that you want to insulate the "cold" lines leading from the AC to the cabin, right?!?!?!? Someone smarter than me will chime in.

CarloSW2

Yes it will help some. You can purchase split insulation hose from Home Depot or someplace like that. On a lot of car's the lines are insulated. I think the manufacturers also count on the fact that it's hose, so maybe they figure those sections won't make that much a difference. It probably won't be noticeable, in terms of mileage, but it should also help the level of cool you can get, since you won't be cooling the engine compartment, so much.

What ever you use for insulation make sure that it will be able to withstand hot under hood temps.

Make sure that the hose you are insulating isn't part of the high pressure side or you may be holding heat in, instead of holding cold in, this would put a higher load on your A/C, if the A/C system was designed correctly this should already be the case so it shouldn't matter that they are not insulated.

this is how A/C works in your car:

- The compressor increases the pressure (and temp) of the LP vapor (R-134a).
- It then goes to the condensor (the 'radiator' in front of the coolant radiator) where heat is removed (read temp dropped) until the R-134a condenses (still at or above ambiant temp). it is still at high pressure.
- the high pressure liquid then flows to the evaporator in the cab (usually under the dash or in a compartment in engine bay passenger side against the firewall)).
- in the evaporator, the R-134a aquires the 'latent heat of vaporization' from the ambiant air in the cab. this heat transfer cools the air flowing over the evaporator. this is when the R-134a gets cold (going from liquid to gas).
- the vapor then returns to the compressor.

Insulating the condesner-to-evaporator line will do nothing, as this liquid is warm already. the time spend in the line means that if there is much of a temp difference, the amount of heat transfered will be neglible (meaning you will spend more money on insulation than you save in gas and you will not be able to measure a any temp difference in the cab).

if you want your system to be more efficient, insulate the cab and ensure your system has the proper amount (not too much or too little) R-134a in it. If you converted from R-12 to R-134a, you will need a bigger condenser to get the same cooling since R-12 is much more efficient of a refrigerant than R-134a.

so, save your time/money for an eco-mod that will work

Today someone at the Polish Peugeot-Klub forum posted that he insulated his A/C line. It was a 2 minute job and he reports a slight improvement. I attached his photo, as you can see the A/C line runs between two very hot things: the radiator and the engine.

You missed one critical element of an A/C system: the expansion valve (sometimes just an oriface). This valve is between the condensor and the evaporator and this is where the refridgerant transitions to low pressure and cools off in the process.

Before the expansion valve, you WANT it to dissapate heat, so it is not really helpful to add insulation. The ONLY part of the system that insulation would help is after the expansion valve and before the evaporator. I've seen this already in place on some newer cars, but a lot of manufaturers place the expansion valve so close to the evaporator that insulation is pointless.

Mike

don't forget about condensation, if you do decide to wrap the lines, make sure that water has a place to go.

Yeah, this problem was mentioned on that forum. If the pipe is insulated, then water will still condense on it, but will take much longer to evaporate, and that may lead to corrosion.