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I got my refrigerant re-filled and observed that the pipe going into the compressor gets very cold on the operation of the AC. IF it is getting cold it means that there is a possible heat loss and the compressor has to do extra work in order to extract the heat gained by the refrigerant while passing from the engine area.
My mechanic recommends it otherwise, but it doesn't make sense to me, should I be insulating the pipe to make my air con system more efficient?
I understand your concern, but you will not find a car coming from the manufacturer which has insulation around the piping. If you think about it, though, it makes sense and here are three reasons why you shouldn't worry about it:
Since the system is designed without the insulation, it may actually be detrimental to some of the working parts for it to be colder (may cause freezing of moving parts/evaporator). Engineers have taken all of this into account when designing the AC unit in the first place.
Remember in order for condensation to form on this pipe it only has to meet two conditions: 1) pipe has to be cooler than the dew point; 2) there has to be humidity in the air. These conditions are very easily met in most situations.
Vehicle AC units are work pretty darn well (even with R134a in them) considering what they have to do and the amount and quickness of cooling they have to do. Why mess with success. If you do, you could be introducing dynamics into the system they weren't designed for and you won't being doing much to improve the efficiency (if you improve it at all).
Yes ,You should insulate the piping of any air condition not only on your car but its a general rule that the piping from the compressor be insulated.
This will not only prevent heat loss but this will also improve the life of the pipe itself.
Will also prevent uneven coolant leaks in the future, even if it leaks with a proper insulation, the leak will be easy to locate and mend.
Regarding "asbestos belt" wrapping. Please do not do this. If you value your health, and if you do not want to get asbestosis tumors (mesothelioma) of the lungs, then do not use any asbestos. I started to use conventional foam rubber on my air conditioning pipes, which is also used for hot water pipes, but I realised that because some of the pipes are close to the exhaust manifold, it could start a fire if they fell onto the pipe. I used some non adhesive 0.3mm aluminium roof flashing to insulate the pipes in places. I also used adhesive rubber backed aluminium that is usually used for roofing repairs. I tried getting adhesive cork but it was not available locally. I drove the car for 10km after completing the insulation (at the time of writing it's early summer in Brisbane, Australia, 28 degrees C, 82 degrees F), and the air conditioning worked very well. I stopped at the shopping center for 30 minutes and when I came out the air conditioning came on cold very quickly when I started the car. Previously it was usually hot at first start due to the non-insulated pipes sitting in the hot engine bay. In general, air conditioning is more efficient if the pipes are insulated. I strongly doubt that I will be "freezing" my compressor. The freezing point of R134A is -103 degrees C. If freezing of the compressor was a problem, then it would not be possible to install air conditioning in cars that are in cold climates for part of the year.
In order to know if you want to put insulation on the pipeing, you need to understand
a) the working of the AC (as Paluster2 explained) b) need to know which pipe you are talking about
I believe you are talking about the return pipe from the evaporator to the compressor, because this is the pipe usually left uncovered or un-insulated as you mentioned.
Working of AC:
Keep the picture in mind posted by Paluster2, the compressor has to heat the gas anyway, with high pressure.
Lets say the compressor heats the gas to 250 F and your ambient temperature is 100 F so if you dont put an insulation the gas enters at 100 degree and leaves at 250. With insulation it will enter at, lets say 60 to 80 degree and leave at 250 degree.
So as mentioned already engineers have catered for this and it doesnt help insulating your reverse pipe AT ALL!
I found my car Ac tube is not insulated and it is moving over the engine. It heated up immediately and affected the efficiency of cooling.I wrapped the pipe by asbestos belt.I amazed to found that the car cooling is even much better than before. Earlier the cooling was not appropriate when I drove the car for 25 minutes.the tube comes out from compressor got heated up so much that I couldn't put my hands over it.after insulating the cooling line pipe I drove the car for 3-4 hours. The results are much better. By doing this I increased my car cooling efficiency by 75 %.about 200 mm of pipe coming out from compressor and 100mm at the end side is still uninsulated. I am trying to cover it up and I am sure it will definitely give me almost 100 %. I am unable to understand why the car manufacturer don't think about it. My car is latest version of Maruti Suzuki zen estilo. Whatever I tried I succeeded. Now I am trying to cover it by glass wool and aluminium foil for better efficiency. I have ordered aluminium foil tape online and kept some glass wool blanket for next .I hope it will definitely change my driving pleasure.
You are absolutely right that the compressor is working harder than it has to. Any time the heat is absorbed, the refrigerant expands and makes the compressor work to compress (and evacuate) the refrigerant. EVERY line in the engine bay should be insulated, including to and from the condenser. You also shouldn't worry about anything freezing over, because, almost invariably, there is a temperature switch on the expansion valve that cuts off the compressor if the line gets colder than 32° F. The only reason this isn't done at the factory is because its cheap to leave them uninsulated (materials and labor).
Efficiency is doing better what is already being done.
I insulated the return lines of a 2006 mustang years ago, because they are very long and run in the very hot engine compartment. At one point inches away from the exhaust manifold. I can't tell that the air is colder but the compressor does cycle on and off more frequently and the high side pressure did decrease between 15 to 25 psi. That is a lot in the 102F + South Texas heat.
I insulated the low side (evaporator) lines on both my 1996 Mazda B3000 and 2017 Honda CRV and had a noticeable improvement (decrease in supply air temp.) in both. I used the foam pipe insulation used for insulating home hot water pipes and silver duct tape from where the evap. line exits from the evap. to as close as I could get to the compressor (~3 ft.). Also insulated the drier/receiver in the Mazda with the adhesive aluminum-backed roofing rubber (6 in. wide).
Insulating the cold side makes sense because the warmer the gas in it, the more energy is required to compress it. If the cold side picks up heat from the engine on it's way to the compressor, then the compressor has to work harder to compress it. That is a simple physical principle. There is also no advantage in the warm side also picking up extra heat since it will merely have to be lost for efficient cooling.
My thoughts are to insulate the cold condenser to dryer line, the dryer and the dryer to evaporator line. Nothing else.
Does anyone see an issue with this?
To insulate pipes to condenser? While your at it why not insulate the condenser. . .the pipes throw off heat as does the condenser, insulating the hot pipes is ludicrous, AFAIK.
The cold pipes, the condensation. Humidity is THE key here. The condensate is from water in vapor form being changed to water in liquid form- a phase change. Water in vapor form holds a large amount of energy, known as latent heat, which is puked into the AC as the vapor becomes liquid water. The problem is humid air hitting those cold lines, not just hot, dry air.
All AC works with latent heat [the refrigeration], swamp coolers work with the latent heat of water. High humidity is the enemy of AC and evaporative coolers.
Experiment- 67 Caprice 327 factory AC, T-Bird electric fan[2 speed]. . .I saw all those water drops on the outlet from the evaporator, then I remembered latent heat. . .Hmmm. . .what if all the heat from water vapor is entering the AC system? So I insulated the metal tube from the evaporator [standard pipe insulation, dirt cheap Lowes or Home Depot.] Outlet temps much improved, coolant temps lowered!
Then I insulated the tube from the POA valve on the way to compressor- now the tube into the compressor is very cold!
Temps all around drop again, vent temp at 32.5 degrees! Coolant temp lowered. Car is at 1000 rpm [est] not being driven Ambient air temp 85 degrees.
It's useful to study up on latent heat and phase changes [gas to liquid, liquid to gas]
Entering the twilight zone- I have a 75 Chevy Monza, factory 350, factory air. Drove a couple of miles to HD to pick up the insulation [yesterday]. Noted coolant temp on arrival home- 200. 85 air temp. So I placed of short section [5"] of insulation on the tube from the combo valve [cold pipe]- a trial fit. Left it on overnight.
So a friend went shopping at the same place I went yesterday- same conditions, humidity, temp [85] and so on. . .coolant temp on arrival at home: 170! Thirty degrees cooler than day before [160 thermostat]! The only change made was adding the short piece of insulation! This truly seems impossible. Did the cooling system suddenly improve [Champion alum with factory flex fan]?? or did the temp gauge suddenly go bad, on this particular day? [SunPro gauge, always reliable] I must assume the gauge is accurate. It seems impossible on two different vehicles.
Advice- insulate cold pipes only. If your pipes show condensation [on the metal] it is humid enough for insulation.
