initial charging of new A/C system questions
 

Hey Pelicans,

I'm in the beginning phases of installing a complete new A/C system. The only component that will be left from the stock system is the front condensor and blower.

My question is: After I have evacuated the system and done a rate of rise leak test, I would then add the PAG oil, correct? To what side would I add the oil (suction or disharge)? It comes in a pressurized canister using refrigerant as the push gas.
If introduced on the suction side, is there a risk of damaging the compressor with the 6 oz of non compressable liquid when the compressor kicks on for the first time?
If on the discharge side, it will take awhile before it gets back to the compressor. Will the oil thats delivered in the compressor be sufficient to lubricate it until the PAG oil is evenly distributed through the system?
Do I add equal amounts to both?
After adding the oil, do I pull into a vacuum again before adding the initial charge of refrigerant?
I bought a book (Haynes-about worthless) and read dozens of threads both here and elsewhere on the interweb, and I haven't found where this is covered.

Thanks in advance!

I am pretty sure you never add anything - ever - to the discharge side.

The below is me talking and not from much experience. Wait till someone else responds.

I read in the 3.2 factory manual that the oil (mineral oil for r12) should be distributed among the various components. I wonder if this is to reduce a buildup of oil in one area and perhaps cause compressor stress like you are concerned about.

Edit: This web page says the compressor is the only part that needs oil so the manual distribution of oil seems to be to reduce a slug of oil all at once. Perhaps the pressurized PAG container allows the oil to flow in at a metered rate and does not cause a mass of oil to enter the system at one.

See about 1/3 of the page down.

http://www.autoacsystems.com/_faqs/detail/compressor.html

This might help:

http://forums.pelicanparts.com/porsche-911-technical-forum/351496-recharging-c.html

See Jim Sims' post #11. When doing my r134a conversion, I found Jim's advice to be thoughtful, helpful, and accurate. YMMV.

Hope this helps.

Did you buy a new kit with instructions or you gathered new A/C components from experience?

New compressors usually have recommended type and quantity of oil when shipped. If shpped empty, you fill it up with correct type and quantity before installation.

Old systems that lost oil due to leakage can be refilled with the oil that you have by introducing the oil charge on the suction side slowly to keep it from slugging the compressor and damaging it.

I take AC stuff to a pro, along with a 6-pack if I had to put new components in, on a friday afternoon. If they put it on the vacuum overnite they get the beer, and I get an AC system that is bone dry rather than a cursory 1 or 2 hour pump-down.

Ok,

I called the kit vendor and he said using the oil charge on the suction side under a vacuum is fine and won't damage the compressor. They've used this method.

The compressor crankcase came pre-filled with oil, so any additional oil added to the system is to just lube the top end of the compressor. I forgot to ask, but I'm assuming additional oil added to the crankcase would not get distributed through the system. I could be wrong in this assumption though.

The method mentioned by Bob is also correct. A couple of ounces added to each condensor and the evaporator can be done during assembly. This is a viable option as I haven't assemble the system in the car yet. I would just be out the cost of the oil charge that I already bought.

Thoughts?

After I have evacuated the system and done a rate of rise leak test, I would then add the PAG oil, correct?

If the system was R12 beforehand then it has mineral oil in it. You can't
mix mineral oil and PAG. Be aware of what type of oil that is left in any old system components and what type of oil may be in a new or reman'd compress. Use Ester if the system has residual mineral oil. You'll need 5-6 ounces of selected oil in total.


To what side would I add the oil (suction or disharge)? It comes in a pressurized canister using refrigerant as the push gas.
If introduced on the suction side, is there a risk of damaging the compressor with the 6 oz of non compressable liquid when the compressor kicks on for the first time?


"Usually" you wont have a few issues with a few ounces of oil sucked through the low side. The issues arises on the low side with liquids when you try to push
30+ ounces of liquid refrigerant through the low side. This can damage the reed valves and wash the oil out of the compressor. As an alternative you could have
added the oil to the compressor before installing it, and then turn the outer hub several revolutions to help push it into the hoses.
Rule: Charge liquid through the high only, engine and compressor NOT
running.


Will the oil thats delivered in the compressor be sufficient to lubricate it until the PAG oil is evenly distributed through the system?

Yes.


Do I add equal amounts to both?
After adding the oil, do I pull into a vacuum again before adding the initial charge of refrigerant?
You can add the oil before you pull the vacuum or add the oil with an injector after you pull a vacuum. When you pull a vacuum the amount of oil that is pulled out is negligible.

I bought a book (Haynes-about worthless)
Not really. Its just basic. However always fun to read.
Have you tried requesting tech support from your parts supplier?

The compressor crankcase came pre-filled with oil

How much?


, so any additional oil added to the system is to just lube the top end of the compressor.

No. When you are doing a nearly complete R&R of the system you need to refill the system with a "total system amount required". In this case you'll need in total 5 to 6 liquid ounces of oil.

I forgot to ask, but I'm assuming additional oil added to the crankcase would not get distributed through the system. I could be wrong in this assumption though.


All oil added to anything inside the refrigerant circuit gets displaced through out the system .... Homogenization . If you are installing an OEM style York compressor it does have a "crank" but level of oil is usually checked (per York) with a dipstick. If you are installing a Nippon or Sanden style, there is no crank.


The method mentioned by Bob is also correct. A couple of ounces added to each condensor and the evaporator can be done during assembly. This is a viable option as I haven't assemble the system in the car yet. I would just be out the cost of the oil charge that I already bought.

Not necessary to pre-displace the oil into each component (rather tedious) The oil will spread out rather quickly once the refrigerant moves through the system. But if you have fun doing it then go for it.

Thanks for the additional info.

As stated before, this is a complete A/C replacement with the only wetted component being reused is the front condensor, which will be removed, flushed, and reinstalled prior to evacuating. Therefore, there will be no prior refrigerant or oil in the system.

The new system will be utilizing a Sanden 507, not the York. I realize the Sanden does not use a crankshaft like the York does. I was using the term "crankcase" generically to describe the mechanical area below the pistons enclosed in the body of the compressor.

How much oil is already in the compressor? That's a good question. The document that came with the compressor didn't say how much, only that it came with oil in it. I suppose I could drain it, measure it, and put it back in.

I did speak to the vendor, he says to add 5-6 oz of oil as you suggest, so that is what I intend to do.

Thanks again Pelicans!

Josh,

If your compressor already has oil in it you don't need to add more. You could slug the valves and ruin the compressor. 6 to 7 ounces is correct - don't add any more.

After you flush the evaporator and front condenser if you have one, evacuate the system and check for leaks - let it set in a vacuume for at least 2 hours. If no leak is noted, charge the system from the discharge side - liquid side and liquid in.

Again, don't overcharge the system - if you use 12 or 18 ounce cans you will be doing just fine. Once you empty the liquid side can, connect another can on the suction side, turn the engine on and run the compressor.

Start charging with gas on the suction side instead of liquid until you get the correct amount in the system. One thing to note is make sure you have air blowing across the condenser - I use a fan for that.

Check the air temperature - should be around 40 - 50 degrees depending on heat load.

One other thing - if your system was using r-22 then you need to change your expansion valve to r-134a. If you don't you won't get the system to work properly.

SteveKJR

You probably meant R12. R22 is hardly used on mobile air-conditioning.

It would be nice to replace the R12 TXV with R134A, but most retrofits use original R12 TXV and they are compatible with R134A unless they are bad and need replacing.

The benefit of using R134A TXV is that it will have a sensing bulb filled with R134A and will operate properly with designed pressure , temperature and superheat setting just for R134A systems.

The R12 TXV has a sensing bulb filled with R12 which has a different pressure/temperature characteristic compared to R134A.