Concerns for 2 a/c service procedures (philippine style :) )

[PatT]

Hello All!
With all due respect to those who practice this, i have always wondered about 2 service procedures that are very common in the philippines. I`m not asking to give you guys a hard time, but to just learn from your knowledge and experience, so that i can improve my method of doing basic a/c evacuation and charging for car at home.

1) Vacuuming the a/c for only 1min to 15 mins (some dont even vacuum anymore) prior to charging freon (and thats with a small vacuum pump only). I`m not a technician of course, but why is it that in other countries like the U.S. they charge for 30mins to 1 hour? And to think the Phil has a very high rate of humidity.. Is it maybe to save on electricity and/or wear and tear on the vacuum pump??

I was concerned with this as i myself use just a cheap surplus refridgerator compressure. I do hook up the manifold gauges (just a cheap kind), but dont entirely trust the little vacuum gauge. One day i plan to locate a more accurate vacuum gauge i can have adapted to the vacuum pump line...

2) Charging liquid freon into the system (tank upside down). I understand that doing this speeds up the charging process, but is risky to the a/c compressor (compressor valves i think).

I myself do it the conventional way, with the right side up (charging system with gaseous freon). I`m guessing people charge liquid freon just to speed things up?? Any help on this topic will be appreciated. Thank You!
patrick

[jick.cejoco]

1. the default vacuum time for robinair RRRR (refrigerant recovery, recycling and recharging) station is at 10 minutes with a vacuum pump that is 6 cfm. you can adjust the time longer or shorter. the longer the vacuum time the better but your vacuum pump and the vacuum pump oil life will be cut shorter. the vacuum pump oil is supposed to be replaced every ten hours of operation cumulative.

a compressor is NOT a vacuum pump. it is not designed to pull deep vacuum of up to 29.92 inHg (inches of mercury). it will leave traces of moisture and will not evacuate the system (the car's refrigeration side of the climate control) of non-condensable gases (nitrogen, oxygen and other gases) that causes higher than normal discharge or high side pressure.


2. charging leeqwid to the system is faster because the refrigerant is more dense (more refrigerant by weight per unit volume of space). if you charge gas, the refrigerant boils and makes the source tank very cold reducing its pressure to push the refrigerant out. this is why there is an electric heater blanket for use around the source tank. you charge liquid into the discharge (high side) service port. before putting the system into service or engaging the compressor to turn with the engine, turn the compressor hub by hand to make sure there is no more liquid above the compressor pistons which will slug or hydraulock the compressor. remember, relatively, liquids can not be compressed.

[PatT]

jick, cejoco-
Thanks so much for your very thorough reply! I just read it now at work, so will have to read it again when i get home to understand it better. But for starters you verified my suspicion of decreased pump life. But change oil every 10 hrs, wow, that critical pala! As for the refrigerator compressor not being a vacuum pump and not pulling a deep enough vacuum, um, i still dont have the budget for a real vacuum pump, thats why i was curious just how much of a vacuum the compressor could pull (hence my desire for an accurate enough gauge). But thinking about it now, my vacuum gauge plan might just be a waste of money, since it will just tell me how "shallow" a vacuum the compressor can pull. I might be better off just having the vacuuming done at a reputable shop until i can get my own a/c vacuum pump.

Thanks also for confirming what i had read about charging gaseous freon into the system. Good to hear from someone locally. By the way, may i know if you do your own a/c maintenance, or do you have a shop? You can send me a pm if you prefer. Thanks Again,
patrick