Sealed System Sweep Charging

[kdog]

Hi Y'all: Was hoping to gain some insight and opinions on the processes relating to sweep charging opposed to using a vacuum pump. All through my carreer, it has been beaten into my head that although sweep charging can be done, it should not be and therefore using the pump is the correct way. I have done a fair bit of system work (wouldn't say I'm good at it), and fing myself in a position where I may need to do it on a regular basis. The worst part of system work is hauling in/out all the various equipment since it becomes so time consuming (vac pump is NOT light either)

Others I have worked with have spoke of doing this sweep charge as it is much quicker and less trips in and out etc., and though I've not actually ever seen anyone do this, their repairs seem to hold up just as well as mine. I'm thinking that maybe I need to "dumb down" the process to save my old carcass from excessive wear, and maybe save a little time as well.

If any of you feel so inclined, perhaps you could explain this sweep process, and feel free to chime in with any opinions/suggestions related to this. I look forward to any pearls of wisdom that you may giveth.:hankywave:

[denrayr]

give this a read http://tinyurl.com/sweepcharge i do sweep charges unless i suspect contamination in the system. I used to use the vacuum pump every time until a had a chat with my whirlpool rep and he talked me into trying the sweep method.

[kdog]

So once you've completed adding a small charge and running (sweeping) the system, the instructions state "leave the compressor running and charge to factory specs", where is it you are charging, obviously not into the access on the drier(due to high pressure). You must have to also access the low side and charge there, but wouldn't that be fatal to the compressor to blast it with liquid refrigerant while running?

[denrayr]

first you open the high side so the low side can go into a vacuum and purge out the air. next you add a small charge and close the system and let it circulate. next open the high side to dump the charge and let the high side sit open for a minute to make sure everything is purged. close the high side and add the factory charge to the low side as a gas, not a liquid.

[kdog]

But aren't you always supposed to charge R134A as a liquid due to the fact that the cocktail "layers", vapor charging strips the layers (and takes a LONG time)

[KurtiusInterupptus]

kdog, i have found it is possible to charge with liquid on the low side aslong as you introduce it slowly, using your gauges to restrict the flow to a trickle not a compressor- ruining blast.

this doesn't take anywhere near as long as vapor charging and i have never had an issue with compressor damage...

[denrayr]

ive never heard that about 134a, i think you are thinking about the r12 replacement blends such as hot shot and in that case charge as a liquid like kurtius says. i always charge 134a as a vapor with the compressor running, i charged a monogram unit the other day that held i think around 11 ounces and it only took about 2-3 minutes to charge using my digital scale (the best investment ive ever made BTW).

[denrayr]

i forgot to mention they do make a throttling valve that goes in line of the low side hose to prevent slugging while charging as a liquid.

[neurodoc]

This method is approved by the EPA under specific conditions that you can find on the EPA refrigeration site. It is generally used with functional compressors that are capable of drawing some minimal vacuum levels. The EPA is mainly concerned about preventing "unnecessary" (basically anything more than de minimus) purging of refrigerant to the environment. Gone are the days when you just opened a petcock at one end of the compressor and filled refrigerant from the other side. So even if you use those plastic gas bags, you've still got to either recycle the refrigerant back into the same machine you just worked on, or you've got to take it to a reclaimer/recycler.

Real problems arise with contaminated systems: mixed refrigerants, H2O in the system, or the dreaded "burn out." For dead compressors, there's a lightweight and nifty hand pump (Spooter) that was (and I think still is) EPA approved. It may be strong enough to clear contamination and moisture from some systems, but to really dry and clean some systems you'll need a deep vacuum pump.

 

[kdog]

Seems odd that the whole movement to eliminate R-12, and convert to this "safe" R-134A - and now claiming that it cannot be vented. If it is safe, why can't it be vented, and if you are going to capture it all, why change to a different gas? No venting=No danger

[neurodoc]

Good questions, kdog!

But those are the EPA rules.

R12 and other Chlorine containing hyrdocarbon refrigerants (e.g."CFC's") are deemed to be ozone depleting and hence enviromental hazards. R12 is the prototype "bad boy." R22 is considered alsmost as bad, and is subject to a phase out plan. 

Fluorine  is considered less damaging to the ozone layer than chlorine, and flourinated hydrocarbons (HFCs) like R134a are considered "less" ozone depleting. You can syill buy them over the counter without an EPA license in most States, but there is a move to ban even these refrigerants.

The EPA actually prohibits venting HFCs as well as CFCs. They are silent about venting pure hydrocarbon (HC) refrigerents, like isopropane.

Though rarely enforced, the EP can levy huge Draconian penalties on folks who vent refrigerants into the air.

As regards the "safety" of R12 versus R134a, the later is more biologically harmful than the former. R12 has few significant adverse medical effects, aside from the fact that you can be asphyxiated  if you are in an environment where it displaces so much oxygen that you can't get enough oxygen to breathe...

If you breathe R134a it gets absorbed through your lungs, gets into the bloodstream, and is very cardiotoxic. It can promote cardiac arrhythmias, which is why medical personnel are warned not to use epinephrine in cases of R134a exposure and cardiac arrest. But who cares about the life of some poor HVAC tech or other human being exposed to R134a? What is that compared to protecting the world from R12 induced ozone depletion?

I won't even mention the fact that R12, in terms of its thermodynamic and practical mechanical engineering properties is a much better refrigerant than R134a.

[denrayr]

r12 burns a hole in the ozone. r134a doesnt, but it does contribute to greenhouse gas pollution and this is why they make us reclaim it. Im sure a heard of cows produce more greenhouse gas than 134a but those are the rules.

[Alfred]

It's interesting to note that every time the space shuttle lifts off, several hundred thousand pounds of Ammonium perchlorate are released into the atmosphere; each booster contains 1.1 million pounds of propellant.  The government doesn't seem too concerned about this fact.

On sweep charging, we did a similar thing years ago (in the 60's and 70's) with GE compressor and sealed system work with no adverse after effects or call backs.  Per GE instruction, we would open the hi side and run the comp, pumping down the low side.  Then, upon closing the hi side purge valve, a small "sweep charge" of a couple ounces was introduced into the system and circulated for a couple minutes.  Then, this charge was purged thru the hi side valve.  I can't remember if it was done in just one sweep, but GE claimed this procedure to reduce non condensibles (air, water vapor, etc.) to be very effective.  I don't recall any call backs on that compressor fiasco GE had in '87 - '88 and we changed dozens.  We also liquid charged (domestic systems) for years, and with a "lo side can", that is, the compressor is in a can at lo side pressure and the suction port is above the sump so as not to pick up oil or liquid refrigerant, we had no problems.  The exceptions were Whirlpool (and possibly others) who used rotary comps where the suction port was brought right out to the suction line - be careful!

As some of you have said, I still prefer a good two stage pump, and when you think about it, with all you must bring in, (scales or charging cylinder, torch set, tool set, filter-drier, compound gauge set....) the trade off between a cumbersome "reclaim bag" (which, of course must be reclaimed itself :? at some point) and a small vac pump & tank isn't a big deal to me.  Those bags don't last forever and they ain't cheap, either.

Also interesting to note that Whirlpool says you don't even need the gauge set, though I would never work on a sealed system without a gauge set to watch pressures on start-up.

[neurodoc]

[user=20474]Alfred[/user] wrote:

It's interesting to note that every time the space shuttle lifts off, several hundred thousand pounds of Ammonium perchlorate are released into the atmosphere; each booster contains 1.1 million pounds of propellant.  The government doesn't seem too concerned about this fact....

As some of you have said, I still prefer a good two stage pump, and when you think about it, with all you must bring in, (scales or charging cylinder, torch set, tool set, filter-drier, compound gauge set....) the trade off between a cumbersome "reclaim bag" (which, of course must be reclaimed itself :? at some point) and a small vac pump & tank isn't a big deal to me.  Those bags don't last forever and they ain't cheap, either....

Re the space shuttle....Yeah, that and all the tons of "greenhouse" gases released by the tousands of jets that take off from airports across the nation  and throughout the world daily...

Couldn't agree more about reclaim bags. My main complaint about these gas bags is their volume. A good vac pump and reclaim cylinder weigh more but contain a lot of refigerent an a lot less volume.

[kdog]

I am told that the bags are not available anymore and will be using a "spooter" (aka tire pump/transfer pump,armstrong) as well as a storage tank filled with some sort of dessicant to transport discarded refrigerant. The thing about the vac pump is that in addition to being a heavy clod to haul around, there is an added program of maintaining the pump(constant oil changing etc) to keep it functioning optimally. Other considerations are the cost of the pump (NOT cheap) and the room it takes up in the vehicle etc.