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True....but how come the two of us are just speculating...where's CY?

I usually see the pressure controls attached to the body of the compressor. So isolating the compressor is the way to go and the service valves are closed except for service.

Originally Posted by pherman

That would depend on where his pressure control lines were located.

True...but he said it was on a semi-hermetic compressor so I assumed it was on the compressor itself.[/QUOTE]

True... but unless it's a service valve with two ports (which I do see occasionally) I would add one else where. Service valves with one port and a control line attached to them are prone to leak. The packing on the stem is not very reliable left open. Most manufactures will use a two port valve or place one elsewhere.

Originally Posted by VTP99

Why would you pump down the system? Why not just isolate the compressor instead of hoping you can change the control out fast enough. If it's a semi-hermetic it has isolation valves....just wondering.

That would depend on where his pressure control lines were located.[/QUOTE]

True...but he said it was on a semi-hermetic compressor so I assumed it was on the compressor itself.

Why would you pump down the system? Why not just isolate the compressor instead of hoping you can change the control out fast enough. If it's a semi-hermetic it has isolation valves....just wondering.[/QUOTE]

That would depend on where his pressure control lines were located.

[QUOTE=cy;13238761]just changed out a hi/lo pressure switch on a semi-hermetic compressor using this tactic. get everything ready for the switch, then crack system open. plug release port with finger, then quickly switch out fittings.

very little refrigerant lost with zero contamination getting into system because positive pressure was never lost. much less refrigerant lost vs pumping down system.
QUOTE]

CY - Why would you pump down the system? Why not just isolate the compressor instead of hoping you can change the control out fast enough. If it's a semi-hermetic it has isolation valves....just wondering.

1/4 turn ball valves.

Ball valves not service valves ?

Got eh done. Ball valves were at the roof mounted condensing unit. Suction & liquid line, thank you to whoever did the install. Had everything on the roof ready to go. Reclaimed the refrigerant. Used a drill bit I have to cut the tube sheet, it cuts on its side. Makes a clean cut out. Brazed some silfos in the hole. New drier. Nitrogen to pressurize and make sure it holds. Vacuum pump. Used reclaim to get refrigerant back in quickly. 3 hours.

Originally Posted by craig1

thats what I usually do. The total amount of refrigerant released is less than you would release pulling a vacuum on the system.


For example on an evaporator repair:

Close the liquid valve

push in the contactor to pump the system down to 2 PSI

crack open your low side gauge valve to let the residual pressure vent.

braze up the leak, close your gauge valves, set your service valves back to the normal position, start up the system.


Although this is probably not considered "deminimus release" I feel that it falls within the spirit of the law to minimize refrigerant release. On a big system, pulling a vacuum on the whole thing releases alot more refrigerant than venting 2 PSI from a 1/4 hose for 10 minutes.

totally agree .. minimum refrigerant released ... if you are worried about running out. quit pumping with at a bit higher pressure.

just changed out a hi/lo pressure switch on a semi-hermetic compressor using this tactic. get everything ready for the switch, then crack system open. plug release port with finger, then quickly switch out fittings.

very little refrigerant lost with zero contamination getting into system because positive pressure was never lost. much less refrigerant lost vs pumping down system.

an empty 30lb tank of R-22 vapor... contains about 12oz of recoverable refrigerant.

Originally Posted by craig1

thats what I usually do. The total amount of refrigerant released is less than you would release pulling a vacuum on the system.

Although this is probably not considered "deminimus release" I feel that it falls within the spirit of the law to minimize refrigerant release. On a big system, pulling a vacuum on the whole thing releases alot more refrigerant than venting 2 PSI from a 1/4 hose for 10 minutes.

Originally Posted by craig1

no, because the idea is to never let the air in in the first place. the system is under a slightly positive pressure at all times. pinhole leaks don't leak under the slight pressure, so its no different than brazing on an empty system.

Originally Posted by craig1

the heat of brazing breaks the refrigerant down into acid similar to a burnout. Its such a small amount though I personally don't worry about it if the system has properly sized, good condition filters

Kinda seems like a lot of suppositions dressed up to resemble facts here.

Given the choice between hoping I don't get caught for venting refrigerant, hoping I can braze under a positive pressure, hoping the pressure doesn't run out and non condensables are introduced to the system, and hoping the acid created in the system by overheating refrigerant is small enough that the system filter/driers can handle it.....I'll recover the gas and hook up a vacuum pump when the leak is fixed - every time.

Originally Posted by KnewYork

One thing I haven't heard mentioned is the effect of brazing kind of heat does to the chemical composition of the refrigerant. This just my opinion...brazing on a system with refrigerant in it doesn't conform to any standard of best practices.

the heat of brazing breaks the refrigerant down into acid similar to a burnout. Its such a small amount though I personally don't worry about it if the system has properly sized, good condition filters

Originally Posted by craig1

Although this is probably not considered "deminimus release" I feel that it falls within the spirit of the law to minimize refrigerant release. On a big system, pulling a vacuum on the whole thing releases alot more refrigerant than venting 2 PSI from a 1/4 hose for 10 minutes.

I don't think the government cares about the spirit of the law. Intentionally venting is intentionally venting. I also disagree with your supposition that if the system was recovered to the EPA regulations that you would vent more refrigerant to the atmosphere when evacuating.

One thing I haven't heard mentioned is the effect of brazing kind of heat does to the chemical composition of the refrigerant. This just my opinion...brazing on a system with refrigerant in it doesn't conform to any standard of best practices.

Originally Posted by Snapperhead

No vacuum pump ? I've heard of people pushing the air out of the other valve when they release the gas , and close the valve when you think all air is gone ... is this what you do ??

no, because the idea is to never let the air in in the first place. the system is under a slightly positive pressure at all times. pinhole leaks don't leak under the slight pressure, so its no different than brazing on an empty system.

Originally Posted by VTP99

Now if you could continue to vent through another port that might work.

thats what I usually do. The total amount of refrigerant released is less than you would release pulling a vacuum on the system.


For example on an evaporator repair:

Close the liquid valve

push in the contactor to pump the system down to 2 PSI

crack open your low side gauge valve to let the residual pressure vent.

braze up the leak, close your gauge valves, set your service valves back to the normal position, start up the system.


Although this is probably not considered "deminimus release" I feel that it falls within the spirit of the law to minimize refrigerant release. On a big system, pulling a vacuum on the whole thing releases alot more refrigerant than venting 2 PSI from a 1/4 hose for 10 minutes.

Here's the problem I have encounter with any positive pressure in the system. It's trying to get out of your weld through a small pin hole Do you know what I'm talking about ? Now if you could continue to vent through another port that might work.

Am I understanding this correctly? Doing brazing repairs with refrigerant in the system?

Hes talking about isolating the charge and keeping minumum pressure on the side with the leak. Its a good way to change out bad switches or fix valve cores or do minor brazing repairs.

Originally Posted by craig1

You don't need to open the system so you don't need the vacuum pump at all?

If the system has valves and ports in the right locations....
use a recovery machine to pump the condenser into the receiver, stop at about 2 psi. Braze the leak. Open the valves. Top up the system. Hand them a bill.

No vacuum pump needed, and down time of less than an hour.

I've fixed leaky condensers a few times like this, and evaps dozens of times (those are really easy since you can use the compressor to pump down.

No vacuum pump ? I've heard of people pushing the air out of the other valve when they release the gas , and close the valve when you think all air is gone ... is this what you do ??

Quite risky i think personally ....

Originally Posted by craig1

You don't need to open the system so you don't need the vacuum pump at all?

If the system has valves and ports in the right locations....
use a recovery machine to pump the condenser into the receiver, stop at about 2 psi. Braze the leak. Open the valves. Top up the system. Hand them a bill.

No vacuum pump needed, and down time of less than an hour.

I've fixed leaky condensers a few times like this, and evaps dozens of times (those are really easy since you can use the compressor to pump down.

Really?

I don't know that I would agree with this - but obviously it has worked for you in the past.

Originally Posted by Peztoy

Customer has approved repair for wednesday. Said its still at 0*f.

It's a small leak or it's got one big receiver