Trouble pulling vacuum

[Kaizen]

I installed an LG 32k 3 head minisplit 5 years ago. Zero issues till a few weeks back i got a low refrigerant code on the head unit, I have a sniffer so found the one fitting that had a small leak. Bubble tested and figured i would just retorque it. Minute i moved the fitting it blew. So now i've fixed that fitting and trying to pull a good vacuum and having issues getting below 500microns with a standing test going up to 650. When i did this last time i purged with nitrogen, used the same equipment for a tripple evacuation, and got it down to around 100 microns.
So far i've ....
Verified the vacuum gauge and pump are working correct by pulling down to 50microns in 30 seconds.
Pressure tested the system at 200psi for 2 hours and soaped the joints. passed both.
Purged the system in the low pressure line and pushed the schrader on the high side for a few minutes.
Did a tripple evacuation breaking the vacuum with nitrogen.

Vacuum is a two stage half horse with clean oil. Am i not going to get down to lower numbers due to oil from previous refrigerant? Something I'm missing? I have a valve core removal tool and a CPS vacuum gauge on the low side. The only strange thing I noticed that i had not seen before was a few times when I stopped vacuuming the microns decreased by 20 or 30. Usually is stops and climbs.

 

[pcmeiners]

If it is the same equipment it could easily have developed leaks, even if the equipment was new 5 years ago. Is your micron gauge on the king valve with NO hoses, vacuum pump isolated and disconnected after pumping down to a low micron level?
My experience, first 2 micron gauges I purchased new leaked on arrival. New hoses purchased, on first use hoses were perfect, 6 months later they leaked.

 

[Just_Steve]

Moisture in the oil.

 

[TOWLC]

How long are you letting the pump run?

How long did it sit after breaking the fitting before being fixed? If it sat open to atmosphere for any amount of time, like Steve said, probably moisture in the oil.

 

[Kaizen]

How long are you letting the pump run?

How long did it sit after breaking the fitting before being fixed? If it sat open to atmosphere for any amount of time, like Steve said, probably moisture in the oil.

It took me a few weeks to get the nitrogen. When it snapped I flared it and resecured it the next day. So if moisture in the oil will it come out with vacuum? I thought doing a tripple would remove any moisture. I just did another tripple and on the 2nd one i ran the pump for 45 min down to 650. Its removing air still but taking forever. Do i just run it on the last one for an hour?

 

[Just_Steve]

Let the pump run 24 hours at least. You can't over vac the system.

 

[Kaizen]

If it is the same equipment it could easily have developed leaks, even if the equipment was new 5 years ago. Is your micron gauge on the king valve with NO hoses, vacuum pump isolated and disconnected after pumping down to a low micron level?
My experience, first 2 micron gauges I purchased new leaked on arrival. New hoses purchased, on first use hoses were perfect, 6 months later they leaked.

I have the yellow one.....CPS i think that i put right on the side of the schrader valve removal tool. No hoses. I verified its good by putting it right on the vaccum pump and took it down to below 100microns quickly. I thought about the hoses and put a different one on for the vacuum with the same result. These are yellow jacket hoses so i doubt they are both bad.

 

[Kaizen]

Let the pump run 24 hours at least. You can't over vac the system.

I'm more worried about it catching fire. After an hour even though its fan is running the oil chamber is hot. Can / should I run for an hour or two and then let it cool down or just push it to the max and kill it?

 

[Just_Steve]

Personally I would run it until I get the desired results providing there are no other leaks.

 

[Just_Steve]

Oh and if you have schrader's on both the high and low side I would pull the vac from both at the same time.

 

[TOWLC]

Try closing the king valves and see if it still does it. That will isolate the condenser (where the oil is) and the evaporator and line set. See if that will pull a vacuum.

If it does, then either there's moisture in the oil or you have another leak.

 

[fitter30]

Old pump oil change it. Lg and other manufacturers want 550 lbs for 24 hours. Close all the service valves on condenser pressurized just the head units and soap the valves for leaks. Compressor oil might have refrigerate trapped playing with your readings.

 

[pcmeiners]

I thought doing a tripple would remove any moisture.

Only if all the moisture is out, no trapped gases and the micron gauge holds and varies little with temperature change.

Agree, If you do not let sit for an extended time it will not a slow leak

These are yellow jacket hoses so i doubt they are both bad

All my hoses are Yellow Jacket, so why can they not leak? Trust nothing.

"I'm more worried about it catching fire"
The actual pump side should run hot, it aids in boiling off the moisture in the oil, pump will get warm enough to cause a burn. Also it can take a while to boil off the moisture.

 

[danski0224]

Some units have a specific reclaim and evacuation mode.

If the proper procedure is not followed, there will be closed solenoids and trapped refrigerant or nitrogen.

 

[Kaizen]

Try closing the king valves and see if it still does it. That will isolate the condenser (where the oil is) and the evaporator and line set. See if that will pull a vacuum.

If it does, then either there's moisture in the oil or you have another leak.

Closed the king valves and vacuum is down below 400 presently. Going to keep it going for awhile. Assuming it holds under 500 then what? Just crack one king valve to see if it applies a larger vacuum to the oil ?

 

[Kaizen]

Some units have a specific reclaim and evacuation mode.

If the proper procedure is not followed, there will be closed solenoids and trapped refrigerant or nitrogen.

Great. This one was a failure and not a reclaim. i will have to see if i find anything listed for my unit

 

[Ohmthis]

What kind of hoses are you using? If it’s the “Charging” hoses that came with a manifold/gauge set they are known to “permeate” (**** air through the sides of the hose). I try to only use vacuum rated hoses. To test a vacuum rig, I always pull a vacuum on a recovery tank with the exact set up as I’d use on a system. That will let the pump run longer than 30 seconds and show any issues.