pressure testing mini split wit argon instead of nitrogen
 

Hi from James.
Jeff5May mentioned on a previous post that he has used argon to pressure test and purge mini split lines.
I have an argon cylinder for mig welding but I don't have a micron gauge to check for moisture, best I can do is do a very long vacuum and observe my gauges, then pressure test / purge with argon, check for leaks, and another very long vacuum. Just want to make sure I have as little moisture in the system as possible.
any opinions would be greatly appreciated.
Thanks guys!

I think nitrogen is the preferred gas because it helps to displace the moisture and that it's a dry gas going in that doesn't contaminate anything. Not exactly sure on the mechanics of it or how argon compares when trying to purge contaminants or moisture. If argon works in doing that I'd say your set. Not sure if it does.

Welding Argon will work fine, I've used it - it has the same moisture % as dry nitrogen. You'll need a regulator that will do upwards of 500 psi, though. A welding regulator won't work. As for actually drying/vacuuming the system without a micron gauge...I highly suggest getting one. If not, vacuum it twice as long as you think you need to.

John

It really depends on the weakest link in your rig. If you are purging a mineral oil based system, the residual water will evaporate out if you draw a deep enough vacuum and hold it for a while. With a super-synthetic oil based system (PAG or POE or AB), the oil retains moisture to a certain extent, even under deep vacuum. After vacuum is pulled, some residual moisture will boil out, making the absolute pressure slowly rise.

The only way to tell how your vacuum pump performs (when to change a seal or oil) is with a micron gauge. It's also the way to tell whether your synthetic oil has moisture in it or not. A manifold gauge or the gauge on the vacuum pump (if equipped) is not sensitive enough. By the time the gauge moves off the bottom of its scale, you usually have 5000-10000 microns of pressure in the system. Most mfr's recommend pulling below 1000 microns, some as low as 400.

straight from Yellow Jacket University:
How Will I Know When I've Reached the Right Evacuation Level? - YELLOW JACKET UNIVERSITY

For your heat pump, a deep vacuum and clean oil will keep it going for many years. A $50 micron gauge is cheap insurance. Not having one is a gamble the pros don't bet on.

Hello jeff5may,
The $50 micron gauge - where could I get one of those? The best price I have seen is just under $140 USD including postage to Australia - 'Fieldpiece' brand which you plug a digital multimeter in to - 1 millivolt = 1 micron.
Regards,
James.

Supco VG60 Electronic Vacuum Gauge 50 to 5 000 Micron LED Display | eBay

CPS VG100A Digital Micron Vacuum Gauge HVAC Refrigeration Air Conditioning Tools | eBay

If you just have to have a brand new one, they start around $100.

Hi all,
I now have my high pressure regulator and pressurised the lines and indoor unit (its a new mini split with the charge in the outdoor unit and the service valves are shut) to 200 psi with argon, checked all the flare fittings for leaks with soapy water - no bubbles to be seen. I left the unit sit about 20 hours or so and the pressure has dropped around 10-12psi - is the small pressure drop of any concern?
regards,
James.

It probably got cold overnight. If you had a leak, the pressure definitely would have dropped much more (like 20 PSI per hour). You should be OK to proceed.

Make sure and read the directions with the micron gauge and/or vacuum pump and get everything rigged up right before you relieve pressure. The argon will help blow out air and water vapor in the gauge lines/rig hoses. Don't over-pressurize anything that doesn't want to see it.

Just waiting on my micron gauge to turn up in the mail...

I think everyone who leaves pressure in a lineset all night has seen a pressure drop, due to the cold.
If you had warm weather the next day, it's likely your pressure will come back up to 200 PSI.
(Unless there is a leak). :(