My Minisplit Install

[jyl]

North side outdoor unit wired. Tomorrow run the NMC through basement, connect to panel, and go borrow my friend’s vacuum pump.

[jyl]

So i’m thinking ahead to the vacuum and open valves part, and I’m confused about something.

Only the gas line valve has a service port, so you pull vacuum on only the gas line.

Why is that? Seems to me both the gas and liquid lines are full of air and the water that is in air. Don’t you want all that air out of both the lines, before you open the valves to release refrigerant into the lines?

[Rawknees'Turbo]

^^^

The liquid and gas lines are on a continuous loop from the service port manifold and through the evaporator - in cooling mode, refrigerant enters the evaporator as liquid and exits as gas (lines change size for that but it is still the "same" line/path). In other words, when you pull a vacuum, nitrogen sweep and nitrogen pressure test from that single port, you are getting all of the liquid and gas lines, and the evaporator core(s).

[jyl]

Originally Posted by Rawknees'Turbo

^^^

The liquid and gas lines are on a continuous loop from the service port manifold and through the evaporator - in cooling mode, refrigerant enters the evaporator as liquid and exits as gas (lines change size for that but it is still the "same" line/path). In other words, when you pull a vacuum, nitrogen sweep and nitrogen pressure test from that single port, you are getting all of the liquid and gas lines, and the evaporator core(s).

Thank you!

I am reconciled to being a monkey following YouTube instructions on most things, but when possible I do appreciate knowing what is going on!

[jyl]

I’m stumped.

I set up the vacuum pump and tried to pull and hold vacuum in the lines. The set up is shown in the photo.



I tighten all the adapter and hose fittings as much as my fingers will, open the blue knob, turn on the pump. Gauge goes to -30 inHg right away. Vapor comes out the pump exhaust, fine, but the vapor never stops coming out which is weird? I run the pump for 15 min, then with the pump still running I close the blue knob, and the gauge immediately goes to zero i.e. the indicated vacuum is instantly lost. I try again, running the pump for 30 min, same result. I check torque on all flares, at the outside unit and at the indoor units. Lube the O-rings in the fittings, retighten them. Try again, same result.

I must be doing something wrong. If there were a big leak, the gauge wouldn’t go to -30 inHg right away - ? If there were a small leak, the gauge wouldn’t go to zero right away - ? Vapor indicates air moisture in the line boiling off, but it should stop eventually - ?

Tried both indoor unit lines, same. Okay, I can’t have screwed up both lines the same way - ?

Am I missing something obvious?

[3rd_gear_Ted]

Try pulling a vacuum on each single isolated unit or line.

[Rawknees'Turbo]

Is the highside/red knob on your manifold set turned all the way clockwise (fully closed)? If not, then that is your leak.

[jyl]

I’m only pulling vacuum on one lineset at a time. Since I have not opened the refrigerant valves, I assume the two lines are isolated from each other.

The red knob was closed . I just closed it with more force and am trying again. I’ve also tightened the adaptor and hose fittings a bit more than max finger tight (visegrip, judiciously).

Could my cheap gauge set be defective/leaky in some way? I don’t want to be the workman who suspects his tools rather than his own lack of qualifications, but if this current attempt yields the same result in both linesets, then . . . I’m running out of ideas.

[Rawknees'Turbo]

Do you have access to a nitrogen rig, even a small one?

When I did my install about 4 years ago, I used nitrogen to test for leaks in all my equipment fittings, adapters, and lineset hoses prior to doing any vacuuming of the copper lines and evaporator - I found at least three leaks at various fittings by putting a little nitrogen pressure in and using soapy water I applied with a small paint brush (had easy access to a nitrogen rig from the airport I work at).

If no nitrogen, you could test your equipment and fittings with air, however that will put air/humidity into the copper lines and evaporator, which is not ideal, but not a terribly big deal as you will pump them out later.

So in short, it is definitely worthwhile to test your equipment at this point.

You can test your gauge set with air, without having them hooked to the service ports, however that will not test the seal at the lowside line and the service port, of course (would need to plug the howside line end fitting, naturally).

[Rawknees'Turbo]

A question - what fitting on the end of your blue hose depresses the shrader valve in the service port, and how do you disconnect it without allowing outside air to enter there when doing so?

Typically you see a hose connection used there that is the quick release style with valve/knob on the end that opens and closes the shrader valve while the hose is still connected.

[jyl]

I did this test - you can see what it was - and it’s not the gaugeset or the vacuum pump hoses, they hold -30 just fine.

Sigh, tmrw I will try to figure out where I messed up. Can I hook my air compressor to the service port and pressurize the system that way? Or should I just redo all the flares? The ones I did were at the outdoor unit when I cut the lines to length, and one flare at the indoor unit end of the liquid line.

[jyl]

Originally Posted by Rawknees'Turbo

A question - what fitting on the end of your blue hose depresses the shrader valve in the service port, and how do you disconnect it without allowing outside air to enter there when doing so?

Typically you see a hose connection used there that is the quick release style with valve/knob on the end that opens and closes the shrader valve while the hose is still connected.

Right now I am just using the adapter that screws on to the service port and has an internal bar that depresses the service port Schraeder valve; the adapter appears to have its own Schraeder valve as well. The blue hose screws onto that adapter and has a bar that depresses the adspter’s Schrader valve.

Hmm, I think what you described came with my vacuum pump/gauge kit. I gazed curiously at it just an hour ago. It doesn’t fit the service port at all though. Or the adapter.

[Rawknees'Turbo]

You will absolutely have to get set up with a hose connection like I described, or whatever vacuum you pull will be lost the moment you unscrew the adapter with the internal nub.

I would not redo flares without testing them first, as you will end up chasing your tail bigtime with that approach.

Air from and air compressor would work for the purpose of soapy water leak testing of your copper line fittings, but there is a risk of pumping who know what into the system (oil, trash from inside the air hose, etc.).

[Rawknees'Turbo]

Is the blue knob in the open or closed position when you've seen the sudden loss of vacuum when you shut the vac pump off?

If it is open, then that is the problem.

Sorry if these are dumbass questions - trying to think of anything I can.

Whoops - just reread you initial post above and you are closing the blue knob, so that's not it.

[Rawknees'Turbo]

About using the quick release fittings - my manifold set with quick release ends is for R134 fittings (I also installed a micron vac gauge on the manifold, using a t-adapter, as that is what the instructions for my Mitsubishi specified), and I found that the service port fittings on the mini split are the same as R12 fittings, so I simply used an R12-to-R134 quick release conversion adapter (that adapter has a rod in it that depresses the service port manifold valve core when the quick release hose end's knob is turned). That worked perfectly (I tested it with both vacuum and pressure before using it in earnest). I hope that jibber jabber makes sense.

[jyl]

Originally Posted by Rawknees'Turbo

About using the quick release fittings - my manifold set with quick release ends is for R134 fittings (I also installed a micron vac gauge on the manifold, using a t-adapter, as that is what the instructions for my Mitsubishi specified), and I found that the service port fittings on the mini split are the same as R12 fittings, so I simply used an R12-to-R134 quick release conversion adapter (that adapter has a rod in it that depresses the service port manifold valve core when the quick release hose end's knob is turned). That worked perfectly (I tested it with both vacuum and pressure before using it in earnest). I hope that jibber jabber makes sense.

Yes, it does, thanks!

Hmm, my gauge set has quick release fittings and came with quick release adapters. Tmrw I will try to figure them out.

I’ve ordered an adapter that is a valve core remover and has a shut off valve too. I think that will let me vacuum the lines more effectively without the core in place, and avoid losing vacuum when disconnecting the vacuum pump hose. And maybe the Schraeder valve adapter I’m using isn’t sealing correctly to the service port . . . kinda grasping at straws here.

I am also getting some “FlareSeal” sets, in case it turns out I just suck at making tight flares.

[billybek]

Are the service valves your gauge lines you are on open to the back seat?
If you take the cap off that valve and turn the stem clockwise, you should get the access port open.
Don’t turn it in clockwise to the stop or it will close to the front seat.

[jyl]

Originally Posted by billybek

Are the service valves your gauge lines you are on open to the back seat?
If you take the cap off that valve and turn the stem clockwise, you should get the access port open.
Don’t turn it in clockwise to the stop or it will close to the front seat.

You mean the cap that says “GAS”? I thought I don’t touch that except to release refrigerant into the lines?

[3rd_gear_Ted]

This scenario is exactly why you get a line set up & gas charge done by those who do it all the time.
Your learning curve will cost you more in the end.

[nocarrier]

Don't pull a vacuum through those gauges. Gauges are notorious for leaking while you are pulling a vacuum.

Also make sure you are using vacuum rated fittings and vacuum rated hose.

What you need is a 5/16 VCRT and a 1/4" vcrt (valve core removal tool), a micron gauge and a vacuum rated hose.

You need to pull a vacuum to below 500 microns. Use the 1/4" vcrt to isolate your micron gauge from pressure when you open the system.

You should actually be doing a nitrogen pressure test and double check with bubbles. Don't use dawn as it's corrosive. In fact right before you do a nitrogen pressure test you can crack the liquid line and let dry nitrogen purge the system first.

After it passes your nitrogen test, then pull your vacuum to below 500 microns and see if it holds for a few minutes.

Then you are pretty much good to go.