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

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?

^^^

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!

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.

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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?

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

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

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.

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).

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.

http://forums.pelicanparts.com/uploa...1751081441.jpg

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.

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.

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.).

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.

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.

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?

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.

Thanks everyone.

Status: picked up nitrogen tank from a welding supply place, on Monday when the HVAC supply place is open I’ll pick up the VCRT and other stuff, and proceed.

Yeah I’m spending money on HVAC tools and the DIY floundering is funny (not so much to me, but to others!) . . . but I have multiple more minisplits to install in the coming year, so it’s worth learning.

Honestly it's worth learning on just the one install. The rare time I have a professional do something I don't know how to do, it always cost 5x the quote and the job is done poorly.

I got lucky with a simple recharge of my Sub Zero for $28 all in. I am guessing a pro would have been $300 to $500 and they would have insisted on putting in a new compressor for $1500. That's just the nature of things these days.

The total spend on tools might be a grand, if that. Around here, what would it cost to have an HVAC company install four indoor and two outdoor units and run lines to second story and through closets with electric across the basement? I suspect the bids would be five figures in labor alone.

On the subject of tool investment......I'm learning how to repair motorcycle fairings (mostly ABS) right now and am not hesitating to buy whatever tools and materials are needed to do the work.

We're not talking big money here and considering how many fairings I have and the % that need at least some degree of repair makes it a no-brainer as an investment.

I also purchased a vacuum pump a while back and have already used it for my truck's AC and at some point will also be installing a mini-split too and will have it for that.

Brake tubing flare tools - yep. For my cars' brake lines.

Tire change tools and equipment - check. For my motorcycles

Etc etc.....whatever is needed to stay as independent as possible.

Yes. Those ones.
Those valves have two seats. Turn the stem fully in and it will tighten down on the “front seat”. All the way counter clockwise it will close off your access port on the back seat.

Is that unit pre-charged?
If so, don’t do what I had suggested.
If it is pre charged the valve should be on the front seat and the back access port should be open for you to access the line set side of the system.
Is there a shrader valve core in the access fitting? Does the blue hose have a shrader depressor in the female end?

Yes, unit pre-charged.

There is a Schraeder valve in the access port, and a Schraeder depressor in the hose end. I an going to remove the core though.

Update: hooked up the nitrogen tank to the service port, crack the valve, what’s that hissing?! The adapter (between hose and port) leaks at the port, more than a teeny bit, and tightening doesn’t help. This adapter came with the uber cheap pump and gauges set. Maybe it’s just a crappy freebie thing. Anyway, offered a set of adapters and we’ll see.

It was that crappy 1/4” to 5/16” adapter. That 10 cent part has cost me a lot of trouble. New adapter, pressurized to 200 psi nitrogen, seems to be holding, will check in the morning. EDIT: next morning, still 200 psi. Then pull vacuum and release refrigerant, repeat for the other lines, hoping no issues.

Sounds like you have it figured out . Good luck with the rest of the job .

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All the lines held pressure and pulled vacuum just fine. Bringing them online now.

Next to get lineset covers made and installed.

Oops, I was rudely reminded of something I’d forgotten. The outdoor units come pre-charged with enough refrigerant for 33 feet of line total. I have more line than that connected to each outdoor unit. So I’d originally figured I’d install then get someone to add more refrigerant. Then I forgot about that part. When the indoor units threw up an “H3” error code after a couple hours of operation, and I looked up what that code is, I was reminded.

Oh well, time to call an HVAC guy to do that.

Nice install!

Heads up for something to check when installing a mini-split!!! I'm helping my neighbor install one in his garage this last week. We got the condenser installed outside, the evaporator installed inside, all the electrical connections made and then went to install the copper lines and ran into a huge problem! I guess the supply houses stock compressors and evaporators separately and then ship out as a set. Well both the LG units are 2 ton but they're not the correct matched set. The condenser has 1/2" and 1/4" lines but the evaporator has 5/8" and 3/8" lines. Didn't even occur to me check it or even look at the connections.

And why would you ever think to check that? Totally seller’s screwup, they should ship out replacements ASAP.

Well, update on my minisplit install.

I installed two systems, each 18K BTU outdoor unit connected to two 9K indoor units. Took a considerable time to run the lines through closets and so on. Pressure tested with nitrogen to 200 psi, pulled 500 micron vacuum in lines, had a problem traced to a faulty 1/4” to 5/8” adapter, after I replaced that all looked good. Had HVAC service come add more R32 for the extra long lines. Tech liked my install.

One system, on south side of house, worked fine and has continued to work fine.

Other system, on north side of house, lost all its refrigerant in a few days. WTF. Got more nitrogen, pressure tested that system, found a flare connection (liquid line at outdoor unit) that was teetering on bad - actually the flare ripped off when I tried to re-torque it. Re-made the flare, this time using a FlareSeal, pressure tested to 400 psi for two days, looks good.

So now I need to vacuum out that entire system - all the refrigerant oil and humidity and so on. Disconnect the hose to nitrogen tank and a cloud of oil sprays out. Connected my $100 El-Cheapo Vevor vacuum pump and my Kinda-Cheapo Hilmor micro gauge. They both decide to fail. Replace oil in pump, clean gauge sensor with isopropyl alcohol, no help. Order a new vacuum pump, a Fieldpiece this time. Make a warranty claim with Hilmor, they say they are shipping me a new gauge, but I order a BluVac gauge anyway.

The tool budget is by now over $1,500 and I wait for the new gear to arrive. In the meantime I repeatedly pressurize each line - by now I also own a nitrogen tank and regulator - and flip open the valve core removal tool’s valve to blow out more oil.

The stuff arrives. Ooo, I feel so pro with this nice kit. I close the service valve to isolate the lines. Pressure test them and blow out oil again. Open service valves, pressurize the whole system, blow oil out again. Close service valves. Hook up vacuum pump and micron gauge to lineset A, pull out down to 350 microns, leave it overnight, next morning reads 650 microns but it’s stable there, not rising. I do the same for lineset B. Okay, I’m sort of satisfied the linesets are tight and mostly purged. Now I open all service valves, and start vacuuming down the entire system.

This takes way longer - like 45 minutes to get to 500 microns. I’ve changed the oil in the Fieldpiece once by now. I close off the VCRT and switch off the pump. I’ll see where the vacuum stabilizes, hopefully it does. Later today I’ll re-insert the valve cores and vacuum down again, planning to get to 350 ish microns, then see if overnight it holds at least 500 microns.

Assuming that works (oh please) then I’ll get my EPA 608 and buy a tank of R32 and learn how to load refrigerant back into the system. I haven’t checked how much I should need but will buy a 20 lb tank.

This is taking forever. I’m spending $ on tools. But I think my HVAC service would charge four figures to do this - they charged me $1,200 to replace capacitor and add R410 to the central AC compressor last month, and were only here for an hour. I have a few more minisplits to install in another building, and I figure I should devote some time and money to at least try to learn how to do this myself. Architect got an HVAC company estimate for those, over $40,000 - no way am I spending that, I know the equipment will cost less than $8,000.

In the meantime, the south side system has been doing a decent job of keeping the second floor bedrooms cool all by itself - set it at 70F in the two bedrooms it is installed in, and use a fan to circulate cool air to the bedrooms that the non-working north side system is not cooling.

So even though we’ve had a couple short heat waves during all of this, the minisplits have been proving their worth even with all the problems.

Meanwhile the copper lineset covers have been fabricated and are sitting under a tarp in the backyard, waiting for me to get back on the ladder. Man oh man, 16 oz copper has jumped in price - a 4’ x 10’ sheet went from $260 to $400 in the past month, so the cost of these covers was $2,300 when I had planned more like $1,600. I have 80 feet of copper covers, need to cut and miter and screw to siding, then use my nibbler to cut the excess half sheet into strips to cover the seams. Spendy but I do not want plastic lineset covers on my house.

I haven’t spent the whole month doing this - life has gotten in the way, I’ve been out of town, maybe two days devoted to minisplit install in the last 30.

First of all you are dealing with the wrong HVAC company. Whatever it takes, find an owner/operator that does nothing but service and vet him carefully.

Secondly, see first sentence. I have all the gear too, but I know when to hold and when to fold.

That’s because you’re a pro. Duffers like me have no idea, we just keep going until failure and defeat. Or until the wife gets mad. And she’s been away this past month.

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I’m putting the micron gauge as far from the vacuum point as I can. I should really buy actual vacuum hoses.

I’m starting to think at this point you are as knowledgeable as the HVAC guys you would have hired. Good luck with the refrigerant install.

As you probably know by now, there are plenty of YouTube videos, showing how to test and replace an AC capacitor.

You'd be surprised at how much technical know-how is involved today as opposed to the R12 days. The lead guy at the HVAC company that I recommend to others when they ask has been back to "school" a couple of times in the last 5 years.

Of course we are talking the refrigerant here, not the scope of all the things inherent with HVAC. Just the electronics troubleshooting is quite a process. My 2016 unit flashes codes when it wants some help much like an engine light on a car.

Yeah, there is no reason to pay hundreds for a capacitor that HD has in stock. Buy 2 when you go. They used to be 35 bucks but I haven't had the pleasure in awhile now.

I am not sure how long this is supposed to take. My vacuum pump takes the system down to 1000 microns fairly quickly, then progress slows and it c-r-a-w-l-s down to 500 and below. From atmospheric to 500 for the whole system might take 30 minutes. Hopefully that is normal-ish.