Drawing a vacuum on a mini split?

[the_extremist]

I have a dual zone Mitsubishi Mr Slim on its way to me and plan on doing the install myself. From what I've read on here, it's a very good idea to draw a vacuum on the lines to rid the system of any moisture.

My question is this: do I need a specific kind of vacuum pump and gauges and fittings? They sell a vacuum pump and gauges at my local Harbor Freight but I think they're for automotive A/C systems. Does this make a difference?

Here are the specs on the Harbor Freight stuff:

Vacuum pump:
1/4" SAE and 1/2" Acme intake fitting w/ dual ports for r134a and r12/r22 systems. 1/3hp, 25 micron / 3 pascal rating.

Gauges:
Complete diagnostic & service gauge set for use on a/c systems with r134a freon.Sight glass, quick connect fittings, high pressure safety valves.

The brand on both of these is U.S. General. I'm sure it's just cheap Chinese crap if it's at Harbor Freight, but I'm only gonna be using these things once (hopefully, lol).

Also, do I need a set of gauges or can I just let the pump run for a few hours?

 

[Midnight]

I have a dual zone Mitsubishi Mr Slim on its way to me and plan on doing the install myself. From what I've read on here, it's a very good idea to draw a vacuum on the lines to rid the system of any moisture.

My question is this: do I need a specific kind of vacuum pump and gauges and fittings? They sell a vacuum pump and gauges at my local Harbor Freight but I think they're for automotive A/C systems. Does this make a difference?

Here are the specs on the Harbor Freight stuff:

Vacuum pump:
1/4" SAE and 1/2" Acme intake fitting w/ dual ports for r134a and r12/r22 systems. 1/3hp, 25 micron / 3 pascal rating.

Gauges:
Complete diagnostic & service gauge set for use on a/c systems with r134a freon.Sight glass, quick connect fittings, high pressure safety valves.

The brand on both of these is U.S. General. I'm sure it's just cheap Chinese crap if it's at Harbor Freight, but I'm only gonna be using these things once (hopefully, lol).

Also, do I need a set of gauges or can I just let the pump run for a few hours?

That won't work, the gauge sizes are wrong and are also the wrong kind for the mini slim refrigerant. Same thing with the vacum pump, it's for the wrong type of refrigerant. You need stuff that is for R410a refrigerant. Whatever you do, make damn sure you have someone vacuum the lineset or the compressor will get damaged!
You need something like this;

http://www.amazon.com/Yellow-Jacket-93560-SuperEvac-Vacuum/dp/B0016H12I0

And something like this;
http://www.amazon.com/Yellow-Jacket-49967-Manifold-Gauges/dp/B0015A14R2/ref=pd_bxgy_hi_img_c

 

[the_extremist]

Damn, those things are expensive. Is there a way that I can just take my linesets to an HVAC contractor's shop and have them vac them and put some kind of quick connector on them? Or does it have to be done once the system is installed? I can't exactly have someone come and do it for me, ya dig?

 

[dunkydunk]

I've done DIY installs on two Mr. Slim's, but I got my vacuum pump and manifold set for under $200, I think the brand name was Viot. You'll have to invest a little $$ in the right tools, otherwise you will screw it up and then you'll have to get a qualified tech out to fix your mistakes, and you're right back to the original problem. You'll need a vacuum pump that is designed for refrigeration, the cheap auto stuff from harbor freight isn't strong enough. The manifold gauge set is a must have because not only do you need to see that the pump is pulling vacuum, you need to see that the lines hold vacuuum after the pump is turned off.

In my experience, vacuuming the lineset is the easy part, it's all quite simple once you have the right tools. The electrical side is much more difficult. You have to run some heavy gauge wire into some pretty tight spots, and it's just a knuckle bustin', finger twisting p.i.t.a.

 

[the_extremist]

Well I'm a journeyman electrician so I have that part covered.

Do you have a link for this $200 pump/manifold set?

 

[odium33]

go to your local grow shop and see if they know an trustworthy HVAC guy. hell here in cali id just call any damn guy in the phone book, and let him know im a patient up front, im sure they deal with it all the time. it would be a damn shame to bork a 2000 dollar AC over a pump, so get it done right!

 

[the_extremist]

Not in Cali. I am a legal cardholder in WA state, but not exactly in an herb friendly locale. And I just couldn't sleep at night knowing that some HVAC guy knows where my garden is.

 

[driftersmokinjo]

Well I'm a journeyman electrician so I have that part covered.

Do you have a link for this $200 pump/manifold set?

You can go to your local hvac supply house and buy a cheap set of gauges that will work. As for the vacuum pump You really need a good 1 for that. You may find 1 at a pawn shop. There Is a reason Hvac guys charge what they do. The tools we have to buy and up date cost big bux. if you do buy a vacuum pump make sure it is at least 5 cfm and 2 stage. you want a real deep vacuum. Min of -28psi on your gauge for at least 30 minutes.

 

[driftersmokinjo]

Not in Cali. I am a legal cardholder in WA state, but not exactly in an herb friendly locale. And I just couldn't sleep at night knowing that some HVAC guy knows where my garden is.

Us hvac guys aren't all bad folks But electricians on the other hand. Weeeeeeeeeelll j/k lol

 

[the_extremist]

Okay, I did a bit more research and determined for a fool-proof installation I will have get a decent vacuum pump and a digital vacuum gauge that reads in microns. No problem, I'll get them.

Could any of you guys give me a step-by-step tutorial on the vacuum process?

After installing the indoor units, the linesets, and the condenser unit and terminating all my lineset connections, then what? Hook up the pump? And where do I hook up the micron gauge?

 

[the_extremist]

 

[driftersmokinjo]

Okay, I did a bit more research and determined for a fool-proof installation I will have get a decent vacuum pump and a digital vacuum gauge that reads in microns. No problem, I'll get them.

Could any of you guys give me a step-by-step tutorial on the vacuum process?

After installing the indoor units, the line sets, and the condenser unit and terminating all my line set connections, then what? Hook up the pump? And where do I hook up the micron gauge?

There are brass valves stems like on a car tire but larger on the outdoor unit where the line sets hook to.
You do not need the digital gauge. Just a cheepo will do as long as it is rated for 410a. Not sure about your set up but most line sets come charged with nitrogen. Some units you hook the lines to the indoor part and then evacuate the lines and pull a vacuum down to 28 microns. It will look like -30 on the suction side gauge. then make connections to the outdoor unit and open freon valves. Some unit you make all connections then release nitrogen and vacuum down the line set. make sore you close the valves on your gauge set before stopping vacuum pump. release freon into lines and done. Your unit should come with detailed instructions if not pm me the unit info and I will see if I can help ya out.

 

[the_extremist]

Awesome. The Mr Slim ought to be here by this weekend, not sure if I'll get to install it until next. Thanks a ton for the info, brother.

 

[dunkydunk]

The installer's manual will have a rundown on how to properly install and vacuum the lines. They won't be precharged with anything, they'll just have plastic plugs on the ends to keep dirt out. Most installs recommend a pressure test with bottled nitrogen, I skipped that step and just pulled vacuum and held it for an hour before releasing the r410a. That was the best I could do to proof against leaks.

 

[driftersmokinjo]

The installer's manual will have a rundown on how to properly install and vacuum the lines. They won't be precharged with anything, they'll just have plastic plugs on the ends to keep dirt out. Most installs recommend a pressure test with bottled nitrogen, I skipped that step and just pulled vacuum and held it for an hour before releasing the r410a. That was the best I could do to proof against leaks.

Not the best method of leak checking but it will work. Also when pulling your vacuum when it gets down to about -20 close your manifold and see how far it goes back up. Usually anything past -15 will indicate a leak. Another Thing I do Is listen to the sound of the vacuum pump. When it gets into a deep vacuum all you will hear is the pump motor running.

 

[Lazyman]

Good thread, I'm buying a few 2.5-3 ton units this spring so this is great info to have. thanks to all who have posted, keep em comin!

 

[dunkydunk]

Not the best method of leak checking but it will work. Also when pulling your vacuum when it gets down to about -20 close your manifold and see how far it goes back up. Usually anything past -15 will indicate a leak. Another Thing I do Is listen to the sound of the vacuum pump. When it gets into a deep vacuum all you will hear is the pump motor running.

No doubt, a vacuum test is kind of the opposite of a pressure test, but I didn't want to buy a bottle of N and the regulator to boot. I closed the manifold gauge and killed the pump and the needle didn't move a smidge for an hour.

I bet on simple installs, some HVAC guys skip the pressure test too. It's a gamble, I admit, but I couldn't find the fitting needed to attach the bottle of N through the manifold gauge and I was running out of time. You can't use compressed air, because it would likely contaminate the lines and make the vacuuming more difficult. Plus, you have to get the pressure up to like 400 psi to test for r410a.

It's only 25 feet of line with 4 compression fittings.

 

[the_extremist]

Mr Slim showed up today. A whole pallet full of stuff, damn. Won't be doing the install for a week or two, I'll keep ya'll posted.

 

[Bullfrog44]

I need the same work done in a couple months and I am in the same spot. I am a carpenter/electrician and I can do all the install but this same step. This thread has helped me a lot but was wondering if anybody could recommend somebody in cali that might be able to help? If so, pm me.

 

[dunkydunk]

There are more threads on mini splits than just this one, do a title search on 'mini splits.'

If you can do the wiring, pulling the vacuum is simple as pie, you just have to spend $200 on a pump and manifold gauge set.