Evacuating a system after repair

[heatingelement]

I've been doing service work for about a year now. I was taught to evacuate through manifold. Recently I've read on here, guys are using the appion kit and such and avoiding the manifolds. Seen the video that was shared on here somewhere which used the core removals and larger vacuum hose. My question is.. seems like that works on a new install but if you had to remove all refrigerant to do a condenser repair how do you charge the system without introducing air and using the valve core removal tools? Wouldn't air be introduced after removing vacuum hoses to insert cores?

[buttwheat]

after vacuum is completed I break the vacuum with refrigerant to a slight positive pressure then close valve on valve core tool reinstall valve core and your good no air got sucked in.

Click here for video

[heatingelement]

Thanks for the video but to heat. Maybe I'm over looking something simple, but I don't quite understand how you break the vacuum. Evacuate, remove pump hose, connect hose to refrigerant bottle or manifold, then allow refrigerant ? Sorry just having a hard time running this through my head.

[buttwheat]

I use a 4 way manifold set like this:

[heatingelement]

So pull off vacuum hoses, connect manifold to core removal tools and apply the slightly positive pressure to removal told and just crack the hose at thw removal tool to bleed air?

[David Goodman]

Well, lets see.
1) Pull vacuum using vacuum rated VCRT(s) and vacuum hoses without manifold.
2) Close VCRT valve(s) and remove vacuum hose(s).
3) Attach charging hoses with ball valves to manifold (three way is fine), refrigerant tank and VCRT's
4) Purge charging hoses with refrigerant
5) Open VCRT valves and charge system to above atmospheric pressure.
6) Close VCRT valves and ball valves on charging hoses. disconnect charging hoses from VCRT's.
Reinstall schrader valves using VCRT's that are still in place.
7) Reattach charging hoses to VCRT's and purge from ball valve to VCRT valves.
Charge system
8) Complete final balance by closing off tank valve and releasing liquid from charging hose while system is running into suction line, then close charging hose ball valve.
9) Disconnect from system by closing VCRT valve on high side, and release liquid in high pressure hose through manifold into suction line. Close high pressure hose ball valve and remove hose from high side VCRT.
10) Close VCRT valve on low side, and the ball valve on low side hose. Then detach hose from low side VCRT.
11) Remove VCRT's from service ports

You still have refrigerant vapor trapped in the hoses. Consider recovering vapor from the hoses depending hose length. Let's say you had to use a fifty foot charging hose, someone other than me on this forum could tell you how many ounces of vapor is still in the hoses.

No doubt I missed something. So, jump in and fill in any gaps.

[David Goodman]

Whoops! The VCRT's will need to come off between steps #6 and #7. Hoses then connect directly to service ports. I knew I forgot something!

[martyinlincoln]

Simple way is connect your refrigerant tank and a hose to one of the side ports in the vcrt. Leaving the tank valve closed will have the hose in a vacuum. Close the valves on the vcrt's then weigh in some refrigerant to break the vacuum.. Reinsert valve cores, remove vcrt , hook up manifold and weigh in the rest of the charge, after purging hoses of course.

[mrkelly]

The Main 'thing is eliminating the Schrader's.
What you decide to do after this,is up to you.

[heatingelement]

Ahhh ok. I get it. Some reason I was having a hard time putting it together in my head. I want to pick up what I need for this setup. If my pump has 3/8"x 1/4" x 1/2" Male Flare, should I get a 3/8" and 1/2" vacuum hose with the 1/4" fittings or two 1/2" hoses?

[captaincompressor]

Same here. I will put it up to 30 psig or so. Then put the cores in.

[captaincompressor]

Manifolds suck for evac. Your never go back to a manifold again and your customer will get a better job.

[David Goodman]

My thought would be two 1/2" hoses. One with 1/4" X 1/2" fittings, and the other with 1/4" x 3/8" fittings. That way you can have both hoses attached to the vacuum machine with as little restriction as possible.

I ordered two 1/2" hoses from TruTech. Both were 1/4" x 1/2". Based on the pump I also ordered, they switched me to the hoses I described above. I think it was a good call on their part.

Thank you TruTech.

[David Goodman]

Simple way is connect your refrigerant tank and a hose to one of the side ports in the vcrt. Leaving the tank valve closed will have the hose in a vacuum. Close the valves on the vcrt's then weigh in some refrigerant to break the vacuum.. Reinsert valve cores, remove vcrt , hook up manifold and weigh in the rest of the charge, after purging hoses of course.

Oh, I see! Evacuate the charging hose to the tank while you are evacuating the system. Nice! I might try that.

[captaincompressor]

My thought would be two 1/2" hoses. One with 1/4" X 1/2" fittings, and the other with 1/4" x 3/8" fittings. That way you can have both hoses attached to the vacuum machine with as little restriction as possible.

I ordered two 1/2" hoses from TruTech. Both were 1/4" x 1/2". Based on the pump I also ordered, they switched me to the hoses I described above. I think it was a good call on their part.

Thank you TruTech.

Get a set of good core remover tools that are vacuum rated. Get a good micron gauge. Change your vacuum pump oil every job and sometimes a couple times on the same job if the microns quit coming down.

[captaincompressor]

Clean your micron gauge sensor every job

[vhdblood]

I have the Yellowjacket Manifold that has a 3/8" in addition to the three 1/4" ports. Is it still way faster to skip the manifold when vacuuming a system down? I typically put the two 1/4" on the system and pull through the 3/8" line, and I'm pretty happy with how fast I can pull a vac.

[David Goodman]

Think about all the restrictions and sources of turbulence in the manifold. Short radius 90 degree turns, valves are not full-flow ball, 1/4" inlet even if you are using the 3/8" out. I'm certainly not an engineer. For what it's worth I did teach 8th grade math for a year (Ha!). Just intuitively, going through the manifold is like kinking your garden hose.

[truck12]

Seems like overkill for anything residential. I could see if you're evacuating a 20 ton system or something. But even 5 ton residential a 5 cfm pump is done moving air in 10 minutes. The rest of the time it's sitting in a vacuum. How much faster does it need to be...

[David Goodman]

Seems like overkill for anything residential. I could see if you're evacuating a 20 ton system or something. But even 5 ton residential a 5 cfm pump is done moving air in 10 minutes. The rest of the time it's sitting in a vacuum. How much faster does it need to be...

I believe, although I can't prove it, that the time in vacuum to pull down below a satisfactory micron level is also determined in part by these restrictions. Changing the hose configuration during the process takes maybe five minutes. If that reduces the time to pull a proper vacuum by 20 minutes, and you were working on a contract bid, then that 15 minutes saved overall just made you $25 more profit on the job.