I bleed a small amount of refrigerant into the system until I get a positive pressure, then I stop, I remove my micron gauge and cap the port, and then I continue to charge the system.

 

If there are no leaks/moisture and the system passes a standing vacuum test, don't worry about that little bit of air that gets in when you disconnect your vacuum gauge. You can do like timebuilder does also.

A lot of guys use core removal tools like Appion, C&D, etc. to pull the schrader valve out and evacuate through the 1/4" suction port. Their vacuum gauge will be installed on the 1/4" liquid port.

 

The gauge will not be damaged by exposure to positive pressure when releasing the refrigerant, so the best practice is to leave the micron gauge attached until it reaches a positive pressure reading. (See the CPS manual for verification of this: http://www.cpsproducts.com/pdf/Man_VG200_EN.pdf)

You will find the need to clean your sensor regularly to avoid oil contamination. Just follow the procedure in the manual and you will be fine.

 

I read that and it seemed a little bonkers to me. They want you to dump denatured alcohol through the brass port on the bottom with the gauge upside down, gently swirl it around and then dump it out? I'm happy to do that it just seemed odd.

 

What you are doing is very poor service practice.

Pulling the vacuum and testing the vacuum from the same access point should be avoided whenever possible. Ideally the vacuum point and the micron gauge should be far apart - on opposite sides of the system. Of course this is not always possible - but you should be trying to get as close as possible to that ideal situation.

You can use a ball-valve to isolate the micron gauge from the system. That is what I always do.

PHM
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Thanks for the heads up on that. The instructions didn't mention that so I'm glad I asked.

 

x2 I use a ball valve to isolate the micron guage when its time to charge.

 

X3 on the ball valve

 

I leave mine connected while charging 99% of the time. Its rated to handle more pressure than some of my gauges and its been fine in the low side.
Call the manufacturer and see what they say about theirs

 

x2 on Timebuilder. Charge to 5-10 psi then remove all the vacuum pump related equipment.

 

x4 Ball valve

 

Simple, cheap

http://yellowjacket.com/product/ball-valves-for-vacuum-charging/

 

That's hilarious. I have a similar set of these on my manifold gauge and I just ordered that exact one for my vacuum gauge. Thanks!

 

It is best to keep the gauge on its own ball valve away from the pump. The access core will not matter at the gauge but does at the pump ports
It is nice to have alternative port at the pump in between 2 large ball valves then you can move the gauge as needed. To blank off the pump or system
More info

http://hvac-talk.com/vbb/showthread.php?1796121-Some-tips-on-using-a-Vacuum-Pump

 

Use a 4 port manifold with the vacuum gage on the charging port. You can close the vacuum port to get an accurate system vacuum reading.

 

SO TRUE!!

I just got a new JB pump myself and it pulled 25 mic's direct. I was doing a test on all my manifold set's and I got a 500 'average' but none would hold with standard hoses.
A dedicated, simple vac set up with the proper equipment is the way for sure.

Plus most hoses are rated for pressure and not vacuum and will permeate like hell once vacuum is turned off.

 

Ive always used the yellow jacket core removal tool. I could be done in a half hour but most manufactures want at least an hour vac time so i do and lock the valve wait 5 min and boom crack a valve wait till some pressure and remove the sensor. I personnel have a big problem with even a squeak of air in the system, only because you work so hard to keep it then to lose a bit seems discerning. I just purchased a yellow jacket micron guage, its their mid level model with a dis connectable thermister and the digital unit itself. Works amazing and leak free. Strange thing happened last use though. opened up put on system and read 25000 mic ok pump down everything acts normal running ump at 350mic lock out at 450 after 10 min had some stuff to do... but when i removed the guage the mic reading was frozen i was like wtf. I will be triyng to recreate the issue later no mic guages needed here in a bit.

 

Your actually putting the vacuum gauge where it is suppose to be, (on the port where the vacuum is being measured). You (MUST) place the gauge at the port to get a reading of the system your working on. Iif you put the gauge between rubber hoses, or away from the actual lines your trying to read you are literally creating a leak by permeation.

A line set is nothing but a big loop. It's hard for people to understand that because the lines run together but really that's all it is. The evaporator connects the lines at one and and the condenser the other end.

When you evacuate a system you are trying to remove any and all moisture and contaminants in the line set and evaporator on a new install. Remember that the condenser is sealed at the service ports and full of refrigerant, it's the line set and evaporator you are prepping for the refrigerant and the cleaner and drier they are the longer the system will last!

Measure vacuum where your suppose to. (ON THE SYSTEM YOUR VACUUMING) Tell ya boss that measuring vacuum through a non vacuum rated hose is a waste of time and will not allow the system to pull to 250 microns or less as most manufacturers specify. Permeation is the enemy!

Actually, i don't know how even vacuum rated hoses perform or even if they can hold a perfect 250 micron vacuum. Personally do it the way i told you, if you get 250 or less then you are doing good and have no leaks. You will see once you get into that groove. Will be like riding a bicycle!

We all have our ways, find what works and stick with it. Trust me, this way works!