Tech Tip: 500 Microns = 500 Microns

So, the other day, a longtime friend of mine called me to discuss an article he had read on pulling good vacuums. Fortunately, the article had been written in an HVAC Magazine I regularly read so I was familiar with the author’s viewpoint. The main subject being questioned was the proper tools for ensuring a good vacuum. My friend wanted to know: Do I need a specific evacuation manifold? Do I need specific vacuum rated hoses? Do I need to be removing all valve cores?

He wanted to know what I thought; knowing my friend well I already knew he used a Micron Gauge and since we are discussing system evacuation, I believe we can all safely give him the benefit of the doubt he is using a vacuum pump. So, the real question came down to are these other tools necessary to ensure a good vacuum on a refrigeration circuit. The following is a summary of our discussion:

If you are using a micron gauge to monitor the level of vacuum being pulled, then the question of using special tools comes down to is the time you save worth the cost of the tools.

A 500-micron vacuum pulled with a standard charging manifold (three hose, not four) and measured with a micron gauge is equal to 500-microns pulled with a specific vacuum manifold tied to your pump, with vacuum rated hoses, and vacuum rated valve core tools having removed the valve cores.

In terms of how low to pull a vacuum, it is irrelevant. How low you pull the vacuum does not matter. Where the vacuum stabilizes is what matters.

If you pull a system to 250-microns and then isolate it, the system then rises and finally stabilizes at 1000-microns … you have a 1000-micron vacuum. On the other hand, if you pull the system down to 400-microns and it stabilizes at 700-microns …. you have a 700-micron vacuum. The latter is the better vacuum for the system.

Too many times technicians get caught up in semantics and ignore actual physics. The level of a vacuum is measured in microns. It does not matter how quickly you get to that micron level.

There are no bonus points for getting the initial vacuum super low. The only thing that matters is once you isolate that system and allow the vacuum to fully stabilize within the system, what is the micron level? That is your vacuum. Everything else is opinion and preference. Now, I’m not chastising anyone for recommending the use of special tools. Many of these tools are a good investment to allow technicians to complete a task properly while also saving time. I applaud people willing to invest in themselves. I encourage practices like double and triple evacuation to help get to that low stabilized vacuum. Sometimes without these practices it would take forever to get a good stable vacuum.

What I do chastise people for is judging others based on your opinion with no substantiating facts. If you prefer a three-hose charging manifold over a four hose, good for you I do too (those four hose manifolds are heavy!)

Put simply: use good tools and make sure they do the job accurately.

There are usually several types of the same tool that will allow for the proper installation or repair. One of the finest HVAC professionals I have ever known is a colleague of mine. He was working with a manufacturer representative on a job site. They needed to test static pressure, so a digital manometer was pulled from my colleague’s tool bag. Well, it just so happened the digital manometer in that tool bag was a single port. The manufacturer began to give my colleague a hard time and lecture him on a dual port digital manometer being the only correct tool for that job.

Now, I believe in a digital manometer. My Fieldpiece SDMN5 dual port digital manometer is one of my most favorite tools and is in my Veto Tech LC tool bag in the back of my truck as I write this. However, my colleague was a skilled HVAC professional and in fact one of the finest I have ever met. He may not have had a dual port, but he sure could take the reading from the supply, take the reading from the return, and then do the math! A 500-micron vacuum equals a 500-micron vacuum. I’m not real concerned how you get there, I just care that you do get there!

Author: Matt Rutland

Matt is our Director of Technical Services and has been with East Coast Metal Distributors since March 2016. He is devoted husband and father to three boys in the Charlotte, NC area. He stumbled into HVAC completely by accident and is now climbing within the industry to be the best he can be.