# Thread: FIGURE OUT the Microns

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## FIGURE OUT the Microns

I am trying to grasp how much moisture is in the system so I can determine where I think its coming from either Materials or oil or water Basically so i can convince myself that its OK to stop pulling the vacuum.

"When they say"... 1 micron is 25,400 of an inch in the water column is that a literate measurement
of what is in the system??? ( no clue)

Hypothetically, If I am pulling 1100 mics for days and I know that when I reach 1000 basically all moisture is gone, I would be safe to assume that 100 mics of moisture is in material, right?
Sooo, how much is 100 mics of moisture 1 teaspoon, 1 spec of water/oil?

2. I don't know the answer to your question although I'm pretty sure there isn't really an answer.
If it's taking that long to pull down I can only think of three reasons. Either it's seriously wet and you're removing a lot of water and in that case you should know because you're changing your vacuum pump oil over and over and over and it's milky or your vacuum pump and/or micron gauge is shot or maybe you've got a leak.

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3. A micron is a measurement of air pressure (very, very, very tiny amount of air pressure). It's not a measurement of moisture.

If you stop pulling a vacuum at say 1,000 microns and it starts rising and stalls, there's a good chance there's still moisture in the system. If it rises and keeps rising to atmospheric pressure, there's a leak.

4. I was in the middle of a conversation about microns a while back.

If you cannot pull under 1000:

1. You are pulling through your manifold and it leaks.

2. There is a leak in the system

3. There is moisture in the system.

Imagine a 1/4" clear glass tube with a bend, like a "J". The bottom of the "J" is full of water. If you apply a bit of pressure to the short part of the "J", the water will rise up the long side. When you apply enough pressure to raise the water in the long side 1 inch, that's 1"wc.

It's a tiny measurement of pressure.

Microns, if I remember correctly is basically a measurement of pressure between 29 and 30"hg (mercury)

Made me realize... Inches WC is for pressure, has nothing to do with vacuum. Sure you didn't mean inch mercury?

Now. As far as the micron issue, did you have moisture in the system prior or think you do?

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5. OP I thought I should let you know to expect some ribbing over your screen name because usually when we refer to a hack we are referring to someone who installs things incorrectly or does sloppy work.
Welcome to the forum. There is a ton of information here to help you on your way to becoming a better tech and it's a really great bunch of guys once you get to know them and probably the largest group of collective knowledge in the industry.

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As far as the micron issue, did you have moisture in the system prior or think you do?

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Yes definitely, Installed this unit last year, discovered a bad braze that had the dried sooty residue,95% r410a was gone. My understanding is...If it leaks out, moisture comes in.

7. If it is still under any pressure above atmospheric, moisture should not get in. Unless the leak is in the section of the system running in a vacuum.

8. Originally Posted by AC Hacker
Yes definitely, Installed this unit last year, discovered a bad braze that had the dried sooty residue,95% r410a was gone. My understanding is...If it leaks out, moisture comes in.

You are not completely moisture free until you are under 500microns. The moisture and refrigerant will create an acid. I'll have to look later and find it.

So, this was on the suction line I am assuming? I don't know why mfr's, excuse me manufacturers, don't put LP controls on all units. I feel like the cost of the switch would be cheaper than all the warranty.

Anyway. First things first.

Did you do a standing nitrogen pressure test after fixing the leak?

Have you tried a triple evac? (Vac/break with nitrogen/vac/break/vac).

The tiny bits of moisture can freeze in a vacuum. Part of the triple evac process is to thaw that bit of ice so you can pull again.

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9. Inch of mercury (inHg and ″Hg) is a unit of measurement for pressure. It is used for barometric pressure in weather reports, refrigeration and aviation in the United States.
It is the pressure exerted by a column of mercury 1 inch (25.4 mm) in height at the standard acceleration of gravity.

In
air conditioning and refrigeration, inHg is often used to describe "inches of mercury vacuum", or pressures below ambient atmospheric pressure, for recovery of refrigerants from air conditioning and refrigeration systems, as well as for leak testing of systems while under a vacuum, and for dehydration of refrigeration systems. The low-side gauge in a refrigeration gauge manifold indicates pressures below ambient in "inches of mercury vacuum" (inHg), down to a 30 inHg vacuum.

Micron is a unit of measurement starting from a perfect vacuum (no pressure) that is expressed in linear increments. One inch= 25,4000 microns thus one micron= 1/25,400 of an inch. When discussing vacuum in terms of microns, this refers to total ABSOLUTE pressure as opposed to GAUGE pressure.

So, for every micron above absolute zero is 1/25,400ths of an inch, which is a unit of length, in this case a 1/25,400ths Inches Mercury.

And lookie what I found!

If you look at the patterns, you can see why you cannot tell microns of a system by a manifold guage.

10. Nice article by AccuTools on evacuations.

https://accutools.com/how-long-shoul...cuate-a-system

11. Also, I keep seeing questions on the forum about the gas ballast on a pump.

https://www.vacuumscienceworld.com/b...mp-gas-ballast

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Take a recovery tank and hook up your vacuum rig and pump. Should hit500 within 15 minutes

13. Originally Posted by pecmsg
Take a recovery tank and hook up your vacuum rig and pump. Should hit500 within 15 minutes
Oh yeah, and #4, your vacuum pump isn't performing (old oil, worn pump)

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Changing oil in your vacuum pump frequently is important. I've suspected leaks before, and it was just old oil. If that doesn't help you have a leak in your gauges, or in your system. Or you need a new pump.

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I'll chime in a bit here. Holding below 500 means the system is absolutely dry.
Getting to an ACTUAL 500 on a system that's been in service is very difficult.
Refrigerant mixes with oil. And the Refrigerant will also be UNDER the oil in a system that's been used.
Hitting the system a bunch of times with nitro when you stall on microns from THE OPPOSITE side you are vacuuming from can get you there.
However, with a used system I'm generally happy with 1500 microns and a new dryer.
At 1500 it's basically a system with zero leaks.
Now the above only applies to a system that hasn't been running in a vacuum.
If it's been running in a vacuum then a full compressor oil change and 500 microns hold is required

16. Originally Posted by Restaurant mech
I'll chime in a bit here. Holding below 500 means the system is absolutely dry.
Getting to an ACTUAL 500 on a system that's been in service is very difficult.
Refrigerant mixes with oil. And the Refrigerant will also be UNDER the oil in a system that's been used.
Hitting the system a bunch of times with nitro when you stall on microns from THE OPPOSITE side you are vacuuming from can get you there.
However, with a used system I'm generally happy with 1500 microns and a new dryer.
At 1500 it's basically a system with zero leaks.
Now the above only applies to a system that hasn't been running in a vacuum.
If it's been running in a vacuum then a full compressor oil change and 500 microns hold is required

I've had leaks on a 1500 micron pull.

Never under 1000.

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I've had leaks on a 1500 micron pull.

Never under 1000.

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Where were you measuring the microns? If you're measuring on the same side you're pulling then it's NOT 1500 microns

18. Originally Posted by Restaurant mech
Where were you measuring the microns? If you're measuring on the same side you're pulling then it's NOT 1500 microns
My boss used my blu vac kit one time and he couldn't get the valve core out but he still used the valve core remover and he was just amazed at how fast it got down to 100 microns.

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So measuring from the same side as pulling?
If you're measuring from the opposite side you'll actually have a true micron reading. Then no need to wait for decay

20. Originally Posted by Restaurant mech
Where were you measuring the microns? If you're measuring on the same side you're pulling then it's NOT 1500 microns
I always have a micron in the middle of th pull.

Eg. Pulling from suction and discharge headers and my micron guage is on the liquid header.

A 17cfm duoseal on a 100+ hp rack with (3) 1/2"

Couldn't get below 1500 microns after a conversion and had to get it going. Get some pressure in it and there's going to be a leak. Somewhere.

And there was.

1000 is leak free

500 is moisture free

Anything else below 500 is a bonus to be proud of.

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