Micron gauge vs U tube manometer

**Shophound** · 06-05-2005, 10:00 PM

Freezeking may not have a problem doing it his way, and he very well may take pride in his work, but I couldn't do it that way, myself. I've pulled brazing trash out of pistons and changed replaceable core suction line driers that were full of crap. Moisture makes the system acidic, which eats away at compressor windings. Non-condensibles rob the system of efficiency and shorten lifespan of compressor.

My take...a CLEAN system is efficient. If it has very little trash, moisture and non-condensibles and is maintained well, it stands a chance to run well for a long time.

**ct2** · 06-05-2005, 10:27 PM

Originally posted by beenthere

You should have asked him to see it, its a museum piece.

I've got one! made by the Meriam Comp out of cleveland...

How do you add fluid on one of these things . the fluid is a silver color , do you just pour it in

ok , I know it's mercury, I was just being sarcastic

**dash** · 06-05-2005, 10:50 PM

Originally posted by shophound
Freezeking may not have a problem doing it his way, and he very well may take pride in his work, but I couldn't do it that way, myself. I've pulled brazing trash out of pistons and changed replaceable core suction line driers that were full of crap. Moisture makes the system acidic, which eats away at compressor windings. Non-condensibles rob the system of efficiency and shorten lifespan of compressor.

My take...a CLEAN system is efficient. If it has very little trash, moisture and non-condensibles and is maintained well, it stands a chance to run well for a long time.

Freeze says he never had a problem,I'd say one that he's seen,or knew was caused by such practices.

I've known guys that say that about a lot of bad practices.

**Black Adder** · 06-06-2005, 01:36 AM

If you are measuring in inches wc there is no way you are going to know how deep a vacuum you are pulling. A micron gauge measures in thousands of an inch. If you don't pull a deep enough vacuum you are wasting your time, gotta get the vac down to where the moisture will boil. A micron gauge is the only way to go.

**Jultzya** · 06-06-2005, 11:44 AM

Originally posted by heetseeker
How do you get rid of moisture in the system without a micron gauge?

With a vacuum pump you silly, the gauge is just that... a measurement!

**Jultzya** · 06-06-2005, 11:48 AM

Originally posted by beenthere
You should have asked him to see it, its a museum piece.

Dwyer makes several different ones, also look in your Grainger catalog... many are listed in the book (in a couple of places)

May be a dinosaur in the refrigeration industry, but they sure are common in the heating industry!

**heetseeker** · 06-06-2005, 12:28 PM

I would like to know if you can pull all the moisture out of a system while monitoring with a U tube manometer as well as with a micron gauge. If you need to pull a vacuum to a specific number or just greater than a number. In the last case the micron gauge would not seem as necessary.

**DeltaT** · 06-06-2005, 01:04 PM

Years and years and years ago some of us would use a U tube which was about 4 foot high which senses pressure in a system, not molecular activity (temperature), which most of the "micro gauges" sense today.

You could see if a fly landed on one of the lines if you knew how to read them. Some old calibration labs still have these types of tubes sitting around if you look.

I find these types of posts rather interesting and funny in that tons of systems, many still in service today, were built, started and tested with these type of "low tech" devices and workmanship way before all this new, gotta do, devices were even thought of. And, from my experience, we had a lot less headaches and a lot more maintenance to do since the systems would work for a pretty long time.

Even in the residential market many of our present replacements are over 20 years old but we mostly know that our "new" replacement stuff will be extremely lucky to make it that long even with all the "high tech" devices we use to install and start them up.

**beenthere** · 06-06-2005, 05:21 PM

Originally posted by jultzya

Originally posted by beenthere
You should have asked him to see it, its a museum piece.

Dwyer makes several different ones, also look in your Grainger catalog... many are listed in the book (in a couple of places)

May be a dinosaur in the refrigeration industry, but they sure are common in the heating industry!

LOL...

I still use a u tube for neg pressure gas valves.

I meant, its a dinosaur using mercury for reading vacuum.

If you look at some micron charts, you'll see they still have a cross reference to inches vacuum mercury.

**Black Adder** · 06-06-2005, 08:38 PM

"I would like to know if you can pull all the moisture out of a system while monitoring with a U tube manometer as well as with a micron gauge. If you need to pull a vacuum to a specific number or just greater than a number. In the last case the micron gauge would not seem as necessary."

The lower the vacuum the lower the boiling point of water, at 500 microns I believe that the boiling point is close to 0 degrees. You can pull all the moisture out with a vac pump and a U tube for measuring, but to be sure you have a deep enough vacuum you should really use a micron gauge. I still can't believe that a U tube will have small enough increments to let you know when you are a 500 microns.

**beenthere** · 06-06-2005, 08:42 PM

Black, which came first, 29.6"mercury, or 500 microns.

**heetseeker** · 06-06-2005, 10:26 PM

beenthere
If 29.6" of mecury is the same as 500 microns then I don't see a problem getting a deep enough vacuum since inches are pretty easy to measure[altho I have no idea how a u tube makes a vacuum]. Are you saying that altho the method is dated it can do the job?
Also if the installer doesn't use nitrogen while using silver solder does the problem with ash cause problems soon after the install or any time in the future.Does it gum up a valve or block an orifice?

**beenthere** · 06-06-2005, 11:11 PM

Neither a u tube, nor a micron guage makes, or pulls a vacuum, they are devices used to measure the amount of vacuum the vacuum pump has pulled, and to see if you have you removed contaiments to a safe level.

There are thousands of systems that nitrogen was not used when brazing and they work fine 20 years later. There is also just as many that had problems shortly after they were installed.

So not using nitrogen while brazing is a gamble IMHO.

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