Micron level problems

[et]

Guys,
Some input please.
I have fought with micron levels while bench testing a new micron guage. I need another brain, mine is exhausted.
Should I forsake the micron idea and just focus on standing pressure and vacuum tests? Books say it works. I've even done it many many times. Now it won't work. Makes no sense to me. I'm out of time to keep bench testing this high- tech, battery operated,micron detecting expensive junk. The old-timers weren't so bad huh!
Somebody throw me a line! I'm not a new comer to this field. I've been here a long time.
Help!
Thanks to you all!


I have the following symptoms. Test includes #1 vacuum pump, one new refrigeration hose connected to the pump, and new digital micron guage #1.
1. micron level down to 400 microns,valved pump #1 off.
2. Pump turned off.Levels of microns climb rapidly to unacceptable levels.
3.Installed 2nd isolation valve to seal before hose connection at pump.Same results.Microns climb just as fast.
4. Same test,new refrigeration hose.(I mean a new one!)
same results.
5. Buy new micron guage.Performed all the same tests as above with new micron guage.Hmmph!The exact same symptoms.
6.Pulled out my "Not so old" analog micron guage,same equipment above.Performed same test.Same results.Microns climb just as fast as always.I even used a second valve a second time to isolate the pump.Nothing bettered.

Fittings good shape,not scratched or pitted.Every concievable idea I have thought of I have done.Still,no worky.
Trash all of this equiment? It is new! I know not of another culprit that it could be. I could condemn the new digital micron guages as a bad design,but the same symptom exists with my analog guage I've had all along. It's not the guages. It's not the hoses. It appears the micron target just cannot be maintained once the pump is isolated. Why? I don't know. Do any of you?
I even used copper tubing instead of a hose! Same symptom.

[chillrdude]

I have never been a fan of these new fangled digital micron gauges, I think all they really read is temperature and try and convert it some vacuum level, I believe ambient temps and batteries give you different readings. All I use is a mercury manometer and it has never failed me yet.

Dude

[coolestacman]

From what you have told me i would say that there is a problem somewhere in connections being that you obtain the same readings with both gauges.
Some questions I have:
-what type of hoses are you using?
-how long did you pull a vacuum?
-where are you connecting your micron gauge?

[moonman1]

Apparently the sensing element in this unit is made of high purity components which make it ultra-sensitive. The use of standard rubber coated hoses can be a problem. Outgassing of the hoses can occur meaning that molecules from the hose material can affect the vacuum reading. Also refrigerant oil trapped in guage "o" rings and throughout the manifold can also be an issue. Thus it is recommended to use stainless hoses to prevent outgassing and trapping of molecules on inner hose walls. Keep hose lengths to a minimum. For best results, change vacuum pump oil prior to each operation. If it is determined that you have oil in guage manifolds then a degassing procedure may be required. Despite our best efforts to prevent this, air can come into contact with guage and hose internal surfaces allowing for the presence of moisture. During use of the vacuum guage, the element must be set upright (connection end down) to prevent refrigeration oil from getting into the sensor which can cause errant readings and improper operation. I have achieved a 250 micron vac by following the above procedures. If you decide to use rubber hoses, it is recommended to go with 3/8" hoses for best results.

[jhd1234]

I use gauges and metal hoses and pump made by JB Industries and consistently achieve micron levels at 250 to 500. I change the pump oil with each use. I blanked off a job one time and then was called away to take care of an immediate problem. 4 hours later, I still had 275 microns. I use separate guages. [separate from my regular charging/testing manifold and hoses] I took the fittings and gauges out of them and resealed with locktite thread sealant. Hooking up the rig can be a PIA, but when you do a 1 hour blankoff test that holds at 400 microns, you know there are no leaks, no moisture and no non condensables. For me, it's worth the trouble.

[et]

Thanks guys,
This crazy meter does describe how it converts some type of reading to a direct and proportional micron reading. Using its ability,it adjusts the current at the sensing element constantly,thereby providing a steady temperature..bla bla bla.....Hey!, I wonder...How far do you think I could throw it? LOL
I would think it might be hoses, but I went to only 1/4" copper on vacuum pump(Short line) straight to this micron meter. Still loses ground rapidly.
I'll be watching this post a little while. If someone can give me a theory why , even with copper line, I get the same results.

ET

[jhd1234]

Tell us more about the micron meter. Like what brand is it? With just a short copper line straight in, it's the meter, the pump or a leak. I found we had a leak on the pump. I took all the fittings out and resealed them with a locktite thread sealant.

[DeltaT]

Alternative would be to connect a compound gauge directly to you inlet port of your vacuum pump through one of those short gauge connectors (about $7.00 or less) and do the same test. If the gauge reachs atmosphere you have a problem with your vacuum pump.

[grayghost]

i believe moonman is right i have had similar response,and after changing gauge manifold and hoses that has solved the problem.so like jhd i now use i gauge set for vacuum only.

[et]

Guys,
See if this sounds correct. I've done some homework. I believe I have an understanding now...here goes.
Acceptable levels of vacuum reached as long as pump running,but lose my target of 400 microns (small systems) or 700 microns (Large systems). After pump isolation levels rise.
Some information I came across stated that (after pump isolation) , levels must stay below 2000 microns in the system for a considerable time period, to assure a clean and dry system. Sounds like an increase is to be expected! I was shooting for my 400 to 700 targets to be maintained after pump isolation and to be my final readings. DUH! Am I wrong or what? I just observed my manifold vacuum guage stay nearly 30" for full duration of test, but the digital micron guage rose to a peak of 1549 microns and finally stop. That is below 2000! Vacuum guage still at 30". This scenerio is working. It looks correct to me too. Do any of you know my latest findings to be wrong?
Thanks for your help!
ET

[jackal]

I don't really know if this will help but I did a similar experiment some years ago and had the same issure with rapidly rising readings after blanking off the vac pump. I think one problem with bench testing a micron gauge like that is you have no reservoir for the vaccum. What I mean by that is when you have a micron gauge hooked up to an entire system you have a large area to pull a vacuum on so tiny leakage is not noticeable, but when you hook up a micron gauge to a hose and blank it off the volume of this "system" is so small that tiny leaks that normally would not be an issue now are. By tiny I mean very tiny like that amount that could come through the stem of the shut off valves etc. which would not be considered significant enough for a leak detector to pick up. If you try that same test but with a recovery cylinder in the system for added volume you might find your readings don't rise to unacceptable levels.

[moonman1]

Originally posted by et
Guys,
See if this sounds correct. I've done some homework. I believe I have an understanding now...here goes.
Acceptable levels of vacuum reached as long as pump running,but lose my target of 400 microns (small systems) or 700 microns (Large systems). After pump isolation levels rise.
Some information I came across stated that (after pump isolation) , levels must stay below 2000 microns in the system for a considerable time period, to assure a clean and dry system. Sounds like an increase is to be expected! I was shooting for my 400 to 700 targets to be maintained after pump isolation and to be my final readings. DUH! Am I wrong or what? I just observed my manifold vacuum guage stay nearly 30" for full duration of test, but the digital micron guage rose to a peak of 1549 microns and finally stop. That is below 2000! Vacuum guage still at 30". This scenerio is working. It looks correct to me too. Do any of you know my latest findings to be wrong?
Thanks for your help!
ET

Micron readings will rise if moisture or non-condensibles are present in the system. The difference between the tiniest of leaks and moisture presence is that the micron reading will continue to climb w/o stopping if a leak is present as opposed to a micron climb and level out with presence of moisture or non-condensibles. Rate of climb in a leaking system of course depends on the size of the Leak(s). The type of vacuum you want to achieve is dependant on the type of system you are working on. Low temp. applications have less tolerance for moisture presence in the system thus 50 to 100 microns initially with a rise to 300 microns within 3 minutes is o.k. maxing out at 500 microns. For any other types of system, achieving and maintaining 500 microns is very good. However, if the level rises to 2000 microns within 2 hours you MAY have a leak. (ASHRAE's standard is 1000 microns) Flush system with dry nitrogen and revacuum. It is recommended to install a ball valve between the system service port and the vacuum guage sensing element. Your compound guage will not budge fromm 29.9+ "hg until the micron level rises above 2000 microns. And of course on top of all this good work a new drier will ensure the integrity of the refrigerant after dehydration and charging has been completed.

[hvacbear]

Where is the gauge installed in relation to the pump?

[moonman1]

The vacuum guage can be hooked indirectly(with a ball valve between port and sensor) to any service port or on a teed service line as close to the system as possible while the vacuum is hooked indirectly to another service port(s).

[caosesvida]

I go with moonman, I find if you have a good vacuum the meter will rise and then start to go back again. I think the problem may be in your hoses. As stated here, they are ususally full of oil and refer, if you use them all the time. A separate set and metal if you are really serious about it. I like the electronic type, and after using and shop testing I found that they work well. I have had 5 or six in the last 13 years or so.

[et]

Guys,
I have arrived at a conclusion. From what you guys have said, to some homework I have done, here, I believe was my problem.
Mostly ignorance. I expected my micron levels to only increase slightly upon isolation of the vacuum pump. Assured that I had no leaks anywhere during this bench test since I had sealed every last one of all the connections myself. I knew, short of multiple bad "new" hoses (not!)I was totally closed from atmosphere and moisture contamination.
After reading your posts I allowed the levels to rise , just to see how far they would go while I observed and drank another cup of coffee. They (Microns)rose to 1,549 during this final test, then stabilized at this reading. This was a 4 valve manifold with all the hoses, and only a vacuum pump.
I see now I was impatient, expecting the meter to quickly stabilize, and show me what I wanted to see. It did no such thing. It showed me that microns, even in a tightly sealed enviroment,and a volume of space so small,still are not removed rapidly,but tend to actually "release" themselves from the volume of their space after isolation of the vacuum pump.This explains the "increase" in my micrometer readings repeatedly. This, I learned, are some of their characteristics.
Sorry this was so long, but this site is fantastic. I hope all this can help someone else like it has helped me.

[caosesvida]

a "micron" is one millionth of a meter, in this case another way to measure inches of mercury as in a barometer for air pressure. If any one was curious

[moonman1]

Try this test. Hook a stainless hose (18") to a brass male 90 elbow and vacuum pump. If your pump does not have an isolating valve built in then install one between the pump inlet and hose. Hook the other end of your hose to the 90 and the other end of the 90 to your vacuum guage. Your micron reading is rising and stabilizing because of outgassing of your hoses and manifold. Oil that has been caught up in the manifold and it's seals and housing acts as a non-condensible. Degassing of the manifold can be accomplished by running a tight vacuum on the manifold at a temp. of 125*F for 24 hrs. Also try disassembling your guages and give them a good cleaning then reassemble and try your test again. You should have no problem getting to 150-250 microns.

[RichardL]

One of my earlier Service Managers in Florida had a policy that would result in "Immediate Termination".....

1- Anyone caught evacuating thru a charging manifold was history... Vacuum pump was to be connected with copper tubing "ONLY", as large and as close to system as possible...

2- Anyone caught with "Soft Solder" on his truck was also toast....
I never asked what he would do if he found anyone actually using it.....

David Drake was his name and he was as good as they come....

[jhd1234]

Any chance this "David Drake" was in Tampa?

[moonman1]

I guess Dave and his crew didn't install water cooled commercial units. Lots of need for soldered water piping.

[lenb]

Must be nice to have a service manager that respects a micron guage. A lot of managers I've had in my career didn't know what a micron guage was, or if they did, thought it was a waste of time.
Felt it would be grounds for termination for spending two days just to achieve proper vacuum level, on say, a 5 ton package RTU.
Standard procedure now is: Make repairs, start vacuum pump, go to lunch. Come back from lunch, start up and charge unit. Sometimes you just have to lower your standards. I don't like it, but it has to be done.
I do have a designated manifold, flex steel hoses, and a micron guage. Only time I use them is when I'm working on enviromental chambers. I spend as much time as I need to make sure I achieve an acceptable vacuum, especially on the low stage. But the customer understands how critical it is, and doesn't have a problem paying for it. Also I want to be as sure as I can that the system is tight when the refrigerent costs about $100 a lb.

[Learner]

ET, you're probably right about the impatience, but here's one more detail that many people are unaware of.

The ball valve which is used to isolate the vacuum pump, traps vapor. Therefore, when you've pulled a vacuum, and are happy with the micron reading, then close the isolation valve, the trapped vapor is released, causing an immediate jump in the micron reading.

To prevent this problem, when closing the ball valve, just partially close it, and allow this newly released vapor from the ball valve to be evacuated. Let the vacuum pump run about one minute with the ball valve partially closed, then close it all the way.

Also, the impatience part plays a big part in how deep the vacuum will go. I've had an acceptable vacuum level at quitting time, but decided to go ahead and leave the pump running overnight. The next morning I checked the vacuum and found it to be under 20 microns. I isolated the pump and left to go do some other work and returned a couple of hours later to find the micron gauge still reading exactly what it was 2 hours earlier. I have experienced this on many occasions. This can only happen on systems with no oil in them, such as new piping and an evaporator. If the system has oil, the vapor pressure of the oil will not allow the vacuum to remain at a level lower than the vapor pressure of the refrigeration oil: approximately 250 microns or so.

The copper piping has molecules of air (or other vapor) attached to the inside, which will remain attached to the copper until enough time of evacuation has caused this vapor to all be evacuated. If you stop the evacuation prior to all of these molecules being removed, then during your standing test the molecules will detach (outgas) from the copper and cause an increase in the micron gauge reading.

I'm not suggesting you need a 20 micron level, I'm just stating my experiences which proves patience is needed for attaining a good deep vacuum.

I've also finished an evacuation on a Friday afternoon, isolated the vacuum pump for the standing micron test, and returned on Tuesday morning after a 3 day weekend to find absolutely no rise in the micron gauge reading at all. This was on a complete system (including compressor) with over 100 feet of piping on a 15 ton system.

By the way, I don't use manifold gauge assemblies for evacuation. I only use the Ritchie (Yellow Jacket) flexible metal hoses, and the Ritchie ball valves. When I leave the job, I leave with confidence, knowing the evacuation was good.

[rob10]

Are not adequate for teasting for a sealed system. 200 psi nitrogen is where you should start!!

[moonman1]

Originally posted by rob10
Are not adequate for teasting for a sealed system. 200 psi nitrogen is where you should start!!

Absolutely! Always varify your system with a standing pressure first. But the ultimate will be the vacuum check. Not so much that it will indicate a leak but moreso the presence of non condensibles that a nirogen pressure test won't indicate.

[Learner]

Originally posted by moonman1

Originally posted by rob10
Micron readings by themselves Are not adequate for teasting for a sealed system. 200 psi nitrogen is where you should start!!

Absolutely! Always varify your system with a standing pressure first. ...

I agree completely with the importance of a pressure test prior to evacuation; however, I'd like to add some comments along these lines.

I've learned from experience that the deep vacuum test is a better test for leakage (but I still want to perform the pressure test first). I could name a few experiences that proved this to me, but I'll shorten the story a bit.

With nitrogen testing, which I do, when the temperature changes, so does the pressure. I've returned later in the day as the temperature warms, to find the nitrogen pressure has increased, but later my micron test indicated a very small leak.

I've returned when the temp is colder and the pressure has dropped while under a nitrogen pressure test. I usually have a few circuits under test at once, and have seen all pressure gauges drop by similar amounts, giving me confidence that there is no leakage, but the pressure drop is solely due to temp drop. This is usually proven later when the micron test has indicated no leak and no moisture.

I've also returned to check on a pressure test when there was little or no temp change and the pressure gauge showed no visible change, but the deep vacuum test later has shown a very small leak. This is because the micron test which has shown an increase of a few thousand microns over a couple of hours or so was too small a leak to show up on a pressure gauge since the leak would have been only a fraction of one psi.

Some of these little leaks have been factory leaks in the evap coil section on split systems. The leaks that have driven me crazy have been the occasional leak that is not leaking to atmosphere, but rather have been the service valves at the condensing units, leaking extremely small amounts of nitrogen pressure into the precharged condensing units. I've been able to confirm these by never having any refrigerant in the evap coil or the piping, and then use my electronic detector inside the piping and pick up an indication of refrigerant, which could only be from the new condensing unit. And the other leaks, well, I must admit, I have been responsible for a leak now and then myself.

By the way, our code requires testing R-22 (and some other refrigerants) piping to 360 psig, with some exceptions. Occasionally I'm on a job where the inspector wants to see this.

[moonman1]

Interesting observations about nitrogen pressures swinging due to temp. change. I have not noticed this except when a nitrogen/R-22 mix is in a system. That being said, I have noticed very small changes (1-2 lb. and less over 24 hr.),depending on the situation. If a system is found to be empty, a repair has been made on a found leak and pressure testing with N2, then I would expect very minute (less than 1 lb. over 24 hr.) changes in pressure during a drop in ambient temps overnight. Of course I would expect to see an equal climb as morning temps warm back up. In a controlled environment there should be no deviation allowed, such would definately indicate a leak.

[Learner]

The pressure change over 24 hours is generaly fairly minimal, in my experience, if the temp is approximately the same 24 hours later. However, sometimes I pressurize in the late afternoon when it's warm outside, and return first thing in the morning (or the morning after that) when it's maybe 30 degrees (give or take) cooler. I've seen changes of about 7 psi in nitrogen pressure readings under test, with no leakage. I've seen this many, many times, and so have my co-workers.

[ruglenr]

REFRIGERATION HOSE ARE NOT MADE TO PULL A VACCUME, THEY HAVE MICROSOPIC LEAKS, THEY ARE SHOWING UP SO RAPIDLY IN YOUR TEST BECAUSE OF THE SMALL AREA YOU ARE EVACUATING. USE COPPER!

[hvacinstallation]

I honestly can not believe you service guys sometimes. I am here to give just an opinion. If you are certain there are no leaks in the system, (1. nitrogen to 150psi on the high side for at least an hour or two), 2. you trust your guages and hoses) pull the vacuum for 2 or 3 hours and leave it for a couple days if possible. Hopefully its still at 175ish. I personally don't trust anything with hoses and a battery but when god created the guages, that all the tech needed. The pump will pull only what the pump will pull.

Later, To the installers.. Semper Fi

[greg o]

I was the first in our shop to buy a micron guage, everyone else pumped it for a "while" and dump in the charge. Usually pumps were run while the site was cleaned up and the charge was added before the tech left.
Sometimes if the equipment was questionable the vac pump was let run over night and call it good.

I have complete faith in my micron guage. If the numbers will not fall I either have a leak, or if they fall slowly, moisture.

I never have had a sealed unit that would not hold a micron test. I shoot for 400, but may sometimes quit at 500 if I am familar with the equipment. I always wait to see if the reading climbs. It often will climb, but settle back close to the 400 mark. I occationally will leave a vac pump run over night. On these times the reading is often less than 300 and sometimes uder 200.

What really sold me on a micron guage is when I started using one, how quick a clean system will pump down. Often I can hit 400 in the time it takes to clean up tools and trash from the repair. I did one circuit of a York RTU, (6 ton circuit), (just a liquid line filter replacement that was not changed when the compressor was changed a week before!), and it took less than 20 minutes to pump below 400 and hold.

I changed out a compressor on a ground source heat pump, that we had many failures on, and it took a full two days on the vacuum pump to get to 400. I ran it for a day, changed oil on the pump, and ran it one more day. Previous techs ran the pump for a 1/2 hour od so and ran. Obviously the system was not clear when charged the last time! Our shop had replaced compressors, about once a year, and a couple reversing valves too. I did the repair over two years ago and although we have checked the unit a few times since, there has not been any failures since!

One problem I have is poor hearing. Because of this I seldom pressure test. I have missed leaks on a pressure test that have not hold a vacuum so I have little faith in a nitrogen pressure test. I will pressure test a large install and use bubbles to leak check. No bubbles, vac it and see if it will hold a micron level. On a small repair, compressor or filter change out I will not pressure test. I will rarely use a trace of R22, nitrogen charge and sniffer if I am stumped on failing a micron test.
Greg

[hvacbear]

I never leave a system in a vacuum overnight. If there is a leak then moisture will be drawn into the system. A nitrogen holding charge is better.

[DeltaT]

In the "old" days leaving a vacuum pump on over night after a good pressure test was common with the larger piped systems. We would even do it on some residential. What a world of different of how long the systems would last.

I have three vacuum pumps and three digital and one analog micron gauge. And all the hoses, connections, fitting are kept exclusively for that purpose.

[indian]

Originally posted by DeltaT
In the "old" days leaving a vacuum pump on over night after a good pressure test was common with the larger piped systems. We would even do it on some residential. What a world of different of how long the systems would last.

I have three vacuum pumps and three digital and one analog micron gauge. And all the hoses, connections, fitting are kept exclusively for that purpose. It has become a full circle with POE oil.

[DeltaT]

Originally posted by indian

Originally posted by DeltaT
In the "old" days leaving a vacuum pump on over night after a good pressure test was common with the larger piped systems. We would even do it on some residential. What a world of different of how long the systems would last.

I have three vacuum pumps and three digital and one analog micron gauge. And all the hoses, connections, fitting are kept exclusively for that purpose. It has become a full circle with POE oil.

OK. Let's talk about this statement. I assume you mean with POE oil that a long vacuum is necessary. Maybe you know something I don't but you can pull all the vacuum you want and you will not rid POE oil of contaminants (acid) once POE oil has been introduced with moisture.

I'm always looking for information that this situation is not true. POE oil must be discarded once contaminated as far as I know. The POE oil manufacturers waltz around this fact but they indicate enough warnings without actually having to come out and use those discard words up front.

[gbfromsd]

200psi nitro is good but . . . the low sides of many systems are pressure tested and certified to a pressure lower than this, say 150. Consult your unit specifications prior. Your mileage may vary.

[uhPrintUs]

Originally posted by hvacinstallation
I honestly can not believe you service guys sometimes. I am here to give just an opinion. If you are certain there are no leaks in the system, (1. nitrogen to 150psi on the high side for at least an hour or two), 2. you trust your guages and hoses) pull the vacuum for 2 or 3 hours and leave it for a couple days if possible. Hopefully its still at 175ish. I personally don't trust anything with hoses and a battery but when god created the guages, that all the tech needed. The pump will pull only what the pump will pull.

Later, To the installers.. Semper Fi

I don't have much experience, but my co-workers have taught me enough and shown me enough to know the importance of using a micron gauge.

This is one experience I personally saw that may help you understand something you haven't thought about. First of all: How many microns are there between the 150 psig on your gauge and 151 psig, assuming you can actually tell the difference by looking at the gauge? Rounding off, there are about 12,500 microns. Now to the experience part.

We pressure tested a new split system to 150 psig and returned about 24 hours later and according to our eyeballs, the gauge still said 150 psig. We pulled a vacuum, starting near the end of the day, so let the pump run overnight. It was evacuating the piping and the evap section. The cond unit was precharged. Returned the next morning to find the system at about 30 microns. Yes, thirty microns. We valved the pump off by closing the valve half way, and a minute later closed it all the way. We used flex stainless steel hoses to pull the vacuum. We came back about a half hour later and the vacuum was about 120 microns. I thought, that's great, but my journeyman said, we've got a problem here. We came back about an hour later and it said about 300 microns. Looked good to me, but the journeyman said No Way!!! We've got a very small leak. After checking all our fittings, we pressurized to about 300 with nitro and began looking. Guess what!?

We found a tiny leak using bubbles. It was at the factory solder joint at the TXV equalizer line on the suction leaving the evap. Soldered the leak, Pulled the vac to about 30 microns again, and it didn't rise a bit. Stayed on the money.

That leak raised the microns about 3 microns a minute, so that would be under 5,000 microns in 24 hours. That means it would take 2 1/2 days to leak equivalent of 1 psi on a gauge.

Is that being too particular? Not where I work. My boss wants the job done right, just like he would want someone to do on his own personal system if he were paying a pro to do it. He says quality is one of the things that separates the real pros from the rest of the guys out there. I've learned to trust the battery operated micron gauge MUCH more than a charging gauge.

[acjourneyman]

Everyone should always use a micron gauge, we always shoot for 400 microns in a 500+ ton chiller with a max of 200 micron risein a few hours.Also , with these systems, and I have even done it on small splits, we always leave the vacuum pump on overnight or even over the weekend.If you are sucking moisture in than the system leaks and the pump shouldn't be on it at all.

[DeltaT]

uhPrintUs
Good example. Nothing more needs to be explained now in my opnion.

[lenb]

Been working on a lot of enviromental chambers and low temp test stands lately, and am taking micron levels more seriously.



http://www.imagewiz.net/usr/hvac/3138_P3290007.JPG
Was working on this the other day, it's a test stand they use to test automotive a/c compressors.



http://www.imagewiz.net/usr/hvac/3141_P3290009.JPG
I bought the inficon a couple years ago, and have since retired my Robinair analog I've had for eons. Started questioning the accuracy of the inficon, wanted something to compare it with. Wanted the Yellow Jacket, but instead of ordering one, bought a Supco off the shelf instead, few weeks ago (charged to the company).
My coworker in the mean time ordered the Yellow Jacket, so here we have all three hooked up to the system, the inficon is attached on the suction line, the other two off of my manifold. Pump has been blanked off for half an hour.



http://www.imagewiz.net/usr/hvac/3142_P3290006.JPG
Yellow Jacket 1640, Supco 680, Inficon 4790. If I believe the supco, I'd be satisfied with that. But I'm leaning more toward believing the Yellow Jacket out of all three. As for the Supco, I returned that today, and applied the credit towards my own Yellow Jacket, which I ordered. When I get it, we'll connect both of them side by side on the next job and see what readings we get. I'll post back then.

[vlt]

Hey there, this looks like a Ransco CTS Stand That would use R-142b as the evap. heat load for the 134a circuit for the auto. a.c compressor can you give me any info on this gas.

[lenb]

Originally posted by vlt
Hey there, this looks like a Ransco CTS Stand That would use R-142b as the evap. heat load for the 134a circuit for the auto. a.c compressor can you give me any info on this gas.
Wish I had info on R142b, only info I could find on the web is in another language. Fact is, you probably know more about it and the stand than I do. Like, at which sightglass should the level be at room temperature?

[lenb]

I like that Ransco blue color though.