i have an apc computer room supplied by others and asked to be piped by us by the contractor that we did the hvac for the rest of the complex for, and the apc startup techs demand 300 microns before starting system. can 300 microns be achieved with a 2 stage 6 cfm vacuum pump? we do mainly residential and light commercial a/c and aren't familiar enough about microns to give a supported opinion. i don't believe this is possible but, what do i know?
Are you using a micron gauge?
Looks like you have a lot of wet systems out there, since it sounds like you use your manifold gauges for a vacuum reading. Yes, 300 microns is achievable, and in the small systems you speak of, pretty quickly with fresh oil, no moisture and no leaks. Don't go below 250 microns as the oil will start to vaporize. Don't use a christmas tree micron gauge, get one with digital display, or the old standby analog so you can see any changes during standing vacuum test. Go to J/B Industries website for tutorial.
Originally Posted by majortom
Yes it is achievable, just pressure test your hoses with nitrogen and soap bubbles to find any leaks in your hoses first. Replace any leaking hoses, change the oil in your pump and use a good micron gauge, not the christmas tree type.
I've pulled 300 microns using the yellow jacket 6 cfm 2 stage pump. It's a two stage, will do 300 microns easily and 6 cfm is a big pump for pulling vacuum.
test the vac pump with a digital vac guage SUPCO DIGITAL GUAGE,check the hoses and guages...... put the vac pump on the yellow hose and tie the suction/discharge into each side of the vac guage open the guages and read the vac alls tight.keep the vac guage off the refer guages when yor doing the vacuum run on the system...put it away from the pull king valve or shradder on a line if availible.anything below 5000 microns is moisture 4000...3000...2000 the oils on the newer freons absorb moisture when open to the atmosphere,so you will sit for a while at 5000 thinking its a leak but give it time.....overnight VAC for a good 1000 or lower is typical.if it is a split system your not going to see 300 microns in a 8 hour run standing there looking at it during the day.if you have a semi-hermetic isolate it and pull a seperate vac to get it away from the overall test should pull down to 200 mics easy..then open it up to the rest of the system and continue the vac...check those packing valves on the service valves....crank them tight
300 is easily achieved but will take time. you can get to 200 too (but takes longer...duh!). change your oil often. use nitrogen purge...lots of nitrogen purging. get a good micron gage and use it one or two (at least) times on other systems first just to get use to it. play with it in the shop too.
Originally Posted by jayguy
practice on a recover tank a couple of times ten go for it man
I watched a guy in a class use a sight glass that was brazed to a evap and put a few drops of water in the glass to show the results and it took 45 minutes to pull down and remove all the water (no nitrogen) just all vacum
To be safe also if you are not 100% confident in your hoses, just use soft copper flared to fit system and unit so no seepage or internal collapse of hose is possible. Valve the micron gauge to the unit, NOT to the vacuum pump and take readings only when vacuum pump is off and isolated from system.
I have never been able to get any of the yellow hoses to hold that kind of vacuum. When in a moisture removal situation I always use copper. Connect directly to system, no manifold. Interesting, pressurize your manifold and hoses and spend a few mins with a good electronic leak detector, you most likely won't be impressed with your new hoses.
when dehydrating a system remember that a pint/lb of water will make 1000
cubic feet of vapor when boiled off by vaccum, you need pumping ratios
of 150 to 0ne, use a pump with a ballast to help keep water out of the
pump, pump connections should be as short & large as possible. a cold
trap wonders to speed up the process.
a newnpump will give you 50 microns or better
If you are just pumping it down to charge it, then the black vacuum hoses and a micron gage. If you have water in the system us nitrogen to blow out as much as you can. Oh don't forget to open the SOLINIOD on the liquid line.
Reply back on how that APC is running im curious. Thank you!
the industry standard to check your vacuum pump is 100 microns.
if you blank off your manifold your pump should pull 100 microns in a couple seconds.
i have ball valves on my ss hoses and usually check my manifold and hoses.
usually can pull 20 microns.
did a 80 ton 38 series carrier split yesterday,
pulled 310 microns and called it good. placing micron gauge far away from pump. of course running the supply fan in the warm building to help speed it up!
i dont know about anybody else but i like the yellow jacket mic gauge.
by the way you can pull 100 microns with any size vacuum pump,
if you are using all 1/4" hoses you do not even need a 6 cfm pump.