I just wanted to share the typical procedure i use to pull a system down and see if you all could improve my procedure any.
1. system is usaully about 82 horsepower
2. a 26 cfm pump is used to it pull it down
3. i paint all fittings in vacuseal
4. i pull from several points in the system, ussaully an 1-5/8 line off the suction, a 7/8 line on the liguid header, two 7/8 lines off each side of the condensor, a another two 7/8 lines off each side of the heat reclaim coil
5. i use a robinar analog style micrometer (havnt found a reliable electronic one yet)the robinar is hooked up typically to the rack somewhere. I also use 2 yellow jacket electronic ones just for refrence points in reguards to looking for pockets . I put one on the oppposite side of the system at the rack and one down on the sales floor on the sys with the longest run.
6.If i have power i energize all controlls allowing valves to cycle through thier normal operations if i dont i manually run in all manual stems
7. i always start with fresh oil
8. first evacuation is taken down to 500 microns at which point i valve off all compressors isolating them from being pulled into any deeper of an evacuation
9. i pull it down twice more changing the oil inbetween each change
10. the entire process ussaully takes 4 or 5 days and i ussaully hit 50 microns or lower but it will typically climb 30 to 50 microns during a standing test on the final pull.
just curious if anyone has a more efficent way to do it
Thats quite elaborate. One thing I question is if these systems have Pressure transducers? If so make sure they are valved off. Unless there made for reading a Vac you will wreck the transducers.
If I undeerstand you correctly, you utylize several vac pumps. Is that correct? Not just one pump operating solo?
And the connecting lines to your vac pump from the system is made of copper tubing or other such materials which will not permeate?
Do you use the tripple evacuation process to cut down on your amont of time spent running the pump(s)?
Why do you choose that level of vacuum on your system?
I assume by yoru description this is a rack system in markets?
yes there are transducers on the racks and they are valved off. I only use one pump and yes all the lines are copper that i use. yes it is a market system. the standard im required to meet is to hit 150 microns and it can not rise more then 100 points in an hour per customers specs. the idea is that there is no more then 1lb of non condensables in the entire system at least that what im told. and yes i do triple evacuate my systems.
I would imagine, with such a spread out affair of pipes and cases and all ... you would be best off using multiple vac pumps. Each located in strategic spots in the system.
Originally posted by gas_n_go
[BI only use one pump. the standard im required to meet is to hit 150 microns and it can not rise more then 100 points in an hour per customers specs. the idea is that there is no more then 1lb of non condensables in the entire system at least that what im told.[/B]
Are you using this practice only on new startups? Or do you use this same method during service on existing systems?
150 microns is quite an achievement.
Tell me more.
I've never heard of vacuseal. Where do i get some? IS it necessary? And also, I use my standard hoses that came with my manifold guage set. Should I be using copper tubing? What size?
150 is a ***** to hit but its its doable. I`ve gotten it down as low as 30 microns on my best pull, and yes its for a new start up, for service i dont consider it nearly as critical to hit numbers that low considering your system is presumably dry to begin with. as far as using multiple pumps goes, you run the risk of one pump overpowering another pump, so its preferable to use one pump, the trick really is to pull from mutilple places in the system. thats why i tap it in the places that i do: high side, low side, condensor, and heat reclaim coil.
also if you try to hit numbers that low with an exsisting sytem , you`ld have to valve off your compressors or you run the risk of pulling in its seals and theres a likely chance your valves will seap through never allowing you to hit those numbers you really cant pull that deep of a vacume except on a new start up. oil in the system is another factor that will kep your micron readings up
ace i dont what kinda systems your evacuating but you should never use hoses always use copper lines. hose are desighned to hold pressure in them not keep pressure out they tend to leak in a vacume. vacuseal can be purchased at any supply house. as far as line size goes i always the largest diameter tap you got is what you use and always pulkl your vacume from at least two points on your system high and low or you wont get a good pull. and once you hit 500 microns isolate your compressor from the vacume, if you go any deeper you may pull in the ectrical seals on your motor
I was just at a training class and the instructor said that he uses nail polish (clear, not pink, we're men for goodness sake) instead of vacuseal. I haven't tried some yet, but I'm sure the nail polish is much cheaper.
Anybody swipe their wife's nail polish?
Whew! Sure glad you stated NEW start up!
Cause I was gonna say your not sober to say you can pull a vacum of even 500 microns no matter how many days you hook a pump up to the system. Not on a market. Not once it has been in operation!
Way too many valves which seep.
But I hate to go jumping to assumptions.
There was some talk about vacum on another thread and it ended with Lmtd saying that when water is being drawn out of a system using a vacum pump, it expands tremendously under 1000 microns.
Well duh. I can agree with that.
But I would never attempt to draw out a significant amount of water/ moisture/ vapor from a system that was classified as "WET".
I would first attempt to dry out that mositrue/ water/ vapor ... whatever ... before I ever connected my vacum pump(s).
AND ... I would utilise a chill chamber also
On a larger system like a market, I would primarily try to remove the non condensibles using the vacum pump. Then I would use the driers to suspend any moisture left inside the sealed system.
If I had to leave a vac pump on for very long ... that means the system is down. Bad idea.
I can change a whole lotta driers for the cost of having a system down.
And what's it take to replace a couple of 4864's? fifteen minutes?
Cheaper than evacuation. Provided you got the non condensibles out of the way FIRST!
For those here who have spent more time and energy pondering the finer points of market work. I would ask them to comment on my thoughts here.
This is not my area of greatest knowledge.
If Dave dont slap me down here ... I guess my thinking is okay.
Or ... he's asleep in the van again and hasnt loged back on yet.
Which is the same to me, as being in agreement
it's discussed in this thread.
Originally posted by gas_n_go
what is a chill chamber?
But the short story is ... it is a metal tank, real small, and it holds dry ice. The vacum pump is connected to the sealed system, in series, with this device. It is used to trap the water vapor as it heads towards the vacum pump.
It saves the pump from premature moisture saturation.
Water in with the oil in a vacum pump raises the vapor pressure at which the vacum pump can pull a system down with.
The drier the vacum pump oil, the better the vacum!
Just to add one more idea for a good vacuum. Make sure no one unplugs the pump when you go home at the end of the day to enjoy a beer or 10. It happen to us once even after we tape sign to the wall socket and tie strap the plug to the wall!
If you're worried about the power going out on you when the vacuum pump is hooked to the system in a deep vacuum, I would strongly suggest that you put a solenoid valve in the vacuum pump header to break the vacuum if there is a loss of power. The solenoid will break the vacuum and not let the pump oil and contaminates be pulled back in to the system. Also this protects the pump since it is never good to stop the pump under a deep vacuum.