i replied on another thread...
i have used 4 vacuum pumps on one chiller before. on medium systems, i might use 2 but most of the time, i just use 1 as there are only so many places to hook up to.
A coworker insists on using 2 vacuum pumps when pulling a single circuit system down. Does any one have any info or opinions on this controversy.
i replied on another thread...
i have used 4 vacuum pumps on one chiller before. on medium systems, i might use 2 but most of the time, i just use 1 as there are only so many places to hook up to.
"Right" is not the same as "Wise".
Don't step on my favorite part of the Constitution just to point out your favorite part.
Just because you can measure it, doesn't mean it is important. Just because you can't measure it, doesn't mean it isn't important.
I've seen it done. Not sure whether i could be bothered hooking up another pump, should theoriticaly do it in half the time??? but... (see the signature)
It depends on the volume of the system, and if there is an appreciable amount of moisture.
Too much vac pump can cause problems.
Most package units can easily get by with one good vac pump.
GO DAWGS!
What controversy,
You are trying to acheive a vaccum, always use a micron guage to check your vaccum.
Domcort
I do it all the time, but it's not really worth the trouble unless you're working on something pretty big.
One thing that will definitely speed up your evactuation on any size system is removing valve cores and valve core depressors, and not running the vacuum pump through a gauge manifold.
I guess it depends on what you are working on as well as the cfm of the vac. A residential unit concern is freezing moisture by drawing down too quickly, then the wait time defeats the purpose.
If you have lets say 2 - 1.5 cfm's then by all means. But if you have 2 - 6 cfm's then!!!!!
I've never tried it but I have wondered what would happen if you put two pumps in series when trying to pull low numbers. If you put two pumps, two stage each in series would you have a four stage pump? Could you pull lower numbers with it? Obvously it wouldn't work real well when first starting to pull a vacuum. One for these days I'll try it and see.
Have done this before only if high and low side isolated from each other. if not what tends to happen is stronger pump will pull through weaker one and not achieve what your trying.also as stated if you pull vaccumm too quickly you can freeze moisture in vessels. As far as putting 2 in series what tends to happen is lead pump runs very hot and even loses oil to 2nd pump.
Good luck..
Drastically increases the efficiency of your first stage pump. Oil management has to be watched, but allows a much deeper pulldown vs time on pump. Works well if you have large amounts of water, but increases the chance of freezing free water under certain conditions. But you can do that with a large, deep vacuum pump, too. As far as just evacuating an otherwise dry system, say in the event of a leak repair, I feel that too many folks think the bigger the better. I've left a 5 cfm hand carried pump on countless chillers up to 2500 tons with 1/2" connecting hoses for overnight pulldown before startup or after repair, and walked in to a 700 micron vacuum the next morning. It just don't require that much pump if it's handled correctly. Dehydration is a more time consuming process, but still don't require multiple oversized pumps, if done correctly.
Also depends on the size of the hose, if I use my manifold with 3/8 vac port on 3/8 vac pump I would not bother with second pump on medium size system. But there are many variables to consider as already stated.
Never even thought about doing this, but I only work on residential/ light to medium commercial. If I'm thinking right, then you'd actually have both pumps fighting each other, and possibly not get a real good vacuum on the system itself. Maybe even have one of the pumps start to overtake, and possibly damage , the other one. That's if they're in series. Somebody correct me if I'm wrong. I keep a 4cfm pump on the truck. But if I have a system that I greatly question (i.e. a lot of moisture), I've got an old but reliable 1.5cfm at the shop I'll pull out. As always, put a micron gauge on it. You can hardly ever go wrong with it.
must be spring time...vacuum questions popping up all over
i can not wait until my next evacuation now!!!!! i love this idea! obviously, you have to wait until you are quite low to begin with otherwise vacuum pump oil management would be an issue.
wrong...sorta. you will not acheive a vacuum lower than the weakest pump...but "pull" through it? not. but i have heard of people claiming that if 1 pump pulls 500 microns by itself and the 2nd pump only pulls 1000 microns by itself, then if the two were used together then the system would only pull 2000 or something...bunch of bull. you would most likely stop around 600-800 microns.
also, if you have that much moisture in a system built with "high heat transfer materials" like copper, brass, aluminum and steel that you can freeze water, then your ambient is VERY cold or you should not have left the system open in the rain. there are many threads here talking about moisture freezing in a system myths. is it possible to freeze moisture in a system? yes, but the conditions are quite rare. is it probable? no.
yep! 1 - 10 cfm and 3 - 7 cfm pumps. it actually helped find a leak. 1 of the 7 cfm pumps was pumping a lot more air than the other 2...i thought that it was a bad pump or something. switched some pumps around to be sure...the same hook up point was still pumping a lot more air regardless of which pump was hooked up to it. turns out that the valve on the chiller was not doped on the threads! re-doped the threads and the leak went away...total luck.
"Right" is not the same as "Wise".
Don't step on my favorite part of the Constitution just to point out your favorite part.
Just because you can measure it, doesn't mean it is important. Just because you can't measure it, doesn't mean it isn't important.