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Funny I had this exact discussion with my boss not that long ago.. I've used 3/8 hoses , valve cores removed and a vacuum tree as my evacuation set up for years. He felt it was a waste of time to go through the procedure.. ........ Until I showed him the difference...

The proof is in the pudding .

I use the Yellow Jacket set up with 3/8 hoses and core removers. I do put Teflon tape on the threads. It works just fine. I pulled a 60 ton tandem compressor circuit down to 450 microns in about 6 hours with a less than new JB pump.

Originally Posted by jpsmith1cm

In many cases, the larger vacuum pumps are severely limited by the size of the hoses used to evacuate with.

You aren't going to get a full 10 or 12 CFM flow through a 1/4" set of hoses and a normal service manifold.

And, as has been said hundreds of times before. If you've got enough moisture in your system that freezing it is an issue, you've got a serious problem.

The speed of the vacuum in that video is fast enough to freeze moisture, btw, without a 12cfm pump.

Edit - Forgot the video wasn't in this thread's OP. It's over here: http://hvac-talk.com/vbb/showthread....to-500-Microns

Like others have said, eliminating the gauge manifold, taking out the shrader cores, and using larger hoses will really improve things. I used to use a 4-Valve manifold and pull a vacuum through that. Now I use two or three 1/2" hoses hooked directly to a tee on my vacuum pump. It is almost unbelieveable how much faster you can pull a good vacuum.

If you really want to use two pumps, braze in some access points on the liquid and suction line at the evaporator, then have one pump hooked to the condensing unit, and one hooked to the evaporator. That would be much better than manifolding them together, but would most likely be unnecessary.

Originally Posted by lytning

Got to be careful with that. Vacuum to fast (cfm) and you could freez any moisture. I use a 10cfm, but always use the gas ballast valve for about 5 minutes to slow things down a bit.


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In many cases, the larger vacuum pumps are severely limited by the size of the hoses used to evacuate with.

You aren't going to get a full 10 or 12 CFM flow through a 1/4" set of hoses and a normal service manifold.

Got to be careful with that. Vacuum to fast (cfm) and you could freez any moisture. I use a 10cfm, but always use the gas ballast valve for about 5 minutes to slow things down a bit.

Originally Posted by rizer68

Why wouldn't you just buy a 12 CFM Vacuum Pump....

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Originally Posted by rizer68

Why wouldn't you just buy a 12 CFM Vacuum Pump....

Kinda like trying to run a firehose through a 1/4" line....

Bigger pumps do not necessarily pump faster... CLEAN oil helps.

What is noted above about ditching the manifold and using core tools is the key to faster vacuums.

OTOH: If one can manage their workflow, get the system closed up and let the pump chug along for 45 min to an hour... one will get the deep vacuum they want/need that way.

Now if you are just determined to use two pumps, you could use a 4 valve manifold and connect one pump each to the 3rd and 4th hose... be an interesting experiment to determine if it really helped. Remember to do it on NEW equipment... as drawing moisture and refrigerant trapped in oil out of a replacement or repair (even the lineset) will taint the test results. Change the oil in the pump before each cycle of the test to get accurate results.

Why wouldn't you just buy a 12 CFM Vacuum Pump....

http://hvac-talk.com/vbb/showthread.php?t=1104411

In this thread, Jim Bergmann shows just how fast a 500 micron vacuum can be reached using a good setup.

Originally Posted by aprophet

FWIW I have used 7/8 soft copper to pull vacums on rack with my pumps mighta been a little larger then yours they were some pretty good sized Kinneys

Any pictures of that rig??

FWIW I have used 7/8 soft copper to pull vacums on rack with my pumps mighta been a little larger then yours they were some pretty good sized Kinneys

Originally Posted by mark beiser

I think it would be kind of pointless if you only have 2 connection points.
It may get you down below 5000 microns a little faster, but most likely will have little impact on overall evacuation speed, especially pulling through a refrigerant manifold and service hoses.

On the other hand, you will get a MASSIVE reduction in evacuation time if you delete the manifold and service hoses, and use a vacuum tree with two 3/8" or 1/2" vacuum hoses between the pump and core removers on the service ports on the unit.

If you are currently evacuating through a service manifold and hoses, with the valve cores in place in the service ports, you could cut your evacuation times in half just by removing the cores, and using hoses with no core depressors.

Fantastic reply!
Guys like you are what this trade needs.
You gave me a clear answer with ways to improve.
Thanks

If you only have two quarter inch service valves it is pointless to use two pumps.

I think it would be kind of pointless if you only have 2 connection points.
It may get you down below 5000 microns a little faster, but most likely will have little impact on overall evacuation speed, especially pulling through a refrigerant manifold and service hoses.

On the other hand, you will get a MASSIVE reduction in evacuation time if you delete the manifold and service hoses, and use a vacuum tree with two 3/8" or 1/2" vacuum hoses between the pump and core removers on the service ports on the unit.

If you are currently evacuating through a service manifold and hoses, with the valve cores in place in the service ports, you could cut your evacuation times in half just by removing the cores, and using hoses with no core depressors.

Parallel Vacuum Pumps

I have thought of making a fitting to pair two vacuum pumps together with some copper tube.
Something I could easily connect when I want a really quick good vacuum when I only have 2 places to connect on a system.
This is what I was thinking..... thoughts?

This would take my 6CFM pump to a 12CFM pump in seconds... Attachment 377341