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Thank you. You've given me important information I need to help me do a good job.

At 144 on your initial pull.....you're good....

A small creep is fine....

If you would have gone from, say, 144 to 500 in a matter of a few minutes,
I would say you have a problem.....

For a residential, split system, it shouldn't be necessary to leave a pump
running over night...

With the proper tools and set ups, a solid, 200 micron (or lower) vacuum
can be pulled in 20 minutes....

Great job using the micron gauge....glad to see more guys taking pride in
their work!

Originally Posted by nlovas

First time I've ever used a micron guage. 410a split system. I pulled vacuum and here are my results:
Pump shut off at 144 microns.
+1 hour: 275 microns (131 increase).
+1 hour: 339 microns (62 increase).
+1-3/4hour:413 microns (76 increase).
So in 3-3/4 hours 269 micron increase.

How much of this creep is from micro leaks? Is this amount of creep normal?

Also, I was thinking of leaving the vacuum pump on overnight but it's getting cold at night (34F low). What is too cold for leaving a pump on?

Thanks and have a great day!

Sounds like a good vacuum and I applaud you for doing it right!!!


Outside pressure differences, improper hoses and/or connections could be the reason for this creep. Internally you have a dry and clean system. Charge that sucker up.

Micron creep

First time I've ever used a micron guage. 410a split system. I pulled vacuum and here are my results:
Pump shut off at 144 microns.
+1 hour: 275 microns (131 increase).
+1 hour: 339 microns (62 increase).
+1-3/4hour:413 microns (76 increase).
So in 3-3/4 hours 269 micron increase.

Is this amount of creep normal? Should this creep have stopped at some point?

Also, I was thinking of leaving the vacuum pump on overnight but it's getting cold at night (34F low). What is too cold for leaving a pump on?

Thanks and have a great day!