evacuation question

[billdozza]

for residential a/c systems is it better to evacuate once for a long period of time or triple evacuate for short periods?

[taz24]

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I think different people will give you different answer.

I have always been told that if possible, tripple vac. It is more effective than a
deep vac, but the last vac must always be below 2 Torr (lower is even better).

The reason behind this is the OFN that you break the vac with. Because it is dry
it absorbs moisture and carries it out and each vac removes a little more moisture than
the last.

But if time is not a factor then put it on vac for 24 hours and suck the thing inside out :) .

Somtimes you have no option.

All the best

taz

.

[sedgy]

hi taz, as allways you are spot on, I had tripple vaced for 40 years , but with the advent of better vac pumps , it is said that one vac is now sufficiant< if lower enough< hope you have enough work to keep you out of troble< sedgy,

[chemi-cool]

The only thing I can add here is my advice, get a good and big 100mm vacuum gauge.
It will show you if you have moisture in the system and how deep is your vacuum.
Just remember - Never charge the system while vacuum gauge is connected.

[Allrounder]

I have never seen any evidence for triple evacuation? I am not convinced that OFN carries out moisture when it is released.
I say go for a long deep vac every time.

[Tayters]

This has puzzled me because of the conflicting theories.

At college I was told that OFN was introduced from high to low side to push all the bad stuff to the larger pipe making it easier for the vac pump to get it out and OFN had no absorption properties.
Have always kept an open mind on this. In practice I bear in mind what the wife says to me - go long, go deep.

Cheers,
Andy.

[Magoo]

generally only due vac test to dry systems , a triple evac as well. As for leaks, not a good test. effectively a negitive 15 psig pressure test. Unless you want to scan vac gauge for a month you will see naf all changes. HP testing above operating conditions is the only real check

[nike123]

Some interesting videos on subject:
http://www.youtube.com/user/HVACRat#p/u/11/_ISUGzoiui4
http://www.youtube.com/user/HVACRat#p/u/10/hCXNL0IWb1I
http://www.youtube.com/user/HVACRat#p/u/9/qdv77SyBgKE