Vacuum out AC System----cheap way???

• $10 vacuum pump

Soundguy

ANY moisture trapped inside will eventually corrode the system from the inside out.

For what a new system co$t$, doing it RIGHT to start out with is worth it.

The must be someone near you with a pump who would do it reasonably, or lend you the pump?

Also, any air left in the system will degrade performance, and add load to the compressor, and heat to the condensor. Unlike the refrigerant, air does not liquify at the high-side pressures encountered in an A/C system, so you are using power to compress the air, then it simply "spings back" to low-side pressure, without absorbing heat in the process, as the refrigerant does.

This adds load to the compressor, wasting power, and heat that must be removed by the condensor, further increasing head pressure and power needed by the compressor.

---Bob (Certified in all classes of mobile and staionary refrigeration)

Clam down and let the shorts unwind from the afore-fixed wad.

The only possible reason to evacuate a system is to boil off any moisture contained in the air within the system.

That little dab of "atmospheric gas", if left in there, isn't going to hurt a darned thing. Far less "load on the system" than that large charge of non-compressible refrigerant oil floating around in there.

Which, by the way, kinda throws a wrench in the "corrosive effects from within" theory.

Yeah, I had all that "Certification" self-promoting propaganda too. Just filed it away with the rest of the toilet paper.

The trouble with living out of "the book" is that ya get stuck in said book and can’t see any other way. There's more than one method to approach things.

Allan

I've always considered you as pretty "level-headed" on here, but this is one time I have to disagree with you 100%.

There's simply NO reason not to properly evacuate an A/C system that has been apart, ESPECIALLY his NEW one. Why spend all the $$$$ on the system, then cut corners on getting it pumped down, only to shorten it's trouble-free service life AND put more strain on the system AND reduce it's cooling effectiveness, even if it's only a little.

Surely, he can find SOMEONE to help him out, without spending too many bucks to get it pumped down!

You stated: "Far less "load on the system" than that large charge of non-compressible refrigerant oil floating around in there."

The refrigerant oil IS "non-compressible". That is GOOD. The oil does not "compress", so no power is wasted compressing it.

The term we need to work with is "condensable".

Any air left in the system is "noncondensable", meaning power is used, and unneeded HEAT is generated by COMPRESSING the air, and, since it does not CONDENSE (as the refrigerant does), it "springs back" (expands) WITHOUT absorbing heat, as the refrigerant does, when it expands from a liquid to a gas through the "TXV" or "FOT".

From the ARI website:

"Air is another contaminant you need to be concerned about because it adversely affects cooling performance. Air is a noncondensable gas and can make a compressor noisy. Evacuating the A/C system with a vacuum pump should pull all of the air and moisture out of the system — assuming the pump is operating correctly, pulls adequate vacuum and is left on long enough to fully evacuate the system."

I can't imagine why you would take this stand against "pumping down" a system before charging it, against ALL "conventional wisdom"???

Hey! Wait a darned minute here! :>)

I'm not taking any stand against the "conventional wisdom". Far from it. And yes, you've probably noticed that I do like to stir the pot from time to time. :>)

Just like you and many other guys here, I've been down the pike more than a few hundred times, have been to every school under the sun and have spent years and years on the line. Just like you, I know air conditioners.

"NORMALLY", I would tell the guy to do just like you have advised. First, spend $2K making sure everything is brand spanking new (just to cover my tracks), pump 'em down, leave it set for fifteen minutes, if it holds then go ahead and fill with oil and freon.

However, look at the title to his post. It clearly asks how to do it cheaply.

Over the years, I have found that you can pretty much ignore all those petty little "laws and rules" we have been spoon fed by the marketing-rich industry with absolutely no ill effects. IF YOU SO DESIRE.

At the end of the day, the bottom line is that the cheapest way is to fill the sucker up and get on with your day. The system will outlast you, your children and their grand-children.

Allan

• Hydrocarbon refrigerant.

This is one of those times where our dry climate really pays off.

I quit evacuating the things about a 100 years ago and just fill 'em up from scratch. Don't even give it a second thought anymore. :>)

Allan

Give 'er a shot of freon while the high side port is open and shut that port within just a few seconds (purge it).

Fill 'er up as normal and be on your way.

Allan