no vacuum pump

[JAWS]

Well I'm sitting here with two compressors and no vacuum pump. I think I read somewhere that you can use a second compressor instead of a vacuum pump. Can anyone give me a link or two explaining how this is done.

Secondly, is some sort of vacuum even needed?

Thanks

[TheDude]

I know you can solder a schrader valve to your suction line to make a pump from your extra compressor, but I don't think it works as well. Someone better qualified will be along soon, hang in there.:D

[aenigma]

Yep you can use the second one as a vacuum pump.Really depend on the type of compressor.Regular refrigerator compressors really don't seem to pull to a strong vacuum, but an a/c compressor will.gauge reads 29" I believe.The bigger compressors actually don't pull as much of a vacuum as the smaller ones, as far as I can remember.

[packrat]

You can use tripple evacuation (three times) to remove gases that are in the system. Do use one of the compressors to pull gas out then fill it with refrigerant. Pull the rifer out wit compressor then fill it again with refer that you using. Actually smaller compressors from refrigerators are designed better than ac compressors.

[aenigma]

That made a whole lot of sense. :eek:
I have used both, the a/c compressor pulls a better vacuum.

[packrat]

WRONG WRONG WRONG . The compression ratio for ac compressor is 4 or 5 to 1 whereas the refrigeration compressor is up to 12 to 1. The design of valves is different or better yet the entire compressor is made for that ratio, such as scroll. O by the way I am also a guy that was involved with project X that you indicated that suck. Another thing is that the statement about ac compressors pulling better vacuum tells me how much you know about HVAC.

[JAWS]

Thanks for the replies. Question: do I even need one? If not, would a second 1/4 compressor be better than nothing?

[aenigma]

Originally posted by packrat
WRONG WRONG WRONG . The compression ratio for ac compressor is 4 or 5 to 1 whereas the refrigeration compressor is up to 12 to 1. The design of valves is different or better yet the entire compressor is made for that ratio, such as scroll. O by the way I am also a guy that was involved with project X that you indicated that suck. Another thing is that the statement about ac compressors pulling better vacuum tells me how much you know about HVAC.

You telling me I am wrong indicates how much YOU know about refrigeration.
Both of my 5000btu a/c compressors pull 29" of vacuum.I've yet to see a little refrigerator compressor pull that much.
I suggest you stop pulling these things out of your ass, as you obviously don't know what your talking about.It doesn't suprise me that you were involved witht he Project X thread.It isn't that it "sucks", just a whole lot of false info if I remember right.

Your name does ring a bell too.

[packrat]

1\4 compressor would be fine. After 10 or 20 minutes of pumping break the vacuum with refrigerant u will be using. Bleed that refrigerant out then put the system again under vacuum using 1\4 HP COMPRESSOR THEN REPEAT THE PROCEDURE AGAIN. U WILL BE ALL SET. THE purpose of the vacuum is to remove as much as possible of noncondensable gasses and moisture

[aenigma]

Oh yeah almost any compressor will work as a vacuum pump, you can assist in removing moisture with heat(even if the compressor pulls to 29").I was just stating that the 5000btu a/c compressors I use, do in fact pull a stronger vacuum than most refrigerator compressors.

You don't want to only vacuum for 10-20 minutes and break the vacuum.I don't know where you came up with that, but if you really wan't a good vacuum, then vacuum it for up to 4 hours.Space heaters will speed up this time.

[packrat]

I personally do not use compressors for pulling vacuum. I do have a two stage vacuum pump. It is used for dehydration of small systems I'll say 15 tons and less. At work we have some that use 1\2 hp motors to drive the vacuum pump. Some are 7cfm and others are 3cfm. But all of them pull to at least 50 microns. At those numbers pumps basically work the same, but at start up of evacuation naturally larger one will pull down faster the difference is 3 or 4 minutes depending on the system volume. By the way they require special vacuum oil and they are oil filled. We do use gauges that measure deep vacuum beyond 29 inches. The way I came up with 10 or 20 minutes for running the 1\4 hp compressor as a vacuum pump, is in the "DARK ROOM". What I do is go to the basement shut all the lights and wait for the sign and then god speaks to my ear "10 to 20 minutes" and that is what he said. I will not argue with him and if you have problems with it you can take it up with him, I hope you understand I just dont want any damnation coming my way. Last time I argued with him he got really pist , he did come down after I informed him that I am going to get a different god if he continues to behave like that.

[TheDude]

ROFLMAO :rotf:

[aenigma]

Yes okay then. ;)



We do use gauges that measure deep vacuum beyond 29 inches.

Uhmmmm I really hope you didn't mean below 30" of vacuum.
You can not go beyond 29.92" of vacuum...

For a good vacuum pump(not compressor, I also use a vacuum pump) you vacuum around 4hours at 70f ambient/coldest temp of the system if you wan't a good dehydration.Use some space heaters and you decrease that time a good bit, 30 minutes would be good then.

10-20minutes with a regular 1/4hp compressor is definately not long enough unless your baking the system... :)

[packrat]

I am not good enough to read 2/100 of an inch on my gauges and yes I have pulled vacuum beyond 30" ,now that is where I excell at times.

[aenigma]

Ok you missed my point.See, it is impossible to pull over 30" of vacuum.Your gauges may say that, but they are wrong.The maximum attainable vacuum is 29.92".
At that vacuum water boils, well, sublimates at about -20f if I remember right.

[packrat]

I did not miss your point at all I set the trap and then took your bait. Yes it is possible to pull vacuum beyond 30 inches. Quite a few times we have violent storms that bring high pressure systems in the area and whenever barometric pressure exceed 30 inches I run down to my basement and pull the vacuum and I can say that at those times I pull vacuum over 30 inches. There now you see my trap. I do feel that I am playing mind games on this tread and my intention is to help but I guess I started it.,

[aenigma]

Ok got me there, so you can cheat to get 30"
Lets see you do it all the time though... ;)