Vacuum Pump question.

I was wondering if this pump would work okay.
http://cgi.ebay.com/ebaymotors/ws/eB...983446377&rd=1
I know it is not the best but I don't have much to spend.

I have a nice one that some one gave me befor I got into Xtreme cooling but I did not know what it was and I think that messed it up :( . (I ran water through it) It ran nice to I think it has a 1/3 hp moter. I got it back out and it was locked up (from rust) I got it moving again and I am going to open it up and see if I can get it to work again but if not would this pump work as a backup plan?

Thanks in advance

air driven pumps won't pull a deep vacuum, so they will not remove moisture.

Hmm it says right on the page that it IS for A/C's

Yes, but the purpose of it is not to remove all air and moisture... its for car, so its most likely to just completely remove the gas.... Which 28HG is enough for that... but not enough for a good evac.....

Okay so it sounds like that vac pump wont work. Is there any thing that I could get for 35 shipped or less that would do the job?

Ummm.... 35$ shipped? You need to be lucky or have good friends I guess.... I am myself looking for one around 120$ not shipped and its hard...beleive me....lol.... So 35$ is very unexpected....

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Originally Posted by _HL4E_HalfLife_

Hmm it says right on the page that it IS for A/C's

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Trust everything you read on Ebay huh?

You should know, that not everyone is honest about how good what they're selling is. And Ebay thinks they can just wash their hands of it... HAH!

You want to get something get something like this for example.

IT sure beats the hell out of that retro looking thing. It doesn't have to be THAT, but THAT is a bona-fide AC system, not for a car, evacuation. :p

There are plenty more there if you just look under vacuum pump, and stay away from the funny looking stuff. And the "Sold as is, we do not test" kinda crap.

erm, lemme edit that...

Wait, cant you use a compressor as an vac pump?

If you ran actual water through it, and let it sit, it's pretty much junk, and the same if you pulled a real lot of moisture out of a system, and let the pump sit with all that moisture-contaminaited oil in it, it is almost junk now. Rebuild time for it. If that costs too much for your needs, then be ready for at the least a couple of triple-evacuations and filter dryer changes before you can even think it will work for very low-temperature applications reliably.

okay what about this one
http://cgi.ebay.com/ws/eBayISAPI.dll...ayphotohosting
If this one wont work then I will try to get the one I have to work.

I personally dont like ebay, but if thats what you're after

http://cgi.ebay.com/ws/eBayISAPI.dll...983303688&rd=1
http://cgi.ebay.com/ws/eBayISAPI.dll...526563330&rd=1
http://cgi.ebay.com/ws/eBayISAPI.dll...526918450&rd=1

Repeating my question: Can't you just use another compressor to vacuum?

It's my opinion that you can't use compressors full stop, yes they move air and yes they work to a certain degree(poorly) and yes, some people will use them (wrongly) using compressor is a bodge it and leg it way, cheap nasty method. Perhaps some of you need a good few years in the industry to realise this. There we go, at least the people that use the proper gear can sleep easy at night. :stick:

I find it also rather alarming that very few use vac guages :eek:

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Originally Posted by expansionvalve

I find it also rather alarming that very few use vac guages :eek:

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what are u refering to? a manifold gauge or a micron gauge? If ur talking about a micron gauge i think the reason very few use one is because there too dam expensive. :(

BTW did you all know that a Vacuum pumps compression chamber is built the same way a rotary compressor's is the only difference is most vacuum pumps have 2 stages so in theory if u connected up 2 rotarys in series they would work just as good as a 2 stage vacuum pump.

Its not just a different chamber. Different mountings, different types of stators, etc etc. Its not as simple as black and white.

hmm i've got a couple of systems sitting here running fine that were vac'd by a compressor.

:stick:

I am watching some pumps on ebay. If I get my systems all finished and still can't get a vacum pump then I may use a compressor. But I realy only want to use it if I have no choice. Does any one know whare I can get a good vacuum pump for $50 or less. Thanks for all the info.

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Originally Posted by _HL4E_HalfLife_

BTW did you all know that a Vacuum pumps compression chamber is built the same way a rotary compressor's is the only difference is most vacuum pumps have 2 stages so in theory if u connected up 2 rotarys in series they would work just as good as a 2 stage vacuum pump.

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A Porche and a lada both has four wheels....

The vaccum pump was made to extract, the compressor was made to push and pull.... they are not made the way way.... Yes on the same compression theories, but not the same way, and not for the same use...

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Originally Posted by skate2snow

A Porche and a lada both has four wheels....

The vaccum pump was made to extract, the compressor was made to push and pull.... they are not made the way way.... Yes on the same compression theories, but not the same way, and not for the same use...

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Have you ever opened up a vacuum pump and a rotary compressor and examined them both?

I'm still waiting for someone to post a pic of a compressor(or 2) boiling water at ambiant temperature. do that and it will resolve the issiue.

I would try it wdrzal but I don't have any compressors that I'm not using at the moment.

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Originally Posted by wdrzal

I'm still waiting for someone to post a pic of a compressor(or 2) boiling water at ambiant temperature. do that and it will resolve the issiue.

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Im trying it as we speak.

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Originally Posted by wdrzal

I'm still waiting for someone to post a pic of a compressor(or 2) boiling water at ambiant temperature. do that and it will resolve the issiue.

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Well I know one compressor won't do it.. maybe 2 large ones will. Most 2 stage vacuum pumps can pull an ultimate vacuum of 25microns or less, and at 500 microns water boils at -10F or so.

Im changing my duel compressor vacuum pump's layout right now i got 2 compressors in parallel but im changing them so there in series this should allow them to pull a deep enough vacuum to start picking up moisture if not ill add a 3rd compressor in the series.

update how many compressors are we up to now ,2,3,4 or more.

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Originally Posted by wdrzal

update how many compressors are we up to now ,2,3,4 or more.

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just 2

any luck with two

Oh BTW... What you can do useful with a compressor, is doing a recovery unit.... not really hard, any size is good, and it doesnt really need to pull a deep vacuum.... Its useful for those who has limited refrigerant resources....

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Originally Posted by skate2snow

Oh BTW... What you can do useful with a compressor, is doing a recovery unit.... not really hard, any size is good, and it doesnt really need to pull a deep vacuum.... Its useful for those who has limited refrigerant resources....

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this is correct, all early recovery units used hermetic compressors.

the industry is getting away from using them because you need to change the oil when you change refrigerent types. Most now are oiless.

any results on this yet HL4E?

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Originally Posted by shinymod

any results on this yet HL4E?

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Not really because today i just changed from paralell to series and we don't know just how fast it would remove the water from the bottle without acualy sucking the liquid water from the bottle u know what i mean? and its not very ez to make a 100% seal from a gauge hose to a bottle.

ah, yeah. i can see that being a problem... well keep us informed wont you :)

All you realy would need to do is get a sight glass and braze its other end shut and braze a schraeder to the remaining end. Then fill it with water just so that the water level is at the sight glass and not above when the thing is mounted vertically.

Theres still the matter of how quickly a vacuum system would remove that water. A large sold amount of water may take many hours to remove compaired to mini droplets in a copper tube.

Isnt that why you can crank up the MAP gas torch and lightly go over the tubes to melt it down?

the point of a large volume is so you can see it boil, like boiling water in a pot, if you can't lower the pressure enough to make that happen the pressure isn't low enough.

Good point, but while its sucking down, you might as well use the time and melt the water on ur own.

you don't need to remove all the water just making it boil will prove the point, you should be able to make it boil in under 1 min, if not it never will.

Well I did it, boiled water at room temperature with regular compressors.

I made a vacume pump from two dirty old compressors I got from the scrap yard for free. They are connected in series.

I took a shrader valve with a stem, and wraped it with electrical tape until it fit snugly into a glass bottle. I put some grease on the tape and shoved it into the bottle. I connected the bottle to the pump with a manifolg gauge, turned on the pump, and a couple seconds later the water started to boil. The water is fresh from the tap, so it is actualy a few degrees below room temperature.

I made a video of the unit getting turned on and pulling a vacume, then the water boiling. I'll post it in a second, I just have to compress it a bit.

Edit:

Ok, it seems I can't upload anything over 200kb, so I can't upload much of the movie no matter how bad I make it look. Essentially the video shows the system turned of, manifold gauge reads 0. The system is turned on, manifold gauge drops to about 30"HG, and the water in the bottle begins to boil. The water temperature is 20 degrees through all of this, which is a bit below ambient. Here is a very bad looking 5 seconds of the video. If someone knows how I can post more of the video, or want's to host it, PM me.

My pump won't work as well as a real vacume pump, but for the price of a shrader valve and some brazing rod, it's pretty damn good.

Congradulations :toast: you just proved 2 compressors will work.what type are you using piston or rotary.

Both of them are piston. I was actually suprised at how easily it made the water boil. I threw the addapter for a bottle together in probably less than 2 minutes and just slapped everything else together. I can't say that I noticed any leaks, but I would be supprised if there wern't some very small ones. Even with the quick construction, the pump had no trouble boiling the water, and it only takes 10 seconds or so from the time you turn the compressors on until the boiling starts. Putting a marshmellow (sp?) in the bottle is also a lot of fun, although I don't think I will ever get it back out.

There is a little bit about the vacume pump at the end of this thread.

Is is just two small piston type R-12 compressors that I picked up from the Bin-O-Compressors at the scrap yeard, connected in series.

I will have to see if I can get a micron reading using 2 compressors. My micron gauge only reads below 2000 microns so not sure if the pressure will get that low.

Hmm my water wasn't doing that when i tried pulling a vacuum in a bottle. What was ur ambient temp? Im in my bacement where its cool so im just wondering what room temp is needed to get the water to boil with 2 compressors in series.

I was boiling the water in my basement at night. The ambient air temperature was around 21 or 22 degrees, and the water temperature was a bit below this, around 20 degrees.

I tried it again but this time a stuck a heater near the bottle for a min and next thing you know the water is bubbling.

BTW the temp in the room im building this was only 18.5c.

Well, you got water to boil off, fair play well done. :toast:
What are the chances of someone testing a pair of compressors on a system with a micron guage?

i would giggle so hard if 2 compressors pulled a 25 micron vacuum ^.^ of course they wont... but it'd be funny to see the so called "halfassed" method kick the ass of the "proper" method :p:

I would giggle too, I would buy that man a few beers lol

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Originally Posted by expansionvalve

I would giggle too, I would buy that man a few beers lol

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don't giggle yet, I hooked 2 compressors togeater and was not able to get a micron reading ,my meter starts at 2000. That alone does not prove 2 comprseeors won't work.

But more testing needs done.One could hook them to the low side of a system while conecting the bottle to the high side,then doing the same experiment. first to see if you can get it to boil.Then by trying to remove just a few drops of water fro the bottle on the other side of system.

lines losses &restrictions are critical in deep vacuum,just havig a condensor and evap in the loop may prove to much to overcome.but maybee not we'll see.

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What are the chances of someone testing a pair of compressors on a system with a micron guage?

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Before wdrzal tried it I would have said low. People who have a micron gauge don't use compressors to vacume a system, and people who use a compressor as a vacume don't own a micron gauge.

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Then by trying to remove just a few drops of water fro the bottle on the other side of system.

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I'm not too keen on the idea of putting a glass bottle on the high side of the pump, but I was thinking of putting volume marks on the bottle and measuring the rate of evaporation.

As far as figuring out how much of a vacume my pump can pull, I was thinking of trying to boil water at lower temperatures. At 20 degrees the pressure needs to be lowered to 2.339 kPa, which my pump was able to do. At 0.01 degrees the pressure must go down to 0.6113 kPa, or about 4600 microns. If my junkyard compressors can do that, I will be thoroughly impressed.

Here's a question though, why do you need to pull such a deep vacume? I understand the need to evaporate the water from a system and remove most of the gases, but why do you need to pull the vacume so deep? At what pressure/temperature would the compressor oil start to evaporate?

What do you define as low vac?
100micron is a normal figure in my field.
Pulling this sort of vac level gives me peace of mind that all moisture/air in the system has pretty much gone thus reducing the chance that the equipment will breakdown/wear out prematurely, it also helps me sleep at night because if it does breakdown at 3am guess who has to be there by 4am to fix it??
Also, by pulling a deep vac or trying to a micron guage will tell you a little more about the condition of the system, it will indicate the tinyest of leaks and also give you a tiny hint into moisture levels. There have been so many times I have leak tested a system to 300psi and it's held the charge overnight only to find I can't pull a vac due to tiny, tiny leak the next day.
A few effects of moisture and air in systems...
blocked expansion devices or a partial blockage reducing perfromance and wasting electricity, copper plating that ruins compressors, the breakdown of compressor oils... all very important.
I reall am going to sit on my boat here, basically, if you cant pull and maintain a low vac the systems only half good.

put the bottle on the high side of a refrigeration loop,while vacuum is connected to the low side.This way you will be pulling vacuum thru the entire system.

Not the high side of the compressor.

by a fast rise in a micron gauge you have a leak.if the pressure rises slowly you still have some moisture in the system.

the reason for such a deep vacuum is that at any pressure above 1 micron there is unwanted gas/air in the system the deeper the vacuum the more that is removed.

A often held misconception is that once you get below 0 psig and read a vacuum there in nothing inside the system, the system is in vacuum, this couldn't be further from the truth, the system is not completly empty until you reach 29.92 "HG of vacuum.

being at 1"hg vacuum just means you are 1" hg below atmospheric pressure not that ther is no pressure present.once you understand the difference between psig(gauge) and psia (absolute)its easy to understand.


you can do your test by boiling the water then put the bottle in a ice bucket, as soon as the boiling stops, note the temperature of the water. We can determine the pressure from this.

That was very well put. :)

Well I tried vacuming water at 0 degrees C and it worked. I half filled a bottle with crushed ice and stuck some water in with it to fill the gaps. I connected this to my vacume pump made of two old compressors, and it was able to make the water boil. With room temperature water there are a few very large bubbles, with this ice water there are hundreds of smaller bubbles from everywhere. I guess all the surface area of the ice changes how the bubbles form or something. In any case, I have figured out that my vacume pump can pull at least a 4600 micron vacume. :)

nicely done matt :D

yellow jacket came out with a model that reads from .5 microns to atmospheric pressure last year. if some has one of those we could get a accurate reading. all the ones I own only read below 2000 microns . other companys also make micron gauges like tif, supco, robinair.

In any case very good work Matt !!!! now you need to buy a gauge to show just "how Loooow you can go" LOL

While 4600 microns isn't ideal,I think its Super for 2 compressors, I think thats low enough with using a heat gun you can do a very good evacuation on a system.

I wondering if adding a check valve will improve performance even more?

Well done on the mission to proving to some degree a compressor or two will do something worth while :)
boy compressor technology has changed.

I think that now you have the task of removing moisture contaminated oil from the compressors. now a vac pump has a little sightglass so you can see the oil and a very handy little drain screw on the bottom, so much easier.
Sorry, I whill shut up about vac pumps now :D :slapass:

I'm not sure if I really have to worry about water contaminating the oil. Every time I turn it on it spits out a little oil, so I think I will just have to continually throw a little oil down the low side.

Measuring how much vacume I can pull on my Ghetto vacume pump with a crazy expensive micron gauge just seems wrong. I will stick to ghetto measurements :toast: Maby I could try boiling some other fluids at different temps to see what it can do.

Water will contaminate the oil. In a vacuum pump application, that is what it's supposed to do. If you see the oil getting milky in a vacuum pump, then you're way past due in changing it. In a low temperature application, you only need a 1/4 of a drop of moisture in your system to clog your cap tubes. Moisture also tends to convert your refrigerant oil to a wax-like substance, also clogging your expansion device, and contributes to increasing your acidity levels in the system from chemical reaction with your hermetic compressor winding insualtion if overheated. Once the acidity level increases, it starts a vicious cycle of increasing further due to more reaction with the compressor windings and further heat due to the failing windings. Eventually the compressor burns out, and you have a very contaminated system on your hands. It's then time for a complete rebuild of your system.
This is a worst case scenario, but not unavoidable. Oversizing your filter-driers will help a bit, and triple-evacuating your systems at least twice may help avoid the bad burnouts. In my opinion, it may be better to invest in an actual vaccuum pump, and have repeated good results in evacuating systems(and save an ass-load of time), than going through troubleshooting a system that may have moisture in it. Hell, if you don't like it, you can always sell it on E-Bay anyways..

Just some toughts from some joker
who does this stuff every day..

I got another used compressor at work today so i added it to my vacuum pump and now with this 3rd compressor i got in series with the other 2. So when i had only the 2 compressors on i couldn't get the water to boil just after it came from the tap because its cool but after i fired up the 3rd compressor the water start boiling right away :D :woot:

this has been a really interesting read :clap: i my self use a compressor to vacuum my system, i only do so as its cheaper and im still fairly new to all this.

would a more powerful compressor work better as a vacuum pump, what would be the minimum for ther job ?

whats the best way to vacuum a system with compressors ?

MW

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Originally Posted by mr-white

this has been a really interesting read :clap: i my self use a compressor to vacuum my system, i only do so as its cheaper and im still fairly new to all this.

would a more powerful compressor work better as a vacuum pump, what would be the minimum for ther job ?

whats the best way to vacuum a system with compressors ?

MW

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The size of the compressor doesn't matter the only difference is the larger the quicker it will pull a vacuum.

MW-"whats the best way to vacuum a system with compressors ?"

set them up just i do in my pic above there in series.

the reason i asked was because i got told running compressors in series didnt work because the second compressor could only move what the first had removed so it didnt increase performance. then i read it was good to have one compressor on the high side and one on the low both vacuuming together ?

MW