Compressor ID for DIY vacuum pump

[mikemac]

Hi everyone,

I'm looking to pick up a hermetic compressor for a DIY project, making a vacuum pump for working on my auto A/C.

How do I tell the difference between a compresor that has a permanent oil reservoir and one that uses oil circulating with the refrigerant? I obviously would need one with a oil reservoir for my needs. This is probably a no brainer for you guys but I couldn't find any info on telling the difference between the two. Thanks for any help. Michael

[nike123]

Hi everyone,

I'm looking to pick up a hermetic compressor for a DIY project, making a vacuum pump for working on my auto A/C.

How do I tell the difference between a compresor that has a permanent oil reservoir and one that uses oil circulating with the refrigerant? I obviously would need one with a oil reservoir for my needs. This is probably a no brainer for you guys but I couldn't find any info on telling the difference between the two. Thanks for any help. Michael

You could not make vacuum pump from compressor!
Those two works in different mode!

[Chunk]

As Nike123 says vac pumps cant be made from fridge compressors.Your best bet is to try e-bay and type in "refrigeration vacuum pumps" they have a lot of cheapies on there to have a look at.

Best of luck.

[mikemac]

Actually I used to have one made from a refrigerator compressor! A guy that worked at the Auto Dealership where I was a tech made it up. You use the suction side of the compressor to pull the vacuum. There are websites all over the net on how to convert them, just not many that give good advice on telling the two types apart. I don't want to go to the trouble of recovering refrigerant from a unit and then find out that the compreesor uses circulating oil for lubrication. I have located a Kenmore mini fridge for 30 bucks and a new in the box R12 compressor for 10 bucks.
From one of thse websites;

The first step, of course, is to investigate a fridge or two until you discover a self-contained hermetic compressor similar to that shown in the photograph. (Be warned that not all canister-style pressurizers are the same. Some have a permanent oil reservoir, while others use the circulating refrigerant as a lubricant and hence will not run indefinitely when salvaged. Ask your local refrigeration mechanic . . . he or she may be able to tell you which type your choice is.)

[Chunk]

I must say that i have never come across one of these machines but i have led a sheltered life.

I shall have a look on t`internet,you have me intruiged.

[Chunk]

Obviously,compressors run in a vacuum when not pumping refrigerant,i cannot find any compressors that are small enough with a seperate oil reservoir as they all come with their own internal one,apart from some scroll compressors i found,but we wont go there if we dont need to.

I did find this which may or may not be helpfull to you,but i quite liked it.

http://www.youtube.com/watch?v=1Dv9uUL80NQ

Some-one showing you how to make a home-made vac-pump using a fridge compressor.

[monkey spanners]

Compressor manufacturers tell us not to run compressors in a vacuum for more than 30 seconds due to the risk of arking between the electrical terminals.
Its a bit like smoking whilst filling your car with gas, just because its been done it doesn't make it safe.
Also another very important point is that a compressor will not reach a low enough vacuum to remove moisture which is one of the main reasons for pulling a vacuum in the first place.

Jon

[Chunk]

Many of the sites that you might have looked only use these homemade vac pumps for doing weird things like sucking air out of clothing bags etc.

In using compressors like this,the maximum you will probably get is about a 1 torr vacuum which is not sufficient for what you want.

As monkeyspanners said these compressors should not be used.This is the reason they invented vac pumps in the first place.

[The Viking]

##NOTE, IMPORTANT:##

In the good old day's (about 5 years ago) car A/C compressors had mineral oil in them. Back then you could get away with a half decent vacuum as the mineral oil is a stable fluid (and you wouldn't notice the performance drop in a car A/C system).

Nowadays, due to the modern "green" refrigerants used not being compatible with mineral oil, the cars' A/C compressors are working on synthetic oil.

SYNTHETIC OIL WILL BECOME ACIDIC AS SOON AS IT COMES IN CONTACT WITH ANY MOISTURE!

Thus, in modern applications with modern refrigerants, a good, deep, standing vacuum is required.

No compressor will be able to reach the level of vacuum required, you do need a purpose built, dedicated vacuum pump.

(Or you will pump acid around inside your A/C system.)

[albionharley]

Thinking about it - another problem you will have is the compressor rapidly overheating. Also as Monkey Spanners states they simply aren't designed to run in a vac for any length of time and scrolls not at all.

[Chunk]

A scroll compressor apparatus comprising a closed scroll compressor, an oil reservoir vessel separate from the closed scroll compressor, a discharge pipe, and an oil supply pipe. The closed scroll compressor includes a closed container having a suction port through which a compression medium is suctioned, a scroll compression mechanism encased in the closed container, a motor encased in the closed container, a first oil supply passage extending through an end plate of a fixed scroll and through which a first opening facing a sliding contact portion with an orbiting scroll is communicated with an oil supply port, a second oil supply passage formed in an end plate of the orbiting scroll and through which the first opening is communicated with a second opening facing an end face of a driving shaft, and a third oil supply passage, formed in the driving shaft, through which the second opening is communicated with the third opening facing a bearing supporting the driving shaft. A discharge port is provided on the closed container at a position opposite to the scroll compression mechanism unit with respect to the motor.

I said i didnt want to go there.

[albionharley]

Hi Chunk - as you did say best not to go there - it's way too late , LOL. I'm off to bed !!!!

[mikemac]

Interesting reading, not sure what to think here. I used a converted compressor as a vacuum pump on an almost daily basis as a professional tech at an Infiniti dealer. It would draw the gauges down as far as they would go all day long. Never had an overheat problem but it was a compressor that had an oil sump too. When other techs needed to pull a long deep vacuum they would come use mine. This was about 8 years ago and was after r134a and pag oils were used in US cars. I'll have to check with my tech friends that are still in the business.

[nike123]

Interesting reading, not sure what to think here. I used a converted compressor as a vacuum pump on an almost daily basis as a professional tech at an Infiniti dealer. It would draw the gauges down as far as they would go all day long. Never had an overheat problem but it was a compressor that had an oil sump too. When other techs needed to pull a long deep vacuum they would come use mine. This was about 8 years ago and was after r134a and pag oils were used in US cars. I'll have to check with my tech friends that are still in the business.

Did you ever measured that reached vacuum, with that compressor, is some decent amount below boiling point of water at that temperature?
Boiling point of water at 68°F is 0,3394 PSI.
You need a lot lower pressure to boil that moisture and suck that out of system.
You can not measure that vacuum with gauges!
What is the point in vacuum drying if you cannot lower system pressure to boil water and then suck that evaporated moisture out?
Compressor is not designed to pull decent vacuum. You need rotary vane vacuum pump
http://en.wikipedia.org/wiki/Rotary_vane_pump
(preferably double stage capable of pulling to 50 microns => 0,05 torr => 0,000967 PSIa)
and electronic micron vacuum gauge to measure reached vacuum, and if water still boils.

[mikemac]

I too the advice given here and picked up a used vacuum pump from an old auto repair shop that was going out of business. It is very similar to a hermetic compressor as far as looks go. I would like to do some maintenance to it before using it but the manufacturers label is partially missing. It has a oil drain plug and a fill plug but I have no idea of what oil and in what quantities to use. I have pictures hosted at a site but can't post URL's until I have 15 posts. Can anyone post them for me if I email them too you? Thanks

[The Viking]

The oil would be a dedicated vacuum pump oil, sold by refrigeration wholesalers.

As to quantity, I have still to come across a vacc pump without sight glass.

Pictures? If you email them to me I will post them for you.

[The Viking]

Pictures from Mikemac:







Link to a similar one currently on fleabay HERE


Sorry mate, to me this looks like a "normal" hermetic compressor that someone has butchered.

A normal rotary vane vacuum pump looks something like this:


But hopefully someone else here will recognise it and be able to tell you more about them.

[monkey spanners]

Looks like a J.F. Jelenko & Co./Pennwalt medical vacuum pump to me.

[mikemac]

It's made by Draf Tool Company in New York USA. It is a purpose built a/c vacuum pump not a conversion. There are lots of these floating around over here. It appears that Draf Tools merged with another company and is possibly the manufacturer that made the one on Ebay.

[Old Codger]

mikemac, I too have one almost identical to the one on eBay. Mine, however, is missing the start capacitor on the side. (It only has three pins/wires sticking out to plug the capacitor on to.) Would you mind looking at yours to see if you can tell what electronics are in the box on the side of your unit?

By the way, mine (like the eBay unit) doesn't have a manufacturer's name but it has that same address in Bedford Hills, NY. When I googled DRAF Tool Co (yours) I learned that they also were located in Bedford Hills, NY. However, I haven't found any current information on them. Nor is there a manufacturer at that address currently.

Anyway, any information to help me get the one I have working again would be appreciated.

Thanks,
OC

[Ohm&Hammer]

I would suspect you put the oil in the filler hole, and remove the plug right below the label. When the oil is at the correct height it will drain out of the lower hole.

Try removing the lower plug, and seeing if there is an oil level visible.

[Brian_UK]

I too the advice given here and picked up a used vacuum pump from an old auto repair shop that was going out of business. It is very similar to a hermetic compressor as far as looks go. I would like to do some maintenance to it before using it but the manufacturers label is partially missing. It has a oil drain plug and a fill plug but I have no idea of what oil and in what quantities to use. I have pictures hosted at a site but can't post URL's until I have 15 posts. Can anyone post them for me if I email them too you? Thanks

Just type it out 'longhand style'..

w w w .refrigeration-engineer.com

We can cut and paste it ourselves then

[vacuum pumps]

If you want to find out more about vacuum pumps there's some information at the bcas website, it's short for British Compressed Air Association.

Hope it helps.