Using Danfoss BD50 as Vacuum Pump

[infinitysail]

I have been using a compressor out of an AC unit as a vacuum pump. It was working great.. until it sucked some water into it.

I can pick up an old BD50 compressor cheap, and I have a spare control unit. Will this compressor work to suck air just as well as refrigerant? I'll put a makeshift dryer inline this time...

Thanks,
Frank

[DeepFrz]

Didn't you just tell us it was working great? ^^

[infinitysail]

That was a different compressor. A 110v Air conditioner compressor. I found lots of people online who have made vacuum pumps from 110v compressors, but none that have used a 12v danfoss compressor. I am guessing they are essentially the same kind of pump, but I'm not sure.

[DeepFrz]

Right, my fingers are working faster than my brain this morning. A common problem these days it seems...

[Richard Kollmann]

infinitysail, A compressor is not going to be a substitute for a two stage refrigerant vacuum pump. It is true that compressors in the past were used to remove gas vapors and can be used as a refrigerant recovery pump although not EPA approved. The real reason for deep vacuuming pump is to dehydrate liquid specifically moisture with a high temperature boiling point at atmospheric pressures. To change liquid moisture in a refrigeration unit to a gas vapor its boiling point must be lowered so it can be extracted as vapor. Removing as much of atmospheric pressure as possible allows liquid moisture to become a vapor.

At a Standard Day temperature or 69 Degree F with a vacuum in system pulled down to 29.22 inches this equals 17,780 microns of vacuum that is not enough. A refrigeration compressor used as a vacuum pump will reduce atmosphere pressure to 20,000 or maybe 10,000 microns.
When refrigeration systems contained Freon and Mineral oil dehydrating between 1,000 and 400 microns was considered adequate. Today with 134a and Ester oil complete system temperature needs to be near 100 degrees F and vacuum of sustained 300 microns in order for moisture dehydration to be effective.

Why worry about a small amount of moisture in 12 volt system with a BD compressor, it has a Filter Dryer? Well filter dryers used on any refrigerator are sized to capture and store forever moisture remaining in system after it is assembled. On boat ice box conversion units these are very small with desiccant material capable of holding as few as 10 drops of moisture. Moisture that travels through system as a vapor mixed with oil and refrigerant at some point will form an acid sludge. Then at some point in time major damage to a refrigeration unit will occur.

[infinitysail]

I am using this to suck moisture out of my rudder while on the hard, rather than as a refrigerant vacuum pump. It sounds like this will work, but may make for a short life for the pump. The pump is costing me only $25, however, so I can live with that.

Thanks for the help.

[Aikiguy]

No lube in the compressor, won't run for long.

Also it moves tiny, and I mean tiny amounts of gas. It is designed to be used on a balanced system so it doesn't need a lot of displacement.

Also it is not meant to operate in a vacuum, the specs of the compressor are for 10" or so of gauge pressure.

A shop vac would work better for your use than a Bd50

Guy
:-)