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Technical
FAQ Pumps


1. My vacuum pump runs, but I cannot get a vacuum.

The coupler between the shaft of the pump and the shaft of the motor is either broken or slipping. Make sure the set screws are tight on the flats of the two shafts.

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2. Why is it so important to change the oil often in my vacuum pump?

The proper oil in a vacuum pump acts as a blotter and absorbs all of the moisture and non-condensables. As the oil becomes saturated with these contaminants, the efficiency of the pump is dramatically reduced. Maintaining clean oil in the pump ensures that the pump will operate at peak efficiency and prolong its life.

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3. Can I use any oil in my vacuum pump?

No. JB Black Gold oil is extremely pure and non-detergent. Black Gold is hydro processed which means it goes through a series of catalytic steps rendering the oil extremely refined, more viscous, and more stable. The result is a clear mineral oil that will alert you to contamination sooner as it becomes cloudy or milky.

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4. Why is it important to change my oil when the pump is hot?

As the pump cools, the moisture and contaminates start to separate in the pump and when drained, the contaminants cling to the walls of the pump. When you refill the pump with new oil, those contaminants will mix in with the new oil as the pump warms up resulting in the new oil quickly becoming contaminated.

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5. If I am always pulling a vacuum on clean, dry systems, is there a way to check my oil in the pump to see if it is contaminated and not have to change it so frequently?

It is recommended that a micron gauge be attached directly to the pump and should pull to 50 microns or lower if the oil is clean. If the micron gauge does not pull to 50 microns, it is an indication that the oil is becoming contaminnated and should be changed.

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6. Other than pulling air out of the system, how does my vacuum pump get rid of the moisture in the system?

Most two stage vacuum pumps will go low enough in vacuum and reduce the atmospheric pressure within the system, thus allowing boiling of the moisture at a lower temperature. Once the moisture is in a vapor form, it is readily removed by the pump.

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7. What is a gas ballast and how do I use it?

On the initial pull of vacuum on a system, the gas ballast is open allowing the initial volume of air in the system to bypass the oil so as to not contaminate the oil immediately. When the pump starts to quiet down, close the gas ballast and the pump will start reducing atmospheric pressure in the system to boil the moisture and non-condensables.

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8. What is a blank-off valve?

The blank-off valve acts no different than a water valve. Open it, and with the pump running you will get your desired vacuum. Close it, and with the pump running there is no vacuum.

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9. If I use a larger CFM pump, will I be able to pull a vacuum on a system faster?

In most cases NO. Using a vacuum pump on air conditioning systems from 1 ton to 10 tons, you will not see the difference between a 3 CFM pump and a 10 CFM pump. For example, if you put a pump on a system and you notice within 2 minutes the pump quiets down and you cannot really feel any air leaving the exhaust. This means that there is no more CFM left in the system and you are now working with molecules. Thus, at this point if you replaced a 3 CFM pump with a 10 CFM pump, there is no change in vacuum or time.

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10. What is a micron?

There are 25,400 microns in an inch. Therefore, with a compound gauge reading 0 inches to 30 inches, there are 762,000 microns.

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11. I have been using my low side gauge to pull a vacuum, is this wrong?

YES. The low side gauge knows only atmospheric pressure and cannot sense moisture or non-condensables. A micron gauge is a heat sensing device that not only reads atmospheric pressure, but also measures the gases created by the vacuum pump as it boils the moisture. For example, if you were to pull a vacuum on an enclosed bottle of water, the low side gauge when pulling a vacuum will read a perfect vacuum. Using a micron gauge, it will immediately tell you with a high reading the you have a problem in you system.

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12. I have been pulling a vacuum on my system using a micron gauge and cannot get it down to a low reading.

See FAQ #1. Another possibility is that some oil may have entered the micron gauge and is giving false readings. The remedy is to pour regular rubbing alcohol into the connector on the micron gauge, shake, and pour out (do not use a q-tip, rag, or any other material - use the liquid alcohol only). Do this about three times, then try to pull a vacuum with the gauge.

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13. I am able to pull a vacuum on my system, but when I blank-off, the micron gauge rises rapidly.

Unless you are using JB`s DV-29, copper tubing, or flexible metal hoses, it is not recommended to use your existing manifold and hoses for blanking-off a system to check for leaks. Hoses work very well under high pressure. Vacuum is very critical in leaks, more so than pressure. All charging hoses, including the black hoses 1/4" or 3/8" permeate. Where the crimp is on the brass to the hose also has possible leak issues, and the gasket at the coupler is a major leak offender. The vacuum industry uses O-rings on most couplers. When you screw down on a gasket, it goes into many contortions and will not seal. When using an O-ring, you screw down on it to get a metal to metal seat and the O-ring lies around the lip of the flare giving it a positive seal.

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14. Can I mount my micron gauge onto the vacuum pump?

It is not recommended to do so as you are reading what the pump is doing and not what the pump is doing to the system (see DV-29). It is suggested that you tee off on the suction side of the system and mount the gauge there.

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15. How low of a vacuum should we pull on a system?

JB recommends that a system be pulled to at least 250 microns and held at least five minutes. On any polyester oils in a system, it is recommended to pull a much lower vacuum as moisture is very difficult to remove even with heat and vacuum.

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16. Why does the micron gauge slowly fall back and then start to hold after pulling a vacuum and blanking-off?

The reason for this is there is equalization within the system. If you pull a vacuum lower, it will then fall back at a shorter range and hold.

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17. Why do I need to check the oil level when the pump is running?

The reason for this is that if the vacuum is not broken before pumps are shut down the oil in the cover will seek the vacuum still in the cartridge and intake chamber. Then the oil level will drop in the sight glass and give the appearance of a low oil level. Then if the pump is refilled to the oil level line and the pump started, the oil that got sucked back into the cartridge and intake chamber will be kicked back into the cover and now you’ll be over filled and the oil will shoot out the handle (exhaust port).   

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