How To Operate an HVAC Vacuum Pump – A Beginners Guide

HVAC Vacuum Pump Kit with MiniSplit Adapters


How To Operate and HVAC Vacuum Punp – A Beginners Guide

For many of the Do-It-Yourselfer’s out there you obviously are wanting to save yourself a little bit of money but still want to do it correctly, right?  Well, Unless you want to pay an HVAC Technician $65 or more an hour to come do it for you.  There is absolutely nothing wrong with having a Professional take care of it for so you will have some sort of satisfaction and guarantee that it may be done correctly. 

Its a very easy task and doesn’t take very long. You really just need an understanding of the equipment, how it works, and what to look for.  In this guide I give you an easy to understand way to vacuum ( or “draw down” as they say in the industry) your lineset to remove any air or moisture in the copper tubing. Any of these or a combination of these in your lines can cause some serious havoc to your Compressor. I do need to emphasize that many of your HVAC dealers or manufacturers will not cover the unit under Warranty unless its completed by a Licensed HVAC Technician.  Even if you prefer to do it as a DIY’er as long as it’s done correctly, you shouldn’t have any warranty issues or the need to file a warranty claim.

All of the Mini Split Systems that we sell come complete with the Compressor, Air Handler, Lineset Installation Kit, and Remote.  To learn HOW TO install your system, you can start  HERE  .

What Exactly is a Lineset, Do you ask?

A lineset is the copper tubing with foam insulation that carries the refrigerant from your Compressor to your Indoor Air Handler unit inside. They are sold in different lengths to fit your need and can be covered by Black or White Foam Insulation.  If you have Copper tubing, flair fittings, and  insulation you can make your own.  If you decide to make your own be careful to be sure your flair fittings and flairs are the correct size for your particular unit.  You can always buy them pre-made to fit your unit and is much faster to connect.

Lineset Kit for Mr Cool Units


What’s the Purpose of a Vacuum Pump?

A vacuum pump is used to remove air and contaminants from an HVAC system after refrigerant recovery. This creates a vacuum state. The deeper and more complete the vacuum, the more contaminants trapped within the system, its components, and even the compressor oil are removed. Vacuuming basically prevents the lines from clogging when the system is operating.

Many of the Mini Split Units on the market today utilize R410a refrigerant to operate.  The units we sell come to your door already pre-charged with the refrigerant needed.  You only need to release the gas for your system to work properly AFTER you have vacuumed or Drawn down the lineset.


The illustration below will give you an idea of the procedure to vac or drawn down your mini split to the proper microns needed.  Its typically ideal to get it down to 500 Microns.  ( Illustration Courtesy of Wiki How)


Setting up Your Vacuum Pump

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    Fill the pump with vacuum oil. Before you use your vacuum pump, make sure it is full of clean vacuum pump oil. Unscrew the oil fill cap, typically located on the top of the pump, and look on the interior edge of the opening for the fill line. Fill the opening with oil until it reaches that line. Then, replace the oil fill cap

    • Be sure to only use oil meant for vacuum pumps. Using other mechanical oils could impact the quality and performance of your vacuum.
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    Attach your gauges to the ports. You will need a gauge set that connects to both your vacuum and your pressure ports on your AC system. The blue gauge and hose should connect to the low-pressure service port. The red gauge and hose will connect to the high-pressure port. The yellow hose in the middle should connect your gauges to your vacuum.

    • In your car, your high-pressure port will generally be physically higher than the low-pressure port.

    Make sure the gauges and gauge hoses are connected tightly. Loose seals can compromise your vacuum.

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    Open your manifold valves. Once you have your gauges in place, you will need to use the valves on your AC system that opens and closes the service port to the refrigerant lines. With the valves closed, your gauges should have little to no pressure reading.

Pulling the Vacuum

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    Start your pump. After you are sure everything has been securely connected, use the switch device on your vacuum pump to turn it on. You should be able to hear the vacuum running once it is switched on.

    • If you are trying to start the pump in cold weather, open the intake ports until the pump reaches normal running speed. Then, close it off again.
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    Open the side gauge valve. Once your vacuum is on, you will need to open the gauge valves, located on the side of each gauge. This allows the vacuum to start pulling air out of the system.

    • If you are unsure which way you need to turn your valves to open them, check the manual that came with your gauges or vacuum.
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    Allow the vacuum to run for 15-30 minutes. Let your vacuum run at full operating speed for at least 15 minutes and up to 30 to completely pull the air out of your AC system. The exact amount of time you will need to let your vacuum run will vary based on your manufacturer’s recommendations, so check any operational manuals you may have for both your AC system and vacuum pump.

    • Generally, you want to let your vacuum run for at least long enough to get the measurement below 1,000 microns. If you can, try to get it down to 500 microns.

Closing Your Vacuum

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    Close the low-side valve and let the vacuum hold for 15 minutes. After you have let your vacuum run for a sufficient amount of time, close the valve that connects to the low-side gauge. Let your pump hold the vacuum for 15 minutes.

    • If it’s not able to hold for that long, you likely have a leak and may need to replace components on your vacuum pump.
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    Shut off the vacuum pump. When you are satisfied with how long your system held the vacuum, shut the pump off using the same switch mechanism you used to turn it on. Let your vacuum disengage completely before you disconnect the system.
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    Disconnect your vacuum. Once your vacuum has fully disengaged, you can disconnect the hose leading to the pump. Your AC system should be fully evacuated at this point, and ready to be recharged or repaired.

If you are in the market for a great Vacuum Pump system we have them available in our Store HERE

Our Complete HVAC Pump Systems include 1/4 HP 3 CFM Single Stage Pump including Mini Split Adapters, Oil, Gauges, with Carrying Case.