HVAC systems such as air conditioning units need a vacuum set on the system before refrigerant is released.
A good vacuum pump will remove airborne moisture and or non-condensable from the system and will boil off moisture.
The deeper the vacuum, the lower the micron level, which is needed for an HVAC system to last and work properly.
Why Does an HVAC System Need a Vacuum?
Any contaminants that mix with refrigerant can cause damage and cause the unit to work less efficiently.
If any water vapor is in the system, the icing up of capillary tubing and expansion valves can damage the system.
Small particles can also damage the unit and need to be removed.
A vacuum pump will remove any small particles, including water vapor, that may be in the system.
What is an Adequate Vacuum Microns Level in an HVAC System?
The American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) recommends a vacuum below 1000 microns for moisture removal and below 500 microns after replacing a compressor. Many HVAC system manufacturers often call for a vacuum below 500 microns, but be sure to check your unit’s documentation.
An adequate vacuum is roughly below 1000 microns.
500 microns or lower is usually considered the best level to have.
Some equipment manufacturers will have 500 microns listed as the recommended level to get to.
A good vacuum pump and micron gauge will be needed to read the state of the vacuum.
Is Below 1000 Microns a Good Vacuum in an HVAC Unit?
Yes, 1000 Microns is considered good or at least adequate for many units.
1000 Microns will remove the majority of the water vapors and other non-condensable from the system.
The manufacturer recommended micron level for a unit should always be followed.
What is a Micron in HVAC?
Micron is a measurement of pressure in an HVAC system.
It is a very small measurement that can measure atmospheric pressure.
The original method to measure atmospheric pressure used a U-shaped tube with mercury inside the tube.
The pressure was applied to one side of the tube, which pushed the mercury up the other side, marked in inches.
This gave the name Inches of mercury which is still a widely used measurement.
Meters are also used for more precise measurements called micrometers and shortened to microns.
How Many Microns Is Good in an HVAC System?
Most HVAC technicians will attempt to get a system below 1000 microns with 500 microns the ideal range.
All equipment manufacturers will have a specified range that a system should be set at.
What is a Perfect Vacuum in HVAC?
Zero (0) microns would be the perfect vacuum in an HVAC system.
While Zero microns would be a perfect vacuum realistically, it can not be reached.
To get to this level, a very good vacuum pump, and electronic micron gauge will be needed.
The time needed to reach this level, even with a good pump, would also be very high.
An analog mechanical gauge will not work to read this level or be very difficult.
A micron gauge should be attached directly to the system and isolated from the pump to get the most accurate reading.
Summary
Vacuuming down an HVAC unit to the proper microns is a necessary part of repairing and installing an HVAC unit.
A good vacuum pump and micron gauge will be needed to read very low levels accurately.
It is also best to follow the manufacturer’s specification and suggested level for the microns needed.
If in doubt, 500-1000 microns is usually considered best for most HVAC systems, such as air conditioners and mini split systems.
Do you have any suggestions or questions on ideal micron levels in an HVAC system? Let us know your thoughts below.
My really cheap vacuum pump gets microns down to 900-1000. Most good stage 5 or better vacuum will get 500 or below. Microns start around 5000 and as you pump down it gets closer to 0 so I agree this article is wrong. 500 is ideal but most vacuum pumps including mine will never pump down to 500 or below.