An HVAC gauge is the most important tool in my most value asset. The HVAC gauge reads the pressure of various liquids and gases in an air conditioning system. It also reads vacuum pressure when pressure testing or charging a cooling system. Occasionally, homeowners will have an HVAC gauge, but that doesn’t mean they know exactly how to use it.

Before you begin, you’ll need to know what the colors on the gauge mean.  The blue gauges the suction pressure of the compressor. The reading ranges from 0 to 99.9 psi and is based on variation in atmospheric pressure.  The red reads the pressure from the hose. For HVAC analog gauges, the reading is usually done manually. You can do this by going through the blue and red color-coding labeled on the dials.

Using the HVAC gauge


First, attach the high-pressure side of the cooling unit to the red port on the gauge.  You’ll want to make sure you are connecting a code-authorized red hose. These particular hoses are designed to tolerate pressure using the flare fittings that come with it to the high-pressure port on the cooling line. On many gauges the high-pressure port is made of a different thread and size than the low-pressure side.  This difference is to prevent the accidental hookup of the incorrect hoses.

Secondly, attach the low-pressure line to the blue port on the HVAC gauge. Connect the low-pressure side with a the blue low-pressure hose and the unit’s blue pressure gauge. This will make way for the proper flow of vacuum pressure, also known as a micron meter, to evaluate the vacuum pressure already in the system.

Then, connect a vent hose or waste hose to the middle of the manifold setup. If you want to discharge a system or vent Freon by connecting the unit, you’ll have to connect the bigger low-pressure hose to the center of the manifold port. By doing so, you’ll be able to connect a refrigerant recovery container to the multiple setups to avoid flaunting state regulations regarding the emission of refrigerant into the atmosphere.

Next, connect micron meters or other gauges to the remaining ports. The extra ports on the manifold can be used to attach vacuum pressure (manifold) gauges or even a vacuum pump that can be connected to any piece of furniture so as to perform the appropriate services to the cooling unit as needed for the repair you’re making.

Now you are ready to read the measurements displayed by the refrigeration gauges. These measurements show the pressure in freezing and air conditioning, refrigeration, industrial refrigerators, cold filling equipment, and in cold rooms.

For example, if you have a reading of r22 on the refrigeration gauge and measure 60 pounds, the scales will display 1 degree Celsius, which of course is 34 degrees Fahrenheit.

The refrigeration gauge has the same features as a general manometer but with stricter reading characteristics. It uses a unique weld and is tested to prevent refrigerant leaks.

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