How HVAC Manifold Gauges Work Tutorial for Beginners

By | May 7, 2020

How HVAC Manifold Gauges Work
HVAC gauges are a very important part of troubleshooting, fixing, and repairing heating and cooling systems.

Understanding how they work is one of the most crucial things a technician will need to know.

Below is a basic overview of how HVAC manifold gauges work along with pictures.
What are HVAC Gauges?
HVAC gauges are a tool built for refrigeration technicians for taking pressure readings and and other tasks.

Tasks include vacuuming, testing, adding refrigerant, and recovery.

A set will have high-pressure and low-pressure sides along with on/off valves that a technician can use to perform a variety of operations.
Components of an HVAC Gauge
An HVAC manifold set has two gauges blue and red.

The blue is for low-pressures and the red is or high-pressures.
Components of an HVAC Gauge
The red and blue valves on the side turn on and off to control gas going to the low and high-pressure valves.

A manifold gauge set will have red, blue, and yellow hoses.
How HVAC Gauges Work Hoses

  • The blue hose goes to the low pressure gauge.
  • The yellow hose can go to either low side or high side depending on which valve is open.
  • The red hose goes to the high pressure valve.

The center where everything attaches is called the manifold.
How HVAC Gauges Work Manifold
The unit in the picture has a sight glass which is a feature most don’t have.

The hoses will attach to the manifold at the bottom with the top connections only there to keep the hoses clean.

For example, here the bottom is the working part and the top part with the hoses disconnected only keeps the hoses clean.

The extra connections that go to nothing also keep the hoses from getting tangled and easy to store away.

How to Use HVAC Gauges
To use the gauges the flow of gas through a set needs to be understood.

Here a diagram shows how gas can flow through a manifold.
How HVAC Gauges Work Diagram
The red and blue hoses go straight to the red and blue gauges while the center yellow hose is separate.

The yellow hose can connect to any external source. For example, a vacuum pump will have the yellow connected to it.

While vacuuming down an HVAC unit the low-pressure blue hose would go to the unit and the yellow hose to the vacuum pump.
How HVAC Gauges Work pump down
While the pump is working the blue valve will be opened to let the pump work.

In this example, refrigerant is being added to an A/C system.
How HVAC Gauges Work Add Refrigerant
The yellow hose is going to the refrigerant bottle and the red hose going to the unit.

The red valve will control how much goes into the unit and turned off when the correct amount as been added.

The gauges can also show the pressures when connected to an HVAC unit.
How HVAC Gauges Work Pressures
The yellow hose will not be used to get pressure readings.

To get pressure readings the red hoses attaches to an HVAC system high-pressure line.
How HVAC Gauges Work Hook Up
The blue hoses attaches to an HVAC system low-pressure line.
Types of HVAC Manifold Gauges
HVAC manifold gauges must match the refrigerant uses in a system to get the correct readings.

Main Types of Manifold Gauges

  • R410A
  • R22
  • R134a

Every heating and cooling system will have a stamp of what type of refrigerant it uses.

Be sure to use gauges that match the refrigerant type or any readings will be wrong.

Some gauges can read multiple types if refrigerant so be sure to know your sets features.
The above is a basic overview of HVAC gauges and how they work.

After a manifold workings is understood more advanced topics such as reading pressures can be learned.

Basic tasks such as vacuuming down a unit can be done with the above basic overview.

HVAC gauges are simple but very powerful tool for troubleshooting for working an any heating and cooling system with refrigerant.

New digital gauges are also available and used by many but the basic principles will still apply.



One thought on “How HVAC Manifold Gauges Work Tutorial for Beginners

  1. Daniel

    Good article. You have a typo. Search fo shoe. I think you mean show.


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