HVAC BASICS: How to use HVAC Gauges


Do you have plans to work in the HVAC industry? Maybe you want to learn some basics of this trade to have an edge in the market? If your answer is yes, learning the workings of HVAC gauges is one of the first steps you’ve to take.

The heating, ventilation, and air conditioning (HVAC) market continues to have a relentless growth trajectory. If you’re an HVAC technician, there are many opportunities available in the market today.

Over the past five years,  Heating & Air-Conditioning Contractors in the US industry grew by 3.1% to reach revenue of $94bn in 2018.

recent study predicts the HVAC industry will achieve a five percent growth in the United States in 2019.  If you want to join this industry as a technician, now is a good time.

However, this is a highly competitive industry, and you need to learn all the basics. Pressure gauges are among the most important HVAC instruments.

Whether you’re a DIY person or a technician joining the HVAC industry, learning how to use HVAC gauges is the smartest move you can make.



You must equip yourself with the necessary HVAC tools every time you work on a project. A set of pressure gauges is one of the most important assets when working on HVAC systems.

An HVAC gauge reads the pressure of various liquids and gases in an air conditioning system. It’s also crucial for reading vacuum pressure when pressure testing or charging a cooling system.

This is the most important set of instruments for measuring if every device in the HVAC system works properly. It’s also crucial as a diagnostic tool, and comes in handy for HVAC servicing and replacement.

Your HVAC gauge set is important in the HVAC work environment as an industrial pressure gauge is in an industrial facility.



A gauge manifold is perfect for measuring both high and low pressure. It’s a popular device with technicians working on condensing units or evaporators in air conditioners.

When training how to read HVAC gauges, you must learn the basic parts. These are:


This component has a double-pronged purpose as a diagnosis and service equipment.  It consists of three chamber devices; low-pressure chamber, high-pressure chamber, and utility chamber.

These chambers provide control over the flow of gas and pressure. These are crucial for HVAC gauges basic performance.

A technician reads the pressure levels in the discharge line after connection of the manifold gauge to the device. The low-pressure side of the device connects to the low-pressure gauge hose.

The high-pressure gauge hose also connects to the corresponding high-pressure side of the unit under repair.

The function of the utility port is to add more refrigerant to the AC unit. This port also connects a hose to a vacuum pump or other recovery units.

Manifold gauges are crucial for servicing air conditioning and other HVAC devices. They remove contaminated refrigerants from the AC system.


A HVAC gauge will have two readout gauges. These are for display of low-pressure chamber and the high-pressure chamber. Some brands added the third gauge for measuring compressor output. However, this is not common in the market today.

There are two types of readout gauges:


    The analog (indicator needle) is the most common on the market. The position of the needle shows the level of vacuum/pressure in the AC system or another device.

    They’re easy to use, and most technicians prefer them over newer gauges. However, analog readout gauges are prone to errors.

    Even after learning the basics of HVAC gauges, many technicians also have problems with pressure conversions.


    These are modern gauges which provide vacuum and pressure readings in numerals. They’re more accurate than analog readout gauges.

    These gauges also come with extra features to ease the work of a technician. You don’t need to convert the readings, and this reduces the risk of error.

    However, many technicians are new to this technology. HVAC manufacturers also add more features which complicate digital readings.


Hose connections carry pressurized gas. Manufacturers color-code the hoses to distinguish between high pressure and low pressure.

Low-side hoses are blue while the high side is red. The blue hose reading ranges from 0 to 99.9 psi while the red hose goes up to 999 psi.


Installing HVAC gauges is an essential skill for an HVAC contractor. After learning the workings of HVAC gauges, making the right connection is critical for the job.

An HVAC gauge uses flexible hoses with connectors on both sides.

For safety and to make work easier, the hoses have the maximum pressure indicated in PSI or bar. Many people trying DIY HVAC maintenance make wrong connections. The higher pressure can burst the hose.

Here are the steps to follow for the right HVAC gauge connection:

  1. Note the correct connection for the hose and the ports. The red port and red gauge go together. These are the high-pressure gauges.
  2. The low-pressure side goes to the blue port on the gauge. You should connect the lower pressure side to the blue pressure gauge using a blue hose.
  3. For discharging a unit, you need a disposal hose attached at the center of the manifold HVAC gauge. Use the larger black low-pressure hose and a refrigerant recovery bottle attached to the manifold. This prevents violation of federal laws on disposal of refrigerant to the environment.
  4. There are additional ports for attaching other gauges or a micron meter. On the manifold, you’ve more ports to attach these gauges. In case you need to connect a vacuum pump, you can use these ports as you service the air conditioning unit.
  5. The AC gauges have pressure and temperature charts in gauges. You can find the pressure of refrigerant using the pressure-temperature chart included. The charts contain temperature scales and various types of AC refrigerant pressure.


HVAC gauges come in different designs and sizes. With this in-depth insight, you’re now set to use any HVAC gauge on the market.

Whatever HVAC service job you plan to do, it is important to carry these crucial instruments. This is the only way to improve accuracy and efficiency in your work.

If you’re in the market for the best HVAC gauge set, continue exploring our site to find more pressure measuring equipment.

You can count on RG Group for excellent quality and service

Contact us today