How to Add Freon to a Home Heat Pump

freon and surrounding tools
What You'll Need
Manifold gauges
Recovery tank
Pressure vacuum
Safety gear: gloves, goggles, and a mask

Adding freon to your home heat pump is crucial to keeping it working properly, however, it can be extremely dangerous to do it yourself unless you follow the right steps. Before you begin, read the four steps below.


It’s highly recommended that you hire a professional to complete this project unless you have previous experience working with refrigerants.

Also, many places have laws regarding freon, so check with your local ordinances before continuing with the project. Exercise caution when working with this substance and always wear safety gear like goggles, gloves, and a mask, as extended exposure to freon is harmful.

Step 1 — Get Your Gauges Ready

A manifold is a set of gauges commonly used for changing or reading pressurized refrigerant systems. These gauges will provide you with the numbers you will need to determine whether you need to change your refrigerant, and if you do, how much is needed.

Identifying Gauges

There are two hoses and two gauges on a manifold — one red, and one blue. The red gauge is for the high side, where the smaller refrigerant line runs, and the blue gauge is for the low side, where the larger refrigerant line connects with your unit.

Make sure that you have these properly identified before making your connections, as it will alter the outcome of your refrigerant readings and the accuracy of your top-off, a crucial element of this project.

Step 2 — Connect the Gauges

You may connect the gauges to the freon lines while the heat pump is running.

The Red Hose

Connect the red hose to the high-side refrigerant line. If the pump is running, the line should be above room temperature.

The Blue Hose

Connect the blue hose to the low side. This line should be insulated, and if you gently pinch it between your fingers, it should be cool. If it isn't, you do not have enough refrigerant in the unit.

Step 3 — Take a Reading

Now that your gauges are connected, it's time to take a reading of your home heat pump. First, look at the high side, where the hose is red. Set the thermometer outside where your heat pump intake is. Check to see that the recommended temperature for your refrigerant, with the outdoor temperature taken into account, is within the required range.

Be certain to use the manufacturer's specifications for your unit and particular type of freon to come up with this number. If the heat pump numbers register below the recommendations given, the heat pump needs additional freon.

Warning: Incorrectly measuring the amount of freon needed can lead to severe personal injury or damage to your home heat pump.

Step 4 – Adding Refrigerant

If the tank is low, and you have decided that you are comfortable enough with this project to proceed, then it is time to add refrigerant to your heat pump.

Add refrigerant through the low side, where the larger tube runs. It is extremely important to never add freon through the high side. And, when charging, do not turn the refrigerant gas can upside down. This sends liquid refrigerant into your heat pump's compressor, destroying your heating and cooling system.

Once the system is charged, disconnect the tubes and check the system with a pressure vacuum for leaks.