Maintaining your Refrigeration Hoses and Gauges

In this chapter you will learn how to properly calibrate the gauges on your HVAC-R equipment, and replace deteriorating hose gaskets. These are the most common maintenance tasks that these components will need, and will contribute most to the lifespan of your investment in these items.

Start by performing these tasks when you begin to find that you cannot produce a reliable vacuum seal, or if you start to question the fine accuracy of the readings being given to you from the gauges themselves.

Calibrating your Gauges

Your gauges are critical to the proper use of your equipment. It’s important to check them periodically to be re-calibrated, so that your work will continue to be accurate and efficient. This guide will describe two easy ways to calibrate your gauges. The first is a simple zeroing, and the second will calibrate your gauges against actual refrigerant. If you have time, perform the second task to get a higher quality calibration. To do this, you will need:

Tools for these Jobs:

• a tank of refrigerant, which has been acclimated to the room temperature for a day or so.
• an adjustment screwdriver to use on the face of each gauge (this and your gauges is all you need to perform the zeroing, the “Quick Job”)
• a pressure-temperature chart for your Refrigerant, which will allow you to convert the temperature reading of your refrigerant to the pressure you expect the gauge to show
• a Digital Psychrometer or an Infrared Thermometer to read both the temperature in the room
• Your gauge set

Step by Step to Zero the Gauges (Quick Job)

• First, disconnect all hoses from the gauge set
• If your gauges have rubberized coverings on them, you will need to remove these to either zero or calibrate the gauges.
• Remove the plastic lens covers from gauge faces. They should pop off.
• In order to zero the gauges, use the screwdriver to turn the screw on the face of the exposed gauge. This changes the resting position of the needle. You should set this to zero on both the low gauge and the high gauge
• Note that sometimes jostling of the unit can result in the miscalibration of these gauges. Make sure they remain zeroed as you replace the protective coverings
• Replace the plastic lens cover and plastic gauge covers, then attach your hoses

Step by Step to Calibrate the Gauges using Refrigerant

• For this calibration, you’ll be using the tank of refrigerant to apply a known pressure to both of your gauges. You’ll want the gauges to accurately report the pressure from the tank, so you know they are calibrated correctly. Perform each of these steps for each gauge separately to calibrate them
• Connect the tank of refrigerant to your gauge
• Turn the tank of room-temperature refrigerant upside down, so the pressure coming from the tank is the result of the liquid in the tank, not the gas. Make sure to open the lines to the gauge being calibrated.
• Remove any rubber covers to the gauge faces
• Remove the plastic lens covers from gauge faces. They should pop off.
• Take a reading of the temperature of the liquid inside your refrigerant tank, if you have an Infrared Thermometer. If you only have access to the ambient temperature in the room, make sure the refrigerant tank you’re using has been acclimated to that room temperature for at least one day.
• Use your Temperature reading and your Temperature/Pressure chart to obtain the amount of pressure coming from the tank into your line to the gauge being calibrated
• This number from the chart is what your gauge should show. If your gauge is correctly displaying the pressure from the tank, it is calibrated
• If the number you are expected is not being read from the gauge, use the screwdriver to adjust the screw on the face of the gauge to read that number
• Switch gauges and make sure to perform the same process for each one.  Make sure refrigerant remaining in hoses is recovered and not released into atmosphere.
• Replace all rubberised covers and plastic gauge lenses before returning the unit to work.

Make sure you perform a regular calibration of your gauges, so your work can remain accurate and efficient. Inaccurate gauges are a simple way to misread information and distract your work.

Replacing Hose Gaskets

If you use your HVAC-R equipment regularly, the small black gaskets in your hose connectors will regularly deteriorate. This normal wear and tear can make it difficult for your equipment to do its job, and for you to do yours. Be prepared to change hose gaskets as often as monthly with heavy use.

When Should I Replace a Gasket?

You will notice the need for a replaced gasket most often when you are attempting to generate a vacuum with your equipment. A deteriorated gasket will make it very difficult for you to create and use a vacuum. Turn off your equipment, and visually inspect the ends of the hoses. The inner black gasket will appear degraded, chewed and worn to the naked eye. These are simple and easy to replace, and if done often, will keep your equipment running well.

Tools for the Job:

• Needle nose pliers to remove the depressor from the end of the hose
• A pick (or similar) to remove the old gasket
• New Gasket(s)

Step by Step for Replacing a Hose Gasket

• Each hose end will have a metal depressor in the center, surrounded by the black gasket you intend to replace.
• Begin by removing the center depressor using your needle nose pliers. These often unscrew for several threads before they will pop out.
• With the depressor out of the way, you can access the old gasket. A pick or a hook of some kind is useful in removing these small pieces from the end of the hose
• Dispose of the old gasket
• Seat the new gasket. It should pop into place at the end of the hose
• Replace the depressor using the needle nose pliers to gently screw it back into place

This kind of maintenance may be the most frequent of your system, since these gaskets can need replacement often with heavy use of your HVAC-R equipment. Keep a store of new gaskets, and enable anyone on your team to replace them whenever they see it has become necessary. Teach everyone what a worn gasket looks like, and the negative effects of working with a deteriorated hose gasket, so that they will be vigilant in changing them when they see the need arise.

In this post you have learned how to perform regular maintenance on your gauges by calibrating them. You have learned two methods for calibrating your gauges: zeroing and refrigerant calibration. Each of these methods are effective, but the use of actual refrigerant pressure in your lines will offer the truest calibration of your equipment, so it should be preferred to the quick zeroing procedure.

You have also learned how to replace a hose gasket for your equipment. Even the longest of these tasks will take less than 15 minutes, but the regular performance of these service tasks can keep you and your equipment productive and on the road for much longer.