Fractional horsepower refrigeration systems typically come from the factory sealed, with no access valves installed. While working on these systems, if some type of access valve has not already been installed, you will need to add one to the system to read its pressures, add refrigerant, or recover its refrigerant charge.
One common access valve initially used is some type of saddle valve. These valves are convenient and generally easy to install, but they are not usually considered to be a long-term type of valve and generally should not be left on a system permanently. They are prone to leaking over time, and it is considered a best practice to remove them after or during the repair process.
When adding a saddle valve to a system, it can be placed on any section of copper tubing within the system. However, it is best to place it on the process tubes left in place by the manufacturer. When installing a saddle valve, make sure to place it on a relatively straight section of tubing. Make sure the tubing is clean and that any gasket required by the valve manufacturer is being used. This is especially important to check if an older saddle valve is being reused. Also make sure the metal plates are in complete contact with each other before piercing the tubing. All of these precautions are necessary to prevent system leaks.
It is a common practice to initially install this type of valve, remove it, and install a more permanent valve, such as a Schrader valve, during a repair. However, there may be times when you cannot easily install a Schrader valve during a repair. For example, you add saddle valves to a system and find out you really do not need to recover the refrigerant from the system to complete the repair. The refrigerant charge and the system’s pressures were normal for its design. Now, you are faced with a decision: Do you recover the refrigerant, add the Schrader valves to the system, evacuate the system, and add the refrigerant back into the system, or leave the valves on the system and walk away?
There is a third choice, which, perhaps, is not often considered by technicians. Using a pinch-off tool, a saddle valve can be removed from a system operating under pressure, if it was installed on a process tube. To do this:
• Using a pinch-off tool, pinch the copper process tube between the system and the valve;
• Then, pinch it again between your original pinch and the valve, but on this pinch, leave the pinch-off tool in place with it firmly biting down on the copper tubing. This will temporarily seal the system;
• Remove the saddle valve from the tubing; and
• Using a torch and some brazing filler, heat the tubing and seal the opening created by the saddle valve. Please note never to apply heat to a system that uses a flammable refrigerant.
This will give you a completely sealed system again — one that is less likely to leak refrigerant in the future.
Publication date: 9/12/2016