The procedure used for disconnecting the gauge manifold set varies, depending on the type of service valves installed in the unit.
If the unit being serviced contains back-seating service valves, the charge remaining in the hoses can be drawn back into the operating system using the following procedure:
1. On the gauge manifold set, close (front-seat) both valves. Make sure you close the valve on the refrigerant cylinder (if used).
2. Start and run the system to check temperatures and pressures.
If they are correct, back-seat the system high-side service valve. This traps refrigerant in the high-side hose and the utility hose.
3. Open both valves on the gauge manifold set to allow any refrigerant trapped in the high side and utility hoses to be drawn into the system through the low-side service valve.
4. Once both manifold gauge pressures have equalized at the low-side pressure, back-seat the low-side service valve. This allows only a minimal amount of refrigerant to escape to the atmosphere when all hoses are disconnected.
If the system is equipped with Schrader valves instead of back-seating service valves, service hoses equipped with fast self-sealing fittings must be used with the gauge manifold set for this procedure to work. To remove the gauge manifold hoses from a system with Schrader valves, use the following procedure:
1. Turn off the equipment or system.
2. Close (front-seat) both gauge manifold set valves. If applicable, make sure you close the valve on the refrigerant cylinder- Remove the high-side hose from the service valve or service port. Leave the low-side hose attached to the service valve or service port. Th is traps refrigerant in the high-side hose at the high-side pressure. It also traps the refrigerant in the utility hose (if used) at the cylinder pressure.
3. Start the equipment or system, then open (crack) both gauge manifold valves. This allows the refrigerant trapped in the high side and utility hoses to be brought down to a lower and safer low-side (suction) pressure by drawing it into the operating system.
4. Remove the low-side hose. This traps the remaining refrigerant in the low-side hose at suction pressure.