This section describes the basic procedures you will need to correctly operate the gauge manifold set. The gauge manifold set is one of the most frequently used items of service equipment It is used to determine system operation, add a charge, recover a charge, and equalize or evacuate a system.
The typical two-valve gauge manifold set (Figure 3-14) has a compound gauge, high-pressure gauge, two hand valves, and three hose ports. The hand valves are adjusted to monitor system pressures on the compound gauge and high-pressure gauge and to route the flow of refrigerant to and from the system during servicing activities.
The gauge manifold set hose ports are connected to the system being serviced and other service instruments through a set of high-vacuum/high-pressure service hoses. It is recommended that these hoses be equipped with fast self-sealing fittings that immediately trap refrigerant in the hose when disconnected. Their use helps meet the non-venting regulations and also greatly reduces the amount of air that can enter the hose once disconnected.
When using self-sealing fittings, it is important to always check the gauge pressure readings before removing or changing any service hose. With the use of self sealing fittings, high pressure refrigerant can he trapped and remain in the service hoses after they have been disconnected from the equipment, causing possible injury or bums. To prevent injury from any refrigerant trapped in the service hoses or to remove the refrigerant trapped in the hoses, always follow the procedures for connecting and disconnecting the gauge manifold set given later in this section.
Generally, the gauge manifold set and service hoses are color-coded. Blue identifies the low-pressure compound gauge, hand valve, and related hose port. A blue service hose is normally connected between the manifold low-pressure hose port and the equipment suction service valve. Red marks the high pressure gauge, hand valve, and hose port. A red service hose is normally connected between the manifold high-pressure hose port and the equipment discharge service valve or liquid line. The center hose port is the utility port. This port normally is connected through a yellow service hose to other service instruments or devices such as a recovery/recycle unit, vacuum pump, refrigerant cylinder, etc.