Valves used in direct-expansion systems
The pilot solenoid (valve B) is a 1/8 in. ported solenoid valve that is direct operated and suitable as a liquid, suction, hot gas, or pilot valve at pressures to 300 lb.
Solenoid valve A is a one-piston, pilot-operated valve suitable for suction, liquid, or gas lines at pressures of 300 lb. It is available with a 9/16 in. or 3/4-in. port.
Solenoid valve C is a rugged, pilot-operated, two-piston valve with spring return for positive closing under the most adverse conditions. It is used for compressor unloading, and for liquid and hot-gas applications. The dual-pressure regulator (valve D) is designed to operate at two predetermined pressures without resetting or adjustment. By merely opening and closing a pilot solenoid, it is capable of maintaining either the low- or high-pressure setting.
Figure 10-8 shows a pilot light assembly. It is placed on valves when it is essential to know their condition for troubleshooting procedures.
A low-temperature defrost system with water being used to defrost the drain pan is shown in Fig. 10-9.