The solenoid valve is an electrically-operated valve. It uses an electromagnetic field to raise a pilot valve. The gas pressure raises the main valve allowing flow. The flow will continue as long as the pilot valve is held off its seat. The valve in Fig. 12-8 is typical. It can be used with liquid as well as vapor or high-pressure gases. In the condensing unit, it can be used for a pump-down liquid-line valve or an anti-slug valve. If used for a pump-down valve, the unit must have a low-pressure control to stop the compressor operation. For use as an anti-slug valve, the valve is wired to close as soon as the compressor stops. It prevents any liquid in a vertical liquid line from dropping down into the compressor. When mounting a solenoid valve, it is good practice to orient the valve for operation in a vertical plane. This would require the inlet and outlet of the valve be in a horizontal plane. The electromagnetic coils are available in 24, 120, and 240 volts.