Hot gas may be required for other systems functions besides bypass capacity control. Hot gas may be needed for defrost and head pressure control. Normally, these functions will not interfere with each other. However, compressor cycling on low suction pressure may be experienced on system start-up when the discharge-bypass valve is operating and other functions require the hot gas also. For example, the head-pressure control requires hot gas to pressurize the receiver and liquid-line to get the thermostatic-expansion valve operating properly. In this case, the discharge-bypass valve should be prevented from functioning by keeping the hot-gas solenoid valve closed until adequate liquid line or suction pressure is obtained.