Service Valve Positions
Service valves have three positions that control refrigerant flow and gauge access. Front-seated: the stem is turned all the way in, closing the port to the system piping and opening the gauge port, isolating the component for service. Back-seated: the stem is turned all the way out, which is the normal operating position where refrigerant flows freely but the gauge port is closed. Mid-seated: the stem is cracked off the back seat, opening all ports so refrigerant flows through the system while also allowing gauge readings.
Front-seated: closes system port for service. Back-seated: normal operation. Mid-seated: all ports open for gauge reading.
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