Three-Way Valve Positions
In this position, the service valve stem is turned fully clockwise, closing off flow to the system and opening the gauge port.
What is front-seated?
This small, spring-loaded valve core inside a service port is similar to the air valve found on automobile tires.
What is a Schrader valve core?
Located at the outlet of the liquid receiver, this service valve is used to isolate the system charge during a pump-down.
What is the King valve (liquid line service valve)?
This square-opening specialized hand tool is designed specifically for turning square service valve stems.
What is a refrigerant service valve ratchet wrench?
To ensure a complete seal on a back-seated 3-way service valve, the stem should be turned firmly counterclockwise until it hits this stop.
What is the back-seat shoulder (or back-seat stop)?
This normal operating position has the stem turned fully counterclockwise, opening system flow and sealing off the gauge service port.
What is back-seated?
This specialized tool allows a technician to replace a damaged valve core without losing system refrigerant charge.
What is a core removal tool (or valve core remover)?
This service valve is located on the low-pressure side of the compressor and isolates the compressor from the suction line.
What is the suction service valve?
This threaded nut surrounding the valve stem compresses internal graphite or Teflon material to prevent shaft leaks.
What is the packing nut (or packing gland)?
If refrigerant bubbles emerge from around the valve stem while mid-seated, a technician should tighten this specific nut.
What is the packing nut?
To read system pressure during normal operation, the service valve stem must be placed in this slightly open intermediate position.
What is mid-seated (or cracked)?
Removing the Schrader valve core during system evacuation speeds up the process by eliminating this internal restriction.
What is flow restriction (or pressure drop / throttling)?
This service valve is mounted on the high-pressure outlet of the compressor leading toward the condenser coil.
What is the discharge service valve?
This protective metal cover must be reinstalled tightly over the valve stem to provide a secondary seal against leaks.
What is the valve stem cap?
Using standard open-end pliers instead of a service wrench on square stems risks causing this physical damage.
What is rounding off (stripping) the square stem corners?
Front-seating the compressor discharge service valve while the compressor is operating creates this dangerous high-pressure condition.
What is compressor damage (or extreme over-pressurization / cylinder blowout)?
Manifold hose ends connecting to Schrader access ports must feature this built-in pin to push open the internal core.
What is a valve core depressor?
Residential split-system condensing units typically feature these non-packless service valves that open using an Allen wrench.
What are packed angle (or hex-wrench / ball) service valves?
Before attempting to adjust a packed service valve stem, a technician should slightly loosen this component to prevent binding.
What is the packing nut?
A valve stem cap should always be tightened using a wrench to specified torque to ensure this primary safety role.
What is providing a leak-tight seal (preventing secondary refrigerant leaks)?
When removing a gauge manifold hose from a service valve port without losing refrigerant, the valve stem should be placed in this position.
What is back-seated?
Schrader access valves are classified as this type of valve because they do not require turning a valve stem to open flow.
What is a push-type (or spring-loaded automatic) access valve?
In commercial refrigeration, performing a 'pump-down' requires front-seating this specific valve while the compressor continues to run.
What is the King valve?
Standard four-size service wrenches usually include square drive socket openings of 3/16", 1/4", 5/16", and this fraction inch size.
What is 3/8 inch?
When brazing near split-system service valves, technicians must protect internal seals from heat damage using this damp material.
What is a wet rag (or heat-absorbent gel/putty)?