The refrigerant cylinder is usually connected to the center port of gauge manifold when adding refrigerant to a system. Which option below shows this correctly?

• A. Center port of gauge manifold
• B. Right-handed port of the manifold gauge
• C. Left-handed port of the manifold gauge
• D. Discharge service valve of the compressor

Answer: (A)

The center port is the charging port on a three-port manifold. When adding refrigerant, you connect the refrigerant cylinder to this center port with the charging hose, so refrigerant can be fed into the system while you monitor pressures on the low- and high-side via the other two ports. The left (low-pressure) and right (high-pressure) ports connect to the system for measurement and control, whereas the discharge service valve of the compressor isn’t used for charging.