CSLB C-20 HVAC ContractorCooling and RefrigerationMedium
An apprentice is connecting a standard refrigeration manifold gauge set to a system for the first time. Which hose color should be connected to the high-pressure (liquid) service valve?
- AYellow
- BGreen
- CRed
- DBlue
Show answer & explanationAnswer & explanation
Correct answer: C. Red
Standard manifold gauge convention uses blue for the low (suction) side, red for the high (liquid/discharge) side, and yellow as the neutral utility hose for charging or recovery. Connecting hoses to the wrong ports can cause misreadings and safety hazards from confusing high and low pressure readings.
Why the other options are wrong
- A. Yellow is the neutral utility hose, not assigned to either high or low port.
- B. Green is not a standard manifold gauge hose color.
- D. Blue is standard for the low side, not the high side.
Manifold Gauge Color Coding
Standard refrigeration gauge sets use blue for low side, red for high side, and yellow for the utility/center port.
- Blue = low/suction side
- Red = high/liquid/discharge side
- Yellow = neutral utility hose for charging/recovery
Memory trick: Red is hot (high side), Blue is cool (low side)