First-Year HVAC Service Certification Practice Test 2026 – The Comprehensive All-in-One Study Guide for Success!

The high side hose on a manifold gauge assembly (MGA) is conventionally designated by the color red. This standardization is crucial for ensuring safety and accuracy during HVAC service and repairs. The high side of the system, which typically operates at a higher pressure, connects to the discharge side of the compressor and receives refrigerant after it has passed through the condenser.

Using red for the high side helps technicians quickly and accurately identify which hose to connect when measuring pressures or adding refrigerant. This efficiency reduces the likelihood of mistakes that could lead to system damage or unsafe conditions.

The other colors, such as blue, yellow, and green, have specific designations as well—blue is typically used for the low side, yellow is often used for refrigerant transfer, and green might be used for specific refrigerants or applications—but these colors do not represent the high side. Understanding these color codes is vital for proper servicing and maintenance of HVAC systems.