🔍 Key Concepts

• Look carefully at the outer red scale versus the inner black scale on the gauge face. • Recall what information standard refrigeration compound gauges provide besides pressure when matched to a specific refrigerant. • Think about the meaning of a temperature scale tied to saturation/boiling conditions for a refrigerant in the system.

💭 Think About

• Ask yourself: Does this gauge show a second pressure value, or does the red scale represent something different from pressure? • When the refrigerant is in a saturated (liquid + vapor) state, what is the special relationship between its pressure and temperature that technicians often use directly from the gauge? • Would the gauge be able to show the actual line temperature without a sensor, or is it instead a temperature value that goes with the measured pressure on a chart?

✅ Before You Answer

• Verify whether the red numbers around the outside are labeled in °F or in another unit. • Confirm that the red scale changes in a way that matches a temperature scale rather than another pressure scale. • Make sure you distinguish between actual temperature at the pipe and the theoretical saturation temperature corresponding to the measured pressure for that refrigerant.