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Lesson 30/52Preview

PT Chart Diagnostics

Use pressure-temperature charts with gauge readings to diagnose non-condensables, charge problems, and heat exchanger performance.

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Non-Condensable Gas Detection

Non-condensable gases like air or nitrogen trapped in a system cause head pressure to read higher than expected for the ambient temperature. Compare the measured head pressure to the PT chart value for the actual condenser outlet temperature. If head pressure is significantly higher than the saturation pressure corresponding to the liquid line temperature, non-condensables are present. Air also introduces moisture, which forms acids that damage the system.

Head pressure higher than expected for condenser temperature indicates non-condensable gases (air) in the system.

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