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High Pressure Rise from Non-condensable Gas (Air) in Circuit

Likely causes

Refrigerant charged without adequate evacuation

Check: Diagnosis: if high-side pressure is clearly above saturated pressure for the condensing temp, air is suspected

What to do: Diagnosis: if high-side pressure is clearly above saturated pressure for the condensing temp, air is suspected → Recover all refrigerant → Evacuate to ≤500 μm Hg (minimum 1 hour) → Hold vacuum for 30 minutes (vacuum loss = repair leak first) → Recharge refrigerant by weight

System opened and re-sealed without recovering refrigerant

Check: Recover all refrigerant

What to do: Recover all refrigerant → Evacuate to ≤500 μm Hg (minimum 1 hour) → Hold vacuum for 30 minutes (vacuum loss = repair leak first) → Recharge refrigerant by weight

Air back-leaked through service valve core

Check: Evacuate to ≤500 μm Hg (minimum 1 hour)

What to do: Evacuate to ≤500 μm Hg (minimum 1 hour) → Hold vacuum for 30 minutes (vacuum loss = repair leak first) → Recharge refrigerant by weight

Field tip

Air in the circuit is adding non-condensable pressure. Perform an air purge. Air contamination raises condensing pressure abnormally, causing repeated high-pressure switch trips and compressor burnout.

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