Library
Deep Technical Chapters · Charge & Metering
Shortage of Refrigerant
Technician
Low charge: low suction, high superheat, low subcooling, bubbles — and a leak that needs finding.
A shortage of refrigerant is almost always a leak. The readings are consistent; the job is to find the leak, not just top up.
Diagnosis at a glance
Symptoms of failure
- •Low suction pressure
- •High superheat
- •Low subcooling
- •Bubbling sight glass
- •Iced coil at the TXV
- •Poor capacity
Measurements to take
- •Suction, head, superheat, subcooling
- •Sight glass
- •Leak test
How to prove the fault
- •Low subcooling + high superheat + bubbles = low charge → find the leak
Common mistakes & callbacks
- •Topping up without finding the leak
