R-Pro › Field cases › Refrigeration systems
Partial Frost Due to Expansion Device Abnormality
Likely causes
Expansion valve under-opening (superheat set too high)
Check: TXV: measure superheat and adjust setting (target 5–8K)
What to do: TXV: measure superheat and adjust setting (target 5–8K) → Confirm sensing bulb is tightly strapped and insulated on suction pipe → Capillary tube: replace filter drier and backflush with nitrogen → If moisture is cause, replace drier, re-evacuate, and recharge
Capillary tube partially blocked by debris or moisture
Check: Confirm sensing bulb is tightly strapped and insulated on suction pipe
What to do: Confirm sensing bulb is tightly strapped and insulated on suction pipe → Capillary tube: replace filter drier and backflush with nitrogen → If moisture is cause, replace drier, re-evacuate, and recharge
TXV sensing bulb incorrectly positioned
Check: Capillary tube: replace filter drier and backflush with nitrogen
What to do: Capillary tube: replace filter drier and backflush with nitrogen → If moisture is cause, replace drier, re-evacuate, and recharge
Frost concentrated at the evaporator inlet indicates partial blockage or under-opening of the expansion device.
All 565 cases work offline in R-Pro, with error codes for 62 brands and P-T data for 108 refrigerants.
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