Walk-in Evaporator Frost Buildup / Defrost Failure

Question

Accepted Answer

Defrost heater open-circuit or burned out. Check: Manually advance timer to defrost cycle — no heater heat confirms open circuit. Measure heater terminal resistance with ohmmeter (infinite = open) What to do: 1) First: force-defrost with 3 kW heat gun or steam gun for 30–60 min (prevent product loss). 2) Replace heater (same spec, confirm ≥200 W/m capacity). 3) After defrost, verify drain line clears Faulty defrost thermostat (thermal cutout). Check: Check fuse trip temperature (normally 45–60°C). Continuity test at room temp (continuity = OK, open = faulty). If tripped below defrost temp threshold, premature failure What to do: Replace with fuse of identical trip temperature spec. After replacement, confirm defrost cycle completes normally (heater on → fuse trips → cooling resumes) Defrost timer failure — defrost not initiating or running too long. Check: Check timer settings — cold storage defrost interval typically once every 6–8 hours. Manually advance to verify defrost cycle entry What to do: Readjust timer settings. If mechanical timer fails, replace with electronic demand defrost controller — defrost based on actual frost level saves energy and protects product Frozen drain line — drain heater failure. Check: Check drain pan for pooled water or ice block. Measure drain heater resistance — infinite indicates open circuit What to do: Check drain heater continuity and heat output, replace if faulty. Re-insulate drain line. Freezer drain lines must always have both heater and insulation Excessive door openings — excess moisture entry accelerating frost buildup. Check: Check door opening frequency and duration. Verify air curtain or strip curtain installation What to do: Install air curtain or strip curtain to minimize outside air ingress. Use thermal tarp during work. Readjust defrost intervals to match door opening patterns

Walk-in Evaporator Frost Buildup / Defrost Failure

Likely causes

Defrost heater open-circuit or burned out

Faulty defrost thermostat (thermal cutout)

Defrost timer failure — defrost not initiating or running too long

Frozen drain line — drain heater failure

Excessive door openings — excess moisture entry accelerating frost buildup

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