R-Pro › Field cases › Freezers & ultra-low temperature

CO2 Transcritical System High Pressure Fault (Gas Cooler Control Failure)

Likely causes

Gas cooler fan motor failure or belt slip → insufficient heat rejection, pressure exceeds 120 bar

Check: Measure fan motor current (within ±10% of rated). Check fan belt tension. Verify discharge pressure with high-pressure gauge

What to do: Replace fan motor or readjust fan belt tension. Always use CO2-rated gauges (max 200 bar) before working on CO2 systems — never use standard R404A gauges

Gas cooler fin fouling (dust/grease) → reduced heat transfer area, discharge pressure spikes

Check: Visually inspect gas cooler fins for dust and grease fouling. Track high-pressure trend to confirm fouling rate

What to do: High-pressure wash gas cooler fins (15–20 bar water pressure), fully dry before restart. Set regular cleaning schedule (at least twice per year)

High-pressure valve (HPV) spool seized or actuator faulty

Check: Check HPV electrical signal (4–20 mA or 0–10 V). If signal is normal but valve does not respond, spool is seized

What to do: Replace valve if no response. Verify high-pressure safety valve setpoint (130 bar), review trip history in controller

Field tip

Always use CO2-rated gauges (max 200 bar) before working on CO2 systems. Never use standard R404A gauges. When recharging, maintain CO2 charge accuracy within ±0.5 kg.

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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