Floating Head Pressure Control Failure → Fixed High Condensing Pressure

Question

Accepted Answer

Outdoor temperature sensor failed or miswired → controller reads maximum ambient, floating lower limit not applied. Check: Compare actual outdoor temperature with controller display — replace sensor if error exceeds ±1°C. Measure NTC 10 kΩ@25°C What to do: Replace sensor → reset floating lower limit: R-404A at 5°C ambient → floor 10–11 bar(g); at 25°C → 16 bar(g) Condenser fan VFD speed signal open-circuit → fan always runs at full speed. Check: Check VFD analog output 0–10V: confirm fan speed at 50% when controller output is 5V. Measure signal wire continuity What to do: Repair signal wire → reset VFD min/max frequency → reconfirm condensing pressure floating targets → verify kW savings Floating lower limit setpoint entered incorrectly → zero energy savings. Check: Check condensing pressure at 10°C ambient — above 18 bar(g) means floating not working. Review controller parameters What to do: Correctly reset floating lower limit → set high-pressure switch setpoint at least 2 bar above minimum floating target

Floating Head Pressure Control Failure → Fixed High Condensing Pressure

Likely causes

Outdoor temperature sensor failed or miswired → controller reads maximum ambient, floating lower limit not applied

Condenser fan VFD speed signal open-circuit → fan always runs at full speed

Floating lower limit setpoint entered incorrectly → zero energy savings

Related cases