Air-Cooled Condenser Reverse Pressure Differential — Short-Circuit Backflow

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Hot discharge air directly recirculates to inlet — insufficient physical shielding around condenser. Check: With fans running, measure inlet air temp — +3°C above ambient signals recirculation. Use smoke tube to visualize airflow. Use thermal imager to confirm hot discharge bending back to inlet. Check height of surrounding shielding (fence, wall). What to do: 1) Extend discharge vertical duct (raise outlet ≥2 m above inlet level) 2) Install shielding panel on intake side 3) Add fan stack or deflector to force vertical discharge 4) Root cause: design separate discharge/intake paths from initial installation (CFD recommended) 5) Alternative: air curtain in front of intake. Insufficient clearance between inlet and outlet due to limited installation space (less than 1 m apart). Check: Measure clearance between inlet and outlet with tape — manufacturer minimum typically 1–2 m. Check side wall clearance (usually ≥0.6 m). Identify obstructions to prevailing wind direction. What to do: 1) Relocate unit to get ≥2 m clearance if possible 2) If relocation impossible, add duct/plenum to separate inlet and discharge volumes 3) Install weather hood for intake expansion 4) Consider removing adjacent obstructions 5) For new installations, follow manufacturer guide +50% margin. Hot air interference between multiple parallel condensers (discharge aimed at adjacent unit's inlet). Check: Visualize airflow between units with smoke or CFD. Measure inlet air temp at each unit simultaneously — look for temp gradient between upstream and downstream. Monitor condensing pressure under various on/off combinations. What to do: 1) Install separation baffles between units to block discharge interference 2) Reconfigure layout so discharges face opposite directions 3) Widen spacing (≥2 m) 4) Implement staged operation control — prioritize upwind unit based on wind sensor 5) Long-term: reserve new site or consider stacked vertical arrangement. Building wall or barrier deflecting discharge air back toward inlet side. Check: Check condenser location vs surrounding buildings/walls. Smoke tube to visualize discharge air deflecting off wall. Measure wind direction/speed (log prevailing wind). Measure building/wall height and condenser separation. What to do: 1) Rotate unit so discharge faces away from wall 2) Raise discharge above wall top (≥1 m above) 3) Add vertical extension duct or stack-style discharge 4) If not feasible, add louvered openings in wall 5) For relocation, position opposite to prevailing wind 6) Consider access road and maintenance clearance simultaneously. Reverse airflow entering operating units from adjacent stopped fan units. Check: Monitor whether condensing pressure rises in running units when some units stop. Visualize reverse airflow through stopped unit's fan casing. Wind measurement: >0.5 m/s face velocity through stopped unit = reverse flow. Log power/refrigerant flow changes across different on/off combos. What to do: 1) Install backdraft dampers (gravity or motorized) on each unit outlet 2) Smart control: auto-close damper on stopped unit 3) Apply staged operation to minimize standalone stops 4) Add physical baffle plate between units if needed 5) Long-term: detect reverse flow and briefly idle-rotate affected unit fan to balance pressure. Excessive winter wind baffle installation to prevent low condensing pressure — causing summer backflow. Check: Check seasonal condensing pressure log — is hunting/high pressure only in summer? Check wind baffle position vs discharge direction. In summer with ambient wind >2 m/s, measure inlet temp rise. Simulate baffle removal (partial) to compare effect. What to do: 1) Replace with removable wind baffle — remove in summer, install only in winter 2) Install automatic variable louver — opening adjusts by wind speed/ambient temp 3) For winter low-pressure compensation, switch to fan VFD or head-pressure controller (e.g., flood-back control) 4) Re-calculate baffle design — keep only minimum necessary coverage 5) Document seasonal baffle procedure in maintenance manual.

Air-Cooled Condenser Reverse Pressure Differential — Short-Circuit Backflow

Likely causes

Hot discharge air directly recirculates to inlet — insufficient physical shielding around condenser

Insufficient clearance between inlet and outlet due to limited installation space (less than 1 m apart)

Hot air interference between multiple parallel condensers (discharge aimed at adjacent unit's inlet)

Building wall or barrier deflecting discharge air back toward inlet side

Reverse airflow entering operating units from adjacent stopped fan units

Excessive winter wind baffle installation to prevent low condensing pressure — causing summer backflow

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