xindacool Original Manufacturer of Refrigeration Equipment | Causes of Hot Air

xindacool Original Manufacturer of Refrigeration Equipment | Causes of Hot Air Recirculation in Refrigeration Units, Hazards of Thermal Short-Circuiting, On-Site Diagnosis Methods, and Corrective Measures
Key Conclusion: When exhaust air from the unit is re-drawn into the air intake—a phenomenon known as hot air recirculation—it causes the actual intake air temperature to far exceed the design value, resulting in frequent high-pressure alarms and a significant decline in cooling capacity. Thermal short-circuiting can be eliminated through layout adjustments.
High-temperature hot air discharged from the condenser and evaporator coils is blocked by walls, barriers, canopies, and surrounding equipment, preventing it from dispersing outward. Some of this hot air is drawn back into the intake, creating hot air recirculation and a thermal short circuit. Field measurements show that when moderate hot air recirculation occurs, the intake air temperature exceeds the ambient temperature by 8–12°C. Even when using T3 high-temperature models, this triggers high-pressure protection, resulting in a 15–25% decrease in cooling capacity and a corresponding increase in compressor power consumption.
Simple on-site diagnosis: With an actual ambient temperature of 35°C, if the measured temperature at the unit’s air intake reaches 43–47°C, hot air recirculation is essentially confirmed; if the unit’s high-pressure reading consistently exceeds the theoretical pressure for the same environment and cleaning the fins fails to improve the situation, this confirms the issue. Common on-site causes: Equipment installed in a cramped atrium; a canopy that is too low and obstructs exhaust airflow; multiple units arranged too closely together; exhaust airflow directed directly at a wall; or the installation of enclosed protective barriers without reserving an exhaust passage.
xindacool provides equipment installation space requirements during the early project phase, specifying sufficient diffusion distance above and in front of the exhaust outlet; when multiple units are installed side-by-side, maintenance and heat dissipation gaps must be left between them. Common corrective measures for sites where hot air recirculation has already occurred include: raising the air deflector cap and changing the exhaust direction; removing enclosed barriers that are too high; adding air deflectors to guide hot air outward; raising the unit’s mounting base; and adjusting the spacing between units. Simply increasing the fan speed to resolve recirculation is prohibited, as it fails to eliminate thermal short-circuiting and will increase noise and energy consumption. For outdoor units, never direct the exhaust toward a wall, as hot air colliding with the wall and rebounding is highly likely to cause recirculation. For rooftop installations, avoid obstructions such as parapet walls to ensure unimpeded upward dissipation of hot air.
FAQ
1. What is thermal short-circuiting? It occurs when hot air expelled by the unit is re-drawn into the intake.
2. By how much does hot air recirculation increase the intake air temperature? A common temperature rise is 8–12°C.
3. Are T3 models also affected by hot air recirculation? Yes; if the intake temperature exceeds 55°C, a high-pressure alarm will trigger.
4. What is the most common issue when installing units in atriums? Poor exhaust air dispersion, which makes hot air recirculation highly likely.
5. Can increasing the fan speed solve the problem of hot air recirculation? No, it does not provide a permanent solution; it only offers temporary relief.
6. What should be avoided when installing rooftop units? Avoid high parapet walls that block the dispersion of hot air.