Compiled by Eamonn Ryan based on a SAIRAC Johannesburg Centre Tech Talk by Jannie Potgieter.
Altitude significantly affects the cooling performance of HVAC systems. This is Part 5 of an eight-part article.
The audience at an earlier in-person tech talk. © RACA Journal
The presentation by Jannie Potgieter, a consulting engineer at Thermologica with advanced degrees in engineering, addressed how altitude influences cooling performance, particularly in high-altitude locations like Johannesburg.
Considering the entire HVAC system, including evaporator, condenser, and compressor, the overall performance is influenced by the combined effects of each component:
- Cooling capacity: The cooling capacity of a complete HVAC system will reduce as the altitude increases due to decreased capacity of the coils and the overall system performance.
- Compressor power: The power draw of the compressor will also be affected. At higher altitudes, the system must work harder to achieve the same cooling effect, leading to changes in power consumption.
For a dummy HVAC system designed for specific conditions:
Sea level design:
- Cooling capacity: 7.16 kW
- Compressor power: 1.97 kW
- Outdoor design temperature: 35°C
- Indoor design temperature: 27°C
When moving this system to a higher altitude:
- Cooling capacity: Expect a decrease due to reduced coil capacity and overall system performance.
- Compressor power: Likely to increase as the compressor has to work harder to maintain cooling performance in lower air density.
