www . refrigerationandaircon . co . za RACA Journal I January 2025 43
Technical data or correction factors for altitude adjustments . Consulting these resources can help in accurately predicting and compensating for performance changes .
• Altitude correction factors : Manufacturers often provide correction factors for altitude in their equipment manuals . For instance , older manuals may list factors like a 3 % reduction in capacity and 1.03 times increase in compressor power at 1 700m . These factors , however , are specific to particular units and designs and may not be universally applicable .
Understanding and addressing the impact of altitude on HVAC system performance is crucial for maintaining efficiency and effectiveness . By analysing system components and employing strategic adjustments , such as compressor sizing and coil oversizing , the performance impact can be managed . Utilising manufacturer data and design software further aids in achieving optimal system performance in high-altitude environments .
CORRECTION FACTORS AND PRACTICAL CONSIDERATIONS When adapting HVAC systems for high-altitude conditions , applying correction factors for capacity and power is crucial but requires careful consideration . Correction factors , such as those provided in various industry resources , can give a rough estimate of performance changes , but they must be used cautiously as they are not universally applicable to all systems .
Correction factors , like those found in sources such as the Bartok
PDF , include :
• Total capacity correction factor : This factor adjusts the total cooling or heating capacity based on altitude . For instance , at 1 800m , you might see a 5 % reduction in total capacity .
• Sensible capacity correction factor : This factor adjusts the sensible ( or temperature-related ) capacity of the system . At the same altitude , a typical correction might show around a 13 % reduction .
• Condenser intake temperature correction factor : This factor adjusts the condenser ' s intake temperature to prevent overheating and ensure proper operation at high altitudes . It accounts for the reduced efficiency of the condenser in higher ambient temperatures .
These factors provide a starting point but are specific to certain systems and conditions . They are not a one-size-fits-all solution and can vary depending on the design and operational parameters of the HVAC system .
From the case study data , the following observations were made :
• Density correction factor : The density at high altitudes reduces , impacting the coil capacity . For example , at 1 700m , a 15 % reduction in coil capacity was observed , while the density change was around 18 %. The overall system capacity reduction was only 7 %, indicating that while individual coil performance suffers , the system ’ s total capacity reduction is less severe due to compensatory adjustments .
• Compressor power correction factor : At high altitudes , the compressor power typically increases by about 5 % to maintain performance , due to changes in condensing and evaporating temperatures .
• Recalculate system performance : Whenever possible , work with suppliers or use advanced software tools to recalculate system performance at high altitudes . This ensures more accurate adjustments and optimises system design for new conditions .
“ When adapting HVAC systems for highaltitude conditions , applying correction factors for capacity and power is crucial but requires careful consideration .”
www . refrigerationandaircon . co . za RACA Journal I January 2025 43