12
Associations
MAXIMISING EFFICIENCY THROUGH VRF BASICS AND PROPER INSTALLATION TECHNIQUES
Edited by Eamonn Ryan
The following article is derived from an ASHRAE Journal public podcast delving into the intricacies of Variable Refrigerant Flow ( VRF ) systems , presented by Kelley Cramm , an ASHRAE Life Member and mechanical engineer with Henderson Engineers .
The Mitshubishi
Electric air conditioners ’ hybrid chilled water VRF system eliminates the need for room leak detection sensors .
The presentation explores VRF systems , proper installation techniques , and addresses common misconceptions surrounding compressor failures .
VRF systems represent an innovative approach to all-electric heat pumps , providing remarkable flexibility . These systems may incorporate heat recovery , offering diverse indoor fan coil unit options , from drop-in ceiling cassettes to compact wall-mounted units and concealed ducted units . The unique feature of VRF is the ability to pipe multiple indoor units to a single set of outdoor condensing units , reducing the overall footprint .
They are highly cost-effective , particularly for spaces demanding individual temperature control , such as buildings with multiple enclosed offices . In comparison to hydronic fan coil systems or classic variable air volume systems with reheat , VRF proves to be a more economical solution . Moreover , its capacity for heat recovery makes it an energy-efficient choice . By utilising heat rejection from cooling zones to provide heat to zones in need , VRF ensures optimal performance and resource utilisation .
COMMON CHALLENGES AND MISCONCEPTIONS While VRF systems offer numerous advantages , the industry has faced challenges , primarily related to compressor failures . Routine compressor replacements have contributed to a negative perception
© RACA Journal of VRF in the market . Manufacturers , keen on maintaining customer relationships , often replace failed compressors under warranty without delving into the root cause of the failures . This practice has led to a persistent issue without a comprehensive resolution .
To mitigate the challenges associated with VRF , proper installation techniques are crucial . It is important to perform a thorough assessment during installation , ensuring that system components are correctly matched and that the system design aligns with the building ' s specific requirements . Adequate training for installers and ongoing maintenance are essential components of ensuring the longevity and efficiency of VRF systems .
On the maintenance side , filters on indoor units need to be changed regularly . This can be challenging for buildings with many indoor fan coil units , especially if the maintenance staff is stretched thin . Failure to change filters can reduce airflow at the indoor unit , potentially leading to compressor failure . Additionally , condensing unit coils , the outdoor units , need regular cleaning at least twice a year . VRF systems often use micro fin condensers , which readily trap dirt and debris . Neglecting this maintenance can result in condenser failures due to reduced airflow across the fouled coil . Since these are heat pumps , condensing units run year-round , requiring more frequent maintenance compared to traditional DX cooling units . If the owner lacks the staff for routine maintenance , engaging a qualified service contractor is essential .
INSTALLATION PRACTICES THAT ARE IMPORTANT FOR VRF
• The number one item is purging the pipe with an inert gas , usually argon or nitrogen , during brazing to prevent slag and poor joints . The brazers must be trained and certified by the VRF manufacturer . Proper pipe installation , following the manufacturer ' s shop drawing , is crucial . If there are changes in the field , an as-built piping drawing must be created , and the manufacturer ' s software rerun to determine the correct refrigerant charge .
12
RACA Journal I July 2024 www . refrigerationandaircon . co . za