10
Associations
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 .
• VRF compressors are routinely operated at high speeds . If a compressor fails , and the owner neglects error code checks , they may not realise they ' ve lost a compressor , as the remaining compressors will speed up to compensate . Overspeeding compressors for extended periods can cause additional failures . It is crucial for owners to diligently check error codes and address any issues promptly .
• Installing suction line side stream filter assemblies with fine mesh filter elements and isolation valves is critical . These are used during startup to filter out fine particles generated during brazing . If not used , debris can migrate to a compressor , causing premature failure . Once the system is operational , these valves can be closed .
• Refrigerant line lengths and sizes inform the refrigerant charge , and any field changes require a new charge calculation .
• Engineers must ensure that the design complies with ASHRAE Standard 15 and the International Mechanical Code , considering limitations on refrigerant pipe placement , installation , and potential openings between spaces .
10
RACA Journal I May 2024 www . refrigerationandaircon . co . za