www . refrigerationandaircon . co . za RACA Journal I May 2024 11
Associations
UNDERSTANDING LIMITATIONS IN REFRIGERANT PIPE PLACEMENT There are several limitations , one being that refrigerant pipe installation is not allowed in egress corridors or paths of egress due to potential leakage concerns . For example , if there ' s an egress corridor without a ceiling , and you need to cross it with refrigerant pipe , finding a way to enclose that pipe is necessary to prevent exposure in the egress corridor .
During the design phase , engineers should be cautious about relying on VRF systems to condition ventilation air , particularly in humid climates . VRF fan coil units have limited capacity to handle latent loads . Therefore , decoupling ventilation air from VRF units , especially in humid climates , is advisable . Utilising dedicated outdoor air systems for delivering conditioned ventilation air directly to the space is a recommended practice . This approach allows for proper sizing and dehumidification of outdoor air , transforming the VRF system into a sensible heat unit . Engineers should also specify that installing contractors provide proof of factory training and certification from the VRF manufacturer for their installers . Regular site visits during construction are essential to assess the quality of the installation . Engineers must crosscheck the installation against the manufacturer ' s shop drawing , ensuring adherence to the design specifications .
Contractors play a vital role in ensuring that the onsite labourers are qualified , trained and certified to install VRF piping and equipment . The responsibility falls on both mechanical contractors and general contractors or construction managers to guarantee that qualified labour is on site for VRF installations . It ' s essential to ensure that labourers have the necessary expertise , especially since one designated installer may not always be present on-site due to simultaneous ongoing projects .
System integration , particularly connecting the VRF controller to the building management system ( BMS ), remains a challenge . Each VRF manufacturer has its proprietary software and control systems , creating what we call ‘ black boxes ’. These closed systems are not easily accessible or compatible with other manufacturers ' equipment . While progress is being made , achieving true integration with the BMS across different VRF manufacturers is still an ongoing challenge . manufacturers provide wind guards for outdoor condensing units , particularly vital in cold climates to counteract capacity reduction caused by cold winds .
VRF systems stand as a cost-effective solution for achieving individual temperature control in multiple spaces . Design engineers should invest time in educating themselves about these systems due to their complexity . Utilising dedicated outdoor air systems for ventilation air is recommended , coupled with adhering to ASHRAE 15 calculations and refrigerant volume regulations in occupied spaces . Rigorous attention to code requirements on refrigerant pipe placement , especially in egress paths , is crucial .
In summary , during construction , vigilant oversight of installations , adherence to shop drawings , and scepticism towards manufacturer-published heating capacities in low ambient temperatures are vital . Providing backup heat in cold climates is wise due to potential overstatement of heating capacities . Moreover , engineers should acknowledge the proprietary nature of VRF systems , differing among manufacturers , and consider bid implications in open-market scenarios . Specification requirements should ensure that successful bidders address any necessary changes to guarantee a seamless installation . RACA
“ 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 .”
CLIMATE IMPACT ON VRF It is essential to recognise that VRF systems operate as heat pumps , and their heating capacity significantly decreases as the outside air temperature falls . This poses a challenge in cold climates where the demand for heat is high , but the heat pump ' s efficiency is reduced . Depending on the project ' s location and climate , it ' s advisable to consider incorporating a source of
backup heat . A practical approach is to integrate backup heat in dedicated outdoor air systems , offering additional heating capacity when needed in extremely cold weather . Additionally , VRF Packaged unit .
Supplied by RPM Engineering Group
www . refrigerationandaircon . co . za RACA Journal I May 2024 11