Project
The energy centre fresh air system .
A decentralised heat recovery hot water plant .
One of the VRF theatre air handling units .
DX condensers ( for one of the server rooms ).
An example of the ducted cassette units and diffusers located in one of the wards of the hospital .
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energy usage on gross lettable area . On the HVAC scope , heat recovery systems would play a major role in obtaining an energy efficient building .
During the course of the project the client brief changed due to the global impact of the COVID-19 virus . The HVAC system in all hospitals plays a major role as a first-line defence in the containment of airborne pathogens of this nature . As such , various design changes were implemented in order to prepare the hospital for future outbreaks .
THE HVAC SYSTEM AND INSTALLATION During the concept design phase , two options were presented to the client for review . This included the use of a 4-pipe chilled water plant and a de-centralised variable refrigerant flow ( VRF ) system . The 4-pipe chilled water solution made use of hot water instead of electrical elements to provide terminal level heating for all variable air volume ( VAV ) ducted systems .
The client opted for the de-centralised VRF system due to the familiarity and success they have encountered with similar installations at their other facilities .
This facility was effectively divided into two sections . The clinical areas ( which included general wards , ICU / HCU ’ s , emergency department and radiology ) that are served by ducted VAV air handling units ( AHU ). These AHU ’ s provide primary and secondary filtration to the area whilst also optimising the opportunity for free cooling by engaging economy dampers which increase the fresh air flow rate . The AHU ’ s are coupled to a heat recovery VRF condenser located on the roof . Each clinical area is served by one AHU-VRF condenser combination in order to improve redundancy across the facility .
The other areas of the facility ( which included doctors suites , back of house / technical departments and administration offices ) are served by a conditioned fresh air unit with VRF cassette units for each space . Each refrigerant control box has been selected to have 20 % spare ports available in order to expand on the system if required . All refrigerant lines have been equipped with high quality shut off valves ( tested to 45-Bar ) to enable separate branches to be isolated without shutting off the rest of the system . As with the clinical areas , the unitary system has been sub-divided into block and floor-specific zones in order to improve redundancy .
There are 11-of ISO Class 7 and 4-of ISO Class 5 operating theatres within the hospital . These are also individually served by air handling units with humidity control that are equipped with high efficiency particulate absorbing ( HEPA ) filters .
The HVAC infrastructure is also utilised to provide hot water generation on site . This is achieved by integrating the hot water plants located around the facility into the VRF heat recovery infrastructure . As hospitals are predominately in a cooling only mode this provides tremendous amount of opportunity to
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RACA Journal I August 2022 www . refrigerationandaircon . co . za