Project
The plant is automatically controlled to provide the required temperature conditions in summer by means of averaging zone sensors , two per zone , and is switched on and off automatically at the plant control panel at each unit .
• Restaurants : The restaurants shall each be served by dedicated chilled water AHUs positioned in closed plant areas adjacent or within each restaurant . Conditioned air from each unit is supplied through systems of P3 ducting and distributed to the areas through ceiling diffusers . Re-circulated air is returned through grilles in the ceiling over the seated area and is ducted back to the plant area . The required quantity of fresh air is introduced through external louvres mounted in each plant room . The plant is automatically controlled to provide the required temperature conditions in summer and winter , and is switched on and off automatically at each plant control panel . Kitchen extract and make-up air is provided by the tenant in accordance with SANS regulations .
• Mall areas : The mall area is partially air-conditioned with recirculated air from the line shops , as well as dedicated AHUs to the atriums in order to maintain acceptable temperature conditions in summer . In addition , a minimum amount of conditioned air is supplied to the mall areas from the plants serving the line shops .
BUILDING MONITORING SYSTEMS ( BMS )
• Chiller control : The BMS time schedule starts and stops the chillers and chilled water pumps . After receipt of the start signal , the chillers operate via their inherent control systems . As this is a mixed-use development the plant runs 24 hours , seven days a week with selected chillers being switched off overnight . Outside of the programmed occupation period , the chillers can be started if any of the AHUs are started and the chilled water control valve more than 10 % open . Supply and return water temperatures and chilled water pumps ’ status are monitored and controlled from the BMS operators terminal .
• Variable volume AHUs ( gym ) and constant volume AHUs ( retail ): The BMS time schedule starts and stops air handling units at the programmed times .
• Supply air temperature control : Averaging zone temperature sensors in each zone modulates the cooling control valve to maintain a constant supply air temperature . The temperature set point , fan air flow switch and safety thermostat status are monitored or adjustable from the BMS operator ’ s terminal .
40
RACA Journal I April 2023 www . refrigerationandaircon . co . za