Projects building from over cooling in certain areas and under cooling in other areas , as a result of building orientation and various external loads throughout the day .
Although the indoor units were thermally zoned , the heat recovery ( HR ) boxes were optimised to ensure that heat recovery is effective at any time of the day . The heat exchange from cooling a particular zone is redirected to a zone that may be required to be in heating . To ensure that this operation was effective , parameter and internal zones were connected to the same HR box increasing the potential of having a zone in heating and a zone in cooling connected to the same HR box . This then further enable the outdoor units plant size to be optimally sized and diversified through this heat recovery design optimisation .
The third floor contained an auditorium , which naturally had to adhere to strict decibel levels . The auditorium was designed as a stand alone system , and only switches on when occupied . This further made the building more energy efficient and economical .
Apart from the third floor , the buildings internal services were exposed as the building has no ceilings . This meant that extra attention was required when selecting the indoor units as ceilings provide an element of noise attenuation , as well as superior quality of the workmanship on site as the services are all exposed .
Over and above the aforementioned , the correct second fix air terminals are imperative as diffuser selection and orientation has a major impact on the comfort of the occupants . Incorrect positioning of diffusers may result in cold and hot spots , causing discomfort to the occupants . To ensure that this risk was mitigated , the diffusers were carefully positioned based on their throw .
Ceilings also play an important role in the distribution of air within the space . In general , the air travelling from the diffuser sticks to the ceiling , this reduces the effects of air dumping and is known as the Coanda effect . With majority of the building being that of exposed services no ceilings were present , as a result constant volume swirl diffusers were selected for its good radial distribution and good air distribution performance index ( ADPI ).
Each hideaway and cassette unit have individual controllers which are clearly linked to each other , this allows individual control . Over and above this , there is a centralised controller located in the facility managers office which enables the facility
1
2
3
4
1 . All indoor units have individual control .
2 . Images generated from the quality report assisted the sub contractor and professional team in determining the exact location of issues and queries .
3 . Diffusers located between bulkheads serving a lounge area . 4 . The exposed heat recovery box and hideaway unit .
www . hvacronline . co . za RACA Journal I January 2021 47