Responsible Refrigeration
FRESH AIR AND VENTILATION
By Barney Richardson
BARNEY RICHARDSON
Barney Richardson is the director of South African Refrigeration and Air Conditioning Contractors Association ( SARACCA ) and sits on various other boards within the HVAC industry , including the South African Qualifications and Certifications Committee for Gas ( SAQCC ) Gas .
This month I am not talking about refrigeration and the competencies required for working in that field nor the safe handling of refrigerant gases .
What we now need to consider as part of the installation of air conditioning is fresh air and ventilation in this crisis of Covid-19 . There are two aspects of ensuring clean fresh air in work spaces , hospitals and shops .
First is that central air conditioning systems and packaged air conditioning units have dedicated intakes for fresh air calculated to meet the occupancy requirements of the space .
Secondly is the major problem when using room air conditioning units in small spaces like offices where no fresh outside air is introduced .
The National Building Regulations , SANS 10400 , require either natural ventilation or a fresh air artificial ventilation system to be a system that draws air free of contamination . An open window should not be exposed to an outside area contaminated by smoke , dust or fumes .
Therefore , a mechanical ventilation inlet should be positioned to ensure that such air is free from local contamination . By the same consideration the ventilation unit should have suitable filtration to minimise contamination from the outside air . The fresh air introduced must be filtered to catch dust , hazardous fumes and , if necessary , odours .
ASHRAE has been releasing recommendations to reduce the infectious fine droplets called aerosols which can contain microorganisms . This is particularly the case with Corvid-19 or , as it is also referred to , as SARS-COV-2 . Now we have a unique South African variant of this micro-organism that is wreaking havoc here and in other countries .
Therefore , our focus must be to reduce the risk of transferring the virus infection via the air conditioning system and to have filtered fresh outside air .
Central air conditioning systems with dedicated fresh air intakes present some new challenges regarding filtration . One is how to increase the volume of fresh air and another is how to upgrade the filtration without having to make major changes to the fans .
MERV-13 or better filters have been recommended . But it is important to check the pressure drops across these filters and the
possible effects on fan performance which can lead to additional energy requirements .
The manufacturers ’ recommendations must be followed regarding cleaning , change out frequency and disposal of old filters . Some have suggested UV-C filtration , but careful investigation is needed before adopting this solution .
The recommendations suggest following regulatory and statutory advice on hygiene and sanitation , wearing masks and washing hands regularly . Further recommendations are :
• Provide the minimum fresh air rates for ventilation and filtration where the effectiveness can be determined .
• Maintenance of equipment like changing filters regularly .
• Run the central system air handling units through the night to flush the building of stale and possibly contaminated air .
• If there is an exhaust system then it must be positioned so contaminated air cannot re-enter the air conditioning system or the building .
When it comes to room air conditioning , particularly with the proliferation of mid wall split units there is just no fresh air introduced to the space . In this respect , the vast majority of installation companies ignore the National Building Regulations .
In many cases room air conditioners are installed in spaces where this is no chance of fresh air being introduced from windows . A dedicated filtered fresh air supply is not even offered to the client . Then there is the client who will not spend the extra money if such a ventilation system were offered or recommended .
Installers of room air conditioning units must fully consider the requirements of the space to meet the National Building Regulations ventilation requirements . Once the space and occupancy has been surveyed a calculation can be done as to how much fresh air is needed .
A ventilation system design can then be prepared with correct fan and filter selection and proper duct sizing to meet the space requirements . There are no short cuts to meeting the regulations and providing good indoor air quality . RACA
www . hvacronline . co . za RACA Journal I March 2021 43