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 micro-organisms. 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.
