Responsible Refrigeration number 67
This month I am not talking about Refrigeration and the competencies required for working in that field and the safe handling of refrigerant gases.
What we 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 workspaces, hospitals, and shops. First is that central air conditioning systems and packaged air conditioning units have dedicated intakes for fresh air calculated the 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” requires 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 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. This introduced fresh air must be filtered to catch dust, hazardous fumes, and if necessary odors.
ASHRAE has been releasing recommendations to reduce the infectious fine droplets called aerosols. This is particularly the case with Corvid-19 or as it is also referred to as SARS-COV-2. Now we have a uniquely South African variant that is causing havoc in the country. Therefore to focus must be to reduce the risk of transferring the virus infection via the air conditioning and to have filtered fresh outside air.
Central air conditioning systems with dedicated fresh air intakes present some new challenges regarding filtration. First is how they increase the volume of fresh air and secondly 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 drop across these filters and the possible effect on the fan performance and additional energy requirement. The manufacturers’ recommendations must be followed regarding cleaning, change-out frequency, and disposal of old filters. Some have suggested UVC filtration but this needs careful investigation before adopting this solution.
The recommendations suggest following regulatory and statutory advice on hygiene and sanitation, wearing masks, and washing hands regularly.
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. The vast majority of installation companies ignore the National Building Regulations.
In many cases the room air conditioner is installed in a space 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 space and occupancy have 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 requirement. There is no short cut to meet the regulation and provide good indoor air quality.