www . refrigerationandaircon . co . za RACA Journal I March 2024 39
Support
In addition to managing the proper ventilation of the interior of a building with outside air and the correct air flow , the AHU performs other functions :
• Filtration and control of the quality of the air that will reach the interior , thanks to the filters , and depending on the retention of these filters , the air will be filtered .
• Control of the air temperature that regulates the airconditioning system so that the temperature in the interior of the building is according to requirements .
• Relative humidity monitoring and control for greater indoor comfort .
AHU are intended for use , for example , where the flow of people is high and with many people at the same time and whose natural ventilation is limited : hotel dining rooms , function rooms , restaurants and convention halls .
AHUs are also suitable option for those spaces with very high hygiene requirements : laboratories , clean rooms or operating theatres , among others . An AHU can also be used to ventilate places where air conditioning is provided .
TYPES OF AIR HANDLING UNITS
• Horizontal and vertical units : Vertical units typically require less floor area .
• Rooftop ( outdoor ) and indoor units : There are specific AHUs made for usage outside . They resist corrosion and are typically positioned on the roof . However , the majority of AHUs are indoor units .
• Draw-through and blow-through units : The AHU is either a blow-through or draw-through mechanism depending on where the fan is located .
• Outdoor air ( makeup air ) or mixing units : While mixing units ( as the name suggests ) can utilise both recirculating air and outside air , makeup air units use only outdoor air , used for example in hospital theatres .
• Single-zone and multi-zone units : For dual-duct systems , a multi-zone AHU is more frequently employed .
• Custom-built units : Standard units are lower in cost and quicker to deliver . More versatility is available with custombuilt AHUs , which may also be made to be the most energyefficient option .
Now Aisha , moving on to the second part of your question , servicing . All safety and usage of personal protection equipment apply . Routine AHU cleaning and maintenance is imperative .
The following consists of most of the servicing items , not all systems will have all of the components mentioned :
• Examine electrical switchgear and safeties including lockouts
• Examine control panel and boxes including labelling
• Check contactors / starters / relays
• Check operating amps
• Tighten all electrical connections
• Check control set points
• Examine / lubricate air dampers , actuators
• Examine filter section
• Change filters if necessary
• Maintain filter frames , seals and filter clips
• Examine heating coil / clean if necessary
• Clean heating coil
• Examine drain line and pan / clean
• Examine cooling coil , clean if necessary
• Examine supply air fan , check for vibration
• Clean fans and housing
• Lubricate fan ’ s shaft bearings if applicable
• Check belts , pulleys and alignment and tension on supply fan drive
• Examine all motors
• Lubricate all fan motor bearings if applicable
• Check fan ( s ) rotation
• Examine heating section ( if applicable )
www . refrigerationandaircon . co . za RACA Journal I March 2024 39