AIR HANDLING UNITS

CUSTOM DESIGNED AIR HANDLING UNITS

Our experience in design, testing, and validation of cleanrooms, as well as a production line for world-class HEPA filter manufacturing facilities, led us to develop custom-designed Air Handling Units for critical areas where there can be absolutely no compromise for quality.

The vertical integration business opportunity presented itself through clients who demanded a design based on cleanroom fundamental construction principles rather than comfort plants which are adapted for use in SABS EN 18644- class 5 to 8 facilities cleanroom facilities.

The Air Handling Unit is often referred to as the heart of the cleanroom HVAC system design. The objective is to ensure continued performance and compliance in areas where processes and people have to be protected at all costs. To achieve this the design must offer a standard that surpasses conventional technology and include adequate redundancy.

As a specialist engineering company with state of the art production equipment, we understand the balance of cost without compromising quality and energy efficiency.

AIR HANDLING UNIT CONSTRUCTION

The structure is constructed from extruded aluminium profiles, joined by precision die-cast corners and GOP joints.

The profiles are precision extrusions, specifically designed for air handling units and include thermal breaks to provide a completely insulated and modular structure.

The cladding consists of double-walled, fully insulated panels. Omega profiles are strategically positioned to provide support to the structure and to separate the modules.

Provision is specifically made for the ease in removing components, such as fans and even coils if and when repairs or replacement becomes necessary.

The Floor

The floor is constructed from aluminium checkered plate, reinforced to create a sealed and strong base. Adequate strength is provided to support the equipment and personnel when entering the air handling units. This is achieved by including support beams that are cast into place throughout the floor.

Access Doors

Access doors are provided for maintenance and service procedures and due care and attention will be provided to ensure a permanent and positive seal. The inlet and outlet flange connection shall be designed for direct adaption to the ducting where necessary. The air handling units will be assembled and tested at our factory prior to delivery before being transported to the site. The entire enclosure shall be weatherproof and re-enforced to withstand the system differential pressure and to create a self-supporting and robust air handling unit.

The base of the unit is constructed from heavy-duty components, engineered for stability and strength which allows the unit to be rigged into position safely. The base elevates the unit off the plant room floor to provide dry conditions for the air handling unit floor if a concrete plinth does not exist.

FAN SELECTION

A wide range of fans are available and selected for the duty. EC plug fans are the product of choice when suitable for the application because it provides a compact and high-efficiency solution for air handling units.

The high-performance impeller, motor, and electronics system are all optimally adjusted to one another, leading to an overall efficiency of well above 60%.

A significant contribution to this efficiency is made by the external rotor design GreenTech EC motor. This is a mains-powered, permanently-energized synchronous motor with electronic computation.

An important feature of these motors is the integrated variable speed drive (VSD) that allows for simple speed control. PI control with sensor input or MODBUS high-level interface (HLI) connection over RS485.

The electronics and motor form one unit, which is a key advantage of EC plug fans over conventional fans.

Not only does the singular unit feature save space, but the reduced quantity of components also required increases reliability and reduces installation time.

MOUNTING TYPES AND FAN GRID CONFIGURATION

Depending on the airflow required, space available, and required redundancy, the mounting arrangement used will vary from one application to the next.

When retrofitting less efficient belt-driven fans in air handling unit (AHU) applications, size is an important consideration. Smaller EC plug fan models are easier to fit through existing access doors, can improve airflow and cooling capacity, and add redundancy to the AHU system. Spider mounting for EC plug fans is typically used for smaller fan sizes (I.e. fans from size 250 to 560) compatible for fan grid formation.

When considering EC plug fans for an upgrade or retrofit project, it is recommended to replace the large belt-driven fan with a spider mounted EC plug fan grid for wall mounting that delivers equivalent air performance.

Larger EC plug fan models ranging from size 630 up to size 900 are available with cube design for floor mounting which offers increased stability with the further increase in mass of larger EC plug fan models. Cube mounted EC plug fans can be further upgraded to include anti-vibration mounts.

EC plug fans have the benefit of pressurizing the space they discharge into, allowing ducting to be cut wherever required.

DAMPERS

Dampers are key to control and balance airflow volumes to air-conditioned spaces. Simply put, the correct amount of air-conditioned air for a given area is necessary to meet the facility design requirements and to ensure continuous airflow compliance.

Dampers can be motor driven and controlled automatically via airflow or CO₂ sensors or adjusted manually to the required setpoint values. The ratio between supply, return and fresh air is balanced and controlled via volume control dampers.

Low leakage dampers with injection moulded gear mechanisms and which have blade with edge seals are used in critical applications where precise volume settings are necessary. These units are generally produced from precision aluminium extrusions whilst standard comfort air models are fabricated from galvanized, stainless steel or aluminium sections.

WEATHER LOUVRES

Weather louvers are installed in air intake systems and on the building facade to protect HVAC systems against rain and large debris such as leaves, paper, and plastic. The primary objective in the case of air handling unit design is to remove water droplets and to drain them away to avoid internal flooding.

The structure is produced from aluminium extrusions which offer low resistance due to the aerofoil blade design and in addition thereto, low air-regenerated noise is guaranteed. Generally, airflow velocities should not exceed 2 – 2,5 m/s to prevent water carryover and bird mesh can be added to the downstream side.

The flanged design makes installation a simple task and for extended life, the material can be anodized or powder-coated.

COILS – COOLING / HEATING / STEAM

Coils are generally produced from copper tubing mechanically fastened to aluminium fins. The header section is likewise produced from copper with the entire assembly encased within a galvanized or preferably stainless steel frame.

Application and climate-specific applications may dictate the use of copper, stainless steel or aluminium fins.

The heat-exchanger design is selected by using specialized software to achieve the very best thermal efficiency as well as differential pressure and by factoring in the refrigerant or chilled water design.

All coils are produced with drain connection and air vents whilst the copper tube thickness must withstand the system pressure whether it be refrigerant or chilled water.

The entire coil assembly is fitted into a generous drain pan to retain condensate before draining it to waste.

HUMIDIFICATION AND DEHUMIDIFICATION

The control of relative humidity is an important factor when maintaining comfort and to create a healthy environment free of mould spores and mildew smells. One might also have to protect products with extreme sensitivity to moisture such as certain pharmaceuticals for instance.

Low humidity levels on the other hand promote bacteria, viruses and other harmful microorganisms.

The type of humidifier selection depends on the psychometric process as well as economic factors. Steam humidification is an isothermal process which does not change the air temperature and which is generated via a central boiler or electrode steam generator. In the alternative an adiabatic process can be used to cool the air whilst inducing moisture at the same time. This can be achieved through pressure atomizing or evaporation of water in the airstream.

Dehumidification on the otherhand is best achieved by passing the air through absorbant dessicant or by cooling the air mechanically beyond its dew point forcing moisture vapour to condense and drop our of the airstream.

PRIMARY FILTERS

Primary filters are produced in washable or disposable form and designed to remove the coarse particulate matter to protect the secondary and more efficient filters.

Coarse filters such as these provide very little protection to coils, ducting, and building interiors.

SECONDARY FILTERS

Secondary filters remove the finer particulate matter and are designed to keep the coils, ducting, and facility internals clean.

Needless to say, it also protects tertiary filters in cleanroom facilities.

Tertiary FILTERS

Tertiary HEPA filters will be included in cleanroom applications to protect people from harmful pathogens or to protect processes or products where absolutely no contaminants can be tolerated.

HEPA filters can be installed in the air handling unit or in separate terminal HEPA filter housings just before the conditioned air enters the cleanroom space.

UNDERSTANDING DECONTAMINATION AND DISINFECTION

RISK MANAGEMENT

The first and most important duty facing management is how to prepare an appropriate risk
management policy and then implement the procedures based on proven and best global
practices.

DECONTAMINATION

Decontamination is a process to clean and remove contaminants and microorganisms from solid surfaces. The method of application and choice of disinfectant is an important consideration because chemical residue and wet spray or mist is harmful and can damage electric/electronic components due to corrosion over time.

OVERCOMING THE LIMITATIONS OF MANUAL CLEANING

Clean does not always mean disinfected

Harmful microorganisms can survive on poorly cleaned surfaces and it is simply impossible to get to all areas during the cleaning process. Infection control personnel in hospitals perform disinfection processes after terminal cleaning to create a truly clean environment.

Despite proper training and assessment of cleaning operatives and the use of adequate cleaning/disinfection products, even hospital environment-related infection rates cannot be lowered above a certain level. It might be because of an intense workload, lack of motivation, or the oversight of some potentially contaminated surfaces.

In some situations, the risk of acquiring an infection is too high to only rely on human performance. COVID-19 is one of those risks where airborne disinfection and surface decontamination using Nocolyse should be considered for the complete destruction of dangerous pathogens.

When one deals with COVID-19 and other infectious pathogens, every square mm must be cleaned and disinfected and this is very difficult to achieve with a manual deep cleaning process. Hard to reach areas include:

Between fins in heating and cooling coils
Behind louvres, dampers and grilles
Behind and in fan inlet systems
Within supply and return air ducts
Between air handling unit panels and joints
On filters and their frames
Airborne spaces in air handling units and plant rooms
The spaces being supplied by airconditioning

DISINFECTION

Disinfection is a process to kill (destroy the DNA) pathogens including COVID-19. Every square mm in the most impossible to reach areas is disinfected including air spaces where airbrone pathogens are transported in the airflow.

THE NOCOTECH AUTOMATED CONCEPT FOR DISINFECTION

The Nocotech automated concept of disinfection consists of a submicron diffusing process using a biodegradable disinfectant (Nocolyse, Nocolyse one-shot, Nocolyse food) which is dispersed via an automated disinfection device. The disinfection device transforms the disinfecting liquid into a completely dry fog. This is achieved by generating a particle size of less than 5 microns through high-speed diffusion.

The process, therefore, creates a dry gas which disinfects all surfaces without exception. This is particularly useful for unreachable areas which are difficult to get to and clean manually. Every square centimeter of the space is disinfected with a lethal effect on COVID-19 as well as staphylococcus (including MRSA), enterococcus (including VRE), H5N1, H1N1, legionella, aspergillus niger, candida albicans, and other highly infectious microorganisms to > 6 -log reduction.