DE LOS SERVICIOS PÚBLICOS PUBLICACIÓN DE TERCERA VEZ

1.0 SCOPE

This specification covers the general design, materials, construction features, manufacture, shop inspection and testing at manufacturer’s works, delivery at site, handling at site, installation, testing, commissioning and carrying out performance test at site of Air Handling Units(AHU’s)

2.0 CODES AND STANDARDS

The design, materials, manufactures, inspection, testing and performance of AHU shall comply with all currently applicable status, regulations, codes and standards in the locality where the equipment is to be installed. Nothing in this specification shall be construted to relive the CONTRACTOR of this responsibility. In particular, the AHU s shall conform to the latest edition of following standards:

IS 7613 Methods of Testing Panel Type Air Filters for Air- Conditioning and Ventilation Purpose.

ASHRAE 33 Methods of Testing – Forced Circulation Air Cooling and Air Heating Coils.

ARI 410 Forced Circulation Air Handling Units. ARI 430 Central- Station Air – Handling Units.

AMCA 210 Laboratory Methods of Testing Fans for Rating. FED STD 209E Clean Room and Work Station Requirements, Controlled Environment

NFPA 90A Installation of Air- conditioning and Ventilating System.

3.0 CONSTRUCTION FEATURES

3.1 TYPE

The AHU shall be draw or below through type as specified in data sheet. The unit shall comprise of various sections such as mixing box, pre-filters, fine – filters, cooling coil, heating coil, humidifier, fan, High Efficiency Particulate Air (HEPA) filters , etc. 3.2 CASING

3.2.1 Single Skin Construction

AHU shall be of sectional construction fabricated out of 16G Galvanised Steel Sheet (GSS) or Cold Rolled Cold Annealed (CRCA) sheet.

3.2.2 Double Skin Construction

Double skin wall panels shall be 25 mm thick made of GSS, pressure injected with polyurethane foam insulation of density 48 Kg/M3 and K factor not exceeding 0.02W/M0C. Double skin wall panels shall be fixed to 2.5 mm thick aluminum alloy twin box section structural framework with stainless steel screws. Outer sheet of the panels shall be made of 0.8 mm thick GSS pre- plasticised or powder coated. Inner sheet shall be 0.8 mm thick plain GSS.

The entire frame work shall be mounted on a 100 mm (minimum) aluminum alloy channel base. The panels shall be sealed to the frame work by heavy duty ‘O’ ring neoprene gaskets held respective in the framed extrusion. All panels be detachable or hinged. Hinges shall be made of die cast aluminum with stainless steel pivots. Handles shall be made of hard nylon and be operational from both inside and outside of the unit. Units supplied with various sections shall be suitable for on-site assembly match drilled, with bolts, nuts and continuous neoprene rubber gaskets. All fixing and gaskets shall be concealed.

Floor and roof panels shall be double skin type and shall be of same construction as the wall panels shall be made of same constructions as the wall panels.

AHU s shall have hinged quick- opening insulated access door on fan and filter sections. Access doors shall be double skin type and shall be of same construction as the wall panels.

Four (4) fittings lugs shall be bolted to each base section for lifting or pacing the AHU in place.

3.2.3 Sloping condensate drain pan shall be fabricated from 18G GSS. It shall be isolated from bottom floor panel through 25 mm thick heavy duty Treated for Fire (TF) quality expanded polystyrene or polystyrene foam. Drain pan shall extend beyond the coil.

3.2.4 Casing shall be of air-tight construction and sufficiently rigid to exclude vibrations, throughout the working capacity range of the AHU.

3.3. FILTERS

3.3.1 Pre- Filter

Each unit shall be provided with a factory assembled filter section containing washable synthetic type air filters having GSS frame. The media shall be supported with High Density Polyethylene (HDPE) mesh on one side and aluminum on the other side. Filter banks shall be easily accessible and designed for easy withdrawal and replacement of filter cells. Filter bank framework shall be fully sealed and constructed from GSS. The efficiency of the filters shall be 90% down to particle size of 20 microns as per IS 7613. 3.3.2 Fine- filter

Flanged microvee filters with HDPE filter media shall be provided. The filter frame and filter bank frame work shall be of GSS construction with neoprene rubber gasket. The efficiency of the filters shall be 99% down to particle size of 5 microns as per IS 7613. Preferably, fine filters shall be located at the downstream side of fan section inside of fan section inside the AHU.

3.3.3 HEPA filter

Flanged HEPA filters having Di- Octy1-Phthalate (DOP) test efficiency of 99.97% down to particle size of 0.03 microns, shall be located at the downstream side of fan section inside the AHU , HEPA filters made of sub-micron glass fibre paper shall be designed for velocities of 1.25 meters per second. The filter frame work shall be of a aluminum and filter shall be of GSS construction. Three (3) mm thick neoprene rubber gaskets shall be provided to prevent any air leakage.

3.4 COOLING COILS AND HEATING COILS

3.4.1 Cooling and heating coils shall have 12.5 to 15 mm diameter tubes of minimum 24G thickness with sine wave aluminium fins firmly bonded to copper tubes assembled in zinc coated steel frame or 1.5 mm thick. Face and surface areas shall be such as to ensure rated capacity from each AHU. The coil face air velocity across the coil shall not exceed 2.54 meters per second for cooling coil and 4 meters per second for heating coil. The coil shall be pitched in the AHU casing to ensure proper drainage. Each coil shall be factory tested to 21 kg/cm2 (g) air pressure under water. Tube shall be mechanically expanded for minimum thermal contact resistance with fins. Fin spacing shall be 4 to 5 fins per cm. Coil piping shall be extended through the casing wall aproximately 150 mm and provided with 1034 kpa raised face flange connection. Incase, multiple coil sections are provided, the coils outside the AHU. The companian flanges with gaskets, nuts and bolts shall be provided piping connections. Pipe extenssion shall be IS 1239 heavy class. A packing gland is required at the casing wall to provide an air tight seal around the opening. Coil piping connection side shall be determined by final layout and arrangement.

3.4.2 Coils shall be sealed in polythene bags and packed in creates properly. Coil with damaged fins shall not be accepted.