| Packaged type supply air units shall
be factory assembled, sectionalised construction,
consisting of individual fan section with motor, adjustable
motor base, V belt drive and belt guard, coil section,
filter section, mixing box section and access sections.
Fans shall be DWDI backward inclined, AMCA rated
and selected at high efficiencies to obtain lower
brake horsepower.
Units with cooling coils shall have interior insulation
and insulated drain pans. Drain pans are to have a
factory applied epoxy seal to prevent rusting.
Cabinets shall be constructed of galvanised steel
completed with electrostatically applied baked enamel
finish.
They should be installed in a machine room with
adequate head height and properly enclosed. Air handling
plant rooms must have pre-filters. Ceiling mounted
units are to be avoided.
Units are to be mounted on a plinth to achieve positive
falls for drainage and reduce noise transmission.
Back draft dampers shall be considered behind external
grills as an energy saving measure.
Fans
Centrifugal fans shall be backward inclined non
overloading type, AMCA rated. Those having 750mm wheel
diameter or greater shall be airfoil type.
Units shall include V belt drive with belt guard,
extended grease fittings, inlet screens. Access doors
shall be included for those fans over 920mm diameter.
Adjustable pitch drives shall be used up to 40 HP
and constant speed drives 50 HP and above.
Axial flow fans shall be vaneaxial type, AMCA rated.
The units shall include a vortex breaker, outlet cone,
extended grease fittings and support legs.
Axial flow fans may only be used in low static pressure
systems. Sound treatment of the fan system shall be
designed in accordance with recommendations of an
Acoustic Consultant.
The major ventilation fans shall be operable from
the Fire Control Centre, for smoke control applications.
Coils
Water (heating and cooling) coils shall be continuous
tube type with helical or plate type fins and cast
iron or brazed copper headers. Coils of 5/8"
O.D. seamless copper tubing with aluminium fins for
cooling and heating. Copper fins or other approved
protection shall be provided where outdoor air is
corrosive. The maximum number of fins shall be twelve
(12) per inch.
Coils shall be provided with a positive means of draining
and venting and factory tested at 21 bar (300 psig).
Coils shall be selected at a maximum face velocity
of 500 fpm and have ARI certified ratings.
Steam coils (for pre heat application) shall be
tube within a tube type, constructed of 25mm O.D.
outer and 16mm O.D. inner copper tubes with continuous
plate type aluminium fins.
Coils shall be factory tested at 4 bar (300 psig).
Coils shall have ARI certified ratings.
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