shall be selected for a minimum service factor of 1.2 and have fixed pitched sheaves.
AIR FILTERING SYSTEM
All filter holding frames shall be of heavy duty construction designed for industrial applications. All filters shall be either side accessible or front loading with access doors provided on both sides of the filter section. All filter media shall be Class II listed under UL Standard 900. Filter efficiencies shall be rated in accordance with ASHRAE Standard 52-76 2" Throwaway Filters with fiberglass media multiple shall be standard
OPTIONAL
Two inch pleated, throwaway filters with 30% efficiency. Rigid filters shall be high performance, expanded area, disposable type filters. Rigid filter sections shall be preceded by a 2 throwaway prefilter assembly. Filter efficiency shall be 95% (Option: 65%) based on ASHRAE Standard 52-76.
AIR INLET SYSTEM
General
Outside Air inlet openings shall be covered by a factory installed rain hood permanently attached to the cabinet to prevent windblown precipitation from entering the unit. The rain hoods on the front and back of the unit shall be rotated into the cabinet and secured for shipment so that upon instal- lation they need only be rotated upwards and screwed into place. The outside air hood shall contain a removable and cleanable filter with an efficiency rating of 50% based on ASHRAE 52- 76. All damper assemblies shall be of low leak design. Damper blades shall be fabricated from a minimum of 16 gauge galvanized steel. Blade ends and edges shall be covered with vinyl seals. Damper shafts shall be fabricated from solid steel and mounted in the frame with bronze bear- ings. On all units not equipped with an economizer, an option shall be available for a manually adjustable outside air damper shall be capable of admitting 0-25% outside air.
Economizer (Optional)
An economizer shall have outdoor air and return air dampers (optional standard or low leak type) that are interlocked and positioned by fully modulating, solid state damper actuators. The actuators shall be spring loaded so that the outside air damper will close when power to the unit is interrupted. The operation of the economizer shall be fully integrated into the cooling control system. The economizer shall be available for control via a dry bulb sensor (Optional: single or dual enthalpy sensors).
RELIEF SYSTEM (Optional)
All units with relief must have an economizer.
Barometric Relief (Optional)
Building air exhaust shall be accomplished through baromet- ric relief dampers installed in the return air plenum. The dampers will open relative to the building pressure. The opening pressure shall be adjustable.
Exhaust Air Fans (Optional)
General - forward curved centrifugal fan(s) shall be installed in the return air plenum for positive power exhaust. Fans shall be on a common shaft, driven by a single motor. The fans, motors and drives shall be of the same quality and design as specified for the Supply Air Fan, except the fans shall be Class I. Fans shall be capable of exhausting up to 100% of the nominal CFM of the unit. Non-modulating Exhaust - Units with non-modulating power exhaust shall have a barometric relief damper to prevent outside air from entering in the off cycle. The fans shall cycle on and off with building pressure. Modulating Operation - The fans shall be capable of modulat- ing the amount of air from 0% to 100% of nominal CFM. Mod- ulation shall be through discharge dampers or variable frequency motor speed modulation. Dampers or VFD shall be controlled by static pressure in the conditioned space or return air duct.
ENERGY RECOVERY VENTILATION (FIELD INSTALLED OPTION)
General
The packaged rooftop unit shall have attached at the jobsite a powered exhaust combined with an air intake through a rotat- ing energy recovery wheel, which captures sensible and latent heat from the exhaust air stream and returns it to the incoming air stream. The energy recovery module will be con- tained in a separate enclosure designed to attach to the end of the Millennium packaged rooftop unit equipped with Sim- plicity® Elite™ control.
The Energy Recovery Ventilation module will be capable of exhausting up to 8,000 (13,000) CFM.
Control parameters for the ERV will be preset in the unit con- trol.
HEATING SYSTEM (OPTIONAL)
Gas-fired Heating Section
One or more gas-fired heating modules shall be installed to provide the heating requirements per the schedule shown on the plans. The heat exchanger shall be of tubular design. Tubes shall be 2-1/4" OD and constructed of minimum 20 gauge, G160 aluminized steel (1.6 mil aluminum silicone alloy) for corrosion resistance (Optional: 409 Stainless Steel). Flue baffles shall be made of 430 stainless steel. Each gas- fired heat module shall have an induced draft combustion fan with energy efficient intermittent pilot spark ignition and redundant main gas valves with pressure regulator. Units with standing pilot ignition shall not be acceptable. An induced draft fan shall be provided to maintain a positive flow of air
