The intermediate pans shall have drop tubes to guide condensate to the main drain pan.
Supply Fan Section
1.Fan: The fan section shall be equipped with a single double-width, double-inlet (DWDI), forward-curved [airfoil optional] centrifugal type wheel for horizontal discharge. An access door shall be provided on both sides of the unit for fan/motor access.
2.Fan Motor: Fan motors shall be NEMA design ball- bearing types with electrical characteristics and horsepower as specified. Motors shall be 1750 RPM, open drip-proof type [TEFC optional]. The motor shall be located within the unit on an adjust- able base.
Mountings: Fan and fan motor shall be internally mounted and isolated on a full-width, isolator-sup- port channel using 1-inch [2-inch] springs. The fan discharge shall be connected to the fan cabinet using a flexible connection to insure vibration-free operation.
Bearings and Drives: Fan bearings shall be self- aligning, pillow block or flanged type regreaseable ball bearings and shall be designed for an average life (L50) of at least 200,000 hours. All bearings shall be factory lubricated and equipped with standard hydraulic grease fittings and lube lines extended to the motor side of the fan. Fan drives shall be selected for a 1.5 service factor and antistatic belts shall be furnished. All drives shall be fixed pitch. Fan shafts shall be selected to operate well below the first critical speed and each shaft shall be factory coated after assembly with an anticorrosion coat- ing.
3.VAV Fan Control: VAV supply fan control shall be accomplished by using a variable-frequency drive matched to the supply-fan motor HP. The VFD shall include an integral DC line reactor to reduce harmonic distortion in the incoming and outgoing power feeds. If a DC line reactor is not provided, an AC line reactor must be provided. Inlet guide vanes shall not be acceptable. VFD control keypads shall be located in the control cabinet for accessibility and servicing while the unit is operating.
4.Optional VFD manual bypass: a three-contactor manual bypass shall be provided to permit replace- ment of the VFD in the event of a power failure.
Discharge Plenum
[SELECT ONE OF THE FOLLOWING HEAT/NO HEAT CONFIGURATIONS]
1.Cooling Only: The discharge-air-temperature sen- sor shall be located in the discharge plenum and be located such that it accurately measures the supply-air temperature. Walls shall be lined with a solid liner to prevent erosion of the insulation and to separate insulation from the air stream.
1.Staged Gas Heat: The heating section shall include an induced-draft furnace with two stages [four stages or six stages] of heating capacity.
Heat Exchanger: The heat exchanger shall be con- structed of tubular aluminized steel [stainless steel], with stainless steel flue baffles and flue assembly.
Burner and Ignition Control: The burner shall include a direct-driven induced-draft combustion fan with energy efficient intermittent direct spark ignition, redundant main gas valves with pressure regula- tor.
Combustion-Air Fan: The inducer fan(s) shall main- tain a positive flow of air through each tube, to expel the flue gas and to maintain a negative pressure within the heat exchanger relative to the conditioned space.
Safety Devices: A high-limit controller with automatic reset to prevent the heat exchanger from operat- ing at an excessive temperature shall be included. An air-proving switch shall prevent ignition until sufficient airflow is established through the heat exchanger. A rollout switch shall provide secondary airflow-safety protection. The rollout switch shall discontinue furnace operation if the flue becomes restricted.
Flue: The furnace flue shall be shipped loose to pro- tect it from damage during transit. The flue shall be field-mounted by the installing contractor. The flue outlet shall be located above the unit to help prevent recycling of combustion gases back through the heat exchanger. Agency Certification: Gas heating sections are both ETC/CETL approved to both US and Canadian safety standards.
1.Heat Exchanger(s): The heat exchanger(s) shall be constructed of tubular aluminized steel [stainless steel], with stainless steel flue baffles and flue as- sembly.
Condenser Section
1.Condenser Fans: Condenser fans shall be matched up with compressors to optimize system control. Condenser fans shall be propeller-type, directly driven by permanently lubricated TEAO motor.
2.Condenser Coil: Condenser coils shall be seam- less copper tubes, arranged in staggered rows,
