Housing
Unit housing shall be constructed of 20 Gauge G-90 galvanized steel. The wall panels and roof panels shall be fabricated by forming double-standing, self-locking seams that require no additional support. The floor and wall panels shall be caulked air tight with a silicone caulk. All casing panels shall be attached with sheet-metal screws or rivets, which can be removed to service large components in the field. The unit base shall be suitable for curb or flat mount. Housing construction should be suitable for outdoor or indoor installation.
An observation port shall be located on the exterior of the unit for observing the coil. All controls and electrical components shall be mounted within the control vestibule. The vestibule shall be an integral part of the unit, not extend outside the exterior casing of the unit, and not be exposed to the main air stream.
The vestibule full-size door shall provide easy access to the controls. The blower door shall provide easy access to the blower, motor, and drives. Access doors shall be provided on both ends of the unit providing full access to every part of the unit.
Base
The base shall be constructed of galvanized steel for improved rigidity. The base shall be structurally reinforced to accommodate the blower assembly and burner.
Blower
Wheels shall be balanced in two planes and done in accordance with AMCA standard 204-96, Balance Quality and Vibration Levels for Fans. The wheel blades shall be aerodynamically designed to minimize turbulence, increase efficiency, and reduce noise. The wheel blades shall be securely attached to the wheel inlet ring. The wheel shall be firmly attached to the fan shaft with set screws and keys. The blower assembly shall be isolated from the fan structure with vibration isolators.
Blower capacity shall be _____ CFM at 70 degrees F standard air, ____ external static pressure.
External Static: The sum of duct loss plus duct component static. Example: louvers, diffusers. All blowers shall be tested and set at rated speed after being installed in the factory-assembled unit.
Belt Drive
Blower(s) shall be forward-curved, centrifugal, Class I or II (depending on requirements of the application), double width, double inlet, and constructed of G-90 galvanized steel. Unit shall have a heavy-duty, solid-steel shaft.
Direct Drive
Direct drive blower assembly shall consist of a centrifugal backward inclined, non-overloading wheel secured directly to a heavy duty, ball bearing type motor via two set screws. The motor and wheel assembly shall be mounted to a heavy gauge galvanized steel frame. The motor shall be controlled by a variable frequency drive, allowing for variable airflow without the need of belts and pulleys.
Motor & Motor Compartment
Motors shall be heavy duty ball bearing type and furnished at the specified voltage, phase, and enclosure. Motor mounting plate shall be constructed of heavy gauge galvanized steel and shall be designed to provide easy adjustment of belt tension. Blower motor shall be suitable for operation on _______ volts, _______ cycle, _____ phase power. Blower motor shall be a ___________________________ HP motor, Open Drip Proof.
Shaft & Bearings
Shafts shall be precision ground and polished. Heavy duty, pre-lubricated bearings shall be selected for a minimum (L50) life in excess of 200,000 hours of operation at maximum cataloged operating speed. They shall be designed for, and individually tested, specifically for use in air handling applications.
Belts & Drives (Belt Drive Units Only)
Belts shall be oil and heat resistant, non-static, grip-notch type. Drives shall be cast type, precision machined and keyed, and securely attached to the fan and motor shafts. Fan operating speed shall be factory set using adjustable pitch motor pulleys; motors over 3 HP will come standard with double groove pulleys.
SCR Electric Coil
Electric coils are controlled using SCR controls. SCR is a time proportioning type controller that modulates the heater and supplies the exact amount of power to match the heat demand.
The SCR electric coil shall be sized to provide an output of ________ KW.
The SCR electric heater shall be capable of heating the entire air supply from _____F° to _____F° ( ______ degrees F temperature rise).
Rear access doors or a removable lid will provide complete access to the SCR electric coil.
SAFETY CONTROLS:
Standard
- Motor starter with adjustable overloads
- Air-flow safety switch
- Blower interlock relay
- High-temperature limit switch
- Non-Fused Disconnect
- Casing insulation shall be 1" x 1.5# density with a foil face
Optional
- Adjustable low temperature blower-safety control with bypass timer to shut down unit if discharge temperature drops below setting.
- Operating lights mounted in a remote-control panel to indicate power, heat ON, and blower ON.
ACCESSORIES:
- Inlet Dampers: Manufacturer shall provide and install on unit (when possible), a two-position, motor-operated damper with internal end switch; this energizes the blower-starter circuit when the damper is 80% open. Blades shall be a maximum of 6” wide 16 Gauge G-90 galvanized steel and shall be made to guarantee the absence of noticeable vibration at design air velocities. Damper blades to be mounted on friction-free synthetic bearings. Damper edges shall have PVC coated polyester fabric mechanically locked into the blade edge. Jamb seals to be flexible metal, compression type.
- Filters: The filters shall be 2" thick, aluminum mesh, and coated with super-filter adhesive. Aluminum-mesh filters shall have aluminum frames; media to be layers of slit and expanded aluminum which vary in pattern to obtain maximum depth loading.
Filter Section: shall be (insulated) (uninsulated) constructed of G-90 galvanized steel with filters supported by internal slides and with removable access panels. Filters shall be provided in a v-bank arrangement.
- Fresh-Air Inlet Hood: Shall be constructed of G-90 galvanized steel with bird screen.
- Fresh-Air Inlet Hood/Filter Combination: Shall be constructed of G-90 galvanized steel with bird screen and 2" washable filters supported by internal slides mounted in the inlet face of the hood.
- Discharge Diffusers: Shall be constructed of G-90 galvanized steel with horizontal and vertical blades capable of four-way diffusion.
- Curb: 20" curb shall be constructed of 18 Gauge G-90 galvanized steel as a completed welded assembly.
- Cooling Coil Section: Cooling coil section shall be bolted directly to the discharge of the blower section. Coil section to be designed to fit onto common curb with main unit. Base of coil section to be constructed the same as the main unit, with double pitch stainless steel drain pan for coil. Casing and roof to be 20 Gauge G-90 galvanized construction. Inside of section to be fully insulated with foil back insulation. DX or chilled water coil to meet scheduled requirements.
TEMPERATURE CONTROL SYSTEMS:
Discharge Air temperature controls shall be shipped as a standard feature on all electric heaters. Optional room controls shall be available.
WIRING AND ELECTRICAL:
The control circuit voltage shall be 115 volts. A control transformer shall be provided, when required. The control wiring shall be carried in wire channel or conduit. Wiring in control enclosures shall be in accordance with the National Electrical Code and the local code, as it may affect the installation. Motor starter shall be provided. Starter shall be line voltage, definite purpose type.
Unit(s) shall be complete with all items such as relays, starters, switches, safety controls, conduit and wire, as previously mentioned and as required for proper operation. All factory-mounted controls shall be factory prewired to the unit control panel.
FACTORY TESTED:
Unit(s) shall be operated, tested, and set at the factory using job-site conditions for electrical and gas input. All operating and safety controls shall be tested and set at the factory. Adjustable, or fixed sheaves, shall be set for proper RPM at specified conditions.
SERVICE AND PARTS:
The supplier shall furnish as built wiring connection and control-circuit diagrams, dimension sheets, and a full description of the unit(s). Service manuals, showing service and maintenance requirements, shall be provided with each unit.
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