HVAC Guide Specifications
Constant Volume Series Flow Terminal Fan Powered Units
Size Range:
90 to 2000 cfm
Carrier Model Number (45Q Units):
45QA (Analog Electronic Control)
45QC (CCN VAV Electronic Control)
45QD (BACnet VAV)
45QN (No Control or DDC by Others)
45QP (Pneumatic Control)
Part 1 — General
1.01 SYSTEM DESCRIPTION:
A. Fan powered terminal unit shall be completely factory assembled and wired, with blower, blower motor, mixing plenum and primary air damper contained in a single unit housing.
B. The induced air fan shall operate continuously during central system operation. Primary airflow controller shall compensate for central system pressure fluctuations. When room temperature requires maximum heating, the (direct digital electronic) (analog electronic) (pneumatic) pressure independent velocity controller maintains the minimum primary airflow setting by modulating the damper. The staged electric heating coil or hot water coil, if supplied, is energized (activated). As room temperature begins to rise, the heating coil is deenergized (deactivated). As room temperature rises above the set point, the primary air damper will modulate to maintain room temperature. When the room temperature calls for maximum cooling, the velocity controller maintains the maximum primary airflow setting. To prevent the fan/motor from running in the backward direction, the unit induced air fan shall be field wired so that it is electrically or pneumatically interlocked with the central system fan.
1.02 QUALITY ASSURANCE
A. Terminals shall be tested in accordance with AHRI Standard 880, latest edition.
B. The terminal unit shall be ETL listed as a complete assembly. All electrical components shall be UL listed and installed in accordance with the NEC. All electrical components shall be mounted in sheet metal control enclosures. Electrical connections shall be single point.
1.03 DELIVERY AND STORAGE
Units shall be stored and handled as per manufacturer’s recommendations.
Part 2 — Products
2.01 EQUIPMENT
A. General:
Factory assembled, externally powered, horizontal fan powered terminal unit with blower, blower motor, mixing plenum and primary air damper contained in a single unit housing with a low height physical dimension of 105/8 inches.
B. Unit Cabinet:
1. Constructed of 20 gage zinc-coated steel. All primary air inlet collars shall accommodate standard flex duct sizes. Unit discharge shall be round or rectangular, suitable for flanged duct connection.
2. Unit casing shall be lined with dual density, 1/2-in. thick, 11/2 lb density fiberglass insulation that meets UL 181 and NFPA 90A.
3. (Optional) Foil Encapsulated Insulation:
Unit casing shall be lined with foil reinforced, wrapped edges, 1/2-in. thick, 11/2 lb density fiberglass insulation that meets UL 181 and NFPA 90.
4. (Optional) Cellular Insulation:
Unit casing shall be lined with 3/8-in. thick, smooth surface, closed-cell elastomeric thermal insulation for fiber free application.
C. Damper Assembly:
The primary air damper assembly shall be constructed of heavy gage steel with solid shaft rotating in Delrin bearings. Damper blades shall incorporate a flexible gasket for tight airflow shutoff and operate over a full 90 degrees.
D. Fan(s):
Fan(s) shall be of the forward curve, centrifugal type. The fan motor shall be single speed, single-voltage (120, 208/240, 277), 60 cycle, single phase, energy efficient design, permanently lubricated, using permanent split capacitor for starting and be specifically designed for use with an SCR (fan speed controller). Motor must have thermal overload protection. The fan motor shaft shall be connected directly to the fan and the entire fan assembly shall be isolated from the unit casing to prevent transmission of vibration.
E. Electrical Requirements:
Units shall have single connection for power, and operate on 120,208/240 or 277 vac (standard) single phase, 60 Hz power as shown on the equipment schedule. Units with three-phase electric heat shall be factory wired for single point performance (including 208/240 v 3-wire or 480 v 4-wire). When specified and coordinated, units shall be wired and shipped with proportionally connected phasing.
F. Controls:
1. Units shall have pressure-independent pneumatic, electronic, or communicating controls, as specified, capable of maintaining required airflow set points ± 5% of the unit's capacity at any inlet pressure up to 6 in. wg. The controllers shall be capable of resetting between factory or field-set maximum and minimum (>350 fpm inlet duct velocity) set points to satisfy the room thermostat demand. The unit shall be equipped with an amplified cross flow sensor. The sensor will provide a differential pressure signal amplified to equal at least 2 times the velocity pressure with an accuracy of at least ± 10% throughout the range of 350 to 2600 fpm inlet duct velocity, depending on the controller employed.
2. Sensor Type:
a. The unit shall be equipped with an amplified linear averaging flow probe located horizontally across the inlet. The sensor will provide a differential pressure signal amplified to equal 3 times the velocity pressure with an accuracy of at least ± 10% throughout the range of 350 to 2600 fpm inlet duct velocity, depending on the controller employed.
b. The unit shall be equipped with a four quadrant linear cross sensor. This is a multi-point center averaging, inlet flow sensor, available for use with pneumatic, analog electric and digital electric control type units.
G. Special Features:
1. Electric Heating Coil:
Electric coils shall be supplied by the terminal unit manufacturer and shall be UL listed. Construct coil casing with minimum of 20-gage zinc coated steel. Elements shall be 80/20 nickel chrome and supported by ceramic insulators. The integral control panel shall be housed in a NEMA 1 enclosure, with hinged access door for access to all controls and safety devices. Electric coils shall contain a primary automatic reset thermal cutout and differential pressure airflow switch for proof of airflow. Electric coils shall include fused or non-fused door interlocking disconnect switch, manual reset cutout, mercury contactors, fuse block, dust-tight enclosure construction, all mounted and/or wired within the control enclosure.
2. Hot Water Coil:
Hot water coil casing shall be constructed with minimum 20 gage galvanized steel. Coils shall be factory installed on the terminal unit. Fins shall be rippled and corrugated heavy gage aluminum, mechanically bonded to tubes. Tubes shall be copper with minimum wall thickness of 0.016 in. and with male solder header connections. Coils shall be leak tested to 400 psig. Number of coil rows shall be selected to provide performance as required by the plans. Coil performance data shall be based on tests run in accordance with AHRI Standard 410.
3. Dedicated Outdoor Air Option (DOAS):
a. Units shall operate in a similar manner as a conventional unit but equipped with a cooling coil on the induced air inlet, which is designed to handle the sensible loads in the space. The primary inlet is supplied with filtered conditioned outdoor air providing ventilation air and latent removal to the space. Ideal for chilled beam and water source head pump systems.
b. Coil offered in two, four, or six row coils, which are constructed of 10 aluminum fins per inch with 7/8 in. OD sweat type. Water leak tested to 400 psig.