General Construction Specifications
PART 1 - GENERAL
01 WORK INCLUDED
A. Furnish all materials, labor, tools, and services required to provide an Airflow Control System as described on the drawings and by the requirements of this section.
02 SUBMITTALS
A. Submit manufacturer's product data to Architect for approval in accordance with Section 15010.
B. Submit schematic control diagrams, including sequence of control, to Architect for approval in accordance with Section 15010.
PART 2 - PRODUCTS
03 MANUFACTURERS
A. Provide products as manufactured by Air Monitor Corporation.
04 ELECTRONIC AIRFLOW CONTROL SYSTEMS
A. The major control instruments shall be of industrial process control quality, (commercial grade controls are not acceptable), and shall be capable of the following minimum performance:
B. System or duct static pressure transducer shall be capable of transmitting a linear 4 to 20 mA dc electronic output signal proportional to the system or duct static pressure input signals within the following minimum performance and application criteria:
1. Span: Not greater than twice the system or duct static pressure
2. Accuracy:+ 1.5% of span
3. Dead Band: Less than 0.5% of output
4. Hysteresis: Within 1% of span
5. Linearity: Within 1.5% of span
6. Repeatability: Within 0.5% of output
7. Response:Less than 1 second for full span input
B. Velocity pressure transducer shall be capable of transmitting a linear 4 to 20 mA dc (1 to 5 V dc) electronic signal proportional to the differential (total minus static) pressure input signals with the following minimum performance and application criteria:
1. Span: Not greater than twice the velocity pressure at maximum flow rate, nor more than 16 times the velocity pressure at minimum flow rate.
2. Accuracy:+ 1.0% of span
3. Dead Band: Less than 0.2% of output
4. Hysteresis: Within 0.5% of span
5. Linearity: Within 1.0% of span
6. Repeatability: Within 0.25% of output
7. Response:Less than 1 second for full span input
C. Square root extractor shall be capable of receiving a 4 to 20 mA dc (for 1 to 5 V dc) electronic signal proportional and linear to velocity pressure and converting it to a similar magnitude signal proportional and linear to velocity with the following minimum performance and application criteria:
1. Accuracy:+ 0.5% of span
2. Hysteresis: Within 0.1% of span
3. Repeatability: Within 0.1% of span
4. Dead Band: Within 0.2% of span
5. Response:Less than 1.0 second for full span input
Square root extractor can be furnished as an integral part of a velocity (flow) transducer provided the minimum performance requirements of either device can be met by the combined device.
C. Multiplier shall be capable of receiving a 4 to 20 mA dc (or 1 to 5 V dc) electronic signal, multiplying that signal by a pre-set value, and producing an output signal which is proportional to the product of the value and the input signal with the following minimum performance and application criteria:
1. Accuracy:+ 0.5% of span
2. Multiplier Adjustable factor, 0.5 to 2.5
3. Hysteresis: Within 0.2% of span
4. Repeatability: Within 0.1% of span
5. Dead Band: Within 0.05% of span
6. Response:Less than 1.0 second for full span input
Multiplier can be furnished as an integral part of the square root extractor provided the minimum performance requirements of either device can be met by the combined device.
D. The air volume, flow synchronizing, system or duct static pressure, and room differential pressure controllers shall have three control mode capabilities of proportional, reset (integral), and derivative (direct or inverse). The controller shall be capable of receiving dual 4-20 mA dc (or 1 to 5 V dc) input signals plus an electronic setpoint adjustment signal, and issuing a 4-20 mA dc (or 1 to 5 V dc) electronic control signal within the following minimum performance and application criteria:
1. Proportional Band: 1 to 100%
2. Reset Rate: 0.5 to 17 minutes per repeat
3. Derivative: 0.5 to 17 minutes per repeat
4. Hysteresis: Less than 0.25% of span
5. Tracking Accuracy: Within 0.3% of span
6. Repeatability: Within 0.2% of span
B. All static and velocity pressure transducers shall be furnished with protective integral air filters on the total and static pressure sensing lines from the airflow measuring and static sensing stations, and static air probes to prevent the migration of moisture or particulate matter into the transducers.
C. All devices shall not be affected by direction of mounting or external vibrations. Velocity pressure transmitters and square root extractors shall be temperature compensated and shall be furnished factory calibrated ready for operation. Static pressure controllers and air volume controllers shall be furnished with integral air purge to prevent the entrance of contamination into the unitary controllers via the velocity sensing tubing.
2.02 AIR FLOW MEASURING STATIONS
A. Each device shall be designed and built to comply with, and provide results in accordance with accepted practice as defined for system testing in the ASHRAE Handbook of Fundamentals as well as the Industrial Ventilation Handbook.
B. Airflow measuring stations shall be fabricated of heavy gauge galvanized steel welded casing with 90o connecting flanges in a configuration and size equal to that of the duct it is mounted into. Each station shall be complete with an air directionalizer and parallel cell profile suppressor across the entering airstream and mechanically fastened to the casing, equal-area and equal-weighted averaging total pressure sensors and manifold, bullet-nose shaped static pressure sensors with averaging manifold, internal piping, and external pressure transmitter ports. An identification label shall be placed on each unit casing listing model number, size, area, and specified airflow capacity.
C. Static pressure sensing stations used for sensing the supply air distribution system static pressure shall be fabricated in accordance with that outlined for airflow measuring stations except that multiple bullet-nose shaped static pressure sensors with averaging manifold will be furnished in lieu of the total pressure sensors and manifold.
D. Where multiple stations serve a common fan or fan plenum, provide all necessary pneumatic or electronic control devices (velocity pressure transmitters, square root extractors, multipliers, and arithmetic relays) to sum or total the station airflow rates for CFM readout and control signal use.
E. The maximum allowable pressure loss through the unit shall not exceed .065" w.g. at 1000 fpm, or .23" w.g. at 2000 fpm. Each unit shall be capable of measuring the airflow rate within an accuracy of 2% as determined by U.S.G.S.A. certification tests and shall contain a minimum of one total pressure sensor per thirty-six square inches of unit measuring area.
F. Stations shall be installed in strict accordance with the manufacturer's published requirements. These stations serve as the primary signals for the airflow control systems, therefore it shall be the responsibility of the Contractor to verify location and installation to assure that accurate primary signals are obtained.
G. The units shall have a self-generated sound rating of less than NC40, and the sound level within the duct shall not be amplified nor shall additional sound be generated.
2.03 AIRFLOW CONTROL CENTER
A. Individual airflow control centers shall be provided for each air handling system and shall be located in the fan room.
B. Each airflow control center shall be complete with velocity pressure transmitters, square root extractors, multipliers, air volume and static pressure, unitary controllers, 4-1/2 inch diameter CFM meters, and static pressure gauges, operating instructions, and identification plates, all mounted and internally connected in a 14 gage steel, hinged-front, key-locked cabinet.
C. Each transducer, square root extractor, multiplier, and controller shall be provided with test terminals to permit the temporary installation of electronic meters to facilitate signal readouts during start-up, adjustments and servicing.
D. Each airflow control center shall be provided with its own power converter system capable of operating the center on the available power supply.
E. Airflow control center shall display (as a minimum) supply air flow, return air flow, and supply system static pressure on front face of control panel. Refer to drawings for additional display requirements.
2.04 BASIC AIRFLOW CONTROL FUNCTIONS
A. The airflow control system shall be capable of performing the basic control functions of: constant system static pressure; control supply air fan capacity by system demand; synchronize supply air fans and return air fan volumes; maintain building pressurization and minimum outside air. In addition the system control center shall continuously monitor the supply air fan volumes, return air fan volume and supply system static pressure.
B. With constant static control, duct or system static pressure is sensed at an airflow measuring or static sensing station with a static pressure signal sent to a static pressure controller. This signal is amplified into a control signal and sent to a receiving controller which compares the signal with its programmed control setpoint and issues an signal to an damper actuator or current-to-pneumatic (I/P) transducer to reposition a static damper (fan vortex, etc.) or variable frequency motor controller to maintain the duct or system at a constant static pressure.
C. With full volumetric synchronization control, fan or duct airflow rates are sensed at multiple airflow measuring stations with total and static pressure signals sent to respective velocity pressure transducers where the differential pressure signals are amplified into control signals linear to velocity pressure. These signals are sent to square root extractors where they are made linear to velocity and then to multipliers where the station area factors are imposed upon the signals to make them linear and scaled to air volume. A dual-input controller receives these signals and compares one signal with the other signal and, based upon a programmed relationship between these signals, issues an signal to an damper actuator or current-to-pneumatic (I/P) transducer to reposition a volume damper (fan vortex, etc.) or variable frequency motor controller to maintain a constant CFM differential between the two air volumes.
PART 3 - EXECUTION
05 INSTALLATION
A. The airflow control system shall be installed in accordance with the supplier's written instructions.
B. Coordinate with other work, including ductwork, electrical, and automatic temperature controls, as necessary to interface the installation of the airflow control systems with other work.
06 WORK BY OTHERS
A. Motorized control actuators shall be furnished by the Automatic Temperature Control Contractor.
B. An electric signal indicating the energizing of the system fans, all external wiring, and a 120 volt power supply shall be provided under Division 16 -Electrical.
C. Vortex dampers mounted at the inlet connection of supply air and return air fans shall be furnished by the fan manufacturer.
07 CALIBRATION AND START-UP
A. The airflow control system supplier shall provide all necessary factory and/or field labor for complete calibration and adjustment of the airflow control components, and shall be responsible for setting all control setpoints and operating sequences to produce the following overall system performance:
1. Constant static control within 2 percent of duct static setpoint without any hunting or cycling.
2. Full volumetric synchronization of supply and return fans within 3 percent of cfm differential setpoint over the entire range of system operation and turndown.
B. In conjunction with the system start-up, the airflow control system supplier shall instruct the Owner's personnel in the proper operation of the airflow control system.
08 SERVICE
A. The airflow control system supplier shall guarantee the proper operation of the system and furnish all required service for one full year from the date of system acceptance.
END OF SECTION
