This article is about general and technical requirements for AirFlow Measuring Stations used in Integrated Automation System or Building Automation System.
AIRFLOW MEASURING STATIONS TECHNICAL REQUIREMENTS FOR IAS
AIRFLOW MEASURING STATIONS (AFMS) <Modify as required to match project design>
- Air Flow Measuring Stations
- The manufacturer’s authorized representative shall review and approve placement and airflow rates for each measurement location indicated on the plans. A written report shall be submitted to the consulting engineer if any measurement locations do not meet the manufacturer’s placement requirements.
- Each air flow measuring station shall consist of one or more sensor probes and a single, remotely mounted, microprocessor-based transmitter capable of independently processing up to 16 independently wired sensor assemblies.
- Each sensor assembly shall contain two individually wired, hermetically sealed bead-in-glass thermistors.
- Thermistors shall be mounted in the sensor assembly using a marine-grade, waterproof epoxy. Thermistor leads shall be protected and not exposed to the environment.
- The airflow rate at each sensor assembly shall be velocity weighted and averaged by the transmitter prior to output.
- Each transmitter shall have a 16-character alpha-numeric display capable of displaying airflow, temperature, system status, configuration settings and diagnostics.
- The Air Flow Measuring Station shall be approved by the manufacturer for the specific application. Contractor shall provide design parameters to the manufacturer for review and acceptance. Contractor shall provide proof of acceptance by manufacturer.
- Acceptable manufacturers: <Confirm list>
- Honeywell
- Ebtron <Gold Series>
- Approved equal
- Each air flow measuring station shall consist of one or more sensor probes and a single, remotely mounted, microprocessor-based transmitter capable of independently processing up to 16 independently wired sensor assemblies.
-
- All sensor probes
- Each sensor shall independently determine the airflow rate and temperature at each measurement point.
- Each sensor shall be calibrated at a minimum of 16 airflow rates and 3 temperatures to standards that are traceable to the National Institute and Standards and Technology (NIST).
- Airflow accuracy shall be ±2% of Reading over the entire operating airflow range.
- Devices whose accuracy is the combined accuracy is the combined accuracy of the transmitter and sensor probes must demonstrate that the total accuracy meets the performance requirements of this specification throughout the measurement range.
- The operating humidity range for each sensor probe shall be 0-99% RH (non-condensing)
- Each sensor probe shall have an integral, U.L. listed, plenum rated cable and terminal plug for connection to the remotely mounted transmitter. All terminal plug interconnecting pins shall be gold plated.
- Each sensor assembly shall not require matching to the transmitter in the field.
- A single manufacturer shall provide both the airflow measuring probe(s) and transmitter for each measurement location.
- Duct and plenum probes
- Probes shall be constructed of extruded, gold anodized, 6063 aluminum tube. All wires within the aluminum tube shall be Kynar coated.
- Probe assembly mounting brackets shall be constructed of 304 stainless steel. Probe assemblies shall be mounted using one of the following options:
- Insertion mounted through the side or top of the duct.
- Internally mounted inside the duct or plenum.
- Standoff mounted inside the plenum.
- The number of sensor housings provided for each location shall be as follows:
Duct or Plenum Area (sq. ft.) Total Number of Sensors / Location <2 4 2 to <4 6 4 to <8 8 8 to <16 12 >=16 16 The operating airflow range shall be 0 to 5,000 FPM unless otherwise indicated on the plans.
- Fan inlet probes
- Sensor assemblies shall be mounted on 304 stainless steel housings.
- Mounting rods shall be field adjustable to fit the fan inlet and constructed of nickel plated steel.
- Mounting feet shall be constructed of 304 stainless steel.
- The operating airflow range shall be 0 to 10,000 FPM unless otherwise indicated on plans.
- Transmitters
- The transmitter shall have an integral LCD display capable of simultaneously displaying airflow and temperature. The LCD display shall be capable of displaying individual airflow and temperature readings of each independent sensor assembly.
- The transmitter shall be capable of field configuration and diagnostics using and on-board pushbutton interface and LCD display.
- The transmitter shall have a power switch and operate on 24 VAC (isolation not required).
- The transmitter shall use a switching power supply fused and protected from transients and power surges.
- The transmitter shall use “watch-dog” circuitry to assure reset after power disruption, transients, and brown-outs.
- All interconnecting pins, headers and connections on the main circuit board, option cards and cable receptacles shall be gold plated.
- The operating range for the transmitter shall be -20 to 120°F. The transmitter shall be installed in a location that is protected from weather and water.
- The transmitter shall be capable of communicating with other devices using <LonWorks, BACnet, MODBUS>.
- The airflow measuring station shall be UL listed as an entire assembly.
- Transmitters
- All sensor probes
- Fan Inlet Probe: Shall consist of vortex shedding multi-sensor probes which are installed in the inlet of the fan. Individual sensors on the probe provide direct proportional and linear signals to airflow velocity.
- Sensor Accuracy: +/- 2.0 percent
- Interchangeability: +/- 0.5 percent
- Velocity Range: 750 to 9000 fpm
- Electronics Accuracy: +/- 0.05 percent
- Temperature Limits: -20 degrees F to 140 degrees F
- Enclosure for Electronics: NEMA 1
- Material: Aluminum
- Operating Range: Select minimum range to accommodate the expected flow range of the equipment
- Acceptable Manufacturers: <Confirm list>
- Honeywell
- Tek-Air Systems Inc. ‘Vortek’ Model 7000
- Approved equal
- Air Flow Traverse Probes:
- Traverse probes shall be a dual manifold, cylindrical, type. The multiple total pressure manifold shall have sensors located along the stagnation plane of the approaching air flow and without the physical presence of forward projecting sensors into the airstream. The static pressure manifold shall incorporate dual offset static tips on opposing sides of the averaging manifold so as to be insensitive to flow-angle variations of as much as ±20o in the approaching airstream.
- Each airflow measuring probe shall contain multiple total and static pressure sensors placed at equal distances along the probe length. The number of sensors on each probe and the quantity of probes utilized at each installation shall comply with the ASHRAE Standards for duct traversing.
- Each flow measuring station shall be complete with its own dedicated microprocessor with a 4-line, 80 character, Alpha Numeric display and full function key pad. The panel shall be fully programmable and display calculated <cubic feet per minute, liters per minute> directly on a LED monitor on the panel face.
- Provide 24 volt single phase power to each flow measuring station.
- The probes, and placement of the probes, shall provide measurement accuracy within +/- 2 percent of actual velocity. Probes shall be of cylindrical cross Section and shall indicate no more than a +/- 3 percent deviation from the centerline velocity at a yaw angle of 30 degrees.
- Probes shall be provided with integral mounting plate, 1/4 compression fitting connections, end mounting rod and be suitable to operate in ambient conditions of 300 degrees F. The probe assemblies shall not have a pressure drop greater than 10 percent of the velocity pressure at the maximum design flow. The probes shall not amplify sound levels in the duct.
- Submit data indicating the developed differential pressure and pressure loss at the minimum and maximum design flows for each duct location. Provide differential pressure transmitter for measuring velocity, with a range selected to match the velocity of the maximum design flow for the duct served.
- Sensor Accuracy: +/- 2.0 percent
- Interchangeability: +/- 5 percent
- Velocity Range: 400 to 9000 fpm
- Electronics Accuracy: +/- 0.05 percent
- Temperature Limits: -20 degrees F to 200 degrees F
- Enclosure for Electronics: NEMA 1
- Humidity Limits: 0 to 100% RH (non-condensing)
- Material: 304 stainless steel
- Operating Range: Select minimum range to accommodate the expected flow range of the equipment
- The following schedule is the minimum probe quantities across either the width or height of the duct sections where the probes are being inserted:
| Insertion Side (inches) | Quantity |
| 6-11 | 1 |
| 12-30 | 2 |
| 31-48 | 3 |
| 48-60 | 4 |
| 61-84 | 6 |
| 85-120 | 6 |
- Acceptable manufacturers: <Confirm list>
- Honeywell
- Ebtron
- Tek-Air Model T-FP5000
- Approved equal