Applications and specifications - Johnson Controls - LIT-12014020 - RA-1270 - Airflow Measuring Station - AFMS

RA-1270 Fan Inlet Airflow and Temperature Measurement Station Product Bulletin

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Install the RA-1270 Fan Inlet Airflow and Temperature Measurement Station at locations shown on the building plans or in accordance with schedules that require advanced thermal dispersion electronic fan inlet airflow and temperature measuring stations. Thermal dispersion (TD) sensors are cantilever-mounted. Units monitor and report the airflow and temperature at each fan inlet location through one or two sensors connected to a host or client that communicate with the building automation system (BAS).

Sensor circuit casings are constructed of UL 94 flame-rated, high impact ABS and include a stainless steel boom arm that positions the TD sensor in the fan inlet at the specified measurement points. Each sensor consists of a pair of thermistors, one passive and one heated, to measure ambient temperature and air velocity. Sensors are designed for operation in a wide range of environments that includes high humidity and rapid thermal cycling.

Use gold-plated contacts to connect the sensor cables directly to the host or client monitor boxes to ensure absolute connectivity and longterm accuracy. One host monitor box and up to 16 client monitor boxes collect data from each sensor and digitally communicate the airflow and temperature of each sensing point to the host monitor box.

Use the menu through the host monitor box and configure each sensor to represent the airflow through the installed fan. Monitor boxes, both host and clients, are wired in daisy-chain fashion to each other and terminate at a host. The daisy-chain communications cable is a non-proprietary twisted and shielded cable similar to the Connect-Air part number W24182P-2306BL, with communications and power in one cable. Alternatively, use a twisted shielded pair 24 AWG low capacitance wire communications cable and an 18 AWG power cable in separate conduits.

The complete assembly is constructed and assembled in an ISO 9001 certified facility. Sensor cables are a minimum of 10 ft (3.05m) in length and are available up to 25 ft (7.62m), when specified. The host or client can process up to two independent sensing points. Up to 16 sensing points for each BACnet® interface are configurable for up to 16 fans that operate independently on different air handlers or as multiple fans as part of one air measurement station on a single air handler.

The RA-1270 operates on 24 VAC. The host user interface features a 16 x 2 character alphanumeric LCD display and is field-adjustable to display either I.P. or S.I. units. The host monitor box has two assignable analog outputs, 4 mA to 20 mA or 2 VDC to 10 VDC across a 500 ohm resistor, and also a BACnet MS/TP interface for optional BAS integration. All electronic components of the assembly are UL-rated and RoHS compliant. Calibrated performance is based on test and balance field measurement that follows three point calibration procedures performed after the sensors are mounted on the fan inlets in accordance with setup instructions.