BACnet Building Controller (20 I/O)

BTL B-BC certified; 8 Universal Inputs, 8 Relay + 4 Analog Outputs

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BACnet Building Controller (20 I/O)


  • BTL B-BC certified BACnet supervisory controller
  • BACnet-IP to BACnet-MS/TP routing
  • 8 Universal Inputs
  • 8 Form A Relays, 4 Analog Outputs
  • Supports up to 3 I/O Expander Modules
  • 100Mb Ethernet, Optional WiFi
  • Optional Modbus Master RTU interface


The 3-9520 is a BTL B-BC certified BACnet Building Controller featuring 20 physical I/O points, with up to 60 more I/O points using expansion modules, onboard Ethernet, BACnet IP to MS/TP routing, a battery-backed real-time clock, and an optional Modbus RTU Master interface. The devices is most often used to supervise a facility, or to control Air Handling Units, Cooling Towers and other mechanical equipment in building HVAC systems.

The 3-9520 has an on-board battery-backed calendar clock, and data is retained through power loss. It is easily networked with Niagara JASIC 8000 devices, Niagara Web Supervisor, ASI IntelliFront and other BACnet front ends, and can also operate standalone without supervision. Red and green LEDs indicate the controller’s receive and transmit communications. A switching power supply is included for AC operation; flash memory is used for program and data storage. Transient voltage suppressors and a 100 mA polyswitch provide a uniquely high degree of protection from power spikes.

The device is easily configured using ASI Visual Expert configuration software that links ready-made objects including scheduling, logic, PID control, alarming, optimum start, trending, run-time accumulation, and electrical demand management. A graphical programming interface provides familiar drag-and-drop and click-to-connect editing tools.

The device offers Ethernet and wired communications, or optional WiFi support via an XBee module. The RS-485 connections support standard BACnet MSTP baud rates up to 115,200 bps. The USB Device connection can operate at full speeds of up to 12 Mbps.

24 Vac relay outputs (8) are ideal for driving contractors and starters. Analog outputs (4) can drive modulated actuators, electronic-pneumatic transducers, variable speed drives and other analog signal devices. Universal inputs (8) can count pulses, read thermistors and contact closures directly, or read any other type of 4 to 20 mA, 0 to 10Vdc, 0 to 5 Vdc or 1 to 5 Vdc input signal. In higher point count applications the 3-9520 controller can add 20 points (8 Universal Inputs, 8 Relay and 4 Analog Outputs) via a USB IO Expansion module, or integrate with up to 3 independently powered USB Expansion modules with 20 I/O points each.

The device can automatically backup configuration data to qualified SD cards.