The Emerson Discharge Air Controller (DAC) (P/N 818-9001) is a compact, packaged HVAC control board designed for rooftop units and zone control applications. It can operate as a standalone controller or integrate seamlessly into an Emerson E2 BX building management system for coordinated control of large zones.

Key Features

• Comprehensive HVAC Control: Controls heat and cool stages, fans, dehumidification devices, and economizers using on‑board I/O and algorithms.
• Rich I/O Configuration: 15 relay outputs (2.0 A max each), 6 analog outputs, 10 analog inputs, and 10 digital inputs (20 digital inputs with default configurations).
• RS485 MODBUS Communication: Communicates with E2 controllers (version 3.00 and higher) via MODBUS network. Supports up to 32 DACs on BX‑300/CX‑300 and up to 50 DACs on BX‑400/CX‑400.
• Flexible Operation Modes: Can be programmed through the E2 front panel. Operates independently without a central controller, but can be networked for centralized monitoring, alarming, and data logging via UltraSite32.
• Field‑Mountable Design: Compact size allows installation directly in rooftop units or nearby enclosures, reducing wiring costs and simplifying sensor connections.
• Pre‑loaded Configurations: Default configurations for space temperature, supply/return air temperature, and fan proofs enable quick commissioning.
• Peripheral Integration: Monitors and interacts with peripherals such as smoke alarms and CO2 sensors for enhanced building safety and air quality management.

Technical Specifications

• Relay Output Rating: 2.0 A max per relay
• Analog Output Use: Air damper, modulated heat/cool control, variable‑speed fan control
• Network Compatibility: E2 BX building control system, Copeland supervisory controller
• Supported Applications: Constant Air Volume (CAV) and Variable Air Volume (VAV) systems
• Configuration Interface: E2 front panel
• Remote Monitoring: UltraSite32 Site Manager
• Flash Memory: Up to 128 MB

Applications

The DAC is ideal for HVAC control in retail stores, commercial buildings, and industrial facilities requiring precise management of rooftop units. It is particularly suited for:

• Standalone rooftop unit control
• Zone control in large buildings with multiple HVAC units
• Integration with Emerson E2 BX building management systems
• Retrofit of existing HVAC systems for improved control and monitoring
• Applications requiring smoke alarm and CO2 sensor integration