A Distech Controls relay interface follows a simple chain: a Distech Controls ECB Series controller issues a BACnet command, a controller output energizes a relay coil, and the relay switches the load while keeping the controller isolated from line voltage. The ECB controller’s outputs are low-voltage, so a relay is what actually switches a fan, pump, valve, or lighting circuit.
Functional Devices, Inc. manufactures RIB® (Relay-In-a-Box®) relays, current sensors, and power supplies for building automation system (BAS) work, including relays that interface with the low-voltage outputs on BACnet controllers like the Distech Controls ECB Series, and BACnet MS/TP network relays that share the same trunk. This guide covers the Distech Controls ECB Series outputs, the RIB® models that suit them, and the wiring and configuration notes for the interface.
Distech Controls ECB Controllers and BACnet Outputs
The Distech Controls ECB Series is a line of BACnet MS/TP programmable controllers (BACnet Testing Laboratories–listed as Advanced Application Controllers) used across commercial HVAC: zone and VAV control with models such as the ECB-VAV, and equipment and central-plant control with the ECB-300, ECB-400, and ECB-600 families.
The Distech Controls ECB controllers provide universal outputs, which can be configured as analog or digital, and, depending on the model, TRIAC digital outputs. Those outputs are low-voltage and cannot switch a line-voltage load directly. A digital or TRIAC output energizes a relay coil; the relay then switches the load and isolates the controller from line voltage. A universal output configured as a 0–10V analog signal is a different case and does not drive a coil relay. Confirm the specific ECB model’s output type, voltage, and current capability against its Distech Controls datasheet before selecting a relay.
Recommended RIB® Models for Distech Controls ECB Controllers
For switching a line-voltage load from an ECB digital or TRIAC output, match a RIB® relay’s coil voltage to the controller output:
To add monitored or controlled points to the BACnet MS/TP trunk without another full controller, Functional Devices also makes BACnet MS/TP network RIB® relays that sit on the network alongside the Distech Controls ECB controllers and use standard BACnet objects (binary input and output, analog input and output). The RIBTW2401B-BC adds BACnet communication and a binary input; the RIBMNW24B-BCAI accepts an analog input and carries an onboard BACnet interface for basic direct control. Confirm interoperability with the specific Distech Controls network and review the relay’s Protocol Implementation Conformance Statement (PICS) before specifying.
Wiring a RIB® Relay to a Distech Controls ECB Output
The interface is the standard BAS controller-to-relay chain covered in the RIB® relays and BACnet controller integration guide: the controller output drives the relay coil, and the relay contacts switch the load.
- Match the relay coil voltage to the ECB output. A 24 VAC TRIAC or digital output pairs with a 24 VAC/DC-rated coil; verify the actual output voltage on the controller datasheet.
- Confirm the output’s current capability covers the relay coil’s inrush and holding draw, particularly for TRIAC outputs.
- In EC-gfxProgram, the controller output maps to a BACnet object. A standard RIB® relay is a physical device downstream of that output, not a network point; a BACnet network RIB® relay is itself a point on the MS/TP trunk.
- RIB® relays are enclosed, UL Listed assemblies, which provides the isolation between the controller output and line voltage.
Application Examples
VAV Reheat or Fan: An ECB-VAV digital output drives a RIB® relay that switches a reheat valve or terminal fan.
Air Handler or Rooftop Staging: An ECB-400 or ECB-600 output drives a RIB2401B to switch a fan or energize a contactor coil for a larger load.
Adding a Network Point: Where a unit heater or similar load sits far from a controller, a BACnet network RIB® relay adds the point to the MS/TP trunk without running back to a DDC panel.
Frequently Asked Questions
Can a RIB® relay connect to a Distech Controls ECB controller?
Yes. A Distech Controls ECB digital or TRIAC output energizes the relay coil, and the relay switches the line-voltage load. Match the relay coil voltage to the controller output and confirm the output’s current capability against the ECB datasheet.
Do Distech Controls ECB outputs switch line-voltage loads directly?
No. ECB outputs are low-voltage universal or TRIAC outputs. A RIB® relay switches the line-voltage load and isolates the controller from it.
Are Functional Devices BACnet relays compatible with a Distech Controls BACnet network?
Functional Devices BACnet MS/TP network RIB® relays use standard BACnet objects and can share an MS/TP trunk. Confirm interoperability with the specific Distech Controls network configuration and review the relay’s PICS before specifying.
Specifying the Interface
A Distech Controls ECB controller handles the logic and the BACnet command; a RIB® relay does the switching and keeps the controller isolated from line voltage. Match the relay coil to the controller output, confirm the output type and current against the ECB datasheet, and use a BACnet network RIB® relay where a point needs to sit on the MS/TP trunk directly.
To select a relay for a Distech Controls ECB interface, browse the RIB® relay lineup and check the coil voltage and contact ratings on the datasheet, or find an authorized Functional Devices distributor. For the broader integration approach, see the main BACnet controller integration guide.