RIB® Relay + Tridium Niagara JACE BACnet Guide

If you're commissioning a Tridium Niagara relay output on a JACE controller, you already know the platform. This guide skips the introduction and gets to what you actually need: how standard RIB® relays wire to a JACE binary output, how BACnet-compatible RIB® relays address on the MS/TP trunk, which models fit which applications, and what to check when something isn't switching.

This is written for BAS integrators working in Niagara 4 on JACE 8000 and JACE 9000 controllers. JACE 6 users will find most of the BACnet MS/TP content applicable, with the caveat that some I/O expansion options differ between platforms.

Why Tridium JACE Controllers Use Relay Outputs

The JACE is a supervisor and controller. It runs logic, schedules, histories, and network communications. What it doesn't do is switch line-voltage loads directly. Its binary outputs are low-voltage control signals: 24 VAC or dry contact closures depending on the I/O module in use. Those outputs need a relay to translate the control signal into a switched load circuit.

In a standard JACE relay application, the controller's binary output energizes a relay coil and the relay contacts switch the line-voltage load. The JACE handles the logic—scheduling, override, interlocks—while the relay handles the physical switching. That electrical isolation between the JACE's control circuitry and the line-voltage load is also what protects the controller from faults on the load side.

RIB® (Relay-In-a-Box®) relays from Functional Devices, Inc. are the standard field choice for this application. They're compact, prewired, UL Listed as standalone assemblies, and available in the coil voltages that match JACE I/O module outputs.

BACnet MS/TP Wiring with RIB® Relays

There are two distinct scenarios for RIB® relay integration with a Niagara JACE: standard relays driven by a JACE binary output, and BACnet-compatible relays addressed directly on the MS/TP trunk.

Standard RIB® Relay—Driven by JACE Binary Output

This is the most common scenario. The JACE I/O module provides a 24 VAC binary output; the RIB® relay coil connects to that output; the relay contacts switch the load.

Wiring

• Connect the JACE binary output terminal (hot) to one coil terminal on the RIB® relay
• Connect the 24 VAC common to the other coil terminal
• Connect the load to the relay's NO (normally open) or NC (normally closed) contact and Common terminal, depending on your control sequence
• Connect line voltage supply to the appropriate relay terminal per the load wiring diagram

Key Point

The coil circuit and the contact circuit are completely separate. The coil terminals connect to the JACE 24 VAC output. The contact terminals connect to the load circuit at whatever voltage the load requires (120 VAC, 208 VAC, 277 VAC). Do not mix coil and contact wiring.

Polarity

RIB® relay coils rated for 24 VAC are not polarity-sensitive. Either coil terminal can connect to the hot leg; the other connects to common.

In Workbench

The JACE binary output point is configured as a BooleanWritable. When the output is commanded True (or On), the output terminal goes active, the coil energizes, and the contacts switch. The relay's state follows the controller output directly—there's no additional configuration required in Workbench for the relay itself.

BACnet-Compatible RIB® Relay—Addressed on the MS/TP Trunk

For applications where a control wire run to the JACE isn't practical, or where device-level status feedback is required, Functional Devices BACnet-compatible RIB® relays (such as the RIBTW2401B-BC) can be addressed directly on the JACE's BACnet MS/TP trunk.

Physical Connection

• Connect the relay to the MS/TP trunk via the RS-485 terminals: A (−), B (+), and Shield/Ground
• Use a daisy-chain topology—no star branches off the trunk
• Terminate the trunk at both physical ends with 120Ω termination resistors. The JACE has a built-in termination option; enable it if the JACE is at one end of the trunk
• The relay requires a separate power supply connection (24 VAC/DC or up to 277 VAC depending on model)—the RS-485 trunk does not supply power to the relay

MS/TP Address and Baud Rate

• Set a unique MS/TP MAC address on the relay (typically via DIP switches—refer to the specific relay's datasheet)
• Set the baud rate to match the JACE's MS/TP trunk configuration (common values: 9600, 19200, 38400, 76800 bps). All devices on the trunk must use the same baud rate
• Cycle power to the relay after any address or baud rate change for the new settings to take effect

In Workbench—Adding the Relay to the Station

1. Ensure the BACnet MS/TP network is configured in the JACE station (Drivers > BACnet Network > BACnet Comm > Network > MstpPort)
2. Open the BACnet Device Manager and run a Discover
3. The relay should appear in the discovered devices list with its configured Device Instance
4. Drag the relay into the station database
5. Open the BACnet Point Manager for the relay device and discover its available points (binary output for relay control, binary input for contact status if available)
6. Add the relevant points to the station database and bind them to your control logic

The relay will appear as a standard BACnet device in Workbench. Its relay output is a Binary Output object; its contact status (where available) is a Binary Input object.

Note: The Workbench steps above reflect general BACnet device discovery procedures in Niagara 4. Specific menu paths and UI details may vary between Niagara 4 versions. Always refer to the current Niagara Workbench documentation for your platform version.

Step-by-Step Configuration Notes

For standard RIB® relay integration on a JACE binary output:

1. Verify I/O module output type. JACE 8000 and 9000 use expansion I/O modules (IO-R-16, IO-R-34, etc.) for relay and analog outputs. Confirm your module's binary output type (24 VAC, dry contact) before selecting a relay coil voltage.
2. Select relay coil voltage to match the output. For 24 VAC outputs, specify a 24 VAC coil relay (RIB2401B, RIBU1C). For dry contact outputs, the JACE provides a voltage-free closure—you'll need to supply your own coil voltage from a separate 24 VAC source, connecting the coil circuit through the dry contact, or use the RIB dry contact input models (RIB21CDC, RIB01BDC, or RIB02BDC are examples.
3. Size the relay contact rating for the load. Verify the relay's contact rating (general use and horse power if switching a motor) against the load's full load current. The RIB2401B handles 20A general use loads and is rated for 1 HP at 120 VAC motor loads.
4. Configure the binary output point in Workbench. Add a BooleanWritable point for the output channel. Set the active and inactive states to match your control sequence (True = relay energized = load on, for a normally open contact configuration).
5. Test the output. In Workbench, use the override function to manually command the output True. Verify the relay clicks (audible), the LED indicator (if present) activates, and the load switches. Command False and verify the relay de-energizes and the load switches off.
6. Commission alarms and safeties. If the load requires proof-of-operation feedback (fan proving, status verification), wire a current sensor or status contact back to a JACE binary input point and configure the appropriate alarm logic in Workbench.

Recommended RIB® Models for Niagara JACE Applications

RIBU1C: 10A SPDT, dual coil voltage (10–30 VAC/DC and 120 VAC on the same model). Light-duty JACE binary output switching: damper actuators, small fan coil units, pilot duty applications. Its universal coil voltage input makes it flexible across different I/O module output configurations.

RIB2401B: 20A SPDT, 24 VAC/DC or 120 VAC coil. The standard workhorse for JACE relay output applications. Fan coil units, VAV box control, lighting switching, make-up air units. 20A contact rating covers the vast majority of BAS switching loads. Prewired NEMA 1 enclosed assembly.

RIB24P30: 30A DPDT, 24 VAC/DC coil. For higher-current loads or applications requiring two independently switched circuits from a single JACE binary output point.

RIBTW2401B-BC: 20A SPDT relay with BACnet MS/TP interface and binary input. For applications where running a control wire to the JACE isn't practical, or where device-level status feedback is required at the BAS level. Addresses directly on the MS/TP trunk. Supports standard BACnet objects.

Browse the full RIB® relay lineup or the Intelligent Field Devices category for BACnet-compatible models.

Frequently Asked Questions

What type of output does a JACE controller use to drive a relay?

JACE 8000 and 9000 controllers use expansion I/O modules for binary outputs. Depending on the module, outputs may be 24 VAC or dry contact closures. The RIB2401B (24 VAC coil) is the standard relay for 24 VAC binary output applications. For dry contact outputs, a separate 24 VAC supply is needed to power the coil circuit through the contact closure or the dry contact input RIB relays may be used (RIB21CDC, RIB01BDC, RIB02BDC, etc.).

Can I use a BACnet RIB® relay directly on the JACE MS/TP trunk?

Yes. Functional Devices BACnet-compatible RIB® relays (such as the RIBTW2401B-BC) address directly on a BACnet MS/TP trunk and appear as standard BACnet devices in Niagara Workbench. They support standard BACnet objects and can be discovered and added to the station database via the BACnet Device Manager.

What BACnet MS/TP baud rate should I use?

All devices on the MS/TP trunk must use the same baud rate. Common values are 9600, 19200, 38400, and 76800 bps. The JACE's MS/TP port baud rate is set in Workbench (Drivers > BACnet Network > BACnet Comm > Network > MstpPort). Set the relay's baud rate to match via its DIP switches and cycle power to apply the change.

How many relays can I put on a single JACE MS/TP trunk?

BACnet MS/TP supports up to 127 devices per trunk segment. In practice, the number is limited by the JACE's licensed point count, network performance, and the physical length and loading of the RS-485 trunk. For large relay counts, consider segmenting the trunk or using a BACnet router.

Do RIB® relays require any special Niagara driver or module?

Standard RIB® relays driven by JACE binary outputs require no special driver; they're passive devices that respond to a coil voltage. BACnet-compatible RIB® relays require the BACnet driver to be installed and licensed on the JACE, which is standard for most JACE configurations. No vendor-specific Niagara module is required for FD's BACnet relays.

What is the maximum wire run from a JACE output to a RIB® relay coil?

There's no fixed maximum, but voltage drop becomes a concern on long runs. At 24 VAC with a relay coil drawing 83 mA (RIB2401B), use wire sized to keep voltage drop within the relay's operating range (minimum ~85% of rated coil voltage, or about 20.4 VAC for a 24 VAC coil). For runs over 100 feet, verify voltage at the coil terminals under load.