Daisy-Chain Wiring - Distech Controls ECB-VAV UUKL Installation Manual

Table of Contents

Daisy-Chain Wiring

Use an external fuse on the 24VAC side (secondary side) of the transformer, as shown below, to protect all controllers against power line spikes.

Maintain consistent polarity when connecting controllers and devices to the transformer. One terminal on the secondary side of the transformer must be

connected to the building's ground. All 24V COM terminals of all controllers and peripherals throughout the BACnet MS/TP network must be connected

to the grounded transformer terminal as shown below. This ensures that the 24V COM terminals of all devices connected to any BACnet MS/TP bus in

the building are at the same potential.

A mechanical ground is unacceptable: Do not use a pipe, conduit, or duct work for a ground. The power supply must

have a dedicated ground wire that comes from the main electrical supply panel.

Failure to maintain consistent polarity throughout the entire network will result in a short circuit and/or damage to the

controller!

Connecting a peripheral or another controller to the same transformer without maintaining polarity between these

devices will cause a short circuit.

The following diagram shows the recommended wiring of the ECB-VAV Controller with and without a 3-wire peripheral. This configuration applies either

to a daisy-chain configuration or configuration with separate transformers. Note that internally, the COM terminals are no longer connected to the 24VAC

COM terminal but rather to the ground terminal.

Without 3-wire

peripheral

UO6

COM

UO5

24V AC

24V COM

Chassis or

Earth Ground

Controller 1

Fuse: 4 A Max.