Specifications

Published in U.S.A. www.johnsoncontrols.com

LONWORKS® LN-Series Network Communication and Interface Guide Technical Bulletin40

Metasys® and Johnson Controls® are registered trademarks of Johnson Controls, Inc.

Building Efficiency

507 E. Michigan Street, Milwaukee, WI 53202

1. Some devices use half-wave rectifier circuits. Verify that consistent polarity is

maintained between all devices and the transformer. Check that the common

terminals of all the controllers are connected and make sure that the 24 V input

of all the controllers are connected.

2. For the auto-reset fuse, disconnect the power, input terminals, and output

terminals. Wait a few seconds to allow the auto-reset fuse to cool down. Check

the power supply and check the input and output wiring. Reconnect the power

without connecting the Input/Output (I/O) terminals. If there is no further

problem indicated by the auto-reset fuse, reconnect the I/O terminals.

3. See the Troubleshooting Using Device Status LEDs section for LED state

descriptions.

4. See the Network Topologies section for more information on network topology,

wire type, wire length, and network termination.

5. Use the Device Manager to view communication errors for devices and

routers. Communication errors can cause many problems in a control process.

For example, if a Rooftop Unit (RTU) controller communicates sporadically

with a Variable Air Volume (VAV) box, the system may not work properly. To

identify communication errors, you can use a protocol analyzer or the Device

Manager to list transmission errors, lost messages, and missed messages.

Troubleshooting Using Device Status LEDs

You can use the device status LEDs for quick troubleshooting of devices. Table 11

describes the possible LED states:

Table 11: Status LEDs

LED State Description

Off The device is in normal operation or is not powered. (If the device is

powered and the LED is off, pressing the Service Pin lights up the LED).

On The device is missing its application binary file (.apb).

Appropriate action: Reload the application binary file.

Repeated Blink

(Some Devices)

The device is in normal operation. The LED blinks with respect to the

device code execution time.

Slow Blink

(1 Second On, 1 Second Off)

The device is not configured.

Appropriate action: Commission the device.

Fast Blink

(0.3 Seconds On, 1 Second Off)

There is a watchdog time out. The application is corrupted.

Appropriate action: Call the device installer, distributor, or manufacturer to

report the problem.