BACNET INTEGRATION MANUAL FOR TB7600 SERIES THERMOSTATS
563-4523—01
Maximum Cable Length
The maximum length of a chain is related to its transmission speed. The longer the chain, the slower the speed. Using proper
cable, the maximum length of an EIA-485 daisy chain is 4000-ft (1200 m). This will only work reliably for data rates up to 100,000
bps. TB7600 themostats' maximum data rate is 76,800 bps.
If you require a maximum network length of more than 4000 feet, then repeaters are required to extend the network.
EIA-485 Repeaters
If you have more than 64 devices, or require a maximum network length of more than 4000 feet, repeaters are required to extend
the network. The BASRT-B repeater by Contemporary Controls can be used if a repeater is needed. The best configuration is to
daisy chain the repeaters to the controller. From each of these repeaters, a separate daisy chain will branch off. Fig. 3
demonstrates a valid use of repeaters in an EIA-485 network.
Fig. 3. Correct usage – repeaters are daisy-chained to the supervisory
controller and separate daisy chains branch from each repeater.
Do not install repeaters in series, as this may result in network reliability problems. Fig. 4 demonstrates an incorrect use of a
repeater in an EIA-485 network.
Fig. 4. Incorrect usage – the second repeater in series may result in an unreliable system.
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M32573
LEGEND
EOL: END OF LINE RESISTOR
R: RS485 REPEATER
SC: SUPERVISORY CONTROLLER
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LEGEND
EOL: END OF LINE RESISTOR
R: RS485 REPEATER
SC: SUPERVISORY CONTROLLER
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DO NOT ADD
SECOND
REPEATER
IN SERIES