What is the unit load of a TC300 thermostat and what are the bias and termination requirements when used with a SmartX Server.
EcoStruxure Building Operation, Field Devices
Documentation does not state the RS-485 transceiver type for the TC300 range, making it unclear how many devices can exist under a SmartX servers RS-485 serial port ComA or ComB.
The answers to the transceiver interface attributes below can be applied with to the Worksheet for Configuration of RS-485 Bus with generic RS-485 devices on Webhelp
Q1 Failsafe Receiver
The TC300 does not use an RS-485 transceiver with an integrated idle-state failsafe receiver.
Q2 Data Transmission Speed
TC300 thermostats manufactured from January 2017 onwards can be configured to communicate at 9600 or 4800 bps. TC-300 thermostats manufactured before this date can only communicate at 4800 bps.
Q4 Isolated Interface
The TC300 does not provide an isolated RS-485 interface.
Q6a Measured Resistance
With no electrical connections to the TC300, the measured resistance between the RS-485 low-side (-) signal and the communications common is 10K ohms. Based on this the unit load of the TC300 is 1.2 (12.000/10,000)
Bias requirements and number of devices
If the length of the RS-485 bus is less than 150M (500ft) then Generic RS-485 Device Configuration 3 from Webhelp can be applied. Using this configuration the recommended 3300 bias resistors present a unit load of 3.6 (12,000 / 3,300). The SmartX server adds 0.5UL. The remaining node budget is calculated as: 32 - 3.6 - 0.5 = 27.9UL. Since the TC300 has a unit load of 1.2 the maximum number of devices that can be placed under each comm port using this configuration is 27.9 / 1.2 = 23.25
If the length of the RS-485 bus is greater than 150M (500ft) then Generic RS-485 Device Configuration 7 from Webhelp can be applied. Using this configuration the dual end-point bias configuration presents a unit load of 24UL (12,000 / (1,000 / 2) = 24). The SmartX server adds 0.5UL. The remaining node budget is calculated as: 32 - 24 - 0.5 = 7.5UL. Since the TC300 has a unit load of 1.2 the maximum number of devices that can be placed under each comm port using this configuration is 7.5 / 1.2 = 6.25
Also check out the SmartStruxure-RS485-Controller Unit Load Quick-Help video on the Exchange.
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Information concerning Linux releases used within the Automation Server.
EcoStruxure Building Operation
Linux Operating System (OS)
Building Operation Automation Server
Building Operation Automation Server Premium
Questions concerning Linux releases used within the Automation Server.
AS versions to 1.4.1 run Linux kernel 18.104.22.168 AS versions 1.5 to 2.0.2 run Linux kernel 3.0.101 AS-P versions 1.7 to 2.0.2 run Linux kernel 3.5.0-lsp-3.3.1
For questions concerning what type of Linux...i.e. Red Hat, Ubuntu, openSUSE - There is no linux distribution in the automation server just vanilla linux kernel. For further reading, download some documentation about the kernel from their website www.kernel.org
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