Connect RS485 to PAS600

[SESA528]

Hi team,

My customer concern about ability number device connect to Panel Server via RS485 (PAS600).

How many is the largest number of RS485 device connect to PAS600?

Thanks very much

[Guillaume_Evrard]

Hello,

PAS support 32 serial devices when connected without modbus repeater. Pay attention to the performance as it is modbus serial. You have to take into account speed, type of device, number of register / frames to be recovered, time for the PAS and Device to return the modbus communication media.

[UdhayakumarAK · Accepted solution]

Hi @SESA_B 

Adding to @Guillaume_Evrard comments, PAS can support up to 32 devices without repeater if the slave devices & RS485 wiring are as per the standard. Please refer this guidance for more information's and follow the wiring recommendations highlighted for better performance. https://www.se.com/in/en/faqs/FA221785/

In case, for example if you have 6 devices with RS485 network length greater than 1200 meters then you must  use Modbus repeater in between the network.

[SESA528]

HI @UdhayakumarAK ,

Yes. Thanks very much.

[Thierry_Baudard]

Hello @SESA528 

As mentioned by  @UdhayakumarAK  the theoretical length of a Modbus serial line is 1200 meters/4000 feets...and more with repeaters.

However, this long bus length requires a lot of care and rigor for the cabling (cable impedance, connection of terminal blocks, etc.) and can be difficult to commission and to maintain.

So it might be a good idea to look at another solution based on Ethernet cables/networks, optical fibers between the cabinets / archi splitted on several Panel Server for a more robust architecture.

Moreover, it states in the Panel Server instruction sheet (JYT244902 for PAS800 / GDE7411905 for PAS600) that all cables wired to the Panel Server must be connected to a single building ground....not really possible when the length of the bus is 1200 meters (screenshot hereunder.

[SESA528]

Hi @Thierry_Baudard ,

Okay thanks for your information. i will notice.

[Romain_Polette · Accepted solution]

Hello @SESA528 , 

The more devices you will add, the more you need to be careful with the Timeout settings.

As mentioned by Guillaume, pay attention to the Modbus Master's requests on the 32 slaves.

Please have a look on the ULP System Guide:

• https://product-help.schneider-electric.com/ED/ES_Power/ULP_System_IEC_Guide/EDMS/DOCA0093EN/index.h...
• https://product-help.schneider-electric.com/ED/ES_Power/ULP_System_IEC_Guide/EDMS/DOCA0093EN/index.h...

This guide gives also some recommendation regarding IFM Modbus communication (also true for any other Serial Device chained to a gateway):

In terms of Modbus communication, it depends on the performance requirement. As it takes approximately 500 ms at 19,200 Baud per device to refresh 100 registers, the more interfaces added the longer the minimum refreshment period. The minimum refreshment period depends on the number of IFM interfaces stacked to one IFE server. Multiply the time to refresh one device by the number of devices to find the minimum refreshment period expected in the application. For instance, an installation with 8x IFM interfaces stacked to one IFE server at 19,200 Baud would take approximately 4 seconds to be read.

500 ms = performances for a breaker connected to an IFM. Will be lower (or worst ?!) depending on the connected device. 

You can also read the following Tech Notes dedicated to the Com'X510 to have some inspiration:

• https://www.se.com/be/fr/download/document/ComX510_Gateway_Response_Calc_Tool_STN/
• https://www.se.com/uk/en/download/document/ESXP1G001EN/

Regards, 

[SESA528]

Hi @Romain_Polette ,

Yes. Thanks very much. This is helpful information.