Master bus connection distance

You should be fine with the setup as you have it.

The normal recommendation is to have a maximum of 200m on a 250kbps bus, we usually recommend less then that because our modules generally are not used in ideal environments.

Hello Mustafa.

The earlier response was not entirely correct of me. The 200m is for CANopen and not J1939.

If you look in the J1939-15 standard they do not recommend any longer CAN-bus than 40m.

IQNAs Master/Diagnostic/Expansion bus are very similar to the J1939 so that length is what you should go after.

So if you go over 40m you could use a CAN repeater to grantee a good connection.

There is a similar topic on this with some more details here: 

http://forum.iqan.se/topics/657-can-communication-distance/

For the 200 meters at 250 kbps that was mentioned, and that can be in documents, it could be worth mentioning that this is more of an upper theoretical limit, in practice the design of the individual controllers and the wiring harness will limit it to a lower length.