Hallo George,

I'm sorry, I have thought, you would have an application in a factory!

But meanwhile I have found your lines:

in an aeroplane (or car for that matter) you connect to frame.
/////// I plan to use this for a Bus Road transport . RS485 cable runs from its HVAC unit to its Engine .The body of the bus or its frame is not at 0v ,or -ve of battery The battery is floating I dont know why ? .I am getting power from a DC/DC( 24Vdc) converter which it self is Floating Should I tie the shield to its body or to my circuit common ,Inside my cable I plan to run T+, T-, +24v and 0v .\\

Heaven, why were you talking so latetly about these important details? Why not from beginning, avoiding all this confusion?

Now the world gets totally different with Malund actually tying his FARADAY CAGE to 0v of his circuit every where.

Not at all! Erik Malund is a very experienced man and confusion arised only because you were so vague with your postings: First you didn't tell anything, then it became a factory application, then aeroplane, then bus road transport,...

Now to your question:
I would connect cable shield at each node to signal ground (0V of circuit, where GND pin of 75176 transciever is connected to). If your signal routing is as shown in one of your former postings, forming a ground loop is impossible.

I'm not familar with safety standards of high voltage powered road bus. But if the battery is really floating, then there will exist a path for leakage currents coming from dangerous high voltage! And I could imagine, that it's not allowed to touch battery terminals or even output voltage of DC/DC converter?! If this is the case, everything of your equipement must be fully isolated! Nothing may be touched by human being and nothing may be connected to bus frame.

MAKE SURE, THAT YOU ABSOLUTELY COMPLY WITH SAFETY STANDARDS, CONTACT AN APPROVED SAFETY ENGINEER AND FOLLOW HIS INSTRUCTIONS!!!!!

Kai