[TriEmbed] OT-ish: TVS best practices?

[Brian]

Hi Group,

I've been working on a design for zoned HVAC which involves having 
electronics at the ends of long cables.  As such, good transient voltage 
suppression becomes a more important concern.

My device will be connected via Cat-5 UTP across which will be supplied 
+6V, GND, and an RS-485 differential pair.

I'm wondering if anyone in the group has suggestions on the ideal 
application of TVS elements.  I've seen reference designs for RS-485 
that have paths to ground for each of the signal lines, but I've also 
got the +6V line to worry about.

Can I just provide paths from each signal to GND, or do I need to 
provide paths from every signal to every other signal?  It seems to me 
that theoretically, all four conductors could be floating at different 
potentials relative to each other, and clamping to GND wouldn't 
necessarily protect against a damaging potential between a 485 wire and +6V.

All input greatly appreciated!
Thanks,
-Brian