Jason Lavoie wrote on Thu, 05 July 2007 01:23 |
I have a situation where I'm running Cobranet from rack to rack and it may be a bit over the 100m maximum length and the only option seems to be to put a switch somewhere in between. the only location that will work is in a drop ceiling air plenum space. is there any way to install a hub in a ceiling that won't violate fire regulations?
any cobranet recommended hubs that are nice and small and can be installed right in a pull box?
I wish there was a better option, but it seems this is the only place I can put it.
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Hello Jason;
This may be a little rude but it's a methodology that's worked for me many times in the past.
When companies state suggested maximum cable runs they play it safe.
Measure the length you require, triple it and run a few tests.
If it works error free, install your "bit over the 100m maximum length" and sleep well.
If the triple length doesn't work, try a double length.
If the double length works, great, if not try 150m.
You've got the idea.
Don't send out anything that's barely shy of the ratty edge but if it works reliably at 3x, 2x or 1.5x the length you need you're probably safe to go with it.
Back in my computer controlled a/c servo drive days, I found I could run RS-232 75' and resolver cable 200'.
The IT folks were telling us that 25' was the max for serial and the servo drive manufacturers were telling us that 40' was their absolute maximum length for resolver cables but only when ran in dedicated conduits.
When we were shipping a/c servos to Germany for 'Tommy', all of our drive cables were off the shelf grey vinyl jacketed control cables.
We'd typically have a 12/4 shielded motor cable, a double shielded resolver cable, a 16/2 shielded DC brake cable and an 18/4or5 shielded hard limit cable bundled together with a few wraps of electrical tape every 2 or 3 feet and no conduit in sight.
Prior to 'Tommy' Frankfurt, our longest cables were 100'.
When we needed 150' and 200' cables for Germany, we took full 1,000' put-ups and connectorized both ends for testing.
We found 1,000' was pretty ratty, pardon the technical word, but cutting the 1,000' in half to 500' seemed to work pretty well as far as we could tell by test running the rig in the shop.
After that, we sent the 200' lengths to Frankfurt and figured we'd be safe to send out anything up to 300' if / when the need were to arise.
Bottom Line: Don't believe all you read, conduct your own exhaustive tests and form your own conclusions.
Toodleoo!
Ron Hebbard