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Analog and Discrete wiring

13K views 17 replies 11 participants last post by  Cow 
#1 ·
Just wanted to get a discussion going here about how you should run the wire for analog and discrete devices, I have been in places where we run conduit for each ( one analog pipe; one discrete pipe) I have been in places where they were mixed together in pipes, some people swear they have to be separated some people say you can mix them, in all cases the discrete has been 24V and the Analog has been 4-20mA, what are the feelings out there?
 
#3 ·
I can't think of a reason to separate them. As far as I know the 4-20ma is nice because induced voltages aren't a problem, not that 24vdc is going to induce much voltage. Can't see any way the 4-20ma would trip up discrete.
 
#6 ·
That is not correct....all of the conductors have to be insulated for the highest voltage circuit that is in the raceway.
You can mix 600 volt rated discrete conductors with the 300 volt rated analog conductors and be code compliant.
300.3(C)Conductors of Different Systems
(1) 1000 Volts, Nominal, or Less. Conductors of ac and dc circuits, rated 1000 volts, nominal, or less, shall be permitted to occupy the same equipment wiring enclosure, cable, or raceway. All conductors shall have an insulation rating equal to at least the maximum circuit voltage applied to any conductor within the enclosure, cable, or raceway.
 
#7 ·
I've mixed them in a single pipe for many years and have yet to have a problem. Even very long runs, no trouble at all.

For that matter, I've pulled 120AC and 4-20 (shielded) in the same pipe, though it was a fairly short run (40'or so) and the 120 had very little current (instrument power).
 
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