little experience with shielded cables


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Old 03-19-14, 11:09 PM
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little experience with shielded cables

I'm an electrician installing a CO and NO2 monitoring system in a large parking garage. I'm using 2 and 3 pair twisted shielded cable. The control module does not have a shield termination for the power wires, and the signal wire shield is shared between 2 channels.
So what should I do with the shield from the 24v power wires? just ground it?
And when splicing, do I need to maintain specific continuity, or can I tap splice the drain? Like, if I have a junction where I come in, make a loop/return, and send out, can I just connect all 4 drains together or do I need to connect from in to loop, then return to send? Is that making sense?

The main issue is, the help I was given (a crew of 7 Dominicans) weren't very careful about keeping the drain wires isolated from the conduit despite repeated instruction and demonstration... so there could be some contact points where the wires enter the sensors (big pain to rework and correct).

I'm thinking I need to find some kind of sleeve that I can slide over the drain wire and force back into the conduit. Going to try stripping some solid 16awg to see if I can use the insulation.

This job has been such a headache...
 
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Old 03-19-14, 11:55 PM
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Welcome to the forums.

I moved your post to its own thread as you are connecting shielded cables as opposed to splicing them.

It's hard to make specific recommendations without knowing exactly what the system requires but I can tell you that shields hitting metal conduit will come back and haunt you. When you're working with low level shielded cables..... usually only one end gets connected. Usually it would be the control end. If the sensors you are connecting aren't metal or connected to ground then the shield may need to be connected at both ends.

Typically power supply wiring is not shielded.

You need to have shrink tubing with you. It comes in a load of colors and sizes. You put it on before connecting the unit..... then just slide it into place and give it a quick shot of heat.

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