Wiring question

This is more of a code issue. Is there any US code restrictions on running wire thought an enclosure without terminating it. For example wires from "Box A" run through "Box B" to get to "Box C". Our shop guys want to get rid of the conduit from A to C.

Each box would be connected by conduit and would run through wireway in Box B.

Thanks in advance,
John

I see this done a lot, but I'm not a code person when it comes to conduit running so I'm not going to go as far as to say it is legal. In my experience this saves time right now but in the future when the panel that is being used as a pass through needs to be replaced for some upgrade project those wires will become a serious hassle. Trying to replace a panel while keeping the rest of the plant running when wires for the rest of the plant pass through this panel will greatly complicate that job.

I am not sure exactly what you are asking. Are you wanting to use an existing panel as an intermediate (pull thru) box just to run the wire through, instead of having to run counduit direct from A to C?

Tell the truth I am not sure at this moment but will review the code, may take some time. With that said, I think I have done something similar in the past and it was acceptable by code.

If you have existing wireway going from Point A to Point C that meets at Point B, assuming there are no issues concerning the wires involved, you could always add a short run of conduit or wireway to go around the panel at Point B. The one issue there is you may need to add a pull box if you exceed your 4-90 degree turns, still easier then making long runs of conduit.

devittjl said:

This is more of a code issue. Is there any US code restrictions on running wire thought an enclosure without terminating it. For example wires from "Box A" run through "Box B" to get to "Box C". Our shop guys want to get rid of the conduit from A to C.

Each box would be connected by conduit and would run through wireway in Box B.

Thanks in advance,
John

Click to expand...

Depends on the voltage and the source. Last thing an inspector wants to see is a PLC enclosure used as a pull box for 575/600 VAC to an MCC enclosure.

Ian

running HV with LV the LV wire/cable has to have the same insulating voltage rating as the HV wire

I am not sure the terms HV and LV are appropriate. Low voltage, with AC is 600vac or below, the code states the wiring insulation must match or exceed that of the highest rated voltage applied. I do not think you can run voltages above 600vac with those below it. Another point I would have to look up.

I think the appropriate section is Article 312 of NEC, as far as I can tell it can be done if space allows. An example is no need to make bends i.e. enters one wall and exits opposite wall. You can have a wire gutter inside the panel if you need to separate the wires for any reason, as I mentioned before you could have an auxilary wire gutter or raceway that by passes the box but connects the raceways together.

I think, to address future possibilities of the box being changed, moved, etc I would consider the auxillary gutter or wireway.

One point that was not brought up was distance. I have seen existing wireways etc used to go from point A to B then C so someone could avoid running conduit etc but the wire run when done this way was hundreds of feet compared to a straight run of a hundred feet.

another major consideration of running HV with LV would be that the LV may be communications and thoes cables/wires should be well seperated. copper/alum foil sheilding is useless in terms of EMI

Well... when you say "enclosure" that can cover some ground. If it's a J-box or pull box, no problem- that's what they're there for, subject to conductor count, fill, yoke sizes and spacing, etc. But if it were that easy you probably wouldn't be asking <g>.

If it's a switchbox or HMI panel or equipment panel, then it may be permissible altho it might not be the best practice. If you're hanging all this on walls and running conduit around a building, how about you suggest they use an auxilliary gutter next to the enclosure? That way, you can bring the stuff to enclosure "B" out to "B", and send the remainder on to the next enclosure in the system.

On the other hand, if this is three boxes on a machine that you're building, and all the boxes are permanently attached to machine elements or framing, then do whatever makes sense from a safety and maintenance standpoint. You'll have to evaluate the wiring, volts and amps, and interference with or from the other stuff in the enclosure. If the enclosure is a purchased assembly like a disconnect or motor control box, you'll also have to look at the mfgr's limitations on the use of the enclosure for other wiring than their own.