i am facing one problem that lighting wires(120V) and control cable(12 V) are combined in one pull box.Can any one tell me NEC,IEC or IEE accept this installation. i am facing one problem that lighting wires(120V) and control cable(12 V) are combined in one pull box.Can any one tell me NEC,IEC or IEE accept this installation. wires and cable are coming through separate conduits only combine in pull box (10 X10).if they have some regulation kindly give me the reference no.

Ajaz,

Check NEC Article 300 for your specific situation. In general for wiring under 600V, as long as the insulation on the lower voltage wiring is the same level as the highest voltage wiring, they can all be in the same conduit/pull box. But keep in mind the NEC is a guide for safety (and many question the safety of this), and not a design guide, so sometimes what is allowed by a code does not always constitute good design principles.

Good engineering practice can always rule above minimum requirements; things like inductive voltages, noise/transient coupling, potential for human error, etc. should be considered. That's why some accept the practice but use barriers to segregate the different voltages from each other, while others simply don't allow it.

Remember, the AHJ (Authorities Having Jurisdiction) always have the final say despite what any particular code might allow, so check with them first before you create a potentially costly time consuming situation (and get it in writing).

Alan

Dear Alan Maltz, Thank you very much....

that condition happened due to design change and 1 & 2 points in every floor and 14 levels building.

Ajaz,

It's important to contact the code enforcement agency in your area, you never know when they might inspect what you've done.

Alan

I strongly disagree with the comment quoted below. i this it is a typo.

"Check NEC Article 300 for your specific situation. In general for wiring under 600V, as long as the insulation on the lower voltage wiring is the same level as the highest voltage wiring, they can all be in the same conduit/pull box."

In none of the codes i have studied i have found this statement. what you will find is the following

Low voltage and high voltage cables "SHALL" not be run in the same conduit.


RGDS

You can check two ways..1 look at the 17th Edition wiring regs..2 contact the IEE..you should be able to get advice there..
Regards

Yes Norman we know but NEC Article 300 give some relaxation if two wires of different level (under 600V) are combined and there is no other option