New conductors in existing conduit with existing conductors

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elGringo

New member
I have been advised that the NEC does not permit the installation of new conductors into an existing conduit that already contains existing conductors. I've been told that the existing conductors must be removed, and then the existing and new conductors can then be pulled into the conduit simultaneously. Where can I find this requirement in the NEC?
 

charlie b

Moderator
Staff member
Location
Lockport, IL
Occupation
Retired Electrical Engineer
The NEC does not forbid this practice, but common sense does. It is not a good idea to pull wire past wire in the same conduit. The problem is that you risk causing damage to insulation.

Please note that if you increase the number of wires in a conduit, you may have to deal with derating.

Welcome to the forum.
 

raider1

Senior Member
Staff member
Location
Logan, Utah
Welcome to the forum.:)

I agree with Charlie, the NEC does not specifically prohibit pulling in new wire with existing wire already in the conduit. But this installation practice can increase the probability that the existing conductors may be damaged during the process, therefore good practice would be to remove the existing conductors and pull in all the conductors at the same time.

Chris
 

nhfire77

Senior Member
Location
NH
I almost always (95%) pull everything out.

Not only is it safer, it's more profitable. If I have to replace a damaged conductor, I did not plan for that in the estimate. Also, it takes longer to pull out and pull in so I charge more,'not too much more.

Oh and the last time I pulled out a 150' run of 9 12 ga solid (I will never understand why solid in long pulls make any sense, it did not appear to be a spec) there was a rats nest from the last guy. The other electrician and I were very happy we pulled it out and found this, and then made $ to fix it.
 
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mxslick

Senior Member
Location
SE Idaho
LOL where's Ceb when you need him? :grin:

On topic, I was working at a motorcycle shop, when the EC decided to try to pull through new conductors in the pipe leading to our air compressor.

Metal fish tape+live conductors+one hard push = blown up fish tape + damaged conductors + tripped main + one very PO'd business owner. :grin:

The unscheduled outage crashed the shops' point-of-sale system and created a huge headache. We lost a few transactions in process.

The EC graciously re-pulled the damaged compressor conductors and the new ones on his dime. :grin:

Needless to say a lot of people learned some valuable lessons that day.

EC (and me), not worth it to try to add conductors without puling all out and back in;

Shop owner, get UPS system for the POS system. (and schedule "major" electrical work on downtime, not regular hours.)

Service manager, bring change of shorts. :) (The blowout happened right over his desk and scared him.)
 
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