Hi i have a question. If you have 3 current carrying conductors in a pre existing conduit, and you haven’t exceed the 40% fill allowances and you decide to use it and add an additional 4 ccc. Now that you have 7 ccc a 70% adjustment must be added. Since the existing conductors are already in the conduit can you just put a ocpd that will protect all conductors at there new ampacity?
De rating
- Thread starter Djelite
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LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
You may not need to change the OCPD.
For example, nine #12s at 70% can still be on (0.7 x 30 = 21) 20a breakers.
- Location
- Chapel Hill, NC
- Occupation
- Retired Electrical Contractor
are your neutrals ccc's if not then you could have as few as 6 ccc's
- Location
- Lockport, IL
- Occupation
- Semi-Retired Electrical Engineer
I sorta recall from ages past that you should never pull new wire into conduit that has wire, as insulation rubbing against insulation could result in damage. My designs therefore called for the existing wire to be removed and all wires (old and new) to be pulled in together. Was that necessary? Just asking.
qcroanoke
Sometimes I don't know if I'm the boxer or the bag
- Location
- Roanoke, VA.
- Occupation
- Sorta retired........
We did it all the time. Pull one out and use it as a pull wire and pull three back in. Two for the new circuit and one to replace the one we pulled out.
"This was before we knew about de-rating"
You were taking a chance of conductors being damaged but it never happened.
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