jar546
CBO
What are your thoughts and what are the code implications of an installation like this that is approximately 36" in length above the panel?
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Bundling NM cable (Romex) in conduit
- Thread starter jar546
- Start date
steveray
SAWHORSE
Bundling/derating.....
Wouldn't allow that....I've turned it down many times....dozens upon dozens of times. Cable clamps solve the problem....and not just one or two clamps.....said no to that many times....ya it's in the dozens.
jar546
CBO
To better help us, under what code do you turn it down?
Trying to build out database here....
Trying to build out database here....
312.5 (C)
(C) Cables. Where cable is used, each cable shall be secured to the cabinet, cutout box, or meter socket enclosure.
Exception: Cables with entirely nonmetallic sheaths shall be permitted to enter the top of a surface-mounted enclosure through one or more nonflexible raceways not less than 450 mm (18 in.) and not more than 3.0 m (10 ft) in length, provided all of the following conditions are met:
(a) Each cable is fastened within 300 mm (12 in.), measured along the sheath, of the outer end of the raceway.
(b) The raceway extends directly above the enclosure and does not penetrate a structural ceiling.
(c) A fitting is provided on each end of the raceway to protect the cable(s) from abrasion and the fittings remain accessible after installation.
(d) The raceway is sealed or plugged at the outer end using approved means so as to prevent access to the enclosure through the raceway.
(e) The cable sheath is continuous through the raceway and extends into the enclosure beyond the fitting not less than 6 mm (o in.).
(f) The raceway is fastened at its outer end and at other points in accordance with the applicable article.
(g) Where installed as conduit or tubing, the cable fill does not exceed the amount that would be permitted for complete conduit or tubing systems by Table 1 of Chapter 9 of this Code and all applicable notes thereto.
Informational Note: See Table 1 in Chapter 9, including Note 9, for allowable cable fill in circular raceways. See 310.15(B)(3)(a) for required ampacity reductions for multiple cables installed in a common raceway.
(C) Cables. Where cable is used, each cable shall be secured to the cabinet, cutout box, or meter socket enclosure.
Exception: Cables with entirely nonmetallic sheaths shall be permitted to enter the top of a surface-mounted enclosure through one or more nonflexible raceways not less than 450 mm (18 in.) and not more than 3.0 m (10 ft) in length, provided all of the following conditions are met:
(a) Each cable is fastened within 300 mm (12 in.), measured along the sheath, of the outer end of the raceway.
(b) The raceway extends directly above the enclosure and does not penetrate a structural ceiling.
(c) A fitting is provided on each end of the raceway to protect the cable(s) from abrasion and the fittings remain accessible after installation.
(d) The raceway is sealed or plugged at the outer end using approved means so as to prevent access to the enclosure through the raceway.
(e) The cable sheath is continuous through the raceway and extends into the enclosure beyond the fitting not less than 6 mm (o in.).
(f) The raceway is fastened at its outer end and at other points in accordance with the applicable article.
(g) Where installed as conduit or tubing, the cable fill does not exceed the amount that would be permitted for complete conduit or tubing systems by Table 1 of Chapter 9 of this Code and all applicable notes thereto.
Informational Note: See Table 1 in Chapter 9, including Note 9, for allowable cable fill in circular raceways. See 310.15(B)(3)(a) for required ampacity reductions for multiple cables installed in a common raceway.
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My thoughts for the original post lead me to 310.15(B)(3), more than three current carrying conductors in a cable or raceway, longer than 24", and then to Table 310.15(B)(3)(a).
It looks to me as though we have between 10 and 20 current carrying conductors in the raceway, thus a 50% capacity of the conductors.
I don't know that I could 'turn it down' because I can't see the overcurrent device ratings the wires are terminated on.
If the #14 AWG wires are terminated on a 10 amp OCD, and
the #12 AWG wires are terminated on a 15 amp OCD, and
the #6 AWG wires are terminated on a 30 amp OCD;
I would say 'Compliant'.
It looks to me as though we have between 10 and 20 current carrying conductors in the raceway, thus a 50% capacity of the conductors.
I don't know that I could 'turn it down' because I can't see the overcurrent device ratings the wires are terminated on.
If the #14 AWG wires are terminated on a 10 amp OCD, and
the #12 AWG wires are terminated on a 15 amp OCD, and
the #6 AWG wires are terminated on a 30 amp OCD;
I would say 'Compliant'.
Joe Engel
Member
I know this is a service panel and the "bundled greater than 24", but as a general rule are you allowed to pull NM cable in conduit?
Michael Klein
REGISTERED
I think bundling or derating
334.80 Ampacity (2017)
Says that the ampacity of NM cable shall be determined by 310.15, and the allowable ampacity shall not exceed that of a 60 degree C rated conductor.
For NM cable, 14 gauge is rated at 15 amps at 60 degree C.
At 90 degrees C, it is rated at 25 amps.
More than 10 current carrying conductors means a 50% ampacity adjustment.
50% of 25 amps is 12.5 amps.
12.5 amps is less than the 15 amp 60 degree C rating for 14 gauge, so it is not compliant.
Less than 10 conductors is adjusted at 70% or less, which comes out to 17.5 amps with 14 gauge wire, which would be compliant.
You will find that 12 gauge romex maths out the same way, under ten conductors is at 70% adjustment, and it works, above ten is 50% adjustment, does not work.
So therefore, more than 4 pieces of romex being bundled together for more than 24" will be a violation, because 4 romex = minimum 8 current carrying conductors, which would be adjusted at 70% = compliant. 5 romex would be a minimum of 10 current carrying conductors, so adjusted at 50% = not compliant.
If I'm wrong, please correct me - I wrote this up this morning and on Friday and I would need to eat crow while its warm...
Says that the ampacity of NM cable shall be determined by 310.15, and the allowable ampacity shall not exceed that of a 60 degree C rated conductor.
For NM cable, 14 gauge is rated at 15 amps at 60 degree C.
At 90 degrees C, it is rated at 25 amps.
More than 10 current carrying conductors means a 50% ampacity adjustment.
50% of 25 amps is 12.5 amps.
12.5 amps is less than the 15 amp 60 degree C rating for 14 gauge, so it is not compliant.
Less than 10 conductors is adjusted at 70% or less, which comes out to 17.5 amps with 14 gauge wire, which would be compliant.
You will find that 12 gauge romex maths out the same way, under ten conductors is at 70% adjustment, and it works, above ten is 50% adjustment, does not work.
So therefore, more than 4 pieces of romex being bundled together for more than 24" will be a violation, because 4 romex = minimum 8 current carrying conductors, which would be adjusted at 70% = compliant. 5 romex would be a minimum of 10 current carrying conductors, so adjusted at 50% = not compliant.
If I'm wrong, please correct me - I wrote this up this morning and on Friday and I would need to eat crow while its warm...
Therefore, even if you sized your breakers smaller to account for the adjustment, I think it would still be a violation because of 334.80. Again, please correct if I'm wrong.