I agree with Brian here in regards to the nipple as for derating ampacity -
*Exception No. 3: Derating factors shall not apply to conductors
*
in nipples having a length not exceeding 600 mm
(24 in.).
However…Chapter 9, Table 1 (notes 4) states
*FONT=Times-Roman Where conduit or tubing nipples having a maximum
*
length not to exceed 600 mm (24 in.) are installed between
boxes, cabinets, and similar enclosures, the
nipples shall be permitted to be filled to 60 percent of
their total cross-sectional area, and 310.15(B)(2)(a) adjustment
factors need not apply to this condition.
However…with this in mind…
**Note 2 of the SAME table says the following…" Conduit fill calculations are not intended to apply to short sections of conduit that are used only to protect exposed wires [such as Romex] from physical damage. Conduit fill calculations pertain only to certain wiring designed sections that is substantially conduit in design." NEC Chapter 9 Notes to tables Note 2
Now are we talking about all NM Cables being sleeved in conduit into this panel for protection…?..well view NEC Article 312.15© as I will post it…
[FONT=Times-Bold]**© 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.
© 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 (1.4 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 allowable
cable fill does not exceed that permitted for complete conduit
or tubing systems by Table 1 of Chapter 9 of this Code
and all applicable notes thereto.
*FPN: See Table 1 in Chapter 9, including Note 9, for allowable
cable fill in circular raceways. See 310.15(B)(2)(a) for
required ampacity reductions for multiple cables installed in a
common raceway.
So are ALL these items MET…if not…not allowed and each cable must be secured when entering the enclosure.
Hope this helps…if not just ask and I will explain more…
For Educational Purposes Only…Paulright Protected…
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