Hi Guys,

Here is an install in a new house I inspected last week. This is the first time I have seen this method for NM installs. The "rings" have a snap-around 3-sided cover to close the sides and bottom.

[Linked Image from joetedesco.com]

[Linked Image from joetedesco.com]

Let's suppose that the securing is not an issue and see if:
(1)the install will comply with the derating and
(2)with the fill allowance of 40% specified by the manufacturer.


Quote
310.15(B)(2)(a) Adjustment Factors.
(a) More Than Three Current-Carrying Conductors in a Raceway or Cable. Where the number of current-carrying conductors in a raceway or cable exceeds three, or where single conductors or multiconductor cables are stacked or bundled longer than 600 mm (24 in.) without maintaining spacing and are not installed in raceways, the allowable ampacity of each conductor shall be reduced as shown in Table 310.15(B)(2)(a).


(1). The install has six 12/3WG NM cables, six 12/2WG NM cables and one 8/3WG NM cable.
Current carrying conductors: (12/2)= 6, (12/3)= 12 and (8/3)= 2, for a total of 20 current carrying conductors.
According to the Table, the derating is 50%. The 12AWG would be reduced to 15A and the 8AWG would be reduced to 22.5A. The breakers installed are 20A and 40A respectively.

(2.) Let's guess the size of the 12/2NM is 3/8", (.375 x 6) = 2.25 sq."
Let's guess the size of the 12/3NM is 1/2", (.5 x 6) = 3.00 sq."
Let's guess the size of the 8/3NM is 3/4" = .75"
That would give us a total of (2.25 + 3.00 + .75) 6.00 sq." fill.

The product has a cross section of 7.25 sq.". When we calculate 40%, we have a result of 2.90 sq.".

Based on the above calculations, (if you agree they are acurate) would you agree that the install does not satisfy these code requirements?

Thanks for your consideration.

Dave