NEC Uses Permitted & Uses Not Permitted

[JCLP]

Hello, I am an Electrical Engineer outside the US. In our country we've adopted the NEC as our local electrical code, so we try to comply with everything stated in the Code. Last cycle adopted is 2014, but i personally always work with the latest edition (NFPA 2023).
When the NEC states "uses permitted" and "uses not permitted" (for example in wiring methods), i get confused with the following:

• "Uses Permitted" uses the wording "shall be permitted" which according to Art.90.5 it falls into Permissive Rules.
• "Uses Not Permitted" uses the wording "shall no" which according to Art.90.5 it falls into Mandatory Rules.

So my two questions are:

1. If it's not specifically permitted in the "Uses Permitted" section, then it's not allowed? Or..
2. If it's not specifically prohibited in the "Uses Not Permitted" section, then it's allowed? (While ignoring the fact that it's not listed in the "Uses Permitted" section)

 

[Dennis Alwon]

does this help any

90.5 Mandatory Rules, Permissive Rules, and Explanatory
Material.
(A) Mandatory Rules. Mandatory rules of this Code are those
that identify actions that are specifically required or prohibited
and are characterized by the use of the terms shall or shall not.
(B) Permissive Rules. Permissive rules of this Code are those
that identify actions that are allowed but not required, are
normally used to describe options or alternative methods, and
are characterized by the use of the terms shall be permitted or
shall not be required.
(C) Explanatory Material. Explanatory material, such as references
to other standards, references to related sections of this
Code, or information related to a Code rule, is included in this
Code in the form of informational notes. Such notes are informational
only and are not enforceable as requirements of this
Code.
Brackets containing section references to another NFPA
document are for informational purposes only and are provided
as a guide to indicate the source of the extracted text.
These bracketed references immediately follow the extracted
text.

 

[don_resqcapt19]

Hello, I am an Electrical Engineer outside the US. In our country we've adopted the NEC as our local electrical code, so we try to comply with everything stated in the Code. Last cycle adopted is 2014, but i personally always work with the latest edition (NFPA 2023).
When the NEC states "uses permitted" and "uses not permitted" (for example in wiring methods), i get confused with the following:

• "Uses Permitted" uses the wording "shall be permitted" which according to Art.90.5 it falls into Permissive Rules.
• "Uses Not Permitted" uses the wording "shall no" which according to Art.90.5 it falls into Mandatory Rules.

So my two questions are:

1. If it's not specifically permitted in the "Uses Permitted" section, then it's not allowed? Or..
2. If it's not specifically prohibited in the "Uses Not Permitted" section, then it's allowed? (While ignoring the fact that it's not listed in the "Uses Permitted" section)

The code is a permissive code. In general, if the NEC does not tell you that you can't do it, you can. Not really sure why we even have a uses permitted as those lists do not cover every possible use of the wiring method.

 

[electrofelon]

In our country we've adopted the NEC as our local electrical code

I'm sorry. Wish your leaders would have made a better choice.

 

[suemarkp]

Exactly. Maybe the only use for explicit Uses Permitted is to eliminate any gray area of what is allowed based on some other rule that an inspector trys to use to deny that method.

Maybe cord pendant drops is an example. They are explicitly permitted. If they were not, the uses not permitted may not allow them (does that connection really have to be flexible, is it really changed often, ...).

 

[jaggedben]

I think 'Uses Permitted' confirms specifics so you don't have to find and read the fine print on products to know if they comply with 110.3(A). 110.3(A) places something of a check on saying anything goes that isn't prohibited; an AHJ could always still ask you to convince them that wiring and equipment is suitable by showing labeling and listing. 'Uses Permitted' prevents an AHJ from abusing that prerogative. It also confirms that there isn't some other rule somewhere else in the book that would prohibit such a use.

 

[LarryFine]

Permitted, Shall be Permitted, Uses Permitted, etc., are effectively saying Shall Not be Prohibited.