two wires under same terminal

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eetwo

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In what code year did it become against code to put two wires under the same screw in a neutral/ground bar?
 
infinity

infinity

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This first appeared in the 2002 NEC as section 408.21. It was later moved to 408.41.

408.41 Grounded Conductor Terminations.
Each grounded conductor shall terminate within the panelboard in an individual terminal that is not also used for another conductor.
Exception: Grounded conductors of circuits with parallel conductors shall be permitted to terminate in a single terminal if the terminal is identified for connection of more than one conductor.
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eetwo

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408.41, was what I was wondering about. So previous to 2002 it would have been legal to put two wires under the same terminal of a neutral bar in a loadcenter?
 
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SEO

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Also look at section 110.14 (A) Terminals for more than one conductor and terminals used to connect aluminum shall be so identified.This sentence has a sidebar in the 1971 Nec so it looks like it was either a new sentence or taken from another section of the NEC but it has been around from at least 1971.
 
480sparky

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SEO said:
Also look at section 110.14 (A) Terminals for more than one conductor and terminals used to connect aluminum shall be so identified.This sentence has a sidebar in the 1971 Nec so it looks like it was either a new sentence or taken from another section of the NEC but it has been around from at least 1971.
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That language goes back to at least 1937. There was a huge renumbering that year, so it will take me a while to see if it predates 1937.
 
480sparky

480sparky

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OK. 1935 is as far back as I can trace it.

Rule 203.c

"....Not more than one conductor shall terminate under a single set-screw unless a form of terminal specially approved for this purpose is used."

I cannot find any similar language in 1933.
 
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SEO

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480sparky said:
OK. 1935 is as far back as I can trace it.

Rule 203.c

"....Not more than one conductor shall terminate under a single set-screw unless a form of terminal specially approved for this purpose is used."

I cannot find any similar language in 1933.
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You are fast 480 sparky. I thought the language was in older codes but I don't have the means to find it that quickly. You are a great source for code information!
 
infinity

infinity

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So from the 2002 and beyond, even if the terminal bar were listed for more than one conductor you can only install a single grounded conductor per hole. This rule is good for new installations but bad for old existing panelbaords where there never were enough holes to begin with. :)
 
LarryFine

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Note that the exception to 408.41 says "Grounded conductors of circuits with parallel conductors shall be permitted to terminate in a single terminal . . . ", which won't apply to almost all branch circuits.

I imagine that the reasoning is that, with parallel conductors, there's no chance that one grounded conductor can still be energized when the other needs to me removed from the neutral bar for any reason.
 
tom baker

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It was not a code change as much as it was to clarify the UL Requirement for this. I suspect it was a UL requirement from the beginning when 3 wire circuits were used, which Thomas Edison invented.
 
don_resqcapt19

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eetwo said:
408.41, was what I was wondering about. So previous to 2002 it would have been legal to put two wires under the same terminal of a neutral bar in a loadcenter?
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No. It has been a 110.3(B) violation for at least 25 years. The rule was placed in the code because too many installers were no reading the instructions that are provided with the panel.
9- 113 - (384-21 (New) ): Accept
SUBMITTER: James T. Pauley, Square D Co.
RECOMMENDATION: Add a new 384-21 to read as follows:
384-21. Grounded Conductor Terminations. Each grounded conductor shall terminate within the panelboard in an individual terminal that is not also used for another conductor.
Exception: Grounded conductors of circuits with parallel parallel shall be permitted to terminate in a single terminal if the terminal is identified for connection of more than one conductor.

SUBSTANTIATION: This revision is needed to coordinate the installation requirements with a long standing product standard requirement. Clause 12.3.10 of UL 67 (Panelboards) states ?An individual terminal shall be provided for the connection of each branch-circuit neutral conductor.? The requirement has been enforced in the past by a close review of the manufacturers markings and by NEC 110-3(b). However, since it is a rule that specifically effects how the installer can make connections, it is important that it be in the NEC.

Even with the manufacturers markings, inspectors still indicate that they see a number of panelboards installed with two (or more) branch circuit neutrals under one terminal or they see an equipment grounding conductor and neutral under the same terminal.

There is very good rationale for the requirement in the product standards. Doubling up on the neutrals creates a significant problem when the circuit needs to be isolated. In order to isolate the circuit, the branch breaker is turned off and the neutral is disconnected by removing it from the terminal. If the terminal is shared with another circuit, the connection on the other (still energized) circuit will be loosened as well. This can wreak havoc, particularly if the neutral is part of a 120/240V multi-wire branch circuit. Also, the neutral assemblies are not evaluated with doubled-up neutrals in the terminals.

The connection of a neutral and equipment grounding conductor creates a similar issue. One of the objectives of the particular arrangement of bonding jumpers, neutrals and equipment grounds is to allow circuit isolation while keeping the equipment grounding conductor still connected to the grounding electrode (see UL 896A - Reference standard for Service Equipment). When the neutral is disconnected, the objective is to still have the equipment ground solidly connected to the grounding electrode. If both the neutral and grounded conductor are under the same terminal, this cannot be accomplished.

This addition to the NEC does not change any product or permitted wiring arrangement from what it is today. It will however, it will help installers to avoid wiring the panel in violation of 110-3(b) and then have to contend with a red-tag from the inspector. The code language is proposed in a fashion to allow consistent enforcement of the provision the the AHJ. Although the UL wording is adequate for the product standard, it is important that the NEC language is as clear an unambiguous as possible. This is the reason for specifically noting that the terminal cannot be used for another conductor. Furthermore, the code requirement has been worded to make sure that both branch circuit and feeder neutrals are covered since it is not uncommon to have feeder breakers as well as branch breakers in the panelboard (the issue for the neutral is the same regardless of branch or feeder). Also, the term ?grounded conductor? is used to be consistent with the code terminology and to recognize that not all grounded conductors are neutrals.

An exception has been proposed to avoid any confusion relative to parallel circuit arrangements. In these instances, multiple neutrals could be in a single terminal if the terminal has been identified as acceptable for multiple conductors.
PANEL ACTION: Accept.
In the proposed exception, change the second instance of the word ?parallel? to ?conductors?.
PANEL STATEMENT: The correction of the typographical error meets the intent of the submitter.
NUMBER OF PANEL MEMBERS ELIGIBLE TO VOTE: 11
VOTE ON PANEL ACTION:
AFFIRMATIVE: 11
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