Old 14-2 NM

[Will Wire]

Is it in violation of the Code to extend a 14-2 NM circuit that has a 16 ga ground, since the minimum size equipment grounging conductor must be 14 ga for a 15 amp circuit?

 

[mjf]

Where I live/work, I am not permitted to extend any circuit with an undersized EGC.

 

[Dennis Alwon]

I would think it is for many of the reason you can't extend a 2 wire circuit.

 

[Hv&Lv]

Would the modification of the circuit make the install non-compliant? How long did they make that wire with the undersized neutral anyway?

 

[mjf]

I would think it is for many of the reason you can't extend a 2 wire circuit.

Would the modification of the circuit make the install non-compliant? How long did they make that wire with the undersized neutral anyway?

I believe the OP is referring to old NM that had 14 gauge ungrounded conductor, 14 gauge grounded conductor and 16 gauge bare (grounding) conductor.

 

[mcnut]

250.130(C) gives you some options.

 

[kwired]

Kind of have to use your own discretion sometimes. If the work done is required to be inspected in theory you shouldn't have much choice (of what to do with the existing). If it does not require inspection - your $500 dollar proposal will end up being done by a $50 handiman and he will extend the existing circuit, and may have more code violations than just an undersized EGC. Of course this happens when inspection is required also so either way you lose the $500 job to someone that will do it for $50 and not do it right.

 

[petersonra]

It was safe when it was put in. It has not caused any problems since. How is it that it became unsafe all of a sudden?

Is there any evidence that #14 NM that used a #16 EGC ever caused any additional problems over those experienced with #14 NM with a #14 EGC?

The code ought to deal with these kind of things in a more rational way. It almost forces people to do it the "wrong" way because no one believes the "wrong" way has any downside and is often the only cost effective way to handle a certain situation.

I am not opposed to not allowing extension of circuits that do not have an EGC. I can see the downside to that. but a residential 15A BC with a #16 EGC will reliably trip the OCPD every bit as well as a #14 EGC. Some might argue that a #16 EGC might not reliably trip an OCPD on a long circuit. That could happen, but the code already covers such a case.

Its like not allowing ring circuits. Where is the downside to that?

 

[al hildenbrand]

Is it in violation of the Code to extend a 14-2 NM circuit that has a 16 ga ground, since the minimum size equipment grounging conductor must be 14 ga for a 15 amp circuit?

This is one of those wonderful grey areas that become obvious when the lighting is just so. . . .

The #16 reduced gage EGC (equipment grounding conductor) in early '60s NM, NM installed to the Code of the Day, was a Code allowed EGC.

Nothing in subsequent editions of the NEC have caused those grounding type receptacles installed on that reduced ground NM to not be connected to that originally approved EGC. Baring conductor continuity failure or a miswire, a polarity tester will verify that those grounding type receptacles ARE grounded.

But, that said, the only opinion that really has sway, is the opinion of the local inspector for the property that is having the circuit extended. I suggest that you call this inspector and describe the existing installation and the condition you have observed it to be in, and then describe the circuit extension, and then ask whether, in this inspector's opinion, you can use the existing EGC for the extension.

Over the years I have had the answer from the inspector go both ways.

 

[jumper]

It was safe when it was put in. It has not caused any problems since. How is it that it became unsafe all of a sudden?

Is there any evidence that #14 NM that used a #16 EGC ever caused any additional problems over those experienced with #14 NM with a #14 EGC?

The code ought to deal with these kind of things in a more rational way. It almost forces people to do it the "wrong" way because no one believes the "wrong" way has any downside and is often the only cost effective way to handle a certain situation.

I am not opposed to not allowing extension of circuits that do not have an EGC. I can see the downside to that. but a residential 15A BC with a #16 EGC will reliably trip the OCPD every bit as well as a #14 EGC. Some might argue that a #16 EGC might not reliably trip an OCPD on a long circuit. That could happen, but the code already covers such a case.

Its like not allowing ring circuits. Where is the downside to that?

This is the NEC, common sense is verbotten!!!

 

[Hv&Lv]

I believe the OP is referring to old NM that had 14 gauge ungrounded conductor, 14 gauge grounded conductor and 16 gauge bare (grounding) conductor.

I was also... I have only seen this old wire in 5-6 old houses. My question was would the modification of the circuit make the install non-compliant. Could you extend the circuit and install a grounding receptacle at the end? Not according to 250.130(C) as was pointed out.

Couldn't the question be changed to "Is it in violation of the Code to extend a 14-2 NM circuit that has NO ground, since the minimum size equipment grounging conductor must be 14 ga for a 15 amp circuit? "

 

[al hildenbrand]

My question was would the modification of the circuit make the install non-compliant. Could you extend the circuit and install a grounding receptacle at the end? Not according to 250.130(C) as was pointed out.

This is an interesting question.

Is 250.130(C) the correct citation? Look at the last sentence of 250.130.

VII. Methods of Equipment Grounding

250.130 Equipment Grounding Conductor Connections. Equipment grounding conductor connections at the source of separately derived systems shall be made in accordance with 250.30(A)(1). Equipment grounding conductor connections at service equipment shall be made as indicated in 250.130(A) or (B). For replacement of non?grounding-type receptacles with grounding-type receptacles and for branch circuit extensions only in existing installations that do not have an equipment grounding conductor in the branch circuit, connections shall be permitted as indicated in 250.130(C).

(A) For Grounded Systems. The connection shall be made by bonding the equipment grounding conductor to the grounded service conductor and the grounding electrode conductor.

I think that leads me to 250.130(A) which then places no specification on the "bonding". The existing EGC that is the reduced gage #16 in the old NM is already "bonded" to the grounded service conductor and the grounding electrode conductor of the common grounded system of a standard American dwelling.

Extending that old reduced gage EGC into a branch circuit extension wired to today's NEC, will mean the extension EGC will be bonded to the GEC and grounded service conductor.

 

[Dennis Alwon]

I believe the OP is referring to old NM that had 14 gauge ungrounded conductor, 14 gauge grounded conductor and 16 gauge bare (grounding) conductor.

Yes I am aware of that. The same issue could be said for extending K&T. If the install was legal at the time that is fine but adding to it IMO is a violation. If an old install had a 3 wire running to a sub panel because the inspector allowed it on an upgrade would you allow new circuits to be installed from it. I don't think we can add to the problems.

Now this is unique in that we are adding a compliant wire but it is still dependent on the rest of the circuit egc to clear a fault.

 

[mcnut]

This is an interesting question.

Is 250.130(C) the correct citation? Look at the last sentence of 250.130.

I think that leads me to 250.130(A) which then places no specification on the "bonding". The existing EGC that is the reduced gage #16 in the old NM is already "bonded" to the grounded service conductor and the grounding electrode conductor of the common grounded system of a standard American dwelling.

Extending that old reduced gage EGC into a branch circuit extension wired to today's NEC, will mean the extension EGC will be bonded to the GEC and grounded service conductor.

I thought the same thing at first but I peeked the in the handbook and it had comentary stating that 250.130(C) applies to both ungrounded AND gounded systems. I know that the commentary is not code but I think it applies here, the word "only" you have in bold applies to "in exisiting installations", not to the rest of the sentence.

 

[al hildenbrand]

. . . I peeked the in the handbook and it had comentary stating that 250.130(C) applies to both ungrounded AND gounded systems.

Here's the difference between the Handbook reference and my red highlight: "grounded system" means grounded Premesis Wiring (System) as defined in Art. 100; while:

existing installations that do not have an equipment grounding conductor in the branch circuit

describes only a part of the Premesis Wiring (System).

I believe that part of the last sentence in 250.130 prevents us from using 250.130(C) in the OP case.

 

[guschash]

The house I used to live in 30+ years had 16 g ground and was a Federal Pacific panel, never had a problem with either. But you never know. Another 30+ years could have a problem, then what. Who knows I think whenever you do a upgrade you go with the newest and the greatest. The code address this and tells us what to do. I would say that if you can upgrade you should.

 

[al hildenbrand]

I think whenever you do a upgrade you go with the newest and the greatest. The code address this and tells us what to do. I would say that if you can upgrade you should.

Running a new homerun is all well and good when it can be afforded, but, in the case of the OP proposed branch circuit extension, it, too, seems to be well within the bounds of the Code. Show me in Code that it isn't.

 

[kwired]

The house I used to live in 30+ years had 16 g ground and was a Federal Pacific panel, never had a problem with either. But you never know. Another 30+ years could have a problem, then what. Who knows I think whenever you do a upgrade you go with the newest and the greatest. The code address this and tells us what to do. I would say that if you can upgrade you should.

If equipment grounding conductor(s) was never called on to carry enough current to clear a fault, it is understandable that you never had a problem. The question is what will happen when it is called upon to carry enough current to clear a fault?

 

[RichB]

I forget who originally posted this--but thank you--
That formula is used to find the "withstand rating" of a conductor. You will not find this in the NEC.

Here's an example of how it is used:

Copper can withstand 1-ampere for 5-seconds for every 42.25-circular mils.

So take a #8 AWG conductor. #8 = 16,510 cm / 42.25 = 391-amperes.

Using the formula, amps squared x time=A. 391 x 391 x 5 = 764,405
(^2 means squareroot of)

To find the withstand rating, consider a 1/4 cycle overcurrent device protecting a #8 AWG conductor.

A 1/4 cycle = .0042 seconds. So, using this information and the answer from above:

The Square Root of (764,405 / .0042) = 13,491 amperes for 1/4 cycle.

What does this mean? If the circuit has an available fault current exceeding 13,491 amperes and the overcurrent device does not open faster
than 1/4 cycle, the #8 conductor will fail.

Using the above formulae 16AWG can handle 2107 amps for 1/4 cycle--or 1489 for a half cycle--
And 14 AWG is 3356A for 1/4 cycle and 2373 for a half cycle

just saying....

 

[kwired]

I forget who originally posted this--but thank you--
That formula is used to find the "withstand rating" of a conductor. You will not find this in the NEC.

Here's an example of how it is used:

Copper can withstand 1-ampere for 5-seconds for every 42.25-circular mils.

So take a #8 AWG conductor. #8 = 16,510 cm / 42.25 = 391-amperes.

Using the formula, amps squared x time=A. 391 x 391 x 5 = 764,405
(^2 means squareroot of)

To find the withstand rating, consider a 1/4 cycle overcurrent device protecting a #8 AWG conductor.

A 1/4 cycle = .0042 seconds. So, using this information and the answer from above:

The Square Root of (764,405 / .0042) = 13,491 amperes for 1/4 cycle.

What does this mean? If the circuit has an available fault current exceeding 13,491 amperes and the overcurrent device does not open faster
than 1/4 cycle, the #8 conductor will fail.

Using the above formulae 16AWG can handle 2107 amps for 1/4 cycle--or 1489 for a half cycle--
And 14 AWG is 3356A for 1/4 cycle and 2373 for a half cycle

just saying....

And table 250.122 probably assumes worst case when it comes to response of an overcurrent device, otherwise it would be 25+ pages long to cover different types of overcurrent devices.