Grounding of two wire circuits

[mivey]

Careful with your pronouns; I don't necessarily contract this way.

You meaning a contractor in general. There is some english stuff about 2nd person or some such related mess but I don't remember. I just throw the words out there and if it needs further explanation, I throw out some more. :grin:

 

[al hildenbrand]

What does that have to do with anything? Are you saying the code does not cover equipment?

Consider 440.61 and 250.114(3) when it comes to existing grounding-type receptacle outlets on a non-bond wire AC wiring method with utilization equipment cord and plug connected by the dwelling occupant?

That is not what I said and that is not what the code says.

In for a penny, in for a pound. A non-bond wire armored cable installed Lighting Outlet was, let us assume, installed to the Code in effect at the time. . . meaning that, by the Code in effect, the Lighting Outlet contains the EGC.

From the Article 100 Definition of Premises Wiring (System) we know that a Luminaire, while mounted and electrically connected to the Lighting Outlet, is not part of the Premises Wiring (System). The Luminaire is Utilization Equipment connected at an Outlet.

A cord and plug connected residential window AC must be connected to the EGC. The air conditioner is Utilization Equipment connected at an Outlet.

See how that works. Your perspective, with respect to using AC cable armor as an effective grounding means, . . . your perspective causes any one who has plugged in Utilization Equipment listed in 250.114(3) to have violated the rules of the Code in effect today.

And, 250.114(3) has been in effect in today's and earlier Codes long before the EGC rule for Luminaires was upgraded to the version in effect today.

Is the Luminaire connection to an EGC special and requiring upgrading of an un-altered existing non-bond wire AC wiring method. Recalling your response in #70:

In this light why stop at the fan outlet if you know the rest of the house is the same?

Because you have only been contracted to deal with the light. The fix will only take care of that one circuit. If they want me to take care of the rest, I can. I would certainly make some recommendations.

If one is in the dwelling and sees grounding-type receptacle outlets then, by your adherence to only the EGCs of today's NEC, you have to see the receptacle outlets as hazards, a term of art generally requiring immediate remedy.

The term "grandfather" is, indeed, not in the Code. That is beside the point. Enforcement of the Code in effect for new construction for new electrical work done on existing occupancies is generally handled through ordinance worded as in 2008 NEC Annex H 80.9. If not in fact the wholesale adoption of the unaltered language of 80.9 as local ordinance. Annex H 80.9(B) and 80.9(C) are the heart of the meaning of the trade slang term "grandfathered".

 

[mivey]

Consider 440.61 and 250.114(3) when it comes to existing grounding-type receptacle outlets on a non-bond wire AC wiring method with utilization equipment cord and plug connected by the dwelling occupant?

I see where you are coming from, but this article does not specify the method of grounding like in section 2008-410.46. 250.114 just says connected. 410.46 goes through the extra effort of specifying the connection method that must be used.

In for a penny, in for a pound. A non-bond wire armored cable installed Lighting Outlet was, let us assume, installed to the Code in effect at the time. . . meaning that, by the Code in effect, the Lighting Outlet contains the EGC.

Meaning that for the old code, the EGC is there. In the new code, it is not a defined EGC and is just some flex around the cable.

From the Article 100 Definition of Premises Wiring (System) we know that a Luminaire, while mounted and electrically connected to the Lighting Outlet, is not part of the Premises Wiring (System). The Luminaire is Utilization Equipment connected at an Outlet.

A cord and plug connected residential window AC must be connected to the EGC. The air conditioner is Utilization Equipment connected at an Outlet.

See how that works. Your perspective, with respect to using AC cable armor as an effective grounding means, . . . your perspective causes any one who has plugged in Utilization Equipment listed in 250.114(3) to have violated the rules of the Code in effect today.

I see what you mean. Then it would be true that those items are indeed in violation of the code today as the code today does not recognize the unbonded armor as an EGC.

Another question becomes: At what point does the NEC exceed its authority?

And, 250.114(3) has been in effect in today's and earlier Codes long before the EGC rule for Luminaires was upgraded to the version in effect today.

Is the Luminaire connection to an EGC special and requiring upgrading of an un-altered existing non-bond wire AC wiring method. Recalling your response in #70:
If one is in the dwelling and sees grounding-type receptacle outlets then, by your adherence to only the EGCs of today's NEC, you have to see the receptacle outlets as hazards, a term of art generally requiring immediate remedy.

I do see them as hazards. It does not mean the homeowner has to contract with me to fix them.

The term "grandfather" is, indeed, not in the Code. That is beside the point. Enforcement of the Code in effect for new construction for new electrical work done on existing occupancies is generally handled through ordinance worded as in 2008 NEC Annex H 80.9. If not in fact the wholesale adoption of the unaltered language of 80.9 as local ordinance. Annex H 80.9(B) and 80.9(C) are the heart of the meaning of the trade slang term "grandfathered".

Actually the heart of grandfathering comes from our constitution. Anyway, 80.9(B) says that you don't have to update an old installation that has not been touched unless the AHJ says so. That is classic grandfathering.

80.9(C) says if you make an addition, alteration, installation, or repair you do not have to gut the building and update stuff you don't touch. What you do touch has to conform to the new code and be safe according to the AHJ. Any extension must also be compliant with the new code. The AHJ has the responsibility and can decide how much of the non-compliant old stuff that you touch will be allowed to remain as is. That is grandfathering with AHJ discretion.

 

[al hildenbrand]

I do see them as hazards.

I understand that you do. That is not the issue.

Actually the heart of grandfathering comes from our constitution.

When we (electrical folk here at this Forum talking about wiring and the Code) say grandfathering, we're not referring to history of the constitution.

Anyway, 80.9(B) says that you don't have to update an old installation that has not been touched unless the AHJ says so.

Yes. This takes the form, in most jurisdictions, by the AHJ issuing written statements that the local electrical inspector can use in the field, and can refer the party calling for inspection to. I would call them "local ordinance" although I am sure there are other terms that can be used.

Note, the person replacing a luminaire doesn't automatically determine that a hazard exists until the AHJ determines that this one luminaire replacement is safe.

Rather, the AHJ makes a ruling that existing installations of non-bonded armored cable can no longer be used for the EGC required at grounding type receptacles, luminaires, etc.

Until the local ordinance or the NEC retroactively declares an existing non-bonded armored cable installation a hazard, it is not a hazard, save that a person in the field can determine by diagnostics and/or observation.

 

[mivey]

Al,
I get your point and I think you get mine. I really can't think of anything else to add that hasn't been covered.

Thanks for the discussion.

 

[al hildenbrand]

Likewise. Thanks again for the recent info in the 2009 study on non-bonded armored cable.

 

[mivey]

Thanks again for the recent info in the 2009 study on non-bonded armored cable.

No problem. That reminds me:

But, I don't get how the AC impedance can be less than the DC resistance in the bonded cases. Once this is cleared up I should be able to calc. the microhenries per foot of the armor. This is at 60 Hz, right?

Yes it was at 60 Hz. They also noted that it was peculiar how the AC impedance was less. It is obviously much more complicated than a uniform cylindrical conductor. I read somewhere about the impedance being calculated and measured and there was a comparison of the two so there must be a model somewhere. I remember seeing a table with calculated impedance and measured impedance but I can't find it. The paper above did not have it. The paper did cite a lot of tests on the impedance testing and current handling capabilities.

FWIW, there is a typo in section 2.3 "Other Testing". It was stated the maximum current that could be continuously carried by a 15 amp fuse was 16.5 amps. They stated that the limiting resistance in a 110 volt circuit would then be 16 2/3 ohms but it should have read 6 2/3 ohms for the entire circuit.

Testing showed that the cables at the max continuous currents would experience temperatures between 115.7?F to 192.2?F but the maximum the rubber could handle without damage was 120?F. The temperature limit, not the fuse limit became the basis for the initial 1.5 ohm/100ft UL limit for #14.

There were also some notes and tables showing the voltage rise on the armor being dangerous during faults, even at normal load current levels. This was from the tests as part of this research project but I don't think they made any reference to UL tests back in the day.

It was found that the armor did not begin to glow until about 45 amps, which was above the level that even a 30 amp fuse would blow. Arcing between the armor coils was produced by running a 120 amp load through the armor and generally produced an immediate meltdown.

They did find the connections to be of minimal resistance (equivalent to less than a foot of armor) but the author does note that they did not consider aged connections (noted as a potential problem in other reports).

Tests in later years (to 1950) covering the long term heating effects under varying load and environmental conditions led them to lower the maximum allowable resistance to 0.75 ohm/100ft for #14 in the 1957 UL spec. It also made the bonding strip mandatory. The concern again was that the cables were overheating even at the rated currents listed in the 1947 NEC.

As for steel vs aluminum, the aluminum was found to result in much lower temperatures. A 1998 test was conducted at various fault levels on AC cable with conductors rated at 194?F. At a 70?F ambient for a #12 cable at 20 amps for 3 hours, the steel cable reached 264?F while the aluminum reached 180?F. At 27 amps for 1 hour (the max allowable trip time for breakers) the steel reached 360?F while the aluminum reached 246?F.