3 prongs configured with ground in 2 wire system?

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Re: 3 prongs configured with ground in 2 wire system?

[/QUOTE]Also make sure that when inspecting older homes that have BX type wiring method, The BX is not used as an equipment ground. This does not include the newer type of BX that has the flat grounding conductor run inside of it, this is legal for grounding, but the older stuff that will only have the current carrying conductors with no extra grounding conductor in it and is not allowed to be used as a ground. Very dangerous as if a ground fault was to occur the casing can heat up like a heating element and cause a fire. Many have changed out 2-prong receptacles with this type of BX and I find it all the time in older houses. A very common over look.

My inspector allowes the old type metel BX jacket to be used for the EGC. I told him about this quote. He wants to know if you can site the NEC section to back up your quote.
 
Re: 3 prongs configured with ground in 2 wire system?

Originally posted by 110.12:
My inspector allowes the old type metel BX jacket to be used for the EGC. I told him about this quote. He wants to know if you can site the NEC section to back up your quote.
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250.118

Old "BX" or AC as it is properly called is not in the list of approved EGCs.

You may say that 250.118(9) permits it but that is talking about AC constructed per 320.100.
 
Re: 3 prongs configured with ground in 2 wire system?

I didn't see anything in 250.118(9)that it's refering to 320.100.
 
Re: 3 prongs configured with ground in 2 wire system?

250.118 (8) in the 2005 refering to 320.108
this is refering to the newer AC with a shorting wire inside the cable.
 
Re: 3 prongs configured with ground in 2 wire system?

Originally posted by 110.12:
I didn't see anything in 250.118(9)that it's refering to 320.100.
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You got me there. :roll:

What you see is "Armor of Type AC cable as provided in 320.108."

Then if you take a look at 320.108

320.108 Equipment Grounding.
Type AC cable shall provide an adequate path for equipment grounding as required by 250.4(A)(5) or 250.4(B)(4).
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Fine so far, however in order to be an adequate path for equipment grounding the AC must be constructed as per 320.100


320.100 Construction.
Type AC cable shall have an armor of flexible metal tape and shall have an internal bonding strip of copper or aluminum in intimate contact with the armor for its entire length.
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Without the bonding strip during a short circuit the armor will very likely become a red hot heating element.
 
Re: 3 prongs configured with ground in 2 wire system?

250.118- The Egc run with or"ENCLOSING" the circuit conductors SHALL be one or more or combination of-
 
Re: 3 prongs configured with ground in 2 wire system?

Originally posted by 110.12:
250.118- The Egc run with or"ENCLOSING" the circuit conductors SHALL be one or more or combination of-
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I am missing your point here.
 
Re: 3 prongs configured with ground in 2 wire system?

Just what it says. The EGC can be run with or ENCLOSE the circut conductors or a combination
 
Re: 3 prongs configured with ground in 2 wire system?

Originally posted by 110.12:
Just what it says. The EGC can be run with or ENCLOSE the circut conductors or a combination
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Yes

250.118 Types of Equipment Grounding Conductors.
The equipment grounding conductor run with or enclosing the circuit conductors shall be one or more or a combination of the following:
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Run with or enclosing it still has to be one or more of the items listed.
 
Re: 3 prongs configured with ground in 2 wire system?

Originally posted by 110.12:
250.118(9)
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Your making a great circle. :p

Yes AC as described in the same year NEC.

But hey what the heck do I know? :roll:

If you are comfortable using BX as a grounding means have a great time.

Personally I feel better not leaving fire starters behind. :eek:
 
Re: 3 prongs configured with ground in 2 wire system?

Originally posted by 110.12:
250.118(9)
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Now read 320.100 construction specs.

the older BX type cable does not meet these requirements.
 
Re: 3 prongs configured with ground in 2 wire system?

Originally posted by 110.12:
Would the NEC allow fire starters??
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It does not.

That is why the old BX is not an approved EGC.

Can you restart the circle now? :D
 
Re: 3 prongs configured with ground in 2 wire system?

320.100 is the construction of type AC cable in the year 2005 new work not 1951.
 
Re: 3 prongs configured with ground in 2 wire system?

Originally posted by 110.12:
My inspector allowes the old type metel BX jacket to be used for the EGC.
Click to expand...
You didnt say "to be left if it was previously installed"
 
Re: 3 prongs configured with ground in 2 wire system?

I'm talking about in old work useing the jacket of the ac thats there as the egc to ground boxes and outlets.
 
Re: 3 prongs configured with ground in 2 wire system?

Originally posted by 110.12:
320.100 is the construction of type AC cable in the year 2005 new work not 1951.
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You bet ya. :)

And 250.118 is the rule for now for 2005.

If the circuit in question was originally feeding two wire receptacles then you come along and install a 3 wire receptacle intending the BX to now be a grounding means IMO you have created a violation of todays NEC.

Leave it feeding two wire receptacles and it is as fine as knob and tube. :p
 
Re: 3 prongs configured with ground in 2 wire system?

JB, you are right in principle, but the amount of current through your bod would be miniscule if the neutral exhibited low resistance, say 0.1 Ohm back to the panel.

I would suggest that the conduit was floating, and someone wired the line to the EGC screw. Something must have been wrong if you were called to investigate.

I have felt 48Vdc with dry hands, but I see no way you would be shocked by 1 or 2 volts relative to ground.
 
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