# 250.20(A)(2) confusion



## swimmer (Mar 19, 2011)

250.20 Alternating-Current Circuits and Systems
System grounding is the intentional connection of one conductor of an alternating-current system to the earth so as to limit elevated voltage on conductors from high voltage surges imposed by lightning, line surges, or unintentional contact with higher voltage lines and to stabilize the phase-to-ground voltage during normal operation [250.4(A)(1)].

(A) AC Systems of Less Than 50 V. Alternating-current systems that operate at less than 50 V are not required to be grounded unless:
(1) The primary exceeds 150 V to ground
(2) The primary is ungrounded

How does this pertain to doorbell, mailibu lights and sprinkler transformers in a house that is wired with old NM cable without equipment grounding conductors?

Now that I've thought about it some more, I guess the primaries for these appliance transformers are grounded via the neutral to ground rod connection back in the service panel so it doesn't matter whether or not there is an EGC.


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## Black Dog (Oct 16, 2011)

Grounded Conductor. A system or circuit conductor that is intentionally grounded.


II. System Grounding
250.20 Alternating-Current Systems to Be Grounded. Alternating-current systems shall be grounded as provided for in 250.20(A), (B), (C), or (D). Other systems shall be permitted to be grounded. If such systems are grounded, they shall comply with the applicable provisions of this article.
Informational Note:  An example of a system permitted to be grounded is a corner-grounded delta transformer connection. See 250.26(4) for conductor to be grounded.
(A) Alternating-Current Systems of Less Than 50 Volts. Alternating-current systems of less than 50 volts shall be grounded under any of the following conditions:
(1) 
Where supplied by transformers, if the transformer supply system exceeds 150 volts to ground
(2) 
Where supplied by transformers, if the transformer supply system is ungrounded
(3) 
Where installed outside as overhead conductors

250.26 Conductor to Be Grounded — Alternating-Current Systems. For ac premises wiring systems, the conductor to be grounded shall be as specified in the following:
(1) 
Single-phase, 2-wire — one conductor
(2) 
Single-phase, 3-wire — the neutral conductor
(3) 
Multiphase systems having one wire common to all phases — the neutral conductor
(4) 
Multiphase systems where one phase is grounded — one phase conductor
(5) 
Multiphase systems in which one phase is used as in (2) — the neutral conductor


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## Black Dog (Oct 16, 2011)

Sorry I cannot edit that, anyhow they are talking about the 'grounded conductor'.


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## bkmichael65 (Mar 25, 2013)

swimmer said:


> 250.20 Alternating-Current Circuits and Systems
> System grounding is the intentional connection of one conductor of an alternating-current system to the earth so as to limit elevated voltage on conductors from high voltage surges imposed by lightning, line surges, or unintentional contact with higher voltage lines and to stabilize the phase-to-ground voltage during normal operation [250.4(A)(1)].
> 
> (A) AC Systems of Less Than 50 V. Alternating-current systems that operate at less than 50 V are not required to be grounded unless:
> ...


The primaries are also only going to be 120 volts L-G


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## Dennis Alwon (May 9, 2009)

Black Dog said:


> Sorry I cannot edit that, anyhow they are talking about the 'grounded conductor'.


I don't think so Harry. The title is System grounding


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## RIVETER (Sep 26, 2009)

swimmer said:


> [Now that I've thought about it some more, I guess the primaries for these appliance transformers are grounded via the neutral to ground rod connection back in the service panel so it doesn't matter whether or not there is an EGC.]


 If the transformer were HOUSED inside of, or ATTACHED to a metal box do you not think it requires an EGC with the feed?:thumbsup:


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## Black Dog (Oct 16, 2011)

Dennis Alwon said:


> I don't think so Harry. The title is System grounding


And---where are they talking about the grounding conductor?

II. System Grounding
250.20 Alternating-Current Systems to Be Grounded. Alternating-current systems shall be grounded as provided for in 250.20(A), (B), (C), or (D). Other systems shall be permitted to be grounded. If such systems are grounded, they shall comply with the applicable provisions of this article.


Informational Note:  An example of a system permitted to be grounded is a corner-grounded delta transformer connection. See 250.26(4) for conductor to be grounded.


250.26 Conductor to Be Grounded — Alternating-Current Systems. For ac premises wiring systems, the conductor to be grounded shall be as specified in the following:
(1) 
Single-phase, 2-wire — one conductor
(2) 
Single-phase, 3-wire — the neutral conductor
(3) 
Multiphase systems having one wire common to all phases — the neutral conductor
(4) 
Multiphase systems where one phase is grounded — one phase conductor
(5) 
Multiphase systems in which one phase is used as in (2) — the neutral conductor .




I think the title should be changed to "Grounded Systems".....


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## chicken steve (Mar 22, 2011)

Old unground*ING* _(no 3rd bare cu) _NM are grandfathered , as long as it is>>>

A) installed to the NEC of the time

B)not added to, altered , modified , etc

C) not a life safety issue (nfpa 101)

~CS~


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## swimmer (Mar 19, 2011)

RIVETER said:


> If the transformer were HOUSED inside of, or ATTACHED to a metal box do you not think it requires an EGC with the feed?:thumbsup:


A house wired in NM without EGC with a metal box would never have been code compliant and is out of the scope of my question.


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## chicken steve (Mar 22, 2011)

swimmer said:


> A house wired in NM without EGC with a metal box would never have been code compliant and is out of the scope of my question.


Originally , an egc 3rd wire was seen as a lethal path and shunned by most in the field. The _'Boston Backwrap_' debuted shortly afterwards, along with groundING capable devicings.

No , it's not '14 compliant , yes it is '62 or so gfathered , you can even purchase non groundING receptacle outlets to this day

~CS~


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## Dennis Alwon (May 9, 2009)

Black Dog said:


> And---where are they talking about the grounding conductor?
> 
> II. System Grounding
> 250.20 Alternating-Current Systems to Be Grounded. Alternating-current systems shall be grounded as provided for in 250.20(A), (B), (C), or (D). Other systems shall be permitted to be grounded. If such systems are grounded, they shall comply with the applicable provisions of this article.
> ...



250.26 is talking about a grounded conductor but not 250.20


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## Black Dog (Oct 16, 2011)

Dennis Alwon said:


> 250.26 is talking about a grounded conductor but not 250.20



Then why is the Informational Note taking you there?




Informational Note:  An example of a system permitted to be grounded is a corner-grounded delta transformer connection. See 250.26(4) for conductor to be grounded.


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## Dennis Alwon (May 9, 2009)

Black Dog said:


> Then why is the Informational Note taking you there?
> 
> 
> 
> ...


Harry, I apologize. I believe you are correct. I am doing too many things at once here at home. Got a new surface pro 3 so I am jumping back and forth between the forums and getting all the downloads on the pro-- not reading carefully enough. :thumbsup:


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## Black Dog (Oct 16, 2011)

Dennis Alwon said:


> Harry, I apologize. I believe you are correct. I am doing too many things at once here at home. Got a new surface pro 3 so I am jumping back and forth between the forums and getting all the downloads on the pro-- not reading carefully enough. :thumbsup:


Lol Dennis --- I knew I had brain that works sometimes...:laughing:


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