200.3

[hurk27]

Just something I stumbled across when looking up something else.

200.3 Connection to Grounded System.
Premises wiring shall not be electrically connected to a supply system unless the latter contains, for any grounded conductor of the interior system, a corresponding conductor that is grounded. For the purpose of this section, electrically connected shall mean connected so as to be capable of carrying current, as distinguished from connection through electromagnetic induction.


From what I'm reading is this is saying that if we have a building that is supplyed by a ungrounded delta we are not allowed to use a transfomer to step off and feed for 120 volts?
This almost says that the service must supply the neutral if we are going to require a neutral in the building? And even sound's like even a zig-zag wouldn't be allowed.

What am I missing?

 

[Ed MacLaren]

Re: 200.3

There is no current flow between the primary and secondary of a transformer, other than an auto-transformer.

The primary and secondary are coupled by electromagnetic induction.

Ed

 

[al hildenbrand]

Re: 200.3

Wayne,

Take a look at the definition of Premises Wiring (System) in Article 100. Specifically,

extends from the service point or source of power, such as a battery, a solar photovoltaic system, or a generator, transformer, or converter windings, to the outlet(s).

The situation you describe in your question has two supplies. The first is the supply from the ungrounded delta, which, if connected to a wiring system that has no grounded conductor, satisfies 200.3. This ungrounded system ends in the magnetic core of the transformer the supplies the next system.

The second supply is from the transformer that has a conductor on its secondary side that is grounded. The transformer secondary is the supply to the next wiring system. If that wiring system uses a grounded conductor then, again, IMO 200.3 is satisfied.

 

[hurk27]

Re: 200.3

Thank's Al
Now I see it. It just sounded like that if we had a building that required both a 240 delta source and neutral loads we would have to install another service to feed those neutral loads. So as long as the first system is a delta to delta, Then we install a separately derived system to feed the neutral loads then all is well as per 200.3

I just seen that last night when I should of been in bed. LOL