Sam,
Did you spend a lot of time talking with Bennie when he was here
?
Oh man, as bad as I can be at times, as much as I loved Bennie's enthusiasm and grit, I'm no match. He was certainly something to be reconed with at times. Rest his soul.
It is the intent of the code that if the secondary of the transformer does not have a circuit conductor that is common to both the primary and the secondary it is a SDS.
Then why in the world doesn't the definition say that? It in fact says the opposite. Here's a definition of derived:
de⋅rive /dɪˈraɪv/ Show Spelled Pronunciation [di-rahyv] Show IPA verb, -rived, -riv⋅ing.
–verb (used with object)
1. to receive or obtain from a source or origin (usually fol. by from).
2. to trace from a source or origin.
3. to reach or obtain by reasoning; deduce; infer.
4. Chemistry. to produce or obtain (a substance) from another.
–verb (used without object)
5. to come from a source or origin; originate (often fol. by from).
Add seperately to that.
I admit that I don't have a lot of experience with SDS's but I do know English pretty well (I mean good :grin
.
In general all transformers other than autotransformers are SDS per the NEC.
Well, OK, but where in the NEC is this put forth and why does it differ, at least as far as I can figure, from Article 100? We both know how nearly unchangeable this article is, therefore, you might think it's a really, really important article.
I do agree that the SDS definition in Article 100 could use some work or a FPN to make it easier to understand. Maybe a FPN along the lines of the handbook commentary for that definition.
I think it would be better to remove the word derived rather than explain that that isn't what is meant sometimes in an FPN.
Bennie's point was that there is a grounding connection between the primary and the secondary and therefore a transformer is not SDS. The grounding connection is not a circuit conductor.
I agree with you there, the whole universe is basically grounded, or it at least is supposed to be.