"Phase or line and system" 210.5

[hurk27]

The only system that would not be separately derived is an autotransformer, as it is not isolating, many buck/boost transformers are configured as such.

To add to the above statement I should add this was in line with the OP talking about transformers, of course a generator that does not have a switched neutral is not an SDS as per the definition in the NEC.

 

[jusme123]

3 Systems

But only two voltage systems.

whos on first

 

[jusme123]

Let's say there's 3 systems.

What means of identification do you use for the two 120/208v systems?

panel numbers

 

[roger]

IMO there are only two voltage systems present but there are three different sources for these two systems.

If you have two chocolate bars and a peppermint candy cane in a bowl you have three pieces of candy but how many flavors do you have?

Roger

 

[chris kennedy]

If you have two chocolate bars and a peppermint candy cane in a bowl you have three pieces of candy but how many flavors do you have?

Roger

Your not dipping into the Halloween candy already are you? Save some for the kids Roger.

 

[jusme123]

IMO there are only two voltage systems present but there are three different sources for these two systems.

If you have two chocolate bars and a peppermint candy cane in a bowl you have three pieces of candy but how many flavors do you have?

Roger

mail a pound of each to me and I'll let you know

 

[roger]

Your not dipping into the Halloween candy already are you? Save some for the kids Roger.

Actually, I must confess that is what gave me the idea for my analogy.

Roger

 

[roger]

mail a pound of each to me and I'll let you know

On it's way.

Roger

 

[chris kennedy]

Here's another point, if we are to say that any system is not a SDS if the secondary is bonded to the building or grounding that is electrically connected to the supplying system's grounded conductor, then much of 250.30 could not even be used, as soon as you bond the secondary, 250.30 would not apply?

Interesting thought.

 

[charlie b]

How many systems are present?

I don't understand the context of the question. What I mean is I don't see what might change, if the answer were 2, instead of 3. Where in the code does it say that if you have two systems you must do this, but if you have three or more you can do this instead?

 

[hurk27]

i don't understand the context of the question. What i mean is i don't see what might change, if the answer were 2, instead of 3. where in the code does it say that if you have two systems you must do this, but if you have three or more you can do this instead?

210.5(c)..........

I guess the question is if you have two systems of the same voltage rating does it have to identified as differant systems, I think it does as the wording in 210.5(C) seems it can be read both ways (see post 17).

 

[roger]

210.5(c)..........

I guess the question is if you have two systems of the same voltage rating does it have to identified as differant systems, I think it does as the wording in 210.5(C) seems it can be read both ways (see post 17).

So, if I am wiring a hospital, shopping center, school, etc... with say 50 dry type transformers with 208y/120 volt secondaries I have to label 50 different systems for this voltage?

The 208y/120 volt in the particular facility is one nominal voltage regardless of the number of sources supplying it.

Roger

 

[billyzee]

2

2

If system means separately derived system then I vote 2. Becuase a SDS is a premises wiring system not a service.

 

[Barndog]

So, if I am wiring a hospital, shopping center, school, etc... with say 50 dry type transformers with 208y/120 volt secondaries I have to label 50 different systems for this voltage?

The 208y/120 volt in the particular facility is one nominal voltage regardless of the number of sources supplying it.

Roger

Then building i work at has a transformer for most of our 208/120 in the building. which would equal about 30 transformers. So i say there is 2 systems in the post. we have 3 here (12470, 480/277, 208/120)

 

[charlie b]

The 208y/120 volt in the particular facility is one nominal voltage regardless of the number of sources supplying it.

Agreed. And I don't see anything in 210.5(C) that says each time you derive a new 208Y/120 SDS with another transformer, you need to create yet another marking scheme. The entire point of 210.5(C), IMHO at least, is that when you open a junction box and see a black wire, or an orange wire, or a red wire, or whatever, you know whether you are dealing with 208/120 or dealing with 480/277 or dealing with some other nominal voltage level. For example, the "Restricted Approach Boundary" is different for a 208 versus a 480. But it is the same, regardless of which transformer the 208 came from.

 

[hurk27]

210.4(D) was originally aimed toward multi-wire circuits prier to the 2005 code change, when it was moved from 210.4(D) to 210.5(C) and reworded with the removal of the multi-wire reference.

I'm not sure the reason for the change but with the addition of the disconnect requirement for multi-wire circuits I would have thought it was no longer needed.

But then I feel the requirment of disconnects for multi-wire circuits is not needed.:roll:

 

[hurk27]

Ok after reading the many proposals for the 2005, and the CMP comments, I am so cornfused

It's like their saying one voltage is safer then the other?
The submitter for:
2-30 Log #2788 NEC-P02
(210-5(C) (New) )
Proposal is says seeing a brown color wire should be a warning, like seeing a black wire is less dangerous?

But the color part of the proposal was rejected, as was some of the requirements to identify the neutral of a multi-wire circuit which can be just as dangerous, but the decision to remove 210.4(D) and create 210.5(C) was accepted with the removal of the multi-wire language.

So from what I can get out of all this, is the intent of making sure an electrician will know where to shut all the power off to the area (such as a junction box) that he is working in, IMHO 210.5(C) does not address this, as even with one nominal voltage, he/she will still not know where each circuit is fed from or from which panel supplying it.

If this is the true intent, then the only requirement that would achieve this level of safety would be a requirement of marking each access point or termination with the info of where they are supplied from such as I mention in post 20. as others have said also we always mark our junction box's with this info.

IMHO codes like 210.5(C) send the wrong message to many who do not understand that 120 volts can be just as dangerous as 277, the the NEC should not be conveying this message.

 

[George Stolz]

It does seem bizarre to me that color matters much, as so much more pertinent info can be written on the conduit and boxes than can be indicated at the terminations as the code requires.

So, if I am wiring a hospital, shopping center, school, etc... with say 50 dry type transformers with 208y/120 volt secondaries I have to label 50 different systems for this voltage?

See, that's just it, it looks that way at first glance. But even in the original example, trying to find different colors for just three "systems" would be prohibitive.

 

[hurk27]

It does seem bizarre to me that color matters much, as so much more pertinent info can be written on the conduit and boxes than can be indicated at the terminations as the code requires.


See, that's just it, it looks that way at first glance. But even in the original example, trying to find different colors for just three "systems" would be prohibitive.

That is why the CMP's of panel 2 did not accept any colors as the only way to identify the conductors, tags, tape, color wires, stripes on the wires, numbers codes, letter codes, Etc... all these can be used, one of the comments by the panel was "restricting to a set color standard would be too restricting to installations"

Most of the proposals were made to try to get the BOY and BRB color standard back into the code again, this is what was rejected.

 

[charlie b]

So from what I can get out of all this, is the intent of making sure an electrician will know where to shut all the power off to the area (such as a junction box) that he is working in, IMHO 210.5(C) does not address this, as even with one nominal voltage, he/she will still not know where each circuit is fed from or from which panel supplying it.

Agreed. That is why I interpret the requirement as letting the electrician know if he or she is dealing with 120 or 480.

IMHO codes like 210.5(C) send the wrong message to many who do not understand that 120 volts can be just as dangerous as 277, the the NEC should not be conveying this message.

Yes, both are dangerous. But we do treat them differently (e.g., working clearances and the "prohibited approach zone" are different). So there is some value in knowing which you are looking at, when you open a box.