Transfo Transformer Output

[steve66]

No, it is not. Primary side only protection is permitted in the same section [240.21(C)], but only where you have no neutral on the secondary, e.g. a 3Ø three-wire delta output, no center tap; 1Ø two-wire output. 240.21(C) does not limit the number of secondary conductors... but each set or parallel sets must terminate in a single OCPD.

You mean each set must terminate with OCPD, which could be a set of fuses or circuit breakers, or a combination of both. So a single feeder could land on a 400A distribution panel, with (2) 200A breakers, and that could feed the two separate smaller panels. Code compliant, but it sure doesn't make the installation any simpler or easier or cheaper.

This is not NEC compliant.

I think it could be if installed as noted above.

This is NEC compliant, provided each panel has main OCPD.

But it is still subject to the tap rules. If the run isn't outside or under a slab, there would probably be a 25' limit on the run from the xformer to each panelboard main.

 

[david luchini]

You mean each set must terminate with OCPD, which could be a set of fuses or circuit breakers, or a combination of both. So a single feeder could land on a 400A distribution panel, with (2) 200A breakers, and that could feed the two separate smaller panels. Code compliant, but it sure doesn't make the installation any simpler or easier or cheaper.

That would violate 408.36

I think it could be if installed as noted above.

A panelboard is not the same thing as a power distribution block.

 

[Smart $]

You mean each set must terminate with OCPD, which could be a set of fuses or circuit breakers, or a combination of both. So a single feeder could land on a 400A distribution panel, with (2) 200A breakers, and that could feed the two separate smaller panels. Code compliant, but it sure doesn't make the installation any simpler or easier or cheaper.
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That would violate 408.36
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Not just 408.36, but also 240.21(C). All the options [other than (1)] require each feeder terminate in a single OCPD. Ffor the purpose of this requirement, a set of fuses, one per ungrounded line, shall be considered a single OCPD. (2) is worded a bit funky, but I have seen no indications in use that it means more than a single OCPD.

 

[Sahib]

This is not NEC compliant.

May be it is CEC compliant: OP is in Canada.

 

[steve66]

That would violate 408.36

A panelboard is not the same thing as a power distribution block.

It used to be allowed when we had a distinction between power panels and lighting panels. Now that distinction is gone, it does look like that allowance is also gone, at least for panelboards.

But I still believe this could be code compliant using a switchboard instead of a panelboard.

Not just 408.36, but also 240.21(C). All the options [other than (1)] require each feeder terminate in a single OCPD. Ffor the purpose of this requirement, a set of fuses, one per ungrounded line, shall be considered a single OCPD. (2) is worded a bit funky, but I have seen no indications in use that it means more than a single OCPD.

But 240.21(C)(3) does allow this in an industrial setting.

I also think this would be allowed in an industrial setting if full size conductors (rated for the sum of the OCPD's) were used, and one set was connected and branched off the other set. (It's not technically a "tap" if the wire size isn't being reduced.)

Again, that's probably not saving anything in terms of installation cost or labor, and it does seem like the most practical way it to just run two separate sets of conductors from the transformer itself.

 

[david luchini]

It used to be allowed when we had a distinction between power panels and lighting panels. Now that distinction is gone, it does look like that allowance is also gone, at least for panelboards.

But I still believe this could be code compliant using a switchboard instead of a panelboard.

But 240.21(C)(3) does allow this in an industrial setting.

Agreed, no problem with switchboards. I believe that 240.21(C)(2)(1)(b) will allow you to use a switchboard without a main OCPD in non-industrial settings as well.

 

[Smart $]

...
But 240.21(C)(3) does allow this in an industrial setting.
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Agreed, no problem with switchboards. I believe that 240.21(C)(2)(1)(b) will allow you to use a switchboard without a main OCPD in non-industrial settings as well.

Well, since we're being uber thorough and going industrial, we have to mention 240.92(C).

 

[steve66]

Well, since we're being uber thorough and going industrial, we have to mention 240.92(C).

I'll pretty much agree to anything if I don't have to try and figure that part out.

240.92 is supposed to give alternate means of complying with overcurrent protection. But (C) reads like its putting additional restrictions in place.

 

[Smart $]

I'll pretty much agree to anything if I don't have to try and figure that part out.

240.92 is supposed to give alternate means of complying with overcurrent protection. But (C) reads like its putting additional restrictions in place.

(C)(1)(1) and (C)(2)(2) do not seem restrictive to me. 240.92(C)(3) is par for even 240.21(C).