what exactly is meant by Engineering Supervision in the NEC

[mshields]

Paragraph 310.10(H) allows parallel conductors down to 1/0. The second exception to this permits #2's and #1's to be paralleled under Engineering Supervision AND only in existing installations.

So actually I have two questions. I'm a PE, if I choose to use #2's and stamp the drawing, does that meet the intent of this code requirement.

Also, does the "existing installation" part mean that your pulling the cable in existing conduit OR could it mean that due to space constraints say, it was advantageous to use 2 sets of the smaller conductors and therefore 2 small conduits rather than a single larger conduit with say, a single set of 250kcmil conductors?

 

[dkidd]

Informational Note to Exception No. 2: Exception No. 2 can be
used to alleviate overheating of neutral conductors in existing
installations due to high content of triplen harmonic currents.

 

[ggunn]

Paragraph 310.10(H) allows parallel conductors down to 1/0. The second exception to this permits #2's and #1's to be paralleled under Engineering Supervision AND only in existing installations.

So actually I have two questions. I'm a PE, if I choose to use #2's and stamp the drawing, does that meet the intent of this code requirement.

Probably, if your PE license regs allow you to stamp electrical. It means that should anything go wrong it's all on you. Are you covered by insurance for any damage that could possibly result from your decision?

 

[charlie b]

Mike, to your first question my answer would be yes. It would meet the intent because of the presumption that, as a PE, you would have done your homework and assured yourself that the installation would have been safe.

To your second question my response would be to suggest you read that exception more carefully. It only allows the smaller wire to be used for the grounded neutral conductors, not for the ungrounded phase conductors. That is why the informational note quoted by dkidd makes sense.

 

[GoldDigger]

To your second question my response would be to suggest you read that exception more carefully. It only allows the smaller wire to be used for the grounded neutral conductors, not for the ungrounded phase conductors. That is why the informational note quoted by dkidd makes sense.

And just to make it perfectly explicit, the existing circuit is just that. Wires in place not just the raceway.
And the existing reduced neutral turns out to be too small now.
So instead of pulling it out and/or a adding a single full sized neutral you can add another reduced neutral in parallel with the first.

 

[dkidd]

Attempts to add a definition of Engineering Supervision failed in 2008 and 2011 cycles because agreement could not be reached on a definition.

 

[ron]

240.86(A) for series ratings expands a little to include "engage primarily in the design or maintenance of electrical installations", then adds that it needs to be stamped.

 

[charlie b]

I am somewhat involved in supporting code development for the City of Seattle. They are revising phrases like "under engineering supervision" or "licensed professional engineer/architect" to read closer to "design professional."

 

[mivey]

I am somewhat involved in supporting code development for the City of Seattle. They are revising phrases like "under engineering supervision" or "licensed professional engineer/architect" to read closer to "design professional."

Why don't they just make it "party accepting responsibility"?:roll: