The manufactures of modular furniture that I see often specify 15 amp OCPDs.

However I find most engineers are unaware of this or choose to ignore it. [Linked Image]

OK I will give this a whirl

IMO you have 8 current carrying conductors.

Quote
310.15(B)(2)(c)On a 4-wire, 3-phase wye circuit where the major portion of the load consists of nonlinear loads, harmonic currents are present in the neutral conductor; the neutral shall therefore be considered a current-carrying conductor.

That is assuming the work stations have PCs, the pencil sharpeners, desk lamps etc. are just a small portion of the load.

I do not know of any NEC requirement to up size the neutral although it makes good sense considering the furniture whip will probably have a 10 AWG grounded conductor? (For extra credit is it a grounded conductor before we connect it to the branch circuit or is just the white wire? [Linked Image])

8 Current Carring Conductors, Table 310.15(B)(2)(a) shows a 70% for 7 - 9 CCCs

Table 310.16 shows 12 AWG Copper THHN rated at 30 amps.

30 x .7 = 21 amps

Table 310.16 shows 10 AWG Copper THHN rated at 40 amps.

40 x .7 = 28 amps

Seems both the 12 AWGs and the 10 AWGs are still rated high enough to use 20 amp breakers.

  • Is this NEC compliant? Yes
  • Will it work? Sure
  • Is this a Design Issue? The use of 10 AWG for the grounded conductor was a design choice
  • Does this example make sense? To me, yes, I deal with this exact situation often. [Linked Image]
  • Will the Penguin escape once again?
Probably......Batman is a major wuss [Linked Image]

Bob




[This message has been edited by iwire (edited 09-25-2004).]

Bob Badger
Construction & Maintenance Electrician
Massachusetts