277v switch loop

[somebadcarma]

I'm new so be gentle. My question is about grouping of conductors. The system is 277/480 wye. I have a lighting control panel next to a lighting panel, can the switch loops to the control relays be run without the grounded conductor in the switch loop conduit ( EMT)? Looking at 300.20 I think the answer is no, but I'm really not sure. In the old half of the building I'm in (1996) the grounded conductors are in the switch loop conduit, in the newer part of the building (2008) the grounded conductor is not in the switch loop conduit.

 

[infinity]

I've heard it argued both ways as being required or not required. I don't see why it's necessary when I can run a switch loop to a switch with only two conductors and no neutral. The two conductor switch loop cancels any induced current your setup would do the same.

 

[kwired]

For the purposes of 300.20, the grounded conductor (neutral) is required to be in the same raceway or cable if ferrous raceway or (ferrous) metal sheathed cable when a grounded conductor is in use.

Whether a grounded conductor must be installed whether used or not is more of a 404.2(C) issue.

 

[hbiss]

I agree with Infinity.

300.20 Induced Currents in Ferrous Metal
Enclosures or Ferrous Metal Raceways
(A) Conductors Grouped Together. Where conductors
carrying alternating current are installed in ferrous metal enclosures
or ferrous metal raceways, they shall be arranged so
as to avoid heating the surrounding ferrous metal by induction.
To accomplish this, all phase conductors and, where
used, the grounded conductor and all equipment grounding
conductors shall be grouped together.

The grounded conductor is not required for the switch loop.

404.2(C) requires a neutral be provided at wall switch locations to power electronic lighting control devices like dimmers and motion sensors that previously relied on the equipment ground that is not supposed to be used as a current carrying conductor. Not only does it have nothing to do with 300.20, many times the neutral will sit there unused with no current passing through it.

-Hal

 

[infinity]

For the purposes of 300.20, the grounded conductor (neutral) is required to be in the same raceway or cable if ferrous raceway or (ferrous) metal sheathed cable when a grounded conductor is in use.

Whether a grounded conductor must be installed whether used or not is more of a 404.2(C) issue.

I this case since he has a raceway so 404.2(C) is not applicable.

As Hal mentioned the words "where used" which seems to be the sticking point for some who argue that the neutral must be looped through the control panel. I thought about writing a PI for clarify this but couldn't come up with clear enough wording to cover every scenario. I've seen neutrals just looped through 30 amp disconnect switches which to me is simply dumb. Dimming panel code compliant?

 

[jaggedben]

... I've seen neutrals just looped through 30 amp disconnect switches which to me is simply dumb. ...

Yup, dumb. I have struggled on occasion to remain diplomatic with AHJ's that require that.

 

[kwired]

I this case since he has a raceway so 404.2(C) is not applicable.

As Hal mentioned the words "where used" which seems to be the sticking point for some who argue that the neutral must be looped through the control panel. I thought about writing a PI for clarify this but couldn't come up with clear enough wording to cover every scenario. I've seen neutrals just looped through 30 amp disconnect switches which to me is simply dumb. Dimming panel code compliant?

View attachment 20694

with lighting control panel neutral probably not necessary unless there would be a system out there that for some reason needs neutrals from the switched circuits. Otherwise doesn't the control panel already have it's own separate control power from the switched circuits? Is written vaguely enough I suppose there can be confusion but I don't see the need for neutrals with the switch loops.

For switch loops in raceway that may someday require a neutral to the switching device - you do need to have enough room in the raceway to pull that neutral according to (C)(1) though.