Grounded conductor required at sub panel?

[rkoeber]

Here's my situation: I have a 277/480Y (solidly grounded) distribution panel, which I need to run a feeder from - to a 3? sub panel. The sub panel will only have 3? loads and 3 pole breakers and will never have any 277V loads. To save money I want to use 277/480Y slash rated breakers in the sub panel and also for cost I don't want to run grounded conductor to the sub panel (since it will not be used).

My questions are:
1. Do I have to pull a grounded conductor to the sub panel or can I eliminate it?
2. If I don't have to pull the grounded conductor, can I still use the slash rated breakers?

Here's what I've found so far (all from the 2011 NEC):

240.85 tells me that if the max voltage to ground is not over 277V then a slash rated breaker is acceptable (regardless of the presence of a grounded conductor in the panel or not because the sub panel is still a 277/480Y solidly grounded system).

215.2(A)(2) tells me that a feeder grounded circuit conductor must not be smaller than required by 250.122 (equipment grounding conductor size), but I beleive this applies only where the grounded circuit conductor is present - not a mandate that every feeder have a GCC.

Thanks in advance for the help.

 

[Dennis Alwon]

You do not have to run a grounded conductor although it limits the panel for future use. If you do run one it can be sized as small as the equipment grounding conductor.

I don't see any reason why you cannot use the slash breaker

 

[augie47]

FWIW, I concur with Dennis.

 

[rkoeber]

Thanks for the help. I assume there is no code refence that specifically says I don't need the grounded conductor, rather its a case of the code not saying explicitly that I do need it.

 

[Dennis Alwon]

Thanks for the help. I assume there is no code refence that specifically says I don't need the grounded conductor, rather its a case of the code not saying explicitly that I do need it.

That is correct. If the equipment does not need a grounded conductor then there is no need for one

 

[rkoeber]

while searching for some info on a obsolete breaker, I ran into a reference to UL67 which says something to the effect:
for a grounded 277/480Y where the grounded conductor is not carried to the panel, the manufacturer must label the panel 480Y/277 3 phase 3 wire. So if I do what I had intended I can't use a standard 480Y/277 3 phase 4 wire panel and just not land a neutral on the neutral bus.

though you all might like to know for future reference.

 

[Dennis Alwon]

while searching for some info on a obsolete breaker, I ran into a reference to UL67 which says something to the effect:
for a grounded 277/480Y where the grounded conductor is not carried to the panel, the manufacturer must label the panel 480Y/277 3 phase 3 wire. So if I do what I had intended I can't use a standard 480Y/277 3 phase 4 wire panel and just not land a neutral on the neutral bus.

though you all might like to know for future reference.

Well that is interesting however I bet that gets overlooked all the time. Why would that really matter- IDK

 

[hardworkingstiff]

Well that is interesting however I bet that gets overlooked all the time. Why would that really matter- IDK

I would think most AHJs would accept a permanent label one the panel installed by the EC that says the grounded conductor is not present. They might want you to remove the neutral bar, I would .

 

[jumper]

while searching for some info on a obsolete breaker, I ran into a reference to UL67 which says something to the effect:
for a grounded 277/480Y where the grounded conductor is not carried to the panel, the manufacturer must label the panel 480Y/277 3 phase 3 wire. So if I do what I had intended I can't use a standard 480Y/277 3 phase 4 wire panel and just not land a neutral on the neutral bus.

though you all might like to know for future reference.

I did a quick search and could not find that information.

This site on UL panel board marking seems to say that if a neutral buss/connection is not installed that it must be marked with the information/part numbers for installing it.

http://www.ul.com/global/documents/...newsletters/PanelboardsMG_March2006_Final.pdf

NEC section 408.58 does not seem to require the neutral information either.

408.58 Panelboard Marking. Panelboards shall be durably
marked by the manufacturer with the voltage and the
current rating and the number of phases for which they are
designed and with the manufacturer?s name or trademark in
such a manner so as to be visible after installation, without
disturbing the interior parts or wiring.

 

[ramonb.usaraga]

Grounded conductor required at sub-panel

Grounded conductor required at sub-panel

As for my opinion, you have to pull a GC but as an Equipment grounding conductor. The purpose of the EGC is to minimize the induction effect of the circuit due to its related displacement angle. If we are talking about supplementary grounding conductor, you have to bond this directly from sub-panel to the grid.

 

[Dennis Alwon]

As for my opinion, you have to pull a GC but as an Equipment grounding conductor. The purpose of the EGC is to minimize the induction effect of the circuit due to its related displacement angle. If we are talking about supplementary grounding conductor, you have to bond this directly from sub-panel to the grid.

If the conduit is metallic then no equipment grounding conductor is required. A grounded conductor is a different animal and is not necessary to be installed except at the service according to 250.24(C).

 

[kwired]

I would think most AHJs would accept a permanent label one the panel installed by the EC that says the grounded conductor is not present. They might want you to remove the neutral bar, I would .

I have simply installed the bonding jumper and used the neutral assembly as a place to land equipment grounding conductors.
Labels indicating there is no grounded conductor are acceptable but not required.

The purpose of the EGC is to minimize the induction effect of the circuit due to its related displacement angle. If we are talking about supplementary grounding conductor, you have to bond this directly from sub-panel to the grid.

The purpose of an equipment grounding conductor is to provide a low impedance path from non current carrying metal components should they come in contact with an ungrounded conductor so that overcurrent protection will open the circuit quickly.

Induction effects are minimized by keeping all conductors of a circuit in close proximity so their opposing effects cancel one another.