300.3

Status
Not open for further replies.

c_picard

Senior Member
Location
USA
Hi,
I've seen as common practice when backfeeding a PV breaker in a service panel, when an outside utility disconnect is also required, installing a Type "T" conduit body and sending Line 1 and Line 2 out to the disco as a switch loop.

Seems like this violates 300.3? There really shouldn't be inductive heating, as inverter outputs are balanced and there is no current on the grounded conductor anyhow. Also, the hot conductors back and forth in the same conduit would cancel each other anyhow?

The short version of the question...Is the grounded conductor required to be present at a switch/disconnect?

Thanks for any input
 

iwire

Moderator
Staff member
Location
Massachusetts
The short answer is that electrically this is just like any switch leg, the current going out will always match the current coming back so there is no issue at all.

As far as the code.

300.3 Conductors.

(B) Conductors of the Same Circuit. All conductors of
the same circuit and, where used, the grounded conductor
and all equipment grounding conductors and bonding conductors
shall be contained within the same raceway, auxiliary
gutter, cable tray, cablebus assembly, trench, cable, or
cord, unless otherwise permitted in accordance with
300.3(B)(1) through (B)(4).

If the neutral is not used it does not have to go along.
 
Last edited:

c_picard

Senior Member
Location
USA
Indeed, that's how I read it as well. Unfortunately for me, those whose have a bit more say see it differently, they're saying the grounded conductor is used(in the circuit) so must be present. So I'll need to start pulling a loop of white wire into the disconnect, unspliced, really just for show as far as I can tell. A side effect is that we'll have to start up-sizing conduit and swapping the T out for a j-box...more fittings, more time...more work,..more cost.
 

Smart $

Esteemed Member
Location
Ohio
... when an outside utility disconnect is also required...
This part has me a bit puzzled. Are you saying the POCO is requiring an outside disconnect for the PV system?

If you are backfeeding a service panel that is inside, the service disconnect would also be inside, in the panel, and a redundant PV system disconnect outside...???

Is the inverter inside or outside?.
 

iwire

Moderator
Staff member
Location
Massachusetts
In my area the power company requires an externally mounted disconnect that has 'visible break' and disconnects the inverter from the service.

In most cases the 'visible break' requirement means even if the inverter is outdoors and has a built in disconnect you will still have to add a safety switch between the inverter and the panel.
 

Smart $

Esteemed Member
Location
Ohio
In my area the power company requires an externally mounted disconnect that has 'visible break' and disconnects the inverter from the service.

In most cases the 'visible break' requirement means even if the inverter is outdoors and has a built in disconnect you will still have to add a safety switch between the inverter and the panel.
I understand what you've explained... but the OP said the PV system is backfed into the service panel while the inverter "feeders" are T'd and run outside. That would mean the service disconnecting means is inside. Seems strange they'd want the PV system disconnect outside while the service disconnect is inside...???

And if the inverter is outside, why not put the "vis-a-break" disconnect where the inverter output conductors enter the building, since one is required there anyway?
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
We discussed the 300.3 issue more generally in this thread. My conclusion is that a grounded conductor is not required to be run to the switch, (and any inspector who thinks otherwise is confused, and hopefully you can explain that to them).

The same goes for a meter, I've run into that situation as well.

Seems strange they'd want the PV system disconnect outside while the service disconnect is inside...???

I agree the reasons are rather opaque. I shared some speculations here.

And if the inverter is outside, why not put the "vis-a-break" disconnect where the inverter output conductors enter the building, since one is required there anyway?
That would be fine. The 'T' situation typically arises when the service disconnect is inside (or behind a fence with a dog in the yard. no joke)
 

iwire

Moderator
Staff member
Location
Massachusetts
the OP said the PV system is backfed into the service panel while the inverter "feeders" are T'd and run outside. That would mean the service disconnecting means is inside. Seems strange they'd want the PV system disconnect outside while the service disconnect is inside...???

Strange? Yes.

A typical situation around here? Yes.

And if the inverter is outside, why not put the "vis-a-break" disconnect where the inverter output conductors enter the building, since one is required there anyway?

I will find the document from the power company for co-generation requirements ........ it is only about 100 pages. :roll:

The basic attitude I was getting from the power company about these installations was this.

'Solar is dangerous, we really don't want to let you connect it to the grid, the only reason we are letting you do this is because we have been forced to, we are going to stall and delay your project as much as the law allows, and when we inspect the system we will send someone that has no clue about the NEC rules, expect this to be slow and painful'
 

iwire

Moderator
Staff member
Location
Massachusetts
Smart,

Here is the whole document

http://www.nstar.com/docs3/interconnections/tariff.pdf?unique=20110804103211


4.2.3.1 Group 1 Facilities

a.
The inverter-based Facility shall be considered Listed if it meets requirements set forth in Section 3.1 ?Simplified Process?.

b.
External Disconnect Switch: For Listed inverters, the Company may require an external disconnect switch (or comparable device by mutual agreement of the Parties) at the PCC with the Company or at another mutually agreeable point that is accessible to Company personnel at all times and that can be opened for isolation if the switch is required. The switch shall be gang operated, have a visible break when open, be rated to interrupt the maximum generator output and be capable of being locked open, tagged and grounded on the Company side by Company personnel. The visible break requirement can be met by opening the enclosure to observe the contact separation. The Company shall have the right to open this disconnect switch in accordance with this Interconnection Tariff.


c.
Disconnect Switch: The Facility shall provide a disconnect switch (or comparable device mutually agreed upon by the Parties) at the point of Facility interconnection that can be opened for isolation. The switch shall be in a location easily accessible to Company personnel at all times. The switch shall be gang operated, have a visible break when open, be rated to interrupt the maximum generator output and be capable of being locked open, tagged and grounded on the Company side by Company personnel. The visible break requirement can be met by opening the enclosure to observe the contact separation. The Company shall exercise such right in accordance with Section 7.0 of this Interconnection Tariff.
 

Smart $

Esteemed Member
Location
Ohio
Strange? Yes.

A typical situation around here? Yes.



I will find the document from the power company for co-generation requirements ........ it is only about 100 pages. :roll:

The basic attitude I was getting from the power company about these installations was this.

'Solar is dangerous, we really don't want to let you connect it to the grid, the only reason we are letting you do this is because we have been forced to, we are going to stall and delay your project as much as the law allows, and when we inspect the system we will send someone that has no clue about the NEC rules, expect this to be slow and painful'

I understand... and I appreciate the follow through. I'll attribute the scenario as one which raw logic does not apply :blink: and move on ;)
 

iwire

Moderator
Staff member
Location
Massachusetts
I'll attribute the scenario as one which raw logic does not apply :blink: and move on ;)

Yeah, same here. It is less stressful once you do that.

The company is still doing solar installs but I am pretty much out of it now.

For all I know the POCO could be changing now that this is more common.
 

jaggedben

Senior Member
Location
Northern California
Occupation
Solar and Energy Storage Installer
Around here (Northern CA), PG&E is now allowing, in place of an outside disconnect, a lock-box with a combo known by them to access a key to the property that allows access to the solar disconnect.

...which makes it pretty clear that the issue is that the solar supplies energy to the grid, and not that it's a fire safety thing or something like that.
 
Status
Not open for further replies.
Top