Generator installed - shared neutral?

[cashpoppper]

I just paid an electrician to do some work.

sub panel in garage, and on the backside of that wall a generator hookup, and back at ground zero an inter-lock kit at the service entrance, and generator supply is ran through the raceways back to service entrance.

the bill of materials was cheaper than i thought, and it's from not running a strand of 150ft of wire. Looking in the panel, he didn't pull a 2nd neutral back to the generator. he just tapped into the subpanel's bar.

granted the hots and ground are kosher, but shouldn't of he ran a 2nd neutral for the generator circuit?

the backup has a floating neutral, and he ran 2 more grounding rods out there next to it 8ft apart 8ft deep, and tied those to the generator's frame as well.

i looked through the code book and can't narrow it to any violations, but i thought all 3 had to be broken through a transfer switch? or is that the advantage of the inter-lock it?

or maybe this isn't a big deal and i'm trying to make a dangerous mountain out of an ant hill.

thanks

 

[Dennis Alwon]

I believe the neutral needs to be run back with the other conductors.

300.3
(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, conduit body, auxiliary gutter, cable tray, cablebus assembly, trench, cable, or cord unless otherwise permitted in accordance with 300.3(B)(1) through (B)(4).

 

[cashpoppper]

service panel -> sub -> generator socket, we agreed on one single 1" conduit run. he pulled the 2nd set of hot's for the generator in the same conduit. used the subpanel as a raceway pass through.

 

[cashpoppper]

sorry brain fart, are you implying him breaking the neutral at the subpanel is a violation because it doesn't continue with the other conductors out to the plug outside though the last 8" of conduit?

 

[cashpoppper]

sorry, other way around, him tapping into the sub panel neutral bar is a violation from not continuing the neutral conductor with the other supplying conductors in the conduit back to the service entrance where the interlock is located?

 

[wwhitney]

service panel -> sub -> generator socket, we agreed on one single 1" conduit run. he pulled the 2nd set of hot's for the generator in the same conduit. used the subpanel as a raceway pass through.

So, from service panel to subpanel you have a single conduit with subpanel supply ungrounded, generator ungrounded, and a single neutral? And from subpanel to generator inlet you have generator ungrounded and neutral?

That's fine, along with the 2-pole interlock in the service panel. When the interlock is on utility, the neutral from the service panel to the subpanel carries the utility power unbalance to the subpanel. And when the interlock is on generator, it carries the generator power unbalance for the service panel. Generator power for the subpanel does travel to the service panel and back again, but just the balanced portion.

Of course, with 4 CCCs in the single conduit between the service panel and the subpanel, derating will apply.

Cheers, Wayne

 

[cashpoppper]

So, from service panel to subpanel you have a single conduit with subpanel supply ungrounded, generator ungrounded, and a single neutral? And from subpanel to generator inlet you have generator ungrounded and neutral?

correct, there is a sheathed ground conductor as well. I was under the impression the generator conductor circuit also needed it's own neutral, but he didn't pull a dedicated neutral for that circuit, just used the subpanel's neutral.

That's fine, along with the 2-pole interlock in the service panel. When the interlock is on utility, the neutral from the service panel to the subpanel carries the utility power unbalance to the subpanel. And when the interlock is on generator, it carries the generator power unbalance for the service panel. Generator power for the subpanel does travel to the service panel and back again, but just the balanced portion.

Of course, with 4 CCCs in the single conduit between the service panel and the subpanel, derating will apply.

Cheers, Wayne

I was concerned of derate as well.

1" EMT from service to subpanel, and we carried 1" through the wall to the generator hookup.

all copper THHN, there is 3x 6ga for hots/neutral and 1 8ga ground conductor for feeding 60amps to subpanel, and he just pulled 2 more 8ga wires for the 50amp generator hookup.

i'm just wondering if he did anything shady or unsafe. but it appears nothing was done incorrectly? The bonding was kept separate and driving more ground rods at the generator's location for peace of mind

I did read and he did mention since the generator is floating, if i ever use it as a portable i need to use a 30amp plug that twists locks into the generator. Is has the neutral and ground bonded in the plug itself.

thanks for the clarifying.

 

[cashpoppper]

actually, feeders get the 125% rule, but is derate applied before the 125% or after? and is the generator circuit not considered a feeder circuit? maybe the wire a fuzz too small if that's the case, derated or not.

uh oh.

 

[letgomywago]

Can you show a Picture with panel cover off?

 

[cashpoppper]

i'm not in town at the moment, which panel? I guess also which detail is in your mind?

 

[letgomywago]

All of them.

 

[letgomywago]

Sounds like either poor install or poor communication to this forum.

 

[cashpoppper]

a very ugly drawing. sorry. i'm like across the country out of town. i'm not catching an airplane for this.


https://i.postimg.cc/ryR62Nyk/untitled.png
he didn't pull a 2nd neutral.
https://i.postimg.cc/ryR62Nyk/untitled.png

 

[cashpoppper]

the service panel has #3 copper 100amp with a #2 copper ground.

ground is 10ga all the way from main panel, to sub, then to generator outlet housing

the (attached) garaged subpanel is 6ga conductor supply, the neutral is also 6ga, and the generator conductors are 8ga.

there is no dedicated generator neutral. the subpanel was used as a raceway out to the generator box, as they're back to back on the garage wall.

 

[cashpoppper]

i forgot to draw the grounding rods, if that makes a difference.

with a UL listed interlock kit (right from SE) is there a code violation having the generator circuit use the subpanel neutral wire for unbalanced load? technically the neutral hasn't been broke anywhere, and the grounds and neutral are still only bonded at the main since the generator is a floating neutral.

 

[wwhitney]

As long as the conductors between the "M" panel (service panel) and "S" panel (subpanel) are all in the same conduit, there's nothing wrong with the two feeders (utility supply to subpanel, and generator supply to service panel) sharing a neutral as per 215.4. And since the two feeders are carrying power in opposite directions, the common neutral size required would be the same as for a single feeder, rather than double sized.

Cheers, Wayne

 

[chorty55]

I'll jump into this.

If he's using thhn 8ga for his generator conductors (hots), and if there's 4 conductors in the conduit since it's sharing the subpanel circuit, doesnt that limit him to 44amps using 80% @ 90c? So is that a 40amp, 45amp. Or round up to 50amp OCPD?

Or is the generator considered a feeder and the 125% rule Begin's?

 

[wwhitney]

If he's using thhn 8ga for his generator conductors (hots), and if there's 4 conductors in the conduit since it's sharing the subpanel circuit, doesnt that limit him to 44amps using 80% @ 90c?

Yes. So the generator output or calculated load on the generator needs to be at most 44A.

So is that a 40amp, 45amp. Or round up to 50amp OCPD?

I was going to say "45A is not a standard size in 240.6(A), so per 240.4(B) it can be protected at 50A." But that's wrong, 45A is a standard size. So indeed that's a violation.

Cheers, Wayne

 

[chorty55]

Yes. So the generator output or calculated load on the generator needs to be at most 44A.


I was going to say "45A is not a standard size in 240.6(A), so per 240.4(B) it can be protected at 50A." But that's wrong, 45A is a standard size. So indeed that's a violation.

Cheers, Wayne

The 125% feeder rule doesn't apply to the generator?

 

[wwhitney]

The 125% feeder rule doesn't apply to the generator?

There is no general "125% feeder rule". What 125% factor are you thinking of?

Cheers, Wayne