Neutral From a Portable Generator

[Little Bill]

By portable I don't mean the small resi type generators. I'm talking about one such as a 75 KW 3 phase that you would rent to use on a job site.

With that said, does the neutral/grounded conductor need to be brought out to equipment or a power distribution box if all the equipment is line-line?

I'm trying to figure out what would cause the OCPD to operate should a line to ground fault occur somewhere downstream of the generator.

Is the grounded conductor and EGC bonded on the generator so that the EGC would be the fault path back to the generator?

 

[zbang]

I'm trying to figure out what would cause the OCPD to operate should a line to ground fault occur somewhere downstream of the generator.

Is the grounded conductor and EGC bonded on the generator so that the EGC would be the fault path back to the generator?

There has to be a bond from the generator's neutral point to ground somewhere; some gensets have it internally and some don't. I always check and install one on the terminal lugs if needed. That said, the frame of the genset needs to connect to the EGC, and usually to a rod or two, too.

Oh, and to answer the first question, I don't think the groundED conductor has to leave the genset, but the EGC certainly does.

 

[GoldDigger]

In the case of a service the grounded neutral, if one exists, must be brought to the first disconnect, but not necessarily any farther.
I am not sure whether a similar requirement exists for generators or even local SDSs.

 

[ActionDave]

In the case of a service the grounded neutral, if one exists, must be brought to the first disconnect, but not necessarily any farther.
I am not sure whether a similar requirement exists for generators or even local SDSs.

Rules for any SDS, transformer or generator, are the same with a little wiggle room for a portable generator.


250.34 Portable and Vehicle-Mounted
Generators

(A) Portable Generators. The frame of a portable genera-
tor shall not be required to be connected to a grounding elec-
trode as defined in 250.52 for a system supplied by the
generator under the following conditions:

(1) The generator supplies only equipment mounted on the
generator, cord-and-plug-connected equipment through
receptacles mounted on the generator, or both, and
(2) The normally non?current-carrying metal parts of
equipment and the equipment grounding conductor ter-
minals of the receptacles are connected to the generator
frame.


250.35 Permanently Installed Generators

A conductor that provides an effective ground-fault current
path shall be installed with the supply conductors from a
permanently installed generator(s) to the first disconnecting
mean(s) in accordance with (A) or (B).

(A) Separately Derived System. If the generator is in-
stalled as a separately derived system, the requirements in
250.30 shall apply.

(B) Nonseparately Derived System. If the generator is in-
stalled as a nonseparately derived system, and overcurrent
protection is not integral with the generator assembly, a
supply-side bonding jumper shall be installed between the
generator equipment grounding terminal and the equipment
grounding terminal, bar, or bus of the disconnecting mean(s).
It shall be sized in accordance with 250.102(C) based on the
size of the conductors supplied by the generator.

 

[Little Bill]

I wonder if lugs on a generator would count as a receptacle?

 

[mwm1752]

By portable I don't mean the small resi type generators. I'm talking about one such as a 75 KW 3 phase that you would rent to use on a job site.

With that said, does the neutral/grounded conductor need to be brought out to equipment or a power distribution box if all the equipment is line-line?

I'm trying to figure out what would cause the OCPD to operate should a line to ground fault occur somewhere downstream of the generator.

Is the grounded conductor and EGC bonded on the generator so that the EGC would be the fault path back to the generator?

Are you serving a single appliance/equipment or are you serving a subpanel which inturn serves several appliances/equipment that do not require a grounded conductor?

 

[Little Bill]

Are you serving a single appliance/equipment or are you serving a subpanel which inturn serves several appliances/equipment that do not require a grounded conductor?

This is more of a "me wondering" question than anything else. But what got me to wondering was hearing the set-up someone was using on large jobs. They have 3 or 4 pieces of equipment that uses 3-ph, line-line, no neutral. I believe they had been using only one at a time. Now they are getting a power distribution box and only running the three line conductors and an EGC from the generator. I was just wondering how the OCPD on the generator would operate during a line to ground fault if the neutral and EGC were not bonded at the generator. Or if it wasn't, would the neutral need to be brought to the dist. box and bonded there.
It seems it would be better if they made sure there was a bond at the generator.

 

[ActionDave]

.... they are getting a power distribution box and only running the three line conductors and an EGC from the generator. I was just wondering how the OCPD on the generator would operate during a line to ground fault if the neutral and EGC were not bonded at the generator. Or if it wasn't, would the neutral need to be brought to the dist. box and bonded there.

There has to be a bond somewhere to clear a fault. At the box or at the genny. Neutral or hot. Something.

It seems it would be better if they made sure there was a bond at the generator.

I think your thinking is good.

 

[iwire]

If you want or can or are required to bond at the generator will depend on how you are connecting the generator to the load.

If you feed the load directly you will have to bond at the temp genset

On the other hand if you are feeding a switch board that is already bonded you can't bond at the genset.

 

[Little Bill]

If you want or can or are required to bond at the generator will depend on how you are connecting the generator to the load.

If you feed the load directly you will have to bond at the temp genset

On the other hand if you are feeding a switch board that is already bonded you can't bond at the genset.

Do these gensets have a way to bond on them, or must you provide a bonding jumper yourself?
These generators are rented.

 

[ActionDave]

Do these gensets have a way to bond on them, or must you provide a bonding jumper yourself?
These generators are rented.

The ones I have worked with have easy access where you tie in your power.

When you say "rented" you are throwing a wild card on the table. Rented from a generator company or a tool or party rental place?

 

[Little Bill]

The ones I have worked with have easy access where you tie in your power.

When you say "rented" you are throwing a wild card on the table. Rented from a generator company or a tool or party rental place?

Just guessing, but from what I gather, either a generator company or heavy equipment rental.