Bullseye in transfer switch

[K8MHZ]

I just ran across a PDF from our POCO, Consumers Energy, that has wiring diagrams and all sorts of cool stuff in it.

http://www.consumersenergy.com/uplo...Service-Metering-Information-Requirements.pdf

If you look at page 61 you will find their wiring requirements for transfer switches. It appears that they consider the transfer switch the point of the first disconnect as that is where the neutral/ground bonding is done.

So, how many of you move the bonding point from the customer's main breaker panel to the inside of the transfer switch box when you install a transfer switch?

Also, take note that the drawings also require that the neutral NOT be switched.

Now, what's odd is that I have seen inspectors require a switched neutral but never a bonding relocation.

As soon as I can find my inspector pal's e-mail address I will forward the PDF to him and solicit his comments, but 'till then, I would really like some feed back from the Holtizens.

Thanks!

 

[augie47]

Locally it's done the same. In 95%+ of the installs the neutral is not switched and bonding is done at the 1st disconnecting means.
The only problem I see is that the DT switches they show do not seem to be fusible and with the non-fusible switches I see the AIC rating is sometimes not acceptable.

 

[brantmacga]

It appears that they consider the transfer switch the point of the first disconnect as that is where the neutral/ground bonding is done. . . . . .

bonding is done at the first disconnect; if you install a service entrance rated transfer switch, then yes that becomes the bonding point.


if you have a disconnect before the transfer switch, that first disconnect is the bonding point.

this is no different than what you find in the NEC. . . .

 

[K8MHZ]

bonding is done at the first disconnect; if you install a service entrance rated transfer switch, then yes that becomes the bonding point.


if you have a disconnect before the transfer switch, that first disconnect is the bonding point.

this is no different than what you find in the NEC. . . .

OK....looking at the drawing, I see the GEC connected to a bonding bar along with the neutrals.

I see a neutral and related hot wires leaving the transfer switch going to the customers panel

I do NOT see a grounding conductor other than the GEC, all that is drawn is three wires for the 120/240 service.

So, what do you do at the panel? To be safe, the panel needs to be bonded and the only way to do it with 3 wire is to make a SECOND 'bullseye'.

I tried to attach the page I am talking about but the pdf was too large. Sorry.

 

[Smart $]

...

So, what do you do at the panel? To be safe, the panel needs to be bonded and the only way to do it with 3 wire is to make a SECOND 'bullseye'.

...

If I were doing this installation, I'd just run a bonding jumper to the panel, where my GES was also connected.

 

[K8MHZ]

If I were doing this installation, I'd just run a bonding jumper to the panel, where my GES was also connected.

I don't understand....

GES??

How do you do what you propose while following the diagrams set forth by the POCO? A bonding jumper would be in parallel with the neutral and would thus be a current carrying conductor. It would not be an EGC, it would just be a paralleled neutral unless all the neutrals and grounds were split up and isolated in the main panel and the grounding electrode conductor was disconnected, spliced and brought into the transfer switch.

In the real world, how often does this happen?

 

[Smart $]

I don't understand....

GES??

How do you do what you propose while following the diagrams set forth by the POCO? A bonding jumper would be in parallel with the neutral and would thus be a current carrying conductor. It would not be an EGC, it would just be a paralleled neutral unless all the neutrals and grounds were split up and isolated in the main panel and the grounding electrode conductor was disconnected, spliced and brought into the transfer switch.

In the real world, how often does this happen?

GES = Grounding Electrode System

Well, let's say you ran a GEC out of the xfer to a rod, and you ran your SEC in metallic conduit to the panel. Wouldn't the conduit be a parallel neutral current path?

Technically, there is no violation... or should I say being in violation is subjective to interpretation. The Code does not permit grounded to grounding reconnection on the load side of the service disconnecting means, but it permit it on the line side. Where the subjective part comes in is objectionable current under 250.6. Objectionable current is not defined, but typically neutral current on non-current-carrying exposed metal surfaces is, as is the potential for neutral current through earth (as is the case how drawn and GES connected at service-disconnecting-means panel)... neutral current on a service bonding jumper that is not exposed you could toss a coin over.

Ultimately, the only solution here is to contact a Consumers' engineer and explain the problem... and of course let us know the response

 

[K8MHZ]

Well, let's say you ran a GEC out of the xfer to a rod, and you ran your SEC in metallic conduit to the panel. Wouldn't the conduit be a parallel neutral current path?

Not unless there was bonding between the neutral and the metal at the panel. If the bonding was removed, and the neutrals and grounds isolated, that would remove the parallel and, as I read things, would be required. I don't see that happening in the field.

Maybe I need diagrams to get this to make sense to me, as it seems that the NEC and the POCO just aren't on the same page.

 

[Smart $]

...

Maybe I need diagrams to get this to make sense to me, as it seems that the NEC and the POCO just aren't on the same page.

I think you are reading too much into the diagram as it is

The GEC connection can be made at any accessible point from the load end of the service drop or service lateral to and including the terminal or bus to which the grounded service conductor is connected at the service disconnecting means.

The diagram simply shows one possible connection point.

 

[ceb58]

My question is why is the poco getting involved with customer equipment on the load side of the meter?

 

[brantmacga]

So, what do you do at the panel? To be safe, the panel needs to be bonded and the only way to do it with 3 wire is to make a SECOND 'bullseye'.

if you put a service entrance rated transfer switch between the meter and panel w/ an existing 3-wire service, you have to replace the existing feeder w/ a 4-wire.