Is overcurrent protection required on this secondary?

[brantmacga]

See pic for reference .....

The schedule calls for panel M to be MLO; I ordered as MCB being that they are requiring shunt trip.

Would the 600A DPDT switch shown be required to have fuses? The secondary is underground from a padmount, and then will go under the slab to panel M.

Square D doesn't make a fusible 600A DPDT switch so I stopped the shipment.

If this switch weren't there, fuses wouldn't be required. Does this situation change that?

Thanks

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[Smart $]

Need to see portion not shown to the right of the image you posted to be certain, but that appears to be a service which will require OCPD integral with an SUSE-rated MTS, or an SUSE-rated fused disconnect ahead of the MTS on the service side.

 

[brantmacga]

Is overcurrent protection required on this secondary?

To the right is a drawing of the padmount. Typically we go from the padmount underground straight to the MDP, and if the jurisdiction requires it, we put a shunt trip main with a break-glass button outside.


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[brantmacga]

Also there will be no CT cabinet; the utility installs CT's in the transformer and will mount the meter on the transformer.


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[brantmacga]

I keep looking at 230.91 and trying to determine would you actually call this the service disconnect? It's a transfer switch ahead of the disconnect..... What I consider the disconnect is the MCB w/ shunt trip.

In my mind, if they do connect a generator, it will have its own overcurrent device, and the 600A MCB will protect from overload on the secondary conductors either way.


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[don_resqcapt19]

The transfer switch must be service rated and is the service disconnect. The code requires that the service OCPD be part of the service disconnect or immediately adjacent thereto. I am assuming the the local rules accept the shunt trip in place of the code required OCPD at the transfer switch.
As drawn, there is no way that Panel M can be MLO.

 

[jim dungar]

Panel M is drawn with a 'main breaker shunt trip' device. What purpose does this serve, if Panel M is a MLO?

As others have said, the transfer switch will need to be suitable for use as service equipment, including N-G bonding.

 

[brantmacga]

Panel M is drawn with a 'main breaker shunt trip' device. What purpose does this serve, if Panel M is a MLO?

As others have said, the transfer switch will need to be suitable for use as service equipment, including N-G bonding.

I think that is an error.

I ordered panel M as MCB w/ shunt.

I just ordered an outdoor I-Line panel w/ breakers & kirk keys instead and cancelled the DPDT switch.

Thanks,

 

[Strathead]

I think that is an error.

I ordered panel M as MCB w/ shunt.

I just ordered an outdoor I-Line panel w/ breakers & kirk keys instead and cancelled the DPDT switch.

Thanks,

It sounds like the drawings are SNAFU (situation normal all fouled up) As stated earlier, the first "switch" the oncoming power goes to has to be a service rated disconnect. Which means it must be fused of have circuit breakers. This can be done with a fusible disconnect prior to the DPDT switch or the DPDT HAS to be equipped with fuses or breakers.

What I am not sure of is whether there needs to be a disconnect for the Temp Gen hook up, if you use the first scenario above. I don't think so, because any temp generator should have breakers on it that serve, but it would be prudent anyway. From a selling point to the customer, the box won't be required and the temp can be wired right in to the line side of the Disconnect.


With all of the above being required, the entire purpose of the shunt trip in moot. They are installed in this application to give the Fire Department the ability to turn off the service without entering the building. Since there is an external disconnecting means, get clarification and get a change order for the exterior work with a credit for the shunt trip and MCB

 

[Strathead]

I think that is an error.

I ordered panel M as MCB w/ shunt.

I just ordered an outdoor I-Line panel w/ breakers & kirk keys instead and cancelled the DPDT switch.

Thanks,

BIG OOPS:slaphead:

The MDP can't be the bonding point for the neutral and ground as drawn. This must be done in the first means of disconnect.

[edit] Like I said, SNAFU

 

[brantmacga]

My confusion was that I wasn't sure the DPDT switch would actually be the first means of disconnect because it could swap power from one source to another.

I'm leaving the shunt because it's in the drawings. It may be an actual requirement in that town; I don't know and i don't care to spend an hour on the phone finding out. Everything else I've done there required the shunt for external means of disconnect, but I've never done this particular setup there with the transfer switch.


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[Strathead]

My confusion was that I wasn't sure the DPDT switch would actually be the first means of disconnect because it could swap power from one source to another.

I'm leaving the shunt because it's in the drawings. It may be an actual requirement in that town; I don't know and i don't care to spend an hour on the phone finding out. Everything else I've done there required the shunt for external means of disconnect, but I've never done this particular setup there with the transfer switch.


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Then, yes it is actually the first means of disconnect, period.

 

[brantmacga]

Is overcurrent protection required on this secondary?

Then, yes it is actually the first means of disconnect, period.

I was trying to actually find that in the code though.

I've gotten differing opinions; even an inspector said he would let it go, but I wanted to know that I was right by code.

I'm not saying anyone is wrong, I just want to see exactly how this is covered under the NEC for future reference.


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[Smart $]

I was trying to actually find that in the code though.

I've gotten differing opinions; even an inspector said he would let it go, but I wanted to know that I was right by code.

I'm not saying anyone is wrong, I just want to see exactly how this is covered under the NEC for future reference.

That's a uh-oh biggy! :rant:

The only equipment permitted on the supply side of a service disconnecting means is listed in 230.82. Note transfer switch or anything resembling a switch is not in the list. But something resembling a switch can be the disconnecting means... :happyyes: ... which is where an SUSE transfer switch comes into the picture, for example.