Electrical service configuration

[rozana81]

I am working on a project where they have a wireway, a disconnect switch, a meter and another disconnect switch configuration. Anyone knows why there are two disconnect switches to the tenant space.

 

[augie47]

Difficult to say without more info and/or a "whole" picture.
it's not unusual in multi-tennant buildings for there to be two spaces with panels covered into one space but that conjecture

 

[Hv&Lv]

I would say one is for the utility to kill the service to change/maintain the meter.
The other is a disconnect after the meter.
But then again, I’m guessing..

 

[ron]

Some jurisdictions request cold sequence metering, which means that the utility can de-energize the meter prior to servicing it.

 

[rozana81]

Looks like some of the jurisdiction requires both meter disconnect and service disconnect. But my question is if the meter disconnect is turned off, would that not kill power to the building? Why do we need another disconnect after meter?

 

[Hv&Lv]

Looks like some of the jurisdiction requires both meter disconnect and service disconnect. But my question is if the meter disconnect is turned off, would that not kill power to the building? Why do we need another disconnect after meter?


View attachment 2571193

I would venture to guess one is utility required, the other is NEC required.

 

[david]

the service disconnect has not been required outside.

here if it is 480/277 AND the meter is line voltage not CT. the utility requires a disconnect ahead of the meter.

here they do not care if it is fusible or not they just want the meter cold before they set it or pull it

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[rozana81]

the service disconnect has not been required outside.

here if it is 480/277 AND the meter is line voltage not CT. the utility requires a disconnect ahead of the meter.

here they do not care if it is fusible or not they just want the meter cold before they set it or pull it

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Thanks David! So, why do you need another disconnect switch after the meter and before the panelboard too?

 

[david]

if I was doing it, the disconnect ahead of the meter would be un fused eather way its not the service disconnect

the service disconnect is outside in your picture. it could have been inside.

Eather way the NEC requires the service disconnect, the utility required the isolation switch.

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[david]

you have the same requirement for central distribution systems on farms

but in that case the NEC and the utility both required an isolation switch that is not required to be fuseable

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[ron]

if I was doing it, the disconnect ahead of the meter would be un fused eather way its not the service disconnect

the service disconnect is outside in your picture. it could have been inside.

Eather way the NEC requires the service disconnect, the utility required the isolation switch.

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You would be hard pressed to find an un-fused disconnect that has an adequate short circuit rating much higher than 5kA, so in many services, it needs to be fused, just to get an adequate SCCR.

 

[Hv&Lv]

Thanks David! So, why do you need another disconnect switch after the meter and before the panelboard too?

See post #6..

 

[LarryFine]

So, why do you need another disconnect switch after the meter and before the panelboard too?

Mayhaps because the service feeds multiple tenants, so they need a way to de-energize one meter without having to de-energize them all.

 

[rozana81]

Mayhaps because the service feeds multiple tenants, so they need a way to de-energize one meter without having to de-energize them all.

it is feeding just one tenant

 

[LarryFine]

it is feeding just one tenant

Then what are the trough and the large switch to the left, and whatever that is on the right, for?

Added: Note that "the service" is made up of more than just one tenant's meter and disconnect(s).

 

[augie47]

The meter disconnects in this area are normally locked on and closed by POCO as they don't want customer access to un-metered conductors.
as such (locked with only POCO access) they are not customer service disconnects.

Is the conduit going up the wall from the higher switch the service conduit or is the service in the wireway ??

 

[LarryFine]

Is the conduit going up the wall from the higher switch the service conduit or is the service in the wireway ??

To me, that's the feeder going up. (technically, it doesn't change the question)

 

[david]

You would be hard pressed to find an un-fused disconnect that has an adequate short circuit rating much higher than 5kA, so in many services, it needs to be fused, just to get an adequate SCCR.

did a quick look at utility req. 480/277 volt 400 amps or less line voltage metering

unfused up to 10kA fused for any metering exceeding 10kA

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[augie47]

To me, that's the feeder going up. (technically, it doesn't change the question)

Still a lot of unknown facts... I though perhaps the service conductors were in the wireway with one set metered out of sight and feeding the two disconencts and one set feeding the meter shiown..... but comjecture

 

[don_resqcapt19]

Thanks David! So, why do you need another disconnect switch after the meter and before the panelboard too?

In my area the meter disconnect is sealed by the utility and not suitable for used as a service disconnect, because you need a tool to cut the seal to operate the switch.