Seperate Building

[ASG]

I was reading this old thread and it said 4 wires to the building is required. Where does it say this? I am running a feed for a mechanical equipment panel and was not planning on running a neutral.

 

[don_resqcapt19]

If you have no line to neutral loads, there is no code rule that says you have to run the neutral to the second building. You are required to install an EGC with the ungrounded conductors.

 

[pete m.]

I was reading this old thread and it said 4 wires to the building is required. Where does it say this? I am running a feed for a mechanical equipment panel and was not planning on running a neutral.

Is there already a feeder for lighting and receptacle loads? Maybe take a look at 225.30 and make sure you are in compliance.

Pete

 

[ASG]

Is there already a feeder for lighting and receptacle loads? Maybe take a look at 225.30 and make sure you are in compliance.

Pete

Yes, this is a hospital where we are feeding a new Emergency Mechanical Equipment panel.

 

[pete m.]

Then it would seem 225.30(A)(2) would allow the additional feeder as long it is classified as "emergency" i.g. essential to the preservation of human life.

Pete

 

[don_resqcapt19]

Then it would seem 225.30(A)(2) would allow the additional feeder as long it is classified as "emergency" i.g. essential to the preservation of human life.

Pete

Even if it is not an emergency circuit or even a legally required stand by circuit, 225.30(A)(4) would permit it.

 

[pete m.]

Even if it is not an emergency circuit or even a legally required stand by circuit, 225.30(A)(4) would permit it.

Agreed.

Pete

 

[ASG]

Little wrinkle: the panel I'm installing is being fed from a transformer. To meet 240.21(C), we installed a main disconnect within 10 feet of the transformer on the secondary side. Now, since this panel is installed in a different building, it will also require a main. How do we do this without creating coordination issues?

 

[jumper]

Little wrinkle: the panel I'm installing is being fed from a transformer. To meet 240.21(C), we installed a main disconnect within 10 feet of the transformer on the secondary side. Now, since this panel is installed in a different building, it will also require a main. How do we do this without creating coordination issues?

The panel in the the other building does not require a main breaker, the building feeder requires a disco, 225.31, as long as the 1st disco can provide OCPD to satisfy 408.36 and protect the feeders also, 215.3.

The disco required by 225.31 has to be service rated, 225.36.

 

[ASG]

May be I'm not understand what you're saying. It requires a disco so I thought the easiest/cheapest way to satisfy that would be with a main as opposed to finding space for an additional unfused disconnect switch.

 

[jumper]

May be I'm not understand what you're saying. It requires a disco so I thought the easiest/cheapest way to satisfy that would be with a main as opposed to finding space for an additional unfused disconnect switch.

The coordination issue you were referring to was the transformer disco vs the panel main correct?

 

[iwire]

May be I'm not understand what you're saying. It requires a disco so I thought the easiest/cheapest way to satisfy that would be with a main as opposed to finding space for an additional unfused disconnect switch.

Which will be cheaper, adding an unfused disconnect or getting and complying with coordination studies for a main breaker? I don't know the answer but I am sure that was what Jumper was suggesting.

 

[jumper]

Which will be cheaper, adding an unfused disconnect or getting and complying with coordination studies for a main breaker? I don't know the answer but I am sure that was what Jumper was suggesting.

It was exactly what I was suggesting.

It relieves the pressure of this part of OPs problem.

Yes, this is a hospital where we are feeding a new Emergency Mechanical Equipment panel.

 

[ASG]

The coordination issue you were referring to was the transformer disco vs the panel main correct?

Yes, and point taken.

 

[kwired]

Maybe I am missing something here.

My understanding is we have a separate building supplied by a feeder. The separate building needs a (service rated) disconnect at/near point it receives its supply.

Next item in the series is a transformer.

Unless there is two wire single phase or three wire three phase transformer output, in which most cases primary overcurrent protection can also protect the secondary, you will almost always need a main overcurrent device on the secondary.

Neutral conductor is not required if there is no load that utilizes a neutral. Equipment ground is required no matter what, unless allowed by previous code at time of installation to use the neutral for equipment grounding at a separate building.

 

[iwire]

Maybe I am missing something here.

My understanding is we have a separate building supplied by a feeder. The separate building needs a (service rated) disconnect at/near point it receives its supply.

Next item in the series is a transformer.

No, as I understand it the layout is more like this

First building > Service > Transformer > breaker > feeder to other building > panel in other building

 

[ASG]

iwire is correct

 

[jumper]

Now the question is how to want to solve the disconnect problem to the second building?

Main breaker or non fused disco?

 

[ASG]

Yes, finding room for a non-fused disco might be difficult but a main breaker won't be coordinated with the fused disconnect.