OCPD on transformer secondary

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Ozymandias

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Missouri
Happy sunday to all!

I am replacing a 100A, 120/208V panel for another 100A panel with more branch circuit space. The original panelboard has a side fed 100A main breaker( I point that out because I am used to top or bottom main breakers)
The conductors travel to a mechanical room about 150' from the electrical closet to another. In this closet, the conductors land in a transformer. On the primary side of the transformer, there is a disconnect.
I received the new panelboard and it turns out to be an MLO with a Surge Protector which at first sight thought was a main breaker. I sent out an RFI to the engineers explaining that I have an MLO panelboard(which is what they spec'd on the prints) that goes directly to the secondary of a transformer. I was told to go ahead with it.
Is this correct? I thought I'd need a main breaker panelboard or a service disconnect. This is a college with many computer and video loads, so I am concerned about harmonics.
Thanks.
 
Ozymandias said:
Happy sunday to all!

I am replacing a 100A, 120/208V panel for another 100A panel with more branch circuit space. The original panelboard has a side fed 100A main breaker( I point that out because I am used to top or bottom main breakers)
The conductors travel to a mechanical room about 150' from the electrical closet to another. In this closet, the conductors land in a transformer. On the primary side of the transformer, there is a disconnect.
I received the new panelboard and it turns out to be an MLO with a Surge Protector which at first sight thought was a main breaker. I sent out an RFI to the engineers explaining that I have an MLO panelboard(which is what they spec'd on the prints) that goes directly to the secondary of a transformer. I was told to go ahead with it.
Is this correct? I thought I'd need a main breaker panelboard or a service disconnect. This is a college with many computer and video loads, so I am concerned about harmonics.
Thanks.
Click to expand...

I would have to say u need a Disconnect on the secondary side of the transformer.
 
Ozymandias said:
Do you say that because conductors exceed 25' without?
How is it non-compliant with a main breaker?
Click to expand...
Panelboard is compliant either way, overcurrent protection on the transformer secondary must be within the mentioned 25 feet of the transformer. Once you comply with that the panelboard is inherently protected by said device and doesn't matter if you have a main in the panel or not.

If this is a feeder to a separate building then you still need a main disconnect for that building, but that doesn't appear to be what you have described having.
 
electrofelon said:
Note without the main breaker you also create a 408.36 violation.
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kwired said:
Panelboard is compliant either way, overcurrent protection on the transformer secondary must be within the mentioned 25 feet of the transformer. Once you comply with that the panelboard is inherently protected by said device and doesn't matter if you have a main in the panel or not.

If this is a feeder to a separate building then you still need a main disconnect for that building, but that doesn't appear to be what you have described having.
Click to expand...
Right, same floor.

infinity said:
That's it, all other scenarios aside you cannot escape that section with an OCPD on the secondary side of the transformer ahead of the panel being required.
Click to expand...

Thanks to all, I've had to be very diligent on this job basically to cover my rear. I have to get this on the record and proceed.
 
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