Transformer clearance dry type indoor 120kva

[dm9289]

I have a clearance question. The large MCC in the back will be replaced. The new one was proposed to start where MCC is painted. The transformer is 480 to240v single phase 120KVA transformer. There is open space opposite side of transformer.There is a large box on transformer 3 rd from left on the rear of it. Would you need a 36” working space from transformer to new MCC side? Or 36” from back of large connection box. I’m having trouble relating this to 110.26 conditions or 450.21. The temp rise is 80c and it is a type S cannot find vent requirements on name plate.

Thank you for your input.

 

[Elect117]

110.26 It is measured from the point where the conductors are connected on the transformer. In my opinion, you would need 3' 6" from the transformer's conductor's terminals to the grounded enclosure of the MCC. I say 3'6" because you are possibly 277V to ground or if corner grounded, 480V to ground on the high side of the transformer.

In my opinion, will also need a way to open that gutter so that it remains accessible. If your MCC is too close you won't be able to remove the screws on the cover plate or access the wiring.

 

[dm9289]

110.26 It is measured from the point where the conductors are connected on the transformer. In my opinion, you would need 3' 6" from the transformer's conductor's terminals to the grounded enclosure of the MCC. I say 3'6" because you are possibly 277V to ground or if corner grounded, 480V to ground on the high side of the transformer.

In my opinion, will also need a way to open that gutter so that it remains accessible. If your MCC is too close you won't be able to remove the screws on the cover plate or access the wiring.

2 wires of a 480 wye to single 240v.
When I looked at the 3 conditions it was hard to determine which to use

 

[Elect117]

2 wires of a 480 wye to single 240v.
When I looked at the 3 conditions it was hard to determine which to use

Some might disagree with how I read it.

I read it as, if you take your voltmeter and measure from any single phase in the transformer and put the other probe on the grounded metal enclosure, that is the voltage you use in that column. The highest nominal voltage to ground.

 

[dm9289]

Some might disagree with how I read it.

I read it as, if you take your voltmeter and measure from any single phase in the transformer and put the other probe on the grounded metal enclosure, that is the voltage you use in that column. The highest nominal voltage to ground.

I was thinking more related to the transformer not being against a wall and being in free space. And yes 277 to ground

 

[Elect117]

I was thinking more related to the transformer not being against a wall and being in free space. And yes 277 to ground

Only a couple of inches depending on if there are any connections that require servicing or inspection (110.16).

If there are vented openings on the back or sides than I would say about 6-12in for vented sections. It also depends on how hot that area is normally. But not much space is needed for the ventilation part.