Panelboard to Transformer cablling

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robbath

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I have an indoor installation where a panel-board will be mounted above its 75kva feeder transformer. The work space requirements defined in 110.26 have been accounted for.

My question is, whether there is a code requirement that would prevent me from entering the transformer through the top, from the bottom of the panel-board, given that the transformer can accommodate top entry?

I have not been able to find anything that addresses this directly. Only a guideline that side or bottom entry is preferred because of the heat rising from the transformer and prematurely aging the cable insulation.
 

roger

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It is as you said, a bad design due to being a chimney for the heat to enter the panelboard. With that being said, have you checked into the transformer manufacturers installation instructions? Many have instructions that specify conduit entry to be towards the bottom of the transformer enclosure and is even marked inside the cover or on the sides.

Roger
 

templdl

Senior Member
Location
Wisconsin
I have an indoor installation where a panel-board will be mounted above its 75kva feeder transformer. The work space requirements defined in 110.26 have been accounted for.

My question is, whether there is a code requirement that would prevent me from entering the transformer through the top, from the bottom of the panel-board, given that the transformer can accommodate top entry?

I have not been able to find anything that addresses this directly. Only a guideline that side or bottom entry is preferred because of the heat rising from the transformer and prematurely aging the cable insulation.

I always ask this, did you contact the transformer manufacturer and simply ask them. More often than not people avoid asking them as they may get an answer that they don't want to hear.
When a transformer is built you can specify terminal location as well as cable entry location.
Commonly terminals are along the bottom and cable entry from either side but there is also a capability for being bottom entry. A drawing for the transformer will show these areas.
The issue with cables entering from the top and mot not the heat but routing the cables in order to get to where the terminals are and bending radiuses. That's why it is imperative to advise the transformer manufacturer of has tour going to enter and exit there transformer such that your installation can be made easier. But a drawing of the transformer will have rectangles designating the areas that are free of obstructions for entering and exiting the enclosure.
 
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infinity

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New Jersey
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I've installed many transformers with connections near the top. As stated it's up to the manufacturer to tell you.

75%2520KVA%2520Transformer.jpg
 

texie

Senior Member
Location
Fort Collins, Colorado
Occupation
Electrician, Contractor, Inspector
I have an indoor installation where a panel-board will be mounted above its 75kva feeder transformer. The work space requirements defined in 110.26 have been accounted for.

My question is, whether there is a code requirement that would prevent me from entering the transformer through the top, from the bottom of the panel-board, given that the transformer can accommodate top entry?

I have not been able to find anything that addresses this directly. Only a guideline that side or bottom entry is preferred because of the heat rising from the transformer and prematurely aging the cable insulation.

There is nothing directly in the Art. 450 on this. But this a classic case of the listed instructions. I have never seen a dry type trans former that did not have this in the instructions and a label inside saying that conductor entry has to be below a certain point. As Rodger indicated, some times the terminations are a little on the high side, but you must have your conduit entry below where the manufacturer indicates. This is usually a big red flag for me when I see this done otherwise as it indicates a lack of experience and code understanding.
 
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