Transformer Location

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Designer371141

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My lead wants to mount two 45kva transformers on one wall with one above the other one, the room is only 7' high so there will not be that much room between them. I have pointed out the dedicated space requirements, his comment is that rule only applies to equipment that needs to be serviced or maintained while energized. I have had inspectors bounce me in the past for putting a disconnect in the space. Help, what is the official rule
 
Your lead is thinking of "Working Space" not "Dedicated Equipment Space".

Dedicated Equipment Space applies to Switchgear, Switchboards, Panelboards, and Motor Control Centers. I don't see any issue with stacking the transformers.
 
The "official rule" is in 110.26:
(A) Working Space. Working space for equipment operating at 1000 volts, nominal, or less to ground and likely to require examination, adjustment, servicing, or maintenance while energized shall comply with the dimensions of 110.26(A)(1), (A)(2), (A)(3), and (A)(4) or as required or permitted else‐ where in this Code.
The situation may get a bit "muddy" since a decision must be made as to a transformer fitting that bill.
My experience has been that most AHJs do not include transformers in that requirement.
 
110.26 (A) (3) Working height answers the question and basically puts the issue to rest
110.26 (E)(1) Additional area of support for not doing what he is talking about
It has also been my experience in the past that the AHJ takes this very seriously and has enforced it to the maximum. Another favorite of the AHJ's I have interfaced with is the 10 electrical foot rule for secondary feeders off transformers, as I recall that change came about in either the 96 or 99 code. All I remember is an inspector educating me on it, you have a tendency never to forget it once its taught in that manner.

Thanks for the input
 
Designer371141 said:
110.26 (A) (3) Working height answers the question and basically puts the issue to rest
110.26 (E)(1) Additional area of support for not doing what he is talking about
Click to expand...

Nothing in 110.26(A)(3) or 110.26(E)(1) prohibits installing the transformers in a stacked arrangement.
 
Nice work infinity, the only thing is the TF pad should have been made smaller, so you’d have level footing in front of panelS workspace
 
jusme123 said:
I’ll bet the TF mounted on top is the first to kick the bucket
Click to expand...
Depending on the exact geometry of the transformers and their air flow patterns, you may benefit from adding sheet metal (or even wood) to keep the heated air convecting from the top of lower transformer from being pulled directly into the air inlet(s) of the upper transformer.
Clearance alone may not be sufficient to eliminate this problem.

Pieces of rack mounted electronic equipment with vertical airflow through their top and bottom were often separated by an inclined sheet that forces cool air to be drawn from inside the rack while heated air is exhausted to the front of the rack.
 
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jusme123 said:
Nice work infinity, the only thing is the TF pad should have been made smaller, so you’d have level footing in front of panelS workspace
Click to expand...
I agree, but unfortunately we didn't layout or pour the pads the concrete guys did. That bottom transformer was also changed from a 30 kva to a 75 kva after the panels were installed that's why it barely fits in the space. The original pad was not in front the panel.

As far as heating goes from the lower transformer to the upper transformer it has never been a problem.

Stacked Transformers.jpg003.jpg
 
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