Knockout a pad mounted transformer

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earmandorobles

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Location
Mexicali, Mexico
Hi everyone

Right now we have an existing pad mounted transformer (2000 KVA, 34.5KV-480/277) which is already connected and functioning. Right now we are trying add two more conductors per phase for an electric FP pump. The right thing to do is with the transformer de-energized demolish a small part of the concrete and include 2 PVC conduits for the new conductors but our client needs to do this in one day which we think won't be enough time.

We we're wondering if we can make a knockout through one side of the pad mounted transformer, maybe with a condulet or simply with a liquidtight flexible conduit and then change to PVC when we reach ground. I can't fin any article or restrictions about doing this, we normally dont do this but if there's the chance to do it without any code violation than we can make an exception.

I hope someone can help me with this, also sorry for my english im sending this from mexico but since i live in the border its very usual that our clients follow the NEC.

Regards
 
earmandorobles said:
Hi everyone

Right now we have an existing pad mounted transformer (2000 KVA, 34.5KV-480/277) which is already connected and functioning. Right now we are trying add two more conductors per phase for an electric FP pump. The right thing to do is with the transformer de-energized demolish a small part of the concrete and include 2 PVC conduits for the new conductors but our client needs to do this in one day which we think won't be enough time.

We we're wondering if we can make a knockout through one side of the pad mounted transformer, maybe with a condulet or simply with a liquidtight flexible conduit and then change to PVC when we reach ground. I can't fin any article or restrictions about doing this, we normally dont do this but if there's the chance to do it without any code violation than we can make an exception.

I hope someone can help me with this, also sorry for my english im sending this from mexico but since i live in the border its very usual that our clients follow the NEC.

Regards
Click to expand...
I've never seen it in practice. If you did do it, you'd have to confirm with the transformer manufacturer. I don't anticipate that the answer would be yes, as keeping walls of a transformer intact could be more essential than you think.
 
I had to bring a 4" RMC for the 13.8 kV priamary of a pad mount transformer.

Instead of a conduit body we use a 4' section of stainless steel 3R or 4X wireway bolted to the side of the transformer and nippled through the back of it into the transformer wiring compartment.

You can see it in this picture I just grabbed from Google Street view. I added the pad mount on the right.
 

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iwire said:
Good point, in my case it was customer owned but I don't think any local power companies would let us do that. They want them easy to swap if the need arises.
Click to expand...

Thanks for your response, and in my case it is also customer owned so i dont think we're gonna have a problem with our loca company.

Regards
 
Carultch said:
I've never seen it in practice. If you did do it, you'd have to confirm with the transformer manufacturer. I don't anticipate that the answer would be yes, as keeping walls of a transformer intact could be more essential than you think.
Click to expand...
He will be entering the terminal cabinet more so then the "walls of the transformer".

I think it would be a good idea to hit a conduit body, pull box, etc. within short distance just so it would be easier to withdraw those conductors should a transformer change out ever be necessary.
 
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