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Steve G.
Steve G., Electrical Engineer
Category: Electrical
Satisfied Customers: 17726
Experience:  Spent 20 years as an Electrical Engineer, designing electrical plans and specifications.
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How do I wire two disconnects on a 30 kva transformer with

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How do I wire two disconnects on a 30 kva transformer with an under ground feed
Hello there and welcome to Just Answer. My name is XXXXX XXXXX I will be assisting you today. I am an engineer with over 30 years of electrical and electronic training, repair and installation experience. I will try and answer your question accurately and precisely so that we can get you on your way.

Now..are you looking for me to size the breakers and wiring?

What are the primary and secondary voltages of the transformers?

Please let me know so that we can continue.

Customer: replied 3 years ago.

480 volts primary 240 secondary I pulled 2/0 to transformer location underground I need to wire two disconnects one for each side how do I go about doing that

Customer: replied 3 years ago.

And what size sealtight I'll need for both sides from disconnects to transformer

And I assume that this is three phase?

If so, you will need a 50A fused disconnect/breaker on the primary side.

On the secondary, you will need a 100A fused disconnect/breaker and assuming that your secondary run is not excessive, you can use #2 conductors and a #10 ground.

If the secondary is delta, then you will not have a neutral. If it is wye then you will.

Is that the information you were looking for?

Please let me know so that we can continue if necessary.

Steve G. and other Electrical Specialists are ready to help you
Customer: replied 3 years ago.

Yes ! How do I route my primary wires since it's underground do I use the transformer as a race way

The transformer is underground?

You can direct bury your wiring (so long as your local codes allow it) or you can run it in pipe.

Primary would be a 1" conduit, secondary would be 1.5".

I'll be here if you need further help with this issue. Please let me know.


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