Dry transformer

[Jpflex]

My boss wants me to find out if there will be any issues with installing a 500 KVA dry transformer delta 4800 to 480 volt outside vs standard oil coil based.

Temp rise?

I believe if rated Over 34k has to be in a vented vault with 4” concrete walls

I don’t think nec book has much on this?

 

[augie47]

See 450.21
It's likely the transformer will meet the exceptions.

 

[zbang]

Many dry-type transformers have rain-tight kits for outdoor installation if they're not already rain-tight as built.

I don’t think nec book has much on this?

Eventually you get out of NEC territory and into professional engineering territory; from the sound of it, your boss isn't close to an engineer and ought to consider retaining one for medium-voltage consultations. (Some of the info is in the IEEE color-books, but they're not for layman.)

 

[David Castor]

It has to be weatherproof and these are available. But generally it's not common to put standard dry-type transformers outside due to concern with moisture in the windings, dirt, etc. Encapsulated or cast coil windings would be preferable to conventional dry but much more $$$. As a designer, I never put one outside, other than cast coil.

 

[jim dungar]

It has to be weatherproof and these are available. But generally it's not common to put standard dry-type transformers outside due to concern with moisture in the windings, dirt, etc. Encapsulated or cast coil windings would be preferable to conventional dry but much more $$$. As a designer, I never put one outside, other than cast coil.

500kVA transformers are readily available with Vacuum Pressure Impregnated epoxy (VPI) construction which is pretty good at reducing moisture problems with the windings.

However I also usually suggested cast coil units.