switches in transformers

[buck33k]

450.8(C) references switches in transformers.

The switch in the image is not accessable with the transformer cover in place. I was wondering how common it is to have switches in transformers.

http://i158.photobucket.com/albums/t108/buck33k/001.jpg

 

[ron]

I've seen that arrangement in the GE transformore product. It is an undersized transformer with fan cooling under loads close to full load. This is how they get their TP1 rating.
When the little pancake fans fail, and they will, and the thermostat reaches some predetermined temperature, it shunt trips the switch you see in the picture and bye bye load.

 

[iwire]

450.8(C) references switches in transformers.

The switch in the image is not accessible with the transformer cover in place. I was wondering how common it is to have switches in transformers.

http://i158.photobucket.com/albums/t108/buck33k/001.jpg

This is a shunt trip molded case switch and is not required to be in the open by the NEC.

It shuts this transformer down in case of over temperature.

 

[buck33k]

Thanks Ron and Bob for that info.

 

[wireguru]

why in the world would anyone ever want one of these transformers?

 

[ron]

I think the concept is that most transformers in regular commercial occupancies will not run anywhere close to full load, and thus will never need the fans. The smaller core makes for less cost, less footprint and easier compliance with the somewhat recent NEMA TP1 standard.