secondary protection required??

[mta145]

I want to install a 480v to 208\120v 75kw transfromer. I have a 125amp breaker available in the main 480v standup. from this breaker i want to feed the transformer and from the secondary mount a 225amp Main lug panel that they have already next to transformer. Will my secondary conductors need to terminate in a 225amp breaker before feeding the panel??
They said it was installed without one in there old plant?

 

[raider1]

Yes, the secondary conductors must terminate in an overcurrent protective device.

Check out 240.21(C) for the requirements for overcurrent protection for transformer secondaries.

Since you have a 4 wire 3 phase secondary the primary overcurrnet protective device can't be used to protect the secondary conductors.

Chris

 

[mta145]

Thanks yeah i read that and thought that was the case. Not sure how they got away without one in the previous installation?

 

[Npstewart]

Anytime someone says "Why? Thats how we did it...."

You should never listen to it, and usually you have to do the opposite.

I live in Florida, usually the rest of that sentence goes "Thats how we did it up north

Always check the code if its your first time doing something, I see illegal stuff everyday. Sometimes it wasn't wrong or illegal when they put it in, but now it is. They update the code based on the number of accidents that happen since the last edition. Goodluck.

 

[augie47]

Under unique conditions you might make an argument if the install fit 240.21(C)(2), but you can't avoid 408.36

 

[jim dungar]

Not sure how they got away without one in the previous installation?

One was not explicity required in previous NEC editions (i.e. <90).