Disconnect means for a transformer

[herndon]

Does anyone know if I have a 75KVA(480v. 3p. to 120/208v. 3p.) step down transformer in a different room from the primary overcurrent protection.

Do I have to have a disconnecting means at the transformer for servicing it?

Thanks....

 

[kripton]

Re: Disconnect means for a transformer

I believe you need a disconnect on the primary side only since it's a step down.

 

[herndon]

Re: Disconnect means for a transformer

Do you know any NEC Art #....

 

[don_resqcapt19]

Re: Disconnect means for a transformer

The NEC does not require either primay or secondary disconnects for transformers. Overcurrent protection is required for the primary, but is not required to be located at the transformer.
Don

 

[herndon]

Re: Disconnect means for a transformer

Don - Is this correct for any size step down transformer?

Thanks...

 

[don_resqcapt19]

Re: Disconnect means for a transformer

Yes.

 

[jp_electric]

Re: Disconnect means for a transformer



[ December 18, 2003, 10:44 PM: Message edited by: jp_electric ]

 

[pierre]

Re: Disconnect means for a transformer

Article 450 covers protection of the transformer, Article 240 covers protection of the conductors.
For the transformer mentioned, table 450.3(B) is the reference for protection of the transformer.
408.16(D) will provide one with the info on the secondary side of the transformer for the protection of the panel on the secondary side.

Pierre

 

[herndon]

Re: Disconnect means for a transformer

What I was looking for, is am I required to have a disconnecting means in sight of the transformer? For protection if I'm working on it...

 

[russ]

Re: Disconnect means for a transformer

NO!

 

[russ]

Re: Disconnect means for a transformer

You can check this post.

http://www.mikeholt.com/cgi-bin/codeforum/ultimatebb.cgi?ubb=get_topic;f=11;t=001023

 

[herndon]

Re: Disconnect means for a transformer

THANKS... TO EVERYONE FOR YOUR HELP...

 

[gregory]

Re: Disconnect means for a transformer

240.40 Disconnecting Means for Fuses.
A disconnecting means shall be provided on the supply side of all fuses in circuits over 150 volts to ground and cartridge fuses in circuits of any voltage where accessible to other than qualified persons.

If you have fuses protecting the transformer primary and it is 277 volts,(over 150 volts to ground) you must have a disconnect for the fuses that protect the primary.