TRANSFORMER DISCONNECTS

[AZJeff2013]

I AM SUSPENDING A 50KVA TRANSFORMER FROM A CEILING @ +84" AFF TO BOTTOM.

THERE WILL BE PRIMARY AND SECONDARY SIDE DISCONNECT SWITCHES.

QUESTION....WHAT IS THE MAXIMUM HEIGHT THE DISCONNECTS CAN BE MOUNTED? OWNER WANTS THEM @ 7'. IS THIS CODE LEGAL?

THANKS!

AZJEFF

 

[qcroanoke]

I AM SUSPENDING A 50KVA TRANSFORMER FROM A CEILING @ +84" AFF TO BOTTOM.

THERE WILL BE PRIMARY AND SECONDARY SIDE DISCONNECT SWITCHES.

QUESTION....WHAT IS THE MAXIMUM HEIGHT THE DISCONNECTS CAN BE MOUNTED? OWNER WANTS THEM @ 7'. IS THIS CODE LEGAL?

THANKS!

AZJEFF

6 ft. 7 in. to the top of the throw.
However,

Look at 404.8 exception#2 2008 NEC

 

[GoldDigger]

6 ft. 7 in. to the top of the throw.
However,

Look at 404.8 exception#2 2008 NEC

That would seem to cover the primary side disconnect, but maybe not the secondary side.
Exception 3 may help too.

 

[wallypiper]

Why are there disconnects on both sides? Why would you turn off the secondary but keep the transformer energized?

I would try to dissuade the owner rather than digging for exceptions. I view disconnects as having two functions - maintenance and "e-stop". For maintenance, yeah, maybe you put it out of reach. But if there's smoke coming out somewhere on the secondary side, I wouldn't want to be searching for a ladder so I can reach the disconnect.

 

[infinity]

Secondary conductor protection that is required by article 240 and is often provided by a fused disconnect adjacent to the transformer.

 

[petersonra]

Why are there disconnects on both sides? Why would you turn off the secondary but keep the transformer energized?

I would try to dissuade the owner rather than digging for exceptions. I view disconnects as having two functions - maintenance and "e-stop". For maintenance, yeah, maybe you put it out of reach. But if there's smoke coming out somewhere on the secondary side, I wouldn't want to be searching for a ladder so I can reach the disconnect.

Disconnects are not used for emergency disconnecting. Normal disconnect switches are only rated to carry the rated current, not make or break it.

 

[fifty60]

So normal disconnects should only be used with the load not energized?