240 rated breaker in 480 panel

[paul hodge]

I have situation were a GE THQB 50A, 3 PHASE breakers has been installed in a 480/277 panel. After determining that a breaker needed replacement I took a picture of the breaker to capture information. As I was looking over breaker specs I noticed the 240 volt rating on the breaker. I have two questions. 1.We're in the NEC is ratings of breaker or equipment addressed and 2. What problems may this have created?

 

[kwired]

I have situation were a GE THQB 50A, 3 PHASE breakers has been installed in a 480/277 panel. After determining that a breaker needed replacement I took a picture of the breaker to capture information. As I was looking over breaker specs I noticed the 240 volt rating on the breaker. I have two questions. 1.We're in the NEC is ratings of breaker or equipment addressed and 2. What problems may this have created?

What panel do you have that is rated 480/277 that a THQB actually fits into? Or was it somehow field made to fit?

 

[paul hodge]

I suspect the panel interior is not rated for 277/480 volts. Usually on GE dead front there is a sticker that indicate voltage for interior, sticker is not readable. I intend to find out for sure.

 

[jumper]

I am getting a bit confused.

Do you have 480/277V in a 240V panel?

or

Do you have a 240V breaker in a 480/277V panel?

 

[electrofelon]

I few years ago I came across a 240 V panel and breakers installed on a 277/480 system. Yikes!

 

[macmikeman]

Somebody hooked a feeder for a 240 volt panel into the secondary of a 480 volt xfmr?. Call the fire dept. this needs to be shut down right now.

 

[Jraef]

So in the "A Series" panelboards, the box and cover are the same regardless of the voltage. it's the interior that is different. So are you sure it really is a 480V panel? Maybe its just a cover from a 480V panel and the interior is a 240V. That's what youy need to check for sure. If the interior is an AL or AQ, that is 240V max and those are the only ones that will accept THQB breakers. If the interior is an AE or AS, then it's 480/277 and it would not accept the THQB breakers, they would have to use TEY frames.

The THQB only bolts on at the bus connection, the other end is supposed to clip into a frame to hold it down. The AE/AS interiors will not have the frame to clip a THQB breaker into. TEYs are bolt-on for both ends and are a lot longer than the THQB. So the only way the THQB could be mounted physically into an AE/AS panel interior is if they either never mounted the back end to anything and it is attached by the bus connection only (!!!), or they cobbled together some sort of makeshift bracket to hold the other end. Either way, its a clear violation of 110.3 of the NEC, the so called "suitable for the intended use" clause. You don't need anything else to justify removing it.