Fused Low Voltage Circuit Breakers

[REM76]

Can limiters be put the load side of low voltage power circuit breakers? I have alawys seen them on the line side. Is there an associated standard like NEMA or ANSI for this application. The reason that we want to put the limiters on the load side is because we are doing a retrofill job where the old breakers are old FPE breakers with fuses on the load side.

Thanks

 

[lansford]

Limiters are "limiter Lugs" usually used for multiple sets of low voltage cable protection. I guess you mean current limiting fuses which gave the basic FPE circuit breaker a higher interrupting rating.
If you are retrofitting or replacing the breaker first you neeed a short circuit study. After that is complete, you will see what you need for interrupting capacity.
The application may not require fused circuit breakers.
JIM

 

[Zogzog]

If you are doing a retrofill with high interuption requirements why wouldnt you do a vacuum retrofit? Costs about the same with little maintanance requirements.

 

[alehman]

I've never seen them on the load side. Normally the original manufacturer would dictate such things. I would not want to change the original design if I could avoid it.

 

[LionelHutz]

There are some circuit breakers with a "fuse block" on the output side. This block basically attaches right into the breaker and extends the output side of it. It allows for a higher interrupting rating. However, this is a factory option only. There's no standard that I know of for installing your own fuses. The rating of the breaker is what it is. It is still upstream of your higher rated fuses.

 

[jraef]

But...
If your goal is not to provide added protection OF THE BREAKER but rather the downstream system, then I don't see a problem with that. In other words, if your existing breaker is already rated for the available fault current, but you want to limit the fault current down stream because other equipment cannot withstand that level, then current limiters are a legitimate choice, maybe your only viable choice.

You need a full detailed coordination study before embarking on any of this.

 

[alehman]

I agree with jraef. I would emphasize that if there is concern for the interrupting duty of the breaker, the manufacturer must be consulted for the proper time-current curve and placement of protectors. At high fault currents, physical location can be important to the performance of the breaker.