fuse sizing

[jociha]

I understand circuit breakers should be sized at 80% for continuos duty unless 100% continuos rated, what about fuses? john

 

[bennie]

Re: fuse sizing

The load is sized to the breaker and fuse.

 

[websparky]

Re: fuse sizing

Depends on what the load is!

Motor?
AC Equipement?
Sub Panel?

 

[jim dungar]

Re: fuse sizing

All overcurrent protective devices are sized using the same principals.

UL Listed enclosed devices are intended to continuously carry only 80% (actually 125% of connected load) of nameplate rating, unless they are specifically listed otherwise.

While the UL testing of a fuse only is different than the testing of a circuit breaker, the testing of enclosed devices is the same. This testing includes the temperature rise of the conductor connection. Temperature rise inside of the enclosure is normally the limitng factor in determining the current carrying capacity.

 

[websparky]

Re: fuse sizing

jim dungar;

Exactly!