Can I put 200A fuse in a 100 A switch box.

[defishu]

I am tyring to upgrade the fuse from 100A to 200A. The catalog No for the fuse is eaton QMB324MW. The 100A fuse will be replace with 200A. The physical size looks same for 100A and 200A. Help...help...

 

[augie47]

Your question is most confusing to me. QMB324MW is a Sqaure D 200 amp Fusible Disconnect.\
Maybe a fuse with that # but it is illusive.
100 amp and 200 amp fuses are not normally interchangeable.
In any event, the fuse should be sized per Code.

 

[tom baker]

Are you currently using a non time delay fuse and replacing with a time delay?
Is this for a motor? Motor short circuit and ground fault protection is allowed to be larger than what you would typically use

 

[Jraef]

The QMB324MW is a 200A Fused Disconnect for an old Square D QMB fused distribution panelboard. The smallest one they made that was a single switch was 200A, the 30, 60 and 100A switches were half the width, so they were sold as “twins”. It was not uncommon for someone to utilize an existing 200A switch with fuse reducers for smaller loads rather than have to buy two smaller switches, one of which they didn’t need. So yes, assuming your conductors are appropriate and you have made sure the panel is not overloaded, you should be able to put 200A fuses in there.
If that’s what this is...