Fused disconnect switch

[anbm]

What is the reason to use fused disconnect switch ahead of a motor or an appliance in lieu of a none-fused disconnect switch?
Is it code? I thought the breaker in electrical panel will protect the load from overload and short circuit already?

 

[tom baker]

Yes a CB will, but a dual element time delay fuse can be sized smaller than a cb.
A few HVAC condensers require fused protection per the mfg
Sometime what’s installed for disconnect is what’s on the truck

 

[JoeStillman]

Non-fused switches are only rated for 10 kAIC. Put a fuse in it and you can jump right up to 100 k. The rating can also be achieved by matching the manufacturer of the upstream breaker, but sometimes you can't. It makes fusing a no-brainer when there is high available fault current. You can almost always skip the calculation and get by with fuses.

 

[anbm]

Non-fused switches are only rated for 10 kAIC. Put a fuse in it and you can jump right up to 100 k. The rating can also be achieved by matching the manufacturer of the upstream breaker, but sometimes you can't. It makes fusing a no-brainer when there is high available fault current. You can almost always skip the calculation and get by with fuses.

Great point. Thank you.

 

[milmat1]

In a control panel I typically place a fused J-class disconnect, then each branch motor circuit is protected by it's own MPCB.

If it is only a single motor circuit, the high SCCR is likely why. And a dual element TD fuse is the best protection for a motor circuit IMO.