No Fused Switches on Solidly Grounded System

[Sunny_92]

I'm currently working on a design/build project and one of the requirements states "Do not use fused switches in a solidly grounded system."

Does anyone know what the reasoning behind this might be? I'm a fairly new engineer and haven't come across that requirement before. Can fused switches have negative effects when used on a solidly grounded system?

Thanks!

 

[Jraef]

I'm currently working on a design/build project and one of the requirements states "Do not use fused switches in a solidly grounded system."

Does anyone know what the reasoning behind this might be? I'm a fairly new engineer and haven't come across that requirement before. Can fused switches have negative effects when used on a solidly grounded system?

Thanks!

Hard to tell, it's either poorly worded or is specific to your project, which we know nothing else about. For example if there is a corner grounded delta system, this makes sense even by code, because you cannot have circuit protective devices in the grounded conductor unless the device opens all three phases simultaneously. That translates to "circuit breaker" for the most part. That may have been what they were getting at, but if your project is using a solidly grounded wye system, that statement was unnecessary in that aspect, because you would not use a 4 pole disconnect and fuse the neutral.

Or, they have some other reason we don't know about, such as just not wanting to allow single phasing of 3 phase loads. That wording seems a little too round-about in that case, but I'm just guessing at their intent. Can you ask anyone?