J Type 350 Amp Fuse Spacing

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dpslusser

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I have an application where I need to mount 12 fuses next to each other (see picture below). They are the branch circuit protection from an MCCB.

Since most J type fuse blocks are so huge I wanted to go with fuse holder/studs (see picture below).

My question is that there has to be some type of limit as to how close these fuses can be mounted due to arcing, correct? I have seen some fuse block where phase barriers separate the fuses so they can be mounted closer.

The fuses are 350Amp J type. They are a little over 7 inches in length. Currently they are spaced at 3/8 of an inch.

Let me know what you guys think.

Thanks



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I wondered the same thing. Thats why I don't think I am going to go with them.

I can't believe there isn't more manufactures that make a fuse block with studs for mounting ring terminals and flexible bussbar too.

I called mersen and they make a single pole 400amp block. Why not a 3 pole? Who know's. It wasn't even on their website. They had to email me the data sheet on it.

I will probably purchase 12 of the mersen blocks and stack them next to each other. Do you think I would have to follow the same code for mounting the blocks next to each other or can I butt them up?
 
dpslusser said:
I can't believe there isn't more manufactures that make a fuse block with studs for mounting ring terminals and flexible bussbar too.
Click to expand...

I had a long chat with a UL508a engineer about this. The reason it is not done is that the plastic base cannot take the force that is generated when a short circuit occurs at high levels of available short circuit current. No one wants a 400A fuse block that is only rated for 10kA SCCR.

I noted that the drawing from Merson does not say anything at all about it being UL listed or recognized, likely because it is not.

personally, if I was going to try something like this I would use bus bar insulators. They are made to take the forces. Something like these.

http://www.erico.com/part.asp?part=559600

The UL engineer told me that some switchboard manufacturers have gotten approval from UL to use them in that way in switchboards, but they had to have them tested to use them above 10 kA.
 
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