High PFC

[sparkinlee]

A fuse box I was working on the other day (doing such things as providing a main earth connection to the fuse box, which I can only assume was missing for years) looks like this:


Having installed the main earth, the PSSC is 8.5kA. Must be close to the transformer...

The mcb 3rd from the left in the picture is shown to have a rated short circuit capacity of 3kA, and I assume the others are the same, and accordingly all are lower than the PSSC.

As far as I can see the simplest remedy would be to replace the push in MCBs with push in fuse carriers and BS 1361 fuses with a rated capacity of 16.5kA according to the onsite guide. Any other suggestions?

If the client requests information on upgrading to a 17th Edition board, who makes MCBs that would be suitable? - my recollection at this time of night is that they are generally 6kA, which would be too low.

 

[JamesBrownLive]

Following on from the site that Spin provided, I also found this publication on there that specifically addresses your concerns..

http://www.beama.org.uk/download.cfm/docid/4E73CCBD-DA14-4CE3-8AC60B8D0A030CD3

Cheers

 

[Inteificio]

I've always thought that it kind of doesn't matter - the 6/10/15/whatever rating is the maximum fault current that the device will switch AND STILL OPERATE afterwards, though we all know that it'll in all likelihood be toast. So, if you're going to fry it, it's fried and therefore doesn't matter.

One of us is wrong on this, hope it is not me.

The 6/10/15 is normally the one time break, the service breaking or whatever it is called is generally FAR lower.

 

[sparkinlee]

Thanks all for the comments... seems I have some reading material to get my head around.

But am I right in understanding the general thinking that the board is OK as it is, so far as PFCs go?