MWC for lighting circuit run from 3A fused spur

[kuffs]

Hi Guys,

I have just added an outside light to an existing lighting circuit which is supplied by a 3A fused spur. Prior to doing this I made good and upgraded the earthing and main bonding. Also replaced a socket outlet which failed iR test on the ring supplying the above mentioned spur. The question is, what device do I put on the MWC as the means of protection. Would it be the 32a MCB in the CU or the 3A fuse in the spur? An additional question is, how do I find out the rating of the main switch on an old Wylex CU (metal case with BS3036 fuses)

 

[Badger]

probably a 60 amp rated main switch if its an old style wylex bs3036 fuse board.

 

[kuffs]

Hi badger, Thanks for your reply, any Ideas about the other part of my question? Cheers!

 

[Badger]

if your certyfying the light youd use the fuse but id put a note in the comments advising of the 32amp trip feeding the spur and write the zs for the spur in the comments box aswell as the zs at the light through the 3amp fuse. the fuse will be bs1362 and your rating will be 3 amp the max zs for a 1362 fuse is 13.62 red regs book 80% value and your value for the 32 amp mcb type b is 1.15 and type 1 is 1.44 type c 0.57 type d 0.29

 

[kuffs]

Hi Again Badger, great advice Do you think it would be okay to just use the Zs reading I got at the light and back through the 3a spur to the CU. The reason I say this is that the reading at the light was the highest, due to it being wired in 1.5mm T&E. The reading was .45 ohms at the light and my Ze was .33 so Zs is 0.78. I think I'm right in saying that it would satisfy the timings for the 3a fuse and the breaker?

 

[Andy™]

you list whatever is protecting the work you done. if you installed the fused spur, then its the breaker in the board. if you added to an existing spur, then its the fuse int he spur. simple.

 

[kuffs]

Okay, Thanks Andy. That also makes sense. Cheers:Salute