Tripping Light Circuit

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Love to see a fuse feeding a submain, don't see it nearly enough though
Well just for you here is a recent photo of some 3036 fuses feeding a submain. They should be 100A wires but there was a random assortment of doubled up fuse wires, each fuse different! This switch fuse is in poor condition in more ways than is shown in the photo. The conductors are 70mm.
upload_2016-9-15_22-1-11.jpeg
 
They don't look like 70mm conductors at all! Looks no bigger than 10mm². Bad photo skills!

Nice carrier on L1, and was L2 ever yellow or did it start out life as white?
 
It really is bigger than it looks! The conduit entries are 2". The L2 insulation is white as it is rather old.
 
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Not really. If we are talking about fault protection as opposed to overload protection then there is liable to be sufficient current to operate any and all devices in most cases.

Fuses or MCCBs are far better for achieving selectivity (discrimination).
I'm pretty sure I have seen some charts (Merlin Gerin / Schneider) which do allow full discrimination of certain MCBs but iirc I think it depends on fault current.
 
Asbestos seal and probably flash pads?
Probably, though the flash pads were missing. The seal looked to be painted over with something clear (PVA?) so perhaps h+s have had a go at making it safer. It would have been better to replace the unit to remove the hazard though. All the other switchgear of this age has been replaced, except this one.
 
So just to close this thread out. I was focusing on the Light circuit tripping, however there were two circuits from the CU, and the Electrician tracked it down to a problem in the socket circuit. A screw from the plasterboard must have damaged it. And I thought I was being careful!! I never got to see the damage, as the wire had been clipped so could not pull it out. A new wire was threaded and only a very small hold in plasterboard had to me made.

I asked him about the RCD being in series, and he was not overly concerned about this. He said the worst thing about it was the inconvenience or more things being taken out if something did cause a trip. It was a different electrician as to who installed the circuit.
 

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