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Based the calcs on 100A. Really can't help but feel youre here to call me out rather than help?You are fitting a fused isolator, so you will not have 100A
Discuss New circuit design question in the UK Electrical Forum area at ElectriciansForums.net
Based the calcs on 100A. Really can't help but feel youre here to call me out rather than help?You are fitting a fused isolator, so you will not have 100A
Based the calcs on 100A. Really can't help but feel youre here to call me out rather than help?
There is no requirement for the fused isolator to protect the DNO side, that have their own fuse. It is so you can justify protection of the sub-main without relying on the DNO's permission.You say the main fuse is 100A and you are fitting a fused isolator, therefore the fused isolator can't be 100A as you would not have any discrimination mate. It has to be lower than 100A.
There is no requirement for the fused isolator to protect the DNO side, that have their own fuse. It is so you can justify protection of the sub-main without relying on the DNO's permission.
True it won't provide selectivity at the DNO if you use the same value (assuming it meets the sub-main disconnection times) but if you are likely to blow the DNO fuse without a major sub-main fault (pick-axe through it, etc) you have under-specified the supply in the first place!
That is why I suggested a 60A fused-switch at each take-off point, as that should provide selectivity with the incoming fuses of both DNO and a customer.
Ok, so in past posts, if someone was to extend their tails from the meter to the CU, and it goes over 3 meters they have been told that they need to install a fused isolator. Why doesn't this apply here then? The principle is the same.
Or have I misread something...
Yes you have missed the bit that says "There is no requirement for the fused isolator to protect the DNO side". Not there is no need for a fused isolator. The point being they can have 100A fuses the same as the DNO.
kiosk one can have 100A fuse switch giving you better flexability with your selectivity futher down the chain.
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