Service fuse and tail size

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Single phase, clipped:
10mm² is good for 65A
16 for 87A,
25 for 114A
35 for 141A

Table 4D1A

Lots of copper wasted nowadays.
 
Out of interest how do you size match these? ... 16mm 60A ... 25mm 80 or 100A ?
... 35mm
Well, if you go by BS7671 (which is not necessarily the relevant regulation), 16mm² singles 'clipped direct' (the 'best' on offer) have a CCC of 87A (although 16mm² T+E in free air is 94A). 25mm² singles have a CCC of 114A if 'clipped direct' or, if they are in free air and not touching (which is usually the case for tails), 130A if vertical and 146A if horizontal. 35mm² singles (are they ever used as 'tails', at leas domestically?) are 141A 'clipped direct', or 162A (vertical) /181A (horizontal) in free air.

So, if one used those figures 16mm² would normally be OK for a 60A or 80A fuse and 25mm² for a 100A one. You would only need 35mm² if the fuse were >130A.

Kind Regards, John
 
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And as there is no whole current meter rated above 100A, the 35mm is never needed
 
Thanks.

I'm sure I saw wickes selling 35mm which started to confuse me what was used for a 100A fuse. They were very dusty though lol.

So if I wanted to purchase a spare service fuse (just in case the present 60A got overloaded and blew) Are all fuses the same physical size?
E.g a bill fuse holder.
 
So if I wanted to purchase a spare service fuse (just in case the present 60A got overloaded and blew) Are all fuses the same physical size?
E.g a bill fuse holder.

No, No and Thrice NO.

That cut-out is not under any circumstances your property, you do not and never will have the appropriate training and authorisation to open it, work on it (even changing fuses) or interfere with it in any way.
If the fuse does operate you MUST contact your DNO who will change the fuse free of charge, inspect the device and if required arrange to change it to a 100A device.

Note that the next fuse behind that one is at least 200A and in some areas up to 800A, if you get it wrong you could well be in a world of pain

If it is a medal clad type, some of these cannot be operated on in any way whilst live. The DNO will simply change one of these.
 
Normally the cut-out unit is fed by a service cable tapped straight off the street main, which can be fused at up to 800amps, especially in Central London Zones One and Two, and 200 amps in say London Zones Four and Five or similar. Nothing else protects the cut-out unit. Yes this is England, and not China, but extremely bad installation practice anyway.
 
Tails after meter.
16mm. Vertical free air.

Arrangement is:
Supply cable , service head and fuse.

Splits out to 3 fuses(60A) and 3 meters.

I don't intend to, but I understand a 60A could be changed to 80A and therefore there is no point me making the tails any bigger.


Post Note:

The 3 fuse carriers are marked on the outside 60A. (and as least 1 contains a 60A fuse).

The main fuse carrier is marked 100A.

It looks like in them days (mid 70's maybe) they actually marked the fuse rating on the outside. (and it is actually correct, unlike these days)
 
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