16mm tails with 100A fuse ???

[Wilko]

Job today to change out old fusebox and I'd noted the 16mm tails but on pulling the fuse this morning it was 100A which I wasn't expecting. Fairly recent new smart meter installed by XYZ who are also the DNO ... Shouldn't the fuse be limited to 60A in this case? Thoughts and advice appreciated

 

[westward10]

so what factor would apply to the cable rating just because it's inside a box? where in BS7671 does it say that a rating factor needs applying.

Derating was probably the wrong choice of words. What I am saying is if the conductors are not clipped direct throughout the ccc should be based upon them being enclosed even if it is for a short length.

 

[HandySparks]

I have already stated clipped direct can be used between heads and meters etc..

What about twin and earth, which clearly has to enter an enclosure to be terminated?

 

[Dave OCD]

I have already stated clipped direct can be used between heads and meters etc..

Ok then but what about the terminations of either end which are both enclosed,meter and cutout, how can that be different from terminations at the CU main switch ?

 

[streamer]

I have already stated clipped direct can be used between heads and meters etc..

That must be the only situation when clipped direct can be used then as everything else I can think of enters an enclosure of some description.

 

[westward10]

Conductors at meters and heads are generally not contained although I admit in some cases they maybe.

 

[telectrix]

OK to be on the safe side. pull the 100A fuse and insert a 60 A nail. nothing burns, nothing blows. everyone's a winner.

 

[happysteve]

That must be the only situation when clipped direct can be used then as everything else I can think of enters an enclosure of some description.

What about twin and earth, which clearly has to enter an enclosure to be terminated?

Guys, guys, you're thinking about this the wrong way! Reference method C also includes "... cable direct in masonary..." (installation methods 57 and 58). So all that is needed to legitimately use reference method C is to fill your enclosure with plaster once you've terminated the cable!

To think, the spreads have been doing us all a favour all these years...

 

[Toneyz]

OK to be on the safe side. pull the 100A fuse and insert a 60 A nail. nothing burns, nothing blows. everyone's a winner.

Don't have proper nails anymore it's all gripfill and nailgun

 

[westward10]

Delete.

What about twin and earth, which clearly has to enter an enclosure to be terminated?

Ah well I could open a can of worms with that also as in theory you could use 4D2A for the complete cable and then refer to 4D1A when it is stripped at an enclosure and effectively becomes singles thus making the rating when clipped direct excessive for the contained conductors

 

[Deleted member 9648]

I took the tails into the board I installed today through a gland with a rubber insert. I guess I should have sized the tails based on being enclosed in thermal insulation.

 

[happysteve]

I took the tails into the board I installed today through a gland with a rubber insert. I guess I should have sized the tails based on being enclosed in thermal insulation.

... only if the gland's more than 50mm. I presume you got your calipers out...?

 

[Deleted member 9648]

Got me what out?
49.5mm.....just got away with it.

 

[happysteve]

Got me what out?

 

[davesparks]

Clipped direct would apply between service heads and meters etc. Once contained at its termination to a CU alternative ccc applies. Really quite simple.

But cable sizes are calculated based on the most onerous conditions they are installed in, so if the last few inches have a lower ccc due to being enclosed then the whole length of the cable must have that lower ccc.

If the termination at a CU is to be considered as being enclosed for the purpose of cable rating then do you also extend that to a switch, socket or joint box, and if not then why not?

I think you need to consider what, if any, the effects of being in that enclosure are. the difference between being enclosed in a conduit or trunking and being in a CU should hopefully be obvious.

 

[davesparks]

Just ordered a couple of 60A fatboy fuses. Not saying where one might go

Edit : ok, just stop right there, you lot are just hopeless

Is this a joke? Or have you come to an agreement with the DNO about preventing the fuse ever being replaced with 100A by their operatives if the cutout is replaced or if someone notices that the wrong size fuse has been fitted?