Switch fuse or not switch fuse

Evening, 

as part of a job the dno ( UKPN)

have installed a 100a tp&n supply in a feeder cabinet typical tnc-s supply. 
 

i have run a 50mm 5c swa to a new shop and terminated in a mem 3ph db.  
 

on the supply end I have terminated the 50mm into a 100a isolator and left 25mm tails for the meter provider. 
 

he came yesterday and won’t connect as “ it needs to be a switch fuse “

I said why ? 
he said because it does. 
 

i am certain it complies. 
 

comments please ( Bare in mind I’ve got the Reg numbers to support my claim)

thanks in advance. 

The DNO will only allow their fuse(s) to protect tails up to 3 metres long.  Your "tails" from the meter to the DB  must be over 3 metres long, so he is right, you need a switch fuse.

It's not a BS7671 issue. The DNO have their own rules and it is these that it does not comply with.

so you have installed 50mtr of cable and not installed any overload or fault protection as required by BS7671 and your moaning because DNO rightfully refuse to connect it?

for a start, 433.3.1(iii) & 434.3(iv) says otherwise...

so what reg do you think says its complies?

Andy™ said:

50mtr

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Should've gone to specsavers.....50mm!

Jest saying

ProDave said:

The DNO will only allow their fuse(s) to protect tails up to 3 metres long.  Your "tails" from the meter to the DB  must be over 3 metres long, so he is right, you need a switch fuse.

It's not a BS7671 issue. The DNO have their own rules and it is these that it does not comply with.

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Thanks for your response.
Two dno , field engineers have confirmed they are happy with my arrangement the 3m tails thing is related to domestic unprotected 6181y type cables. 

Andy™ said:

so you have installed 50mtr of cable and not installed any overload or fault protection as required by BS7671 and your moaning because DNO rightfully refuse to connect it?

for a start, 433.3.1(iii) & 434.3(iv) says otherwise...

so what reg do you think says its complies?

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433.3.1 says a device for protection against overload need NOT be provided (iii) if dno has provided overload device and agree it affords protection ( which they have agreed) and 434.3 says the same re: fault current 

why do you interpret differently?

Oh and the dno are happy it’s the meter provider who isn’t 

kerching said:

Should've gone to specsavers.....50mm!

Jest saying

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:slap

mr mark sparks said:

433.3.1 says a device for protection against overload need NOT be provided (iii) if dno has provided overload device and agree it affords protection ( which they have agreed) and 434.3 says the same re: fault current 

why do you interpret differently?

Oh and the dno are happy it’s the meter provider who isn’t 

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if DNO have put it in writing that they are happy to allow their fuses to allow you to use the exemptions in 433 & 434 then sho that to meter monkey and tell them to go complain to someone else

there is also nothing in BS7671, or 433 / 434 that states that it only applies to 6181y cable, so it applies to any cable

how long is the cable?

Andy™ said:

:slap

if DNO have put it in writing that they are happy to allow their fuses to allow you to use the exemptions in 433 & 434 then sho that to meter monkey and tell them to go complain to someone else

there is also nothing in BS7671, or 433 / 434 that states that it only applies to 6181y cable, so it applies to any cable

how long is the cable?

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Not 50mm long
50 m ducted in the ground. 
 

Is the 3m thing from 433.2.2 ? 
 

just to satisfy my curiosity what would have another set of 100a fuses at the origin achieve? 

Regards the 3m thing is that not where there is a reduction in ccc ? Which in my case there isn’t 433.2.1. 

everything after the meter is BS7671. therefore its needs overload & fault protection. DNO will allow you to use their fuse to achieve this upto 3mtr, and this ties in with 433.3.1(iii) & 434.3(iv). note than some DNO its 2mtr

have DNO put it in writing that you can use their fuse to adequately protect the cable, since they normally say 3mtr. cant imagine them being happy with 50mtr

I don’t have anything in writing, so will have to “try” and get this tomorrow 

the other situation I’ve had this was when ukpn put a new substation in and we ran 500mm single core swa to our feeder pillar and the connected those directly with no additional overload or fault protection. 
more often than not there is a switch fuse to down rate the supply.  
ultimately that’s why I’m here tonight to get some clarification. Cheers 

Now I’m confused I said what’s above not Andy

mr mark sparks said:

433.3.1 says a device for protection against overload need NOT be provided (iii) if dno has provided overload device and agree it affords protection ( which they have agreed) and 434.3 says the same re: fault current 

why do you interpret differently?

Oh and the dno are happy it’s the meter provider who isn’t 

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But they DO NOT agree in this situation that it does.

Its the 3 mtr rule  as far as I know ,   with a 50m run of sub-main  the sw/fuse is start of  BS 7671  & the end of whatever the DNO rules are .

Meter monkeys are getting much more full on training these days  and your guy probably has  a checklist to work to ....they are not allowed to connect anything  they consider wrong in any way .

I once had a DNO guy tell one of my customers that it would be ok to use some of their Al/Cu straight concentric cable as a sub main to his garage... so he dug a trench and buried 30m of it.... I told him that I couldn't use it and that it would need replacing with some SWA

The moral of this is that sometimes the DNO workers talk ****

NozSpark said:

The moral of this is that sometimes the DNO workers talk ****

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Yes When I had them move my supply I asked their forman guy  to give me PME     ( It was TN-S  before with a poor Ze )      He said its not allowed in this area  .   Having worked in dozens of houses in my road  I knew any replaced supplies were PME   so I put the same request to the jointer  who said  " No problem "