Tail sizes

[sparks1234]

We come across 16mm tails on 100 service fuses quite a lot.
What are peoples thoughts on this? usually they are fairly short but neverthe less!!
We are just carrying out one job on a brand new installation and we have this scenario, somebody has installed the dis board and lighting installation but all on 16mm

 

[Octopus]

Show me a house which can draw 100A and I'll take this debate seriously.

Tin hat on!

 

[Noton1205]

Ive been to a house in the past week that have blown a 100a fuse because there drawing to much. 2 electric showers, cooker and hob and swimming pool. They also only had 16mm tails, needless to say the cables were slightly scorched

 

[Geordie Spark]

I had Central Networks out to an old Georgian House a couple of weeks ago, I'm doing a rewire there and they came to look at the supply cable, I said that I was upgrading tails to 25mm for the 100A fuse, and said about their 16mm tails to the meter, and he shrugged his shoulders and said 'they should be ok'.......one rule for us.......and one for them it seems!

I recently replaced the CU in my own house & fitted 25mm tails & isolator because I have a 100 amp main fuse and was wondering what to do about the 16mm tails that run from the cutout to meter & from meter to isolator.

A few days later, a bloke arrived to do a meter swap so I gave him some 25mm tails & asked him to use them to replace the 16mm ones. He refused & said he wasn't allowed to !!!

 

[Noton1205]

I recently replaced the CU in my own house & fitted 25mm tails & isolator because I have a 100 amp main fuse and was wondering what to do about the 16mm tails that run from the cutout to meter & from meter to isolator.

A few days later, a bloke arrived to do a meter swap so I gave him some 25mm tails & asked him to use them to replace the 16mm ones. He refused & said he wasn't allowed to !!!

What supplier was he from? Should of changed the, or down grade your fuse

 

[malcolmsanford]

100a fuse should be on 25 mm tails. 16 mm tails can have a maximum of an 80a fuse in the cutout. If the cutout has a 100a fuse in and the tails from. The cutout to the meter are undersize, you need to get your supplier in to change them. If the tails from the meter to the CCU are under sized then you need to get a sparks to upgrade them, but you still need your supplier out to install an isolater

I have yet to see a DNO that work to BS 7671-2008 though they recognise it in the ESQCR-2002, they still do not work to it and therefore you can not make them do anything. If they have supplied a 100amp BS 1361 fuse, or whatever it is called these days BS 88 whatever, and they decide that the tails from their head to the meter is good enough, then that is end of. Good enough for me as I'm not concerned with their installation, if it goes belly up then the DNO have to answer for it, not us, and unlike us their bible is the law.

As for the Isolator, again each DNO will be different, I'm sure that the majority of them have realised that it is a nice little earner for them to fit one, but again as per the ESQCR-2002 it is not something they have to do ............some will some won't it is the luck of the draw. In fact the only mention of double pole isolators for the customer installation in the ESQCR-2002 is in REg 7(2) concerning the continuity of the neutral conductor.

 

[Noton1205]

Unless the dno are your supplier aswell they do not get involved with upgradingyour tails.its down to your supplier to upgrade the tails. I know british gas, eon, southern elec and npower do upgrade. At least in my area they do.

 

[malcolmsanford]

Maybe so but it is still DNO/Suppliers call as to what size tails are fitted from the head to meter. There is nothing wrong in calling and informing them of your concerns, as during the past, a 60amp fuse may have blown and someone ........may have fitted a 100amp without the DNO knowing that I can understand, but you can not dictate to the DNO what size tails are undersized, that is their respnsibility.

 

[mogga]

Show me a house which can draw 100A and I'll take this debate seriously.

Tin hat on!

Put in an electric oiler your nearing 100A without shower cooker lights

 

[impecc]

Are DNO mandated to change tails to 25mm2 when we carry out CU change? I called Edf last week for a proposed CU change job and not interested in upgrading the tail to 25mm2. Am I allowed to go ahead or what next can I do?

 

[impecc]

My experience on the DNO fuse suggest it could be misleading. They write 100A on the fuse holder but actual fuse within sometimes is 60A with 16mm2 tail.

 

[Noton1205]

The supplier will only upgrade tails on request or if they are damaged. 16mm tails will take up to 80amps but 25mm will take 100amps as per the mocopa. If you want to change the CU then you can either get intouch with the supplier and ask for an isolator to be fitted between the meter and CU which could cost you up to £50 or you could install the new CU then connect the new tails from the CU to a double henley block. The only disadvantage to fitting the block is you will have to work live unless you cut the seals on the cut out.

Impec, it says 100A on the fuse carrier as this is the maximum that the cut out is rated at, it doesnt mean that is the size of the fuse inside.

 

[telectrix]

in which case, in order to complete a certificate of any sort, we have to pull the main fuse just to be able to enter it's rating on the cert.

 

[Noton1205]

I agree you should be able to pull the main fuse, but unless you have your MOCOPA cert your " not " allowed.

 

[Knobhead]

So you have a 100A service head feeding 25mm tails. If the house is over 30 years old you may have a 7/.064 service if your lucky. Large houses could be 19/.044.

The supplies are only just up to the job.