Domestic meter tail isolator

[Soulsurfer]

Hey all,

I have a few installs coming up where I need to upgrade cu's and want to install isolators between DNO service head and new consumer units. I have only ever fitted before to twin supply houses on off peak storage heating and was under the impression that a straight enclosure with a 100A DP main switch would be good enough. But DNO have just told me that they also require over-current protection. On two supply i usually use a Hager 4P switch and 2 x 63A MCB's for feed tails but could I use a 100A dp and a separate MCB in enclosure on Brown tail ? or does anyone use easily sourced different equipment?

Thanks,

 

[Andy78]

This is the standard bit of domestic kit for fused isolation for tails. Readily available and easy to use with tails.
You don't want to be using an upfront MCB for the discrimination issues involved which can result in possible non compliance with the regs.

 

[Richard Burns]

But of course from January we will all love using the Amendment 3 all metal switch fuses!


Joking aside I would echo Andy78 do not use an MCB, use a Switch fuse.
The DNO usually specify overcurrent/fault protection for longer tails runs (often over 3m), but should generally be happy with just an isolator for a short run to a CU.

 

[Midwest]

But of course from January we will all love using the Amendment 3 all metal switch fuses!
View attachment 30822

They look nicer than their CU's

 

[Octopus]

Hey all,

I have a few installs coming up where I need to upgrade cu's and want to install isolators between DNO service head and new consumer units. I have only ever fitted before to twin supply houses on off peak storage heating and was under the impression that a straight enclosure with a 100A DP main switch would be good enough. But DNO have just told me that they also require over-current protection. On two supply i usually use a Hager 4P switch and 2 x 63A MCB's for feed tails but could I use a 100A dp and a separate MCB in enclosure on Brown tail ? or does anyone use easily sourced different equipment?

Thanks,

Why??? What is their reason?

 

[Simonslimline]

Which DNO is it out of interest?

 

[Soulsurfer]

Hi DNO is Jersey Electricity Co and usually they like isolator before cu as they say good practice but if I am having homes on 100A single phase supplies there seems no benefit to use 63A to protect the line tail as you can't then take your higher supply current so counter productive. If I could work out how to post up a pic or two I could show you what is usually fitted by others.

 

[Soulsurfer]

Something like this for Economy 7 and standard supplies

 

[Risteard]

That must be new. I don't remember the JEC requiring that before.

Although ESB requires a 63A MCB for meter tails exceeding 3 metres. (Not a fan of this for reasons of discrimination/selectivity mentioned.)

 

[Soulsurfer]

Just picked up a 100A Wylex all metal switch fuse but it's like £70 ! & the size of the cu ! Meter tails are approx a foot max so don't know what's going on there. Think I'll call them again as it's nuts

 

[Soulsurfer]

Built this up for a customer with an AMD 3 Hager cu for on & off peak boards surely they can't have issue
with that setup ?
Will have blanks in too !

 

[Richard Burns]

The DNO should be happy with that, the customer wont be when a short circuit takes out their main supply.
The DNO asks for overcurrent protection so it does not have to be discrimination from the DNO fuse.

 

[telectrix]

and circuit ID i hope.

 

[tomspark93]

But of course from January we will all love using the Amendment 3 all metal switch fuses!
View attachment 30822

Joking aside I would echo Andy78 do not use an MCB, use a Switch fuse.
The DNO usually specify overcurrent/fault protection for longer tails runs (often over 3m), but should generally be happy with just an isolator for a short run to a CU.

That does look nice, anyone used one yet?

 

[Soulsurfer]

I don't get how else I'm going to get overcurrent protection without the usual Mcb route as used for comfort heat boards / isolators, spoke to them & they say Mcbs are usual requirement and at 63A. Or should DNO fuse be the only required overcurrent protection ?