100A DP Isolator Installation Between Meter and CU

[jaydub]

Forgetting about whoever installs it then, IF an isolator can be fitted that is of a plastic nature, surely then, that answers all of our questions?

 

[Andy78]

Wylex seem to take a different view point;
https://www.electrium.co.uk/media/20151123152755_0_Wylex Domestic Switch Fuse Unit.pdf

Whilst their drive might be financial, they must of received guidance from somewhere.​

I think that is because that article is about switch fuses which provide circuit protection and therefore provide a similar function. They are also tested to the same product standard as CUs.
Fair play to them for upping standards of products.

 

[Andy78]

421.1.201 refers to consumer units and similar switchgear. In BS7671 Switchgear is defined as 'an assembly of main & auxiliary switching equipment for operation, regulation, protection or other control of an electrical installation'. That's sounds like an isolator to me?

Yep an isolator would fall under the definition of switchgear, but the IET guidance on the matter clearly says that similar switchgear refers to switchgear similar to a CU in function. It's poorly written in my opinion though.

 

[Midwest]

Forgetting about whoever installs it then, IF an isolator can be fitted that is of a plastic nature, surely then, that answers all of our questions?

Systems for the distribution of electricity to the public, is excluded from the scope of BS7671, reg 110.2 (i). So if the DNO/Supply fit an isolator, it does not need to comply with BS7671, as far as I'm aware.

 

[Midwest]

Just to show I'm not trying to be argumentative, here's my question and answer I received from Certsure technical (I've even left in the spelling mistake);

1. Sometimes the installation of meter tails to a new consumer have to protected by a switch fuse. Would the use of Wylex plastic switch fuse, REC 2 or similar plastic isolators, being installed in an external plastic meter box on an external wall, be defined as being installed ‘within domestic premises’?


'The Suppliers and meter equipment would fall outside the scope of BS7671.
As a designer installing any equipment in external meter enclosures we would suggest a risk assessment is carried out to make a judgment of the likelihood that fire originating inside the enclosure or similar switchgear might lead to the outbreak of fire in the household building. We trust this answers your questions'.

 

[Strima]

'The Suppliers and meter equipment would fall outside the scope of BS7671.
As a designer installing any equipment in external meter enclosures we would suggest a risk assessment is carried out to make a judgment of the likelihood that fire originating inside the enclosure or similar switchgear might lead to the outbreak of fire in the household building. We trust this answers your questions'.

So basically they haven't got a clue and just pass the blame onto you...

 

[jaydub]

So what they are saying is, if you choose to install an isolator you should carry out a risk assessment to cover your own --- in case it catches on fire through fault or negligence. That is what it sounds like to me...?

 

[Midwest]

Some might recall the Elexshow Harrogate 2015 vid, this subject is touched on at 25:45mins;

Side step

 

[multimick]

that wylex unit has a 16mm earth terminal why does it not have a 25mm terminal,when normally you would be using 25mm swa in it ?.fitted one last week real pain for the earth

 

[Ian1981]

that wylex unit has a 16mm earth terminal why does it not have a 25mm terminal,when normally you would be using 25mm swa in it ?.fitted one last week real pain for the earth

Why would you use a 25mm earthing conductor in domestic?
25mm 2 core swa or 16mm for the line and neutral and a separate 16mm earthing conductor ran in parallel surely?

 

[Midwest]

So what they are saying is, if you choose to install an isolator you should carry out a risk assessment to cover your own --- in case it catches on fire through fault or negligence. That is what it sounds like to me...?

IMO I can rarely see the time when 'I' would install an isolator. I can see the occasion when I would install a switch fuse isolator, in which case I would install a metal one.

However, the other consideration is, would the DNO/Supplier allow you to fit a metal enclosure in 'their' meter cabinet?

 

[Midwest]

Why would you use a 25mm earthing conductor in domestic?
25mm 2 core swa or 16mm for the line and neutral and a separate 16mm earthing conductor ran in parallel surely?

I probably go for a 25mm 3c myself, mostly if it weren't too long. Installing one thing instead of two things. But then I'm lazy.

 

[Ian1981]

IMO I can rarely see the time when 'I' would install an isolator. I can see the occasion when I would install a switch fuse isolator, in which case I would install a metal one.

However, the other consideration is, would the DNO/Supplier allow you to fit a metal enclosure in 'their' meter cabinet?

To be honest I can’t see you fitting one in their meter box as you just don’t have the room.
It’s hard work trying to convince a builder to fit a 2nd meter box to house the fused isolator

 

[multimick]

Why would you use a 25mm earthing conductor in domestic?
25mm 2 core swa or 16mm for the line and neutral and a separate 16mm earthing conductor ran in parallel surely?

yeah i ran 25mm 3 core it was only 10 meteres

 

[jaydub]

Crikey this really is minefield of what if's isn't it...

Maybe I will not bother with it...

 

[Ian1981]

yeah i ran 25mm 3 core it was only 10 meteres

You can get a reducer pin for the 25mm so you can terminate into the terminal easier.

 

[multimick]

Crikey this really is minefield of what if's isn't it...

Maybe I will not bother with it...

just getting my post count up

 

[Midwest]

To be honest I can’t see you fitting one in their meter box as you just don’t have the room.
It’s hard work trying to convince a builder to fit a 2nd meter box to house the fused isolator

I did come close to fitting one in a cabinet on one job. Was room just. Got to the point of enquiring with the DNO, but when I measured my tails run, it was 3m.

 

[Midwest]

just getting my post count up

Ask that Chinese chick to add you to her spybot list, that will ramp things up for you.

 

[Ian1981]

I did come close to fitting one in a cabinet on one job. Was room just. Got to the point of enquiring with the DNO, but when I measured my tails run, it was 3m.

My experience regarding the length of the ‘tails’ with the DNO is basically “we don’t care”