100A DP Isolator Installation Between Meter and CU

[jaydub]

Hi guys,

When installing a new CU does anyone ever install a 100A double pole isolator switch between the meter and the consumer unit?

Very often I come across 16mm tails which need to be upgraded to 25mm so I join the old tails to new in a Henley block and get the DNO to come and upgrade their side at their convenience.

Instead of using a henley block could I use an isolator instead?

In anyones opinion would there be any disadvantages to this?

I wouldhave thought having an isolator would be very handy but the meter guys hardly ever bother putting one in, even now.

They're also relatively inexpensive. Another thing, I cannot seem to finda 2-module metal enclosure so would this would be okay in a plastic enclosure? That to me seems like a bit of grey area.

Any help appreciated. Thanks

 

[Ian1981]

Working for dno, meter tails governed by rating of cu, NOT supply fuse. 100amp cu=25mm tails.

Domestic consumer unit Main switches are rated upto a maximum rating of 100amp , does not mean you have to be using 100amp as your maximum demand.

 

[Ian1981]

Working for dno, meter tails governed by rating of cu, NOT supply fuse. 100amp cu=25mm tails.

Domestic consumer unit main switches are rated upto a maximum rating of 100amp , does not mean you have to be using 100amp as your maximum demand.

 

[Deleted member 26818]

421.1.201 as everyone knows requires the enclosures of CUs and similar switchgear to be made from a non-flammable material (essentially metal).
However 421.1.201 also requires that they comply with BS EN 61439-3, which most everyone seems to forget.

So if your DP 100A isolator or switchfuse does not comply with BS EN 61439-3, you cannot install it irrespective of whether the enclosure is metal or even if you enclose it within a metal cabinate or enclosure.

Unfortunately, BS EN 61439-3 only applies to CUs, so you won’t be able to install either a DP 100A isolator or switchfuse.

 

[Deleted member 26818]

Should point out, that the previous post only applies if you believe DP 100A isolators and switchfuses are similar to CUs.
If you don’t believe they are similar, then you can still install them and they can be plastic, metal or whatever.

 

[Midwest]

Should point out, that the previous post only applies if you believe DP 100A isolators and switchfuses are similar to CUs.
If you don’t believe they are similar, then you can still install them and they can be plastic, metal or whatever.

I believe I'm paying too much tax to HRMC. I'm arguing, they are not believing.

 

[mhar]

Working for dno, meter tails governed by rating of cu, NOT supply fuse. 100amp cu=25mm tails.

You should have been checking the rating of the meter, not the cu.
A lot of meters only rated at 80A

 

[telectrix]

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?

an isolator does not have auxiliary switching equipment, so is not "similar switchgear".

 

[Midwest]

an isolator does not have auxiliary switching equipment, so is not "similar switchgear".

See now I read that as main (and/or) auxiliary switching.... Reg 421.1.201 refers to 'similar switchgear', which is not defined. The 'grown ups' in the vid I posted seem to suggest (to me) that the REC2 isolators could fall under this reg.

But hey hoe, who am I to say. I keep asking these bodies, but no one appears to want to give a definitive answer. I know some forum members here, are full IET members. Perhaps they could ask them for some guidance on our behalf?

 

[willy fixit]

just getting my post count up

101 posts - congratulations MM!
(Just getting my post count up!)

 

[Spoon]

101 posts - congratulations MM!
(Just getting my post count up!)

Go to the New Members section and welcome them...

 

[Pat H]

I needed tom upgrade my DNO fuse to 100A so needed to increase my tails to 25mm.
Contacted DNO and they agreed to replace tails and increase fuse to 100A
I ordered a 100A isolator (in a plastic enclosure)
When the DNO arrived I asked if they would fit supplied isolator. They were happy to and even added their seals to it. I asked about it needing to be a metal enclosure and they said it was part of their installation so outside the requirement.

 

[Midwest]

I needed tom upgrade my DNO fuse to 100A so needed to increase my tails to 25mm.
Contacted DNO and they agreed to replace tails and increase fuse to 100A
I ordered a 100A isolator (in a plastic enclosure)
When the DNO arrived I asked if they would fit supplied isolator. They were happy to and even added their seals to it. I asked about it needing to be a metal enclosure and they said it was part of their installation so outside the requirement.

Thanks for that (#24), but we are arguing, sorry discussing whether us electricians who have to comply with BS7671, can fit metal or plastic in this situation.

 

[Deleted member 26818]

It’s not a question of whether it’s metal or plastic, the Regulation allows for either.
It can be metal, or it can be plastic inside a metal box.
The question is whether the item (whether it’s a CU or similar) meets the standard of BS EN 61439-3.

Oh and by the way, it’s not similar switchgear, it’s similar switchgear assemblies.

See here: http://electrical.------.org/wiring-matters/55/-files/consumer-units-pdf.cfm?type=pdf

 

[Midwest]

It’s not a question of whether it’s metal or plastic, the Regulation allows for either.
It can be metal, or it can be plastic inside a metal box.
The question is whether the item (whether it’s a CU or similar) meets the standard of BS EN 61439-3.

If we're being picky, its not metal, but an enclosure manufactured from non-combustible material or in enclosed in a cabinet or enclosure constructed of....blar blar.

Ferrous metal is an example of etc. Aren't you a remember of the IET? Ask em for a definitive definition of 'similar switchgear', and we can put this one to bed, forever.

 

[Deleted member 26818]

I repeat, it’s not similar switchgear, it’s similar switchgear assemblies.
Similar items are easily determined, as they are covered by the same standard.