Main Isolator.

[EdwardCurrent]

Hello All,

Where two consumer units are installed and there is need for one common point of isolation, with the neutral being classed as 'live', is it correct to fit a double pole 100A isolator ?? Or a 100Amcb ??

TN-C-S system. 537.1.2. gives me the impression that the 'neutral' is not required to be switched, then 537.1.4. says both live conductors should be interrupted ???

Any help appreciated.
Thank you

Ed

 

[electronicsuk]

537.1.4 is pretty clear that "a switch intended for operation by ordinary persons... shall interrupt both live conductors of a single phase supply". On a domestic install I would use a DP isolator on a SP supply regardless of 537.1.2.

Whether you use a DP isolator or DP MCB is up to you, table 53.2 allows the use of an MCB for isolation and emergency & functional switching, assuming it complies with one of the listed BS.

 

[EdwardCurrent]

Cheers E'UK.

I am just a tad confused, the DNO seem to fit a 100A mcb sometimes, without splitting the neutral ??. .

Is it case where you must break one reg to comply with another ???


Sorry, I have read other 'posts' and see that I should get the DNO out to fit a DP isolator, not carry out the work myself. Ooops


Ed

 

[Spark123]

Can you get MCBs as big as 100A?? The biggest I can recall seeing is 63A.

 

[ban-all-sheds]

MCCB

 

[Adam_151]

Can you get MCBs as big as 100A?? The biggest I can recall seeing is 63A.

Yes, but 100A is the highest rating available in an MCB AFAIK

 

[flameport]

I am just a tad confused, the DNO seem to fit a 100A mcb sometimes, without splitting the neutral ??.

I have seen plenty of single pole isolators which have been fitted by DNOs, but never an MCB. (In this area they are usually the Proteus ones, http://www.proteusswitchgear.co.uk/product_images/100S1.jpg

No reason to fit a 100A MCB - would cost significantly more and not provide any benefit.

 

[EdwardCurrent]

Thank you all for your input.

I am trying to source a pic of the 100A mcb (eaton) but I am still confused as to the single or double pole isolation ?
Double pole I think, or am I wrong ??


Ed

 

[Spark123]

MCCB

Yep, that is what I first thought - moulded case circuit breakers go up to the hundreds of amps. I have only ever seen a miniature circuit breaker up to 63A, but the regs book does go up to 125A in table 41.3 for MCBs.

 

[plugwash]

Can you get MCBs as big as 100A?? The biggest I can recall seeing is 63A.

You can but the ones i've seen are two modules wide and can't be connected direct to a CU/DB busbar.

 

[EdwardCurrent]

Hello All,

100A mcb's
I am sorry for the poor quality pictures.


http://i171.photobucket.com/albums/u315/exwomble/DSC00100.jpg

http://i171.photobucket.com/albums/u315/exwomble/DSC00101.jpg


These mcb's I have seen fitted by the local DNO.


Should I fit a DP isolator to cover both c/units or a single mcb ???

Thanks once again for your help/advice.


Ed

 

[RF Lighting]

Thats a single pole isolator.

You can see it carries a marking of 'BSEN 60947-3'

That is the standard number for an isolator.

If it were an MCB it would carry 'BSEN 60898'

 

[ricicle]

Those are not MCBs they are isolators !

EDIT: Tooo slllooooowwwwww !!!

Beaten by RF

 

[EdwardCurrent]

Sorry , my mistake.
Isolator it is.

Back to my original question as to the SP/DP isolation ??, this shows single pole isolation, shouldn't both 'L-N' be switched ??? ('ordinary folk and that !) Sorry to go on but I want to be sure.

Thank you
Ed

 

[RF Lighting]

I see no need to use a DP isolator in this scenario.

You are using this switch to provide a single point of isolation.

Presumably each CU contains a DP main switch anyway, so this IMO satisfies 537.1.4