A situation that I can't found an answer to ...
There is a DP isolator before the main CU (which has an isolator). This
CU will be fitted with a 50A MCB feeding a 20m sub-main to a second CU
elsewhere in the house. There are therefore 3 ways to isolate the sub-main.
Is there a requirement for the second CU (at the end of the sub-main) to
have an integral isolator switch?

wrote:

A situation that I can't found an answer to ...
There is a DP isolator before the main CU (which has an isolator). This
CU will be fitted with a 50A MCB feeding a 20m sub-main to a second CU
elsewhere in the house. There are therefore 3 ways to isolate the sub-main.
Is there a requirement for the second CU (at the end of the sub-main) to
have an integral isolator switch?

I've no idea about the regulatory position, but I'd certainly fit an
isolating switch unless there was an important reason (such has not
having the extra 2" where I wanted to put the CU) not to. If just for
convenience.

--

Roger Hayter

On Wednesday, 13 February 2019 12:18:07 UTC, wrote:
Is there a requirement for the second CU (at the end of the sub-main) to
have an integral isolator switch?

It will have an integral main switch.

If it doesn't have a main switch it's not a consumer unit, it's a distribution board.

Owain

On 13/02/2019 13:36, wrote:
On Wednesday, 13 February 2019 12:18:07 UTC, wrote:
Is there a requirement for the second CU (at the end of the sub-main) to
have an integral isolator switch?

It will have an integral main switch.

If it doesn't have a main switch it's not a consumer unit, it's a distribution board.

Owain

Fair point, but this will be a custom confing of RCBOs, rather than
being a standard, pre-configured, box.

On 13/02/2019 12:18, wrote:

A situation that I can't found an answer to ...
There is a DP isolator before the main CU (which has an isolator). This
CU will be fitted with a 50A MCB feeding a 20m sub-main to a second CU
elsewhere in the house. There are therefore 3 ways to isolate the sub-main.
Is there a requirement for the second CU (at the end of the sub-main) to
have an integral isolator switch?

If its a CU and not a distribution board, then you will need a main
switch. There are two main reasons that spring to mind:

1) Expectation - from a user's PoV they expect there to be a main switch
present. A guest / future owner etc will not have the background
knowledge to know its a sub CU fed from another, and might be looking
for a way of killing the power in an emergency.

2) Practical, you need some way to terminate the live of your incoming
sub main on the the live bus bar(s) of the CU. The live bus bar has no
terminals of its own, and relies on those of the main switch to connect
the incoming feed to the bus bar.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On Thursday, 14 February 2019 11:15:49 UTC, John Rumm wrote:
2) Practical, you need some way to terminate the live of your incoming
sub main on the the live bus bar(s) of the CU. The live bus bar has no
terminals of its own, and relies on those of the main switch to connect
the incoming feed to the bus bar.

Squidging the wire under the busbar in one of the MCB terminals would be really rough wouldn't it...

Owain

John Rumm wrote:

On 13/02/2019 12:18, wrote:

A situation that I can't found an answer to ...
There is a DP isolator before the main CU (which has an isolator). This
CU will be fitted with a 50A MCB feeding a 20m sub-main to a second CU
elsewhere in the house. There are therefore 3 ways to isolate the sub-main.
Is there a requirement for the second CU (at the end of the sub-main) to
have an integral isolator switch?

If its a CU and not a distribution board, then you will need a main
switch. There are two main reasons that spring to mind:

1) Expectation - from a user's PoV they expect there to be a main switch
present. A guest / future owner etc will not have the background
knowledge to know its a sub CU fed from another, and might be looking
for a way of killing the power in an emergency.

2) Practical, you need some way to terminate the live of your incoming
sub main on the the live bus bar(s) of the CU. The live bus bar has no
terminals of its own, and relies on those of the main switch to connect
the incoming feed to the bus bar.

I had been wondering the same question. And, now that you mention it,
your point 2) is pretty conclusive. It would be a shame for an amateur
such as myself to discover one had insufficient ways to fit a main
switch and and no other way of putting the thing together *after*
ordering the parts!

--

Roger Hayter

On 14/02/2019 11:15, John Rumm wrote:
On 13/02/2019 12:18, wrote:

A situation that I can't found an answer to ...
There is a DP isolator before the main CU (which has an isolator).
This CU will be fitted with a 50A MCB feeding a 20m sub-main to a
second CU elsewhere in the house. There are therefore 3 ways to
isolate the sub-main.
Is there a requirement for the second CU (at the end of the sub-main)
to have an integral isolator switch?

If its a CU and not a distribution board, then you will need a main
I thought that, in a domestic situation, the terms "distribution board"
and "CU" were interchangeable ...
switch. There are two main reasons that spring to mind:

1) Expectation - from a user's PoV they expect there to be a main switch
present. A guest / future owner etc will not have the background
knowledge to know its a sub CU fed from another, and might be looking
for a way of killing the power in an emergency.
It's quite a large house and the main DP isolator (after the meter) will
be both more easily accessed than this sub-board and will isolate the
whole electrical system, rather than just the one segment.

2) Practical, you need some way to terminate the live of your incoming
sub main on the the live bus bar(s) of the CU. The live bus bar has no
terminals of its own, and relies on those of the main switch to connect
the incoming feed to the bus bar.
I'd planned to terminate the cable in crimped tags, bolted onto the busbar.

It's only a question of spec'ing a slightly larger CU (12 way rather
than 10 way) so I'll keep an isolator. Thanks, as always, for taking the
time.

The next question is which manufacturer: Hager, MK, BG, Wylex ... ? At
the moment I'm leaning towards Hager or MK because of space for RCBOs
and ease of getting parts.
Are there any good deals out there?

On Thursday, 14 February 2019 12:19:37 UTC, wrote:
On Thursday, 14 February 2019 11:15:49 UTC, John Rumm wrote:
2) Practical, you need some way to terminate the live of your incoming
sub main on the the live bus bar(s) of the CU. The live bus bar has no
terminals of its own, and relies on those of the main switch to connect
the incoming feed to the bus bar.

Squidging the wire under the busbar in one of the MCB terminals would be really rough wouldn't it...

Owain

I'm imagining someone discovering the cable is too thick to do that & splitting the strands over 3 MCBs


NT

On 14/02/2019 12:19, wrote:
On Thursday, 14 February 2019 11:15:49 UTC, John Rumm wrote:
2) Practical, you need some way to terminate the live of your incoming
sub main on the the live bus bar(s) of the CU. The live bus bar has no
terminals of its own, and relies on those of the main switch to connect
the incoming feed to the bus bar.

Squidging the wire under the busbar in one of the MCB terminals would be really rough wouldn't it...

You have never fitted a Schneider Easy 9 CU then.


--
Adam

On Wed, 13 Feb 2019 12:18:03 +0000, wrote:

A situation that I can't found an answer to ...
There is a DP isolator before the main CU (which has an isolator). This
CU will be fitted with a 50A MCB feeding a 20m sub-main to a second CU
elsewhere in the house. There are therefore 3 ways to isolate the sub-main.
Is there a requirement for the second CU (at the end of the sub-main) to
have an integral isolator switch?

You have to step back a bit and think things through.

You fit the DB and depart the area.

Bonzo comes along later and wants another breaker, feed whatever.

Bonzo is too bone idle to find the power source, or just forgets after
perusing the breakers for something looking like a power switch.

Bonzo live connects a cable and fries himself.

You then have to ask yourself the following:-

Did I do everything reasonable to ensure Bonzo's and other users
safety.

Have I a lot of money to defend the decision.

Will I sleep soundly even if my work is found to be legal and "safe".

DB's are normally supplied with switches. I have come across "isolate
Elsewhere" units in industry, but they are a rarity and tight lockoff
controls are employed.

As far as I'm concerned it's a no brainer.

AB

On 15/02/2019 13:12, wrote:
On 14/02/2019 11:15, John Rumm wrote:
On 13/02/2019 12:18, wrote:

A situation that I can't found an answer to ...
There is a DP isolator before the main CU (which has an isolator).
This CU will be fitted with a 50A MCB feeding a 20m sub-main to a
second CU elsewhere in the house. There are therefore 3 ways to
isolate the sub-main.
Is there a requirement for the second CU (at the end of the sub-main)
to have an integral isolator switch?

If its a CU and not a distribution board, then you will need a main
I thought that, in a domestic situation, the terms "distribution board"
and "CU" were interchangeable ...
switch. There are two main reasons that spring to mind:

1) Expectation - from a user's PoV they expect there to be a main
switch present. A guest / future owner etc will not have the
background knowledge to know its a sub CU fed from another, and might
be looking for a way of killing the power in an emergency.
It's quite a large house and the main DP isolator (after the meter) will
be both more easily accessed than this sub-board and will isolate the
whole electrical system, rather than just the one segment.

2) Practical, you need some way to terminate the live of your incoming
sub main on the the live bus bar(s) of the CU. The live bus bar has no
terminals of its own, and relies on those of the main switch to
connect the incoming feed to the bus bar.
I'd planned to terminate the cable in crimped tags, bolted onto the busbar.

It's only a question of spec'ing a slightly larger CU (12 way rather
than 10 way) so I'll keep an isolator. Thanks, as always, for taking the
time.

The next question is which manufacturer: Hager, MK, BG, Wylex ... ? At
the moment I'm leaning towards Hager or MK because of space for RCBOs
and ease of getting parts.
Are there any good deals out there?

https://www.hager.co.uk/news-exhibit...rcbo/72306.htm

are good. I just called one of my wholesalers and I would pay £27 inc
VAT for them. TLC do them for £28.14 inc VAT.

If you want cheaper then CPC do ProElec RCBOs for about £18 and a main
switch CU with 19 spare ways for £50.

I have fitted ProElec and was happy with it.

And the mainswitch need not be part of the board. Although personally it
would IMHO be silly not to buy one without a main switch.



--
Adam

On 16/02/2019 09:40, ARW wrote:

https://www.hager.co.uk/news-exhibit...rcbo/72306.htm


are good. I just called one of my wholesalers and I would pay £27 inc
VAT for them. TLC do them for £28.14 inc VAT.

If you want cheaper then CPC do ProElec RCBOs for about £18 and a main
switch CU with 19 spare ways for £50.

I have fitted ProElec and was happy with it.

And the mainswitch need not be part of the board. Although personally it
would IMHO be silly not to buy one without a main switch.

Any views pl. on the Contactum range which I saw from TLC's email last
week they are doing for £16 incl VAT?

https://www.tlc-direct.co.uk/Products/CPDD141MS.html

Asking only 'cos I've long thought I ought to replace the CU with all
RCBOs "when their price comes down" and wonder if I've now run out of
excuse.





--
Robin
reply-to address is (intended to be) valid

On 16/02/2019 10:03, Robin wrote:
On 16/02/2019 09:40, ARW wrote:

https://www.hager.co.uk/news-exhibit...rcbo/72306.htm


are good. I just called one of my wholesalers and I would pay £27 inc
VAT for them. TLC do them for £28.14 inc VAT.

If you want cheaper then CPC do ProElec RCBOs for about £18 and a main
switch CU with 19 spare ways for £50.

I have fitted ProElec and was happy with it.

And the mainswitch need not be part of the board. Although personally
it would IMHO be silly not to buy one without a main switch.

Any views pl. on the Contactum range which I saw from TLC's email last
week they are doing for £16 incl VAT?

https://www.tlc-direct.co.uk/Products/CPDD141MS.html

Asking only 'cos I've long thought I ought to replace the CU with all
RCBOs "when their price comes down" and wonder if I've now run out of
excuse.




I would say avoid.

Now I had forgotten about TLC when looking for prices.

TLC are doing the BG reduced height RCBOs for £15.72

I have never had a problem with BG CUs.


--
Adam

On 16/02/2019 09:40, ARW wrote:

https://www.hager.co.uk/news-exhibit...rcbo/72306.htm


are good. I just called one of my wholesalers and I would pay £27 inc
VAT for them. TLC do them for £28.14 inc VAT.

Sweet...


--
Email does not work

On 16/02/2019 10:40, ARW wrote:
On 16/02/2019 10:03, Robin wrote:
On 16/02/2019 09:40, ARW wrote:

https://www.hager.co.uk/news-exhibit...rcbo/72306.htm


are good. I just called one of my wholesalers and I would pay £27 inc
VAT for them. TLC do them for £28.14 inc VAT.

If you want cheaper then CPC do ProElec RCBOs for about £18 and a
main switch CU with 19 spare ways for £50.

I have fitted ProElec and was happy with it.

And the mainswitch need not be part of the board. Although personally
it would IMHO be silly not to buy one without a main switch.

Any views pl. on the Contactum range which I saw from TLC's email last
week they are doing for £16 incl VAT?

https://www.tlc-direct.co.uk/Products/CPDD141MS.html

Asking only 'cos I've long thought I ought to replace the CU with all
RCBOs "when their price comes down" and wonder if I've now run out of
excuse.




I would say avoid.

Now I had forgotten about TLC when looking for prices.

TLC are doing the BG reduced height RCBOs for £15.72

I have never had a problem with BG CUs.


ta



--
Robin
reply-to address is (intended to be) valid