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On 24/10/2013 08:26, Dave Liquorice wrote:
On Wed, 23 Oct 2013 23:20:47 +0100, Stephen wrote:

boiler & immersion


Hum, so if a leakage fault develops in the immersion (fairly common)
it trips off the heating... Remember N-E faults can trip and RCD,
though I guess the immersion switch will be DP. Still makes it harder
to work on one or the other independantly though.


apologies for the confusion. The old circuit was for an immersion. The
old boiler was fed as a spur from a ring main.

I replaced the old boiler with a combi system and did away with the
immersion cylinder.

I then repurposed the original immersion circuit to feed the new boiler.
I left the original 2.5mm2 cable T&E in place but with a 5A RCBO to feed
the combi boiler via a 3A fused spur in place of the old 13A immersion
DP neon FCU.

This way, if ever necessary, a immersion cylinder can be put back in and
a new supply run for the boiler to give separation from the new immersion.
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On 24/10/2013 21:15, Stephen wrote:

Split load does not have to mean a 50/50 split. Some 17th edition CUs
may have say 4 RCDs and some unprotected (aka "high integrity") ways as
well (for feeding circuits that meet the requirements for not being RCD
protected). You can also arrange the split in various combinations of
ways as suits your application.


One thing to bear in mind. a single RCD will take at least the same
width as two or possibly 3 MCBs. WIth 4 RCD's you're loosing space for
for your MCB's.

The beauty of a RCBO is that in the same width as a single MCB, you are
combining RCD and MCB functionality in one.

So with a 19 module wide CU, two is taken up with 2 pole isolator,
leaving you with 17 spare ways.

you can then either fit:

(a) 4 RCDs (assume double width so thats 8 ways taken) and then up to 9
MCBs for up to 9 circuits, and still have the issue of 2 or more
circuits losing power when 1 RCD trips.

or

(b) fit up to 17 RCBO's, have up to 17 circuits and if any one RCBO
trips, only one circuit is affected, leaving the rest alone.

I know which I'd prefer..... :-)

Yes I am competent to do it, just nervous that I may have missed a
fundamental flaw in the idea.


The things in my limited experience is that:

You need to ensure that your choice of CU *can* accommodate RCBOs

It often helps if you use the same make for both teh CU and the RCBOs.


It certainly does in this case, as Starbreakers use their own, specific,
plug in MCBs and RCBOs and a proprietry busbar. There's no facility for
connecting normal breakers.

SteveW

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On 24/10/2013 14:15, RobertL wrote:
On Thursday, October 24, 2013 8:23:49 AM UTC+1, Bill wrote:



Do they have some fancy way of detecting meter bypasses these days?


With a database history of historical usage...


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On 24/10/2013 19:50, chris French wrote:
In message , Bill
writes
In message , John
Rumm writes


I am fortunate that the CU is mounted on a panel that in turn is
mounted
on 2" X 2" battens so there is a reasonable amount of space behind it,
unfortunately many of the cables were bundled together when it was
installed and trying to get a bit of slack to move them around may be
difficult, but not impossible. My only restriction in size is that I
cannot fit a longer unit, I would need to go for a second one above the
existing one.

You may have to crimp extensions onto some of the circuit ends...
especially if the neutrals have been cut shorter than the lives (they
both need to reach the RCBO)


I am reminded of a photo that surfaces on here occasionally of some
ones install where they fitted a separate DIN rail box and then
patched into the CU, an exceptionally neat job.


sounds like Anndrew Gabriel's


This one probably:

http://www.cucumber.demon.co.uk/cu1.jpg

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John.

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In message , John
Rumm writes

You may have to crimp extensions onto some of the circuit ends...
especially if the neutrals have been cut shorter than the lives (they
both need to reach the RCBO)

I am reminded of a photo that surfaces on here occasionally of some
ones install where they fitted a separate DIN rail box and then
patched into the CU, an exceptionally neat job.


sounds like Anndrew Gabriel's


This one probably:

http://www.cucumber.demon.co.uk/cu1.jpg


That's the one. Ta.




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On Thu, 24 Oct 2013 06:15:39 -0700 (PDT), RobertL
wrote:


They don't seem bothered any more. I had a CU replaced a few years ago and they cut the seal and pulled the EB fuse but nobody has commented on it being missing.

The people who installed my panels pulled the company fuse, breaking
the seal. I asked about it and they said that it the did it the proper
way they would have to pay once to have the fuse pulled and again to
have it replaced/sealed. The amount required was/is out of all
proportion to the work done. The seal is still broken.
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Bill wrote:
In message , ARW
writes


If it matters the CU is a Crabtree Starbreaker with a single 80A
switch/30mA RCD and 14 MCBs and a DIN mount bell transformer.



Apart from the cost, am I crazy?


Bill.

Whip off the front cover and take a photo of the inside of the CU.
That looks like the SB6000 and you cannot get single module RCBOs
for that model. And it would be cheaper to replace the CU
considering Crabtrees prices.


There should be one at

http://s117.photobucket.com/user/G8I...zps52f6bcf2.jp
g.html

If I do end up having to use something else do you recommend any one
in particular?


You will struggle to get the RCBOs to fit that.

As Stephen says the Denmans Curve is rather good. But so is the Hager
Invicta (a bit more commercial). Maybe Tim Watts could post a photo of his
Hager board.

My own view is that the Hager will cost more but is more future proof should
you wish to add modules such as the door bell transformer.

--
Adam


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On 25/10/2013 17:07, ARW wrote:
Bill wrote:
In message , ARW
writes


If it matters the CU is a Crabtree Starbreaker with a single 80A
switch/30mA RCD and 14 MCBs and a DIN mount bell transformer.



Apart from the cost, am I crazy?

Bill.

Whip off the front cover and take a photo of the inside of the CU.
That looks like the SB6000 and you cannot get single module RCBOs
for that model. And it would be cheaper to replace the CU
considering Crabtrees prices.


There should be one at

http://s117.photobucket.com/user/G8I...zps52f6bcf2.jp
g.html

If I do end up having to use something else do you recommend any one
in particular?


You will struggle to get the RCBOs to fit that.

As Stephen says the Denmans Curve is rather good. But so is the Hager
Invicta (a bit more commercial). Maybe Tim Watts could post a photo of his
Hager board.

My own view is that the Hager will cost more but is more future proof should
you wish to add modules such as the door bell transformer.


I have a Hager Invicta 3 board - a 36 way one, so plenty of room for
expansion (which is planned). Very happy with it - oddles of room for
wiring inside, but it's big and obvious - so you need to want a big
obvious CU!

With the Invicta you need to be careful to buy the Hager ADB RCBOs, not
the ADNs. (I think they're pretty similar, but the ADBs have much
longer flying neutral and earths to fit the Invicta boards.)
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On Thursday, October 24, 2013 7:35:28 AM UTC+1, Tim Watts wrote:
I would advise not putting all the larger RCBOs (32A rings, heaters) next to
each other - apparantly localised heat build up is a problem. I left a 1
module gap every 2-3 on mine and the middle RCBO is a low current one
(lights).


I asked MK about this long ago, after he wibbled for a bit, I pointed out diversity must surely apply in domestic installs.

GCH fails:
- 14+ RCBO in a row, 11x 32A with 3x 6A at the end.
- Even if #2 & #3 are feeding 32A continuous you only have 16A left on an 80A fuse.
- RCBO heating is thus localised with nearby breakers running cooler.

E7 NSH is the heaviest domestic load:
- NSH are a fixed heating load, so fuse rating is the limit.
- Even 80A is spread over 6x 16A RCBO, each feeding a 13A 3.4kW NSH.
- RCBO heating above IIRC 40oC will reduce their actual trip rating, but not below 13A in 7hrs.

For domestic it should be quite ok, even on a 100A supply.

Whereas multiple 50A RCBO instant water heaters in a commercial environment may create a problem whereby the ambient is higher (nearby DIN transformer, timer motor) and the RCBO do not get time to cool down due to duty cycle.

An increased number of RCBO may actually reduce local heating - because loads may be better distributed across more RCBO re multiple final circuits.
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Bill wrote:

To get a quick, ball park, idea of cost I checked on TLC's web site
earlier and although scary I managed to not quite fall off my chair.


You're only doing it once, and when it's done you'll be pleased with it.

Bill


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On 25/10/2013 17:07, ARW wrote:
Bill wrote:
In message , ARW
writes


If it matters the CU is a Crabtree Starbreaker with a single 80A
switch/30mA RCD and 14 MCBs and a DIN mount bell transformer.



Apart from the cost, am I crazy?

Bill.

Whip off the front cover and take a photo of the inside of the CU.
That looks like the SB6000 and you cannot get single module RCBOs
for that model. And it would be cheaper to replace the CU
considering Crabtrees prices.


There should be one at

http://s117.photobucket.com/user/G8I...zps52f6bcf2.jp
g.html

If I do end up having to use something else do you recommend any one
in particular?


You will struggle to get the RCBOs to fit that.

As Stephen says the Denmans Curve is rather good. But so is the Hager
Invicta (a bit more commercial). Maybe Tim Watts could post a photo of his
Hager board.

My own view is that the Hager will cost more but is more future proof should
you wish to add modules such as the door bell transformer.


The Denmans Curve CUs are all white plastic cases and there is a flip
down door on the CU.

For me this has two important advantages.

The first is that I can stick Dymo labels on the inside of the door
giving a text description of what each RCBO is.

Also, previous CU's looked ugly so I ended up boxing it in with an
access door.

Not needed with the Denmans Curve unit. Just close the door on the
RCBO's and its actually easy on the eye so no need to box it in. Even
the main switch is covered by the flip down lid.

If you want pictures let me know and I'll put some online.



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Right,

1st hurdle crossed, RCBOs and main switch purchased, well sort of
anyway. I went into the wholesaler that I use for work and ordered
them, I thought that I made it obvious that they were for me and not the
company. The fact that I haggled the guy down on cost should have given
it away as well!! Last week our storeman asked had I been buying some
strange electrical bits as he had just had a delivery with just "Bill"
as the order number. The so and so's had billed them to the company,
luckily we are quite small and have a very understanding accounts
department!

Any way, as I recall someone commenting on, my first problem is going to
be space, if it had been a new install I would probably have managed it,
but as it is it's going to be a very tight squeeze. So I think the
Andrew Gabriel method of having a separate box, as per famous cu1.jpg
photo, is called for, except that I will end up having 2 boxes, one
above and one below the CU. This is beginning to sound messy, but
there are cables coming from above and below the CU and not enough slack
to pull enough through to gain any extra length. I'm fortunate that the
CU is mounted on a board with a few inches gap behind it and can easily
move the board forward to give more space without it looking out of
place. This will also allow me to put the 2 boxes further back than the
CU and then board over them.


Yes I could crimp leads and use one box of terminals, I use crimps
frequently for lower voltages and I'm quite happy with them, but for
some reason just don't fancy the idea here.

Of course the short days and long dark nights are just the right time of
year to do this, I'm not known for my forward planning :-)


So, the one technical question that I have. I would imagine that 4mm
singles should be adequate to link the DIN terminals to the RCBOs,
certainly OK for lighting, but should I be thinking of 6mm for some of
the others?


All comments most welcome, thanks in advance.

--
Bill
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On 26/11/2013 00:22, Bill wrote:
Right,

1st hurdle crossed, RCBOs and main switch purchased, well sort of
anyway. I went into the wholesaler that I use for work and ordered
them, I thought that I made it obvious that they were for me and not the
company. The fact that I haggled the guy down on cost should have given
it away as well!! Last week our storeman asked had I been buying some
strange electrical bits as he had just had a delivery with just "Bill"
as the order number. The so and so's had billed them to the company,
luckily we are quite small and have a very understanding accounts
department!

Any way, as I recall someone commenting on, my first problem is going to
be space, if it had been a new install I would probably have managed it,
but as it is it's going to be a very tight squeeze. So I think the
Andrew Gabriel method of having a separate box, as per famous cu1.jpg
photo, is called for, except that I will end up having 2 boxes, one
above and one below the CU. This is beginning to sound messy, but
there are cables coming from above and below the CU and not enough slack
to pull enough through to gain any extra length. I'm fortunate that the
CU is mounted on a board with a few inches gap behind it and can easily
move the board forward to give more space without it looking out of
place. This will also allow me to put the 2 boxes further back than the
CU and then board over them.


Sometimes its a case of needing to carefully identify the wires already
there, disconnect everything and start again neatly dressing (and
extending if required) the wires...

Adding a RCBO to an already full box can be difficult. (when I replaced
my CUs in similar circumstance - I did not spend that much time making
it particularly pretty, which I came to regret later when adding an
RCBO. Fortunately it went in, but not in the position I would have
chosen normally).

Yes I could crimp leads and use one box of terminals, I use crimps
frequently for lower voltages and I'm quite happy with them, but for
some reason just don't fancy the idea here.


You could also use Wago terminals - but to be fair crimps are smaller
and slimmer when space is important.

Of course the short days and long dark nights are just the right time of
year to do this, I'm not known for my forward planning :-)


Head torch, spare batts, and battery power tools that are *charged* ;-)

So, the one technical question that I have. I would imagine that 4mm
singles should be adequate to link the DIN terminals to the RCBOs,
certainly OK for lighting, but should I be thinking of 6mm for some of
the others?


IME RCBOs will come with the required fly lead to connect back to the
neutral bus bar.


--
Cheers,

John.

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On Tuesday, November 26, 2013 10:57:46 AM UTC, John Rumm wrote:
Of course the short days and long dark nights are just the right time of
year to do this, I'm not known for my forward planning :-)

Head torch, spare batts, and battery power tools that are *charged* ;-)


And a thermos of tea for when you're four hours into the job, no power, and another four hours to go before getting power.

Owain

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Head torch, spare batts, and battery power tools that are *charged* ;-)

So, the one technical question that I have. I would imagine that 4mm
singles should be adequate to link the DIN terminals to the RCBOs,
certainly OK for lighting, but should I be thinking of 6mm for some of
the others?


IME RCBOs will come with the required fly lead to connect back to the
neutral bus bar.



JOOI what's the part P situation regarding this nowadays changing a
Consumer unit?..

--
Tony Sayer



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"tony sayer" wrote in message
...
Head torch, spare batts, and battery power tools that are *charged* ;-)

So, the one technical question that I have. I would imagine that 4mm
singles should be adequate to link the DIN terminals to the RCBOs,
certainly OK for lighting, but should I be thinking of 6mm for some of
the others?


IME RCBOs will come with the required fly lead to connect back to the
neutral bus bar.



JOOI what's the part P situation regarding this nowadays changing a
Consumer unit?..


It's notifiable.



--
Adam

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In message , John
Rumm writes
Sometimes its a case of needing to carefully identify the wires already
there, disconnect everything and start again neatly dressing (and
extending if required) the wires...



Identifying and labelling is one of the things that I need to do, there
are 2 very large bundles at the moment, 1 heading upwards and 1
downwards,.


Adding a RCBO to an already full box can be difficult. (when I replaced
my CUs in similar circumstance - I did not spend that much time making
it particularly pretty, which I came to regret later when adding an
RCBO. Fortunately it went in, but not in the position I would have
chosen normally).


I had a look and I might, only might, manage to squeeze 1 in! So a
definite tidy up is needed.



Yes I could crimp leads and use one box of terminals, I use crimps
frequently for lower voltages and I'm quite happy with them, but for
some reason just don't fancy the idea here.


You could also use Wago terminals - but to be fair crimps are smaller
and slimmer when space is important.

Of course the short days and long dark nights are just the right time of
year to do this, I'm not known for my forward planning :-)


Head torch, spare batts, and battery power tools that are *charged* ;-)


I can actually cheat a bit here, I have an annexe that will still have
power, so an extension lead and lamp could be used. Still not as good
as real daylight though. Also if I give up for the night I can adjourn
to the annexe!!

Where the feed from the meter comes into the main house I put a Henley
block that then goes to 2 100A fused switches, 1 for the main house and
1 for the annexe. I must have been forward planning! :-)



So, the one technical question that I have. I would imagine that 4mm
singles should be adequate to link the DIN terminals to the RCBOs,
certainly OK for lighting, but should I be thinking of 6mm for some of
the others?


IME RCBOs will come with the required fly lead to connect back to the
neutral bus bar.


They do, I was asking in regard to the tails from the separate DIN
terminals, if I went down that route.





--
Bill
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On 26/11/2013 20:49, Bill wrote:
In message , John
Rumm writes
Sometimes its a case of needing to carefully identify the wires
already there, disconnect everything and start again neatly dressing
(and extending if required) the wires...



Identifying and labelling is one of the things that I need to do, there
are 2 very large bundles at the moment, 1 heading upwards and 1 downwards,.


Adding a RCBO to an already full box can be difficult. (when I
replaced my CUs in similar circumstance - I did not spend that much
time making it particularly pretty, which I came to regret later when
adding an RCBO. Fortunately it went in, but not in the position I
would have chosen normally).


I had a look and I might, only might, manage to squeeze 1 in! So a
definite tidy up is needed.



Yes I could crimp leads and use one box of terminals, I use crimps
frequently for lower voltages and I'm quite happy with them, but for
some reason just don't fancy the idea here.


You could also use Wago terminals - but to be fair crimps are smaller
and slimmer when space is important.

Of course the short days and long dark nights are just the right time of
year to do this, I'm not known for my forward planning :-)


Head torch, spare batts, and battery power tools that are *charged* ;-)


I can actually cheat a bit here, I have an annexe that will still have
power, so an extension lead and lamp could be used. Still not as good
as real daylight though. Also if I give up for the night I can adjourn
to the annexe!!

Where the feed from the meter comes into the main house I put a Henley
block that then goes to 2 100A fused switches, 1 for the main house and
1 for the annexe. I must have been forward planning! :-)



So, the one technical question that I have. I would imagine that 4mm
singles should be adequate to link the DIN terminals to the RCBOs,
certainly OK for lighting, but should I be thinking of 6mm for some of
the others?


IME RCBOs will come with the required fly lead to connect back to the
neutral bus bar.


They do, I was asking in regard to the tails from the separate DIN
terminals, if I went down that route.


Ah, yes I see what you mean. In that situation then either use the same
or greater CSA as used for the circuit wires you are extending. In the
case of a ring, you ought to either extend both ends, or bring them in
on a thicker single wire which is man enough for the nominal current for
the protective device in question.

So arguably with a ring with a B32 MCB that has two 2.5mm^2 ends, you
would mathematically arrive at 5mm^2 (hence 6mm^2 in practice), however
a 4mm^2 would be acceptable since we know that it can take the full 32A
load.

--
Cheers,

John.

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On 2013-11-27, John Rumm wrote:

On 26/11/2013 20:49, Bill wrote:
Rumm writes


So, the one technical question that I have. I would imagine that 4mm
singles should be adequate to link the DIN terminals to the RCBOs,
certainly OK for lighting, but should I be thinking of 6mm for some of
the others?

IME RCBOs will come with the required fly lead to connect back to the
neutral bus bar.


They do, I was asking in regard to the tails from the separate DIN
terminals, if I went down that route.


Ah, yes I see what you mean. In that situation then either use the same
or greater CSA as used for the circuit wires you are extending. In the
case of a ring, you ought to either extend both ends, or bring them in
on a thicker single wire which is man enough for the nominal current for
the protective device in question.

So arguably with a ring with a B32 MCB that has two 2.5mm^2 ends, you
would mathematically arrive at 5mm^2 (hence 6mm^2 in practice), however
a 4mm^2 would be acceptable since we know that it can take the full 32A
load.


Does that apply outside the CU too, though? Would it be acceptable to
run a 4 mm^2 cable from a CU up to a junction box upstairs (let's say
it's a good one with Wago lever blocks in it) & then make a ring of
sockets with 2.5 mm^2 starting & ending at the junction box?
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On 27/11/2013 10:49, Adam Funk wrote:
On 2013-11-27, John Rumm wrote:

On 26/11/2013 20:49, Bill wrote:
Rumm writes


So, the one technical question that I have. I would imagine that 4mm
singles should be adequate to link the DIN terminals to the RCBOs,
certainly OK for lighting, but should I be thinking of 6mm for some of
the others?

IME RCBOs will come with the required fly lead to connect back to the
neutral bus bar.

They do, I was asking in regard to the tails from the separate DIN
terminals, if I went down that route.


Ah, yes I see what you mean. In that situation then either use the same
or greater CSA as used for the circuit wires you are extending. In the
case of a ring, you ought to either extend both ends, or bring them in
on a thicker single wire which is man enough for the nominal current for
the protective device in question.

So arguably with a ring with a B32 MCB that has two 2.5mm^2 ends, you
would mathematically arrive at 5mm^2 (hence 6mm^2 in practice), however
a 4mm^2 would be acceptable since we know that it can take the full 32A
load.


Does that apply outside the CU too, though? Would it be acceptable to
run a 4 mm^2 cable from a CU up to a junction box upstairs (let's say
it's a good one with Wago lever blocks in it) & then make a ring of
sockets with 2.5 mm^2 starting & ending at the junction box?


Its not a standard circuit as such, although its close to being a trunk
and branch radial in some respects. Its one of those things that you can
demonstrate will work, but at the same time has the potential to cause
confusion later. Its not ideal since you then can't adequately test the
circuit from the CU since you don't have access to both ends.


--
Cheers,

John.

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On 2013-11-27, John Rumm wrote:

On 27/11/2013 10:49, Adam Funk wrote:


Does that apply outside the CU too, though? Would it be acceptable to
run a 4 mm^2 cable from a CU up to a junction box upstairs (let's say
it's a good one with Wago lever blocks in it) & then make a ring of
sockets with 2.5 mm^2 starting & ending at the junction box?


Its not a standard circuit as such, although its close to being a trunk
and branch radial in some respects. Its one of those things that you can
demonstrate will work, but at the same time has the potential to cause
confusion later. Its not ideal since you then can't adequately test the
circuit from the CU since you don't have access to both ends.


Good points (as always), thanks.
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In message , chris French
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In message ,
writes
On Tuesday, November 26, 2013 10:57:46 AM UTC, John Rumm wrote:
Of course the short days and long dark nights are just the right time of
year to do this, I'm not known for my forward planning :-)
Head torch, spare batts, and battery power tools that are *charged* ;-)


And a thermos of tea for when you're four hours into the job, no
power, and another four hours to go before getting power.

And a plan for what happens when you hit some kid of problem and your
wife comes home, it's dark and the power still isn't on.


Emigration



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"Adam Funk" wrote in message
...
On 2013-11-27, John Rumm wrote:

On 26/11/2013 20:49, Bill wrote:
Rumm writes


So, the one technical question that I have. I would imagine that 4mm
singles should be adequate to link the DIN terminals to the RCBOs,
certainly OK for lighting, but should I be thinking of 6mm for some
of
the others?

IME RCBOs will come with the required fly lead to connect back to the
neutral bus bar.

They do, I was asking in regard to the tails from the separate DIN
terminals, if I went down that route.


Ah, yes I see what you mean. In that situation then either use the same
or greater CSA as used for the circuit wires you are extending. In the
case of a ring, you ought to either extend both ends, or bring them in
on a thicker single wire which is man enough for the nominal current for
the protective device in question.

So arguably with a ring with a B32 MCB that has two 2.5mm^2 ends, you
would mathematically arrive at 5mm^2 (hence 6mm^2 in practice), however
a 4mm^2 would be acceptable since we know that it can take the full 32A
load.


Does that apply outside the CU too, though? Would it be acceptable to
run a 4 mm^2 cable from a CU up to a junction box upstairs (let's say
it's a good one with Wago lever blocks in it) & then make a ring of
sockets with 2.5 mm^2 starting & ending at the junction box?



As John said, it's not a standard circuit. Appendix 15 of the 17th edition
is only a serving suggestion and not a reg.

The junction box in this case should be accessible for testing purposes.

--
Adam



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On 2013-11-27, ARW wrote:

"Adam Funk" wrote in message
...
On 2013-11-27, John Rumm wrote:


So arguably with a ring with a B32 MCB that has two 2.5mm^2 ends, you
would mathematically arrive at 5mm^2 (hence 6mm^2 in practice), however
a 4mm^2 would be acceptable since we know that it can take the full 32A
load.


Does that apply outside the CU too, though? Would it be acceptable to
run a 4 mm^2 cable from a CU up to a junction box upstairs (let's say
it's a good one with Wago lever blocks in it) & then make a ring of
sockets with 2.5 mm^2 starting & ending at the junction box?



As John said, it's not a standard circuit. Appendix 15 of the 17th edition
is only a serving suggestion and not a reg.

The junction box in this case should be accessible for testing purposes.


I only mentioned the details of the box to avoid the idea of using a
round lighting junction box with various cable sizes jammed into the
screw terminals. ;-)

Dont worry: I'm not planning to do this --- I was just curious. In
practical terms, I doubt that running a 4 mm^2 T&E cable from A to B
would be significantly easier than running two parallel 2.5 mm^2
cables the same way.
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On 27/11/2013 13:11, Adam Funk wrote:
On 2013-11-27, John Rumm wrote:

Its not a standard circuit as such, although its close to being a trunk
and branch radial in some respects. Its one of those things that you can
demonstrate will work, but at the same time has the potential to cause
confusion later. Its not ideal since you then can't adequately test the
circuit from the CU since you don't have access to both ends.


Good points (as always), thanks.


Don't forget that 4 mm^2 T&E only has a 1.5 mm^2 earth core, so you need
to take care to ensure that the disconnection time and CPC thermal
protection requirements are met in the event of a line-earth fault.
Probably OK on a PME supply and with MCB protection, but full
calculations advised if it's TN-S and fuses.

Also this ring-on-a-stick idea won't meet the high-integrity earthing
requirements (where applicable).

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In message , Bill
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Hi all, especially the knowledgeable electricians on here.

What are your thoughts on me replacing all of the MCBs in my CU with
RCBOs? At present I have 14 MCBs all protected by one 30mA RCD main
switch. Over the last few years I've had tripping problems from a
trapped L to E fault in a metal clad light unit, it too 10 years before
this became a problem! Water blowing into an extractor fan, water in
an outside light and the big issue of too many switch mode PSUs in the
house. While some of the genuine faults were a pain and time
consuming to locate the SMPSUs are something I have to live with and
they are taking my overall leakage too near the 30mA limit on the CU.

This has been brought to a head by a few trips this evening, no one
circuit being the culprit, leave any 2 or 3 MCBs off and it is happy,
just not happy with all on, I'm assuming something is leaking a bit
more than normal and has taken the main RCD to it's limit. I've left
one circuit off that has a number of SMPSUs on it and so far all is
stable again.

Yes I will turn everything off and check the trip current of the1 RCD
in case it has become overly sensitive, but NOT tonight!

So my thought was to replace the main switch/RCD with a simple switch
and then all of the MCBs with RCBOs, everything will be protected and
in the event of a real problem I don't lose the whole darn house, just
the one errant circuit.

So is it a practical idea? I think so, but would welcome any thoughts,
good or bad about doing it. I know the 17th edition suggests a split
load CU, but that would still leave me with a 50/50% split and a gamble
as to what worked and what didn't.

Yes I am competent to do it, just nervous that I may have missed a
fundamental flaw in the idea.

If it matters the CU is a Crabtree Starbreaker with a single 80A
switch/30mA RCD and 14 MCBs and a DIN mount bell transformer.



Apart from the cost, am I crazy?



I think that I can now answer that. I am crazy.

OK I'm not the best electrician in the world and I certainly don't do it
for a living, but from start to finish, well almost finished, took nigh
on 12 hours today.
Fitting 2 boxes with DIN mount terminals above and below the CU to
accommodate cables coming from above and below. Identifying each cable,
disconnecting each from the CU and then removing the CU from the wall
and striping it and rebuilding. Then connecting each circuit to the DIN
mount terminals and then jumpering these into the CU.

I even tested out the rings for continuity and all was OK, something I
had been meaning to do for a while.

A plus point is having a separately fed annexe, some where to run a lead
light from and more importantly, somewhere to boil the kettle!

I did look at just fitting the RCBOs into the CU and not bothering with
the terminals, HA!! not a chance, it is cramped even with just one
single L&N from each RCBO Never again!

Any way, thanks to all for their advice a while back, it was much
appreciated.


--
Bill
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"Bill" wrote in message
...
In message , Bill
writes
Hi all, especially the knowledgeable electricians on here.

What are your thoughts on me replacing all of the MCBs in my CU with
RCBOs? At present I have 14 MCBs all protected by one 30mA RCD main
switch. Over the last few years I've had tripping problems from a trapped
L to E fault in a metal clad light unit, it too 10 years before this
became a problem! Water blowing into an extractor fan, water in an
outside light and the big issue of too many switch mode PSUs in the house.
While some of the genuine faults were a pain and time consuming to locate
the SMPSUs are something I have to live with and they are taking my
overall leakage too near the 30mA limit on the CU.

This has been brought to a head by a few trips this evening, no one
circuit being the culprit, leave any 2 or 3 MCBs off and it is happy, just
not happy with all on, I'm assuming something is leaking a bit more than
normal and has taken the main RCD to it's limit. I've left one circuit
off that has a number of SMPSUs on it and so far all is stable again.

Yes I will turn everything off and check the trip current of the1 RCD in
case it has become overly sensitive, but NOT tonight!

So my thought was to replace the main switch/RCD with a simple switch and
then all of the MCBs with RCBOs, everything will be protected and in the
event of a real problem I don't lose the whole darn house, just the one
errant circuit.

So is it a practical idea? I think so, but would welcome any thoughts,
good or bad about doing it. I know the 17th edition suggests a split load
CU, but that would still leave me with a 50/50% split and a gamble as to
what worked and what didn't.

Yes I am competent to do it, just nervous that I may have missed a
fundamental flaw in the idea.

If it matters the CU is a Crabtree Starbreaker with a single 80A
switch/30mA RCD and 14 MCBs and a DIN mount bell transformer.



Apart from the cost, am I crazy?



I think that I can now answer that. I am crazy.

OK I'm not the best electrician in the world and I certainly don't do it
for a living, but from start to finish, well almost finished, took nigh on
12 hours today.
Fitting 2 boxes with DIN mount terminals above and below the CU to
accommodate cables coming from above and below. Identifying each cable,
disconnecting each from the CU and then removing the CU from the wall and
striping it and rebuilding. Then connecting each circuit to the DIN mount
terminals and then jumpering these into the CU.

I even tested out the rings for continuity and all was OK, something I had
been meaning to do for a while.

A plus point is having a separately fed annexe, some where to run a lead
light from and more importantly, somewhere to boil the kettle!

I did look at just fitting the RCBOs into the CU and not bothering with
the terminals, HA!! not a chance, it is cramped even with just one single
L&N from each RCBO Never again!

Any way, thanks to all for their advice a while back, it was much
appreciated.



Photos please if you could be so kind

--
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In message , ARW
writes

A plus point is having a separately fed annexe, some where to run a
lead light from and more importantly, somewhere to boil the kettle!

I did look at just fitting the RCBOs into the CU and not bothering
with the terminals, HA!! not a chance, it is cramped even with just
one single L&N from each RCBO Never again!

Any way, thanks to all for their advice a while back, it was much
appreciated.



Photos please if you could be so kind


I'm not sure that I am brave enough to do that, but here goes.

Taken with a rather washed out phone. The spaghetti to the right is
alarm and door bell wiring. The 3 terminal combination on the right
hand side of the DIN rail is for the smoke detectors and their
interconnecting line.

Yes there is still an MCB in there, not too sure what to do about that,
it is the feed to the garage, about 3m of internal cable to a 2 way
"garage" CU with RCD and 2 MCBs for lights and power. Ideas please?

There is about a 2" gap behind the CU Don't look too closely at the 2
copper pipes to the right, they are central heating, when it was put to
bed the cabling was cable tied together and away from the pipes.


http://s117.photobucket.com/user/G8IAY/media/rbo_zpsc9d77b32.jpg.html

All thoughts, comments etc. most welcomed, what ever they maybe.
--
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"Bill" wrote in message
...
In message , ARW
writes

A plus point is having a separately fed annexe, some where to run a lead
light from and more importantly, somewhere to boil the kettle!

I did look at just fitting the RCBOs into the CU and not bothering with
the terminals, HA!! not a chance, it is cramped even with just one
single L&N from each RCBO Never again!

Any way, thanks to all for their advice a while back, it was much
appreciated.



Photos please if you could be so kind


I'm not sure that I am brave enough to do that, but here goes.

Taken with a rather washed out phone. The spaghetti to the right is alarm
and door bell wiring. The 3 terminal combination on the right hand side
of the DIN rail is for the smoke detectors and their interconnecting line.

Yes there is still an MCB in there, not too sure what to do about that, it
is the feed to the garage, about 3m of internal cable to a 2 way "garage"
CU with RCD and 2 MCBs for lights and power. Ideas please?

There is about a 2" gap behind the CU Don't look too closely at the 2
copper pipes to the right, they are central heating, when it was put to
bed the cabling was cable tied together and away from the pipes.


http://s117.photobucket.com/user/G8IAY/media/rbo_zpsc9d77b32.jpg.html

All thoughts, comments etc. most welcomed, what ever they maybe.



CONGRATULATIONS

It looks rather neat inside the CU and DIN rail box.

Much neater than the cows **** of a job I did on my parents Starbreaker CU
yesterday morning when I fitted a couple of RCBOs and an MCB in 10 minutes
before ****ing off to the pub at 11am and going out on an all day bender in
Bridlington.

You asked for comments. I have only one.

The DIN box and CU need to be IP4X rated.

Did the cables originally run behind some sort of boxing in? Did your
reference "put to bed" mean that you have now replaced the front of this
boxing in and hidden the cables?. The boxing in may provide the IP4X rating
for the DIN box and CU. If not then it is only a small job to meet that
requirement.

Thank you for posting the photo. It just goes to prove that DIYers can do a
good job.


--
Adam

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"ARW" wrote in message
...
"Bill" wrote in message
...
In message , ARW
writes

A plus point is having a separately fed annexe, some where to run a
lead light from and more importantly, somewhere to boil the kettle!

I did look at just fitting the RCBOs into the CU and not bothering with
the terminals, HA!! not a chance, it is cramped even with just one
single L&N from each RCBO Never again!

Any way, thanks to all for their advice a while back, it was much
appreciated.


Photos please if you could be so kind


I'm not sure that I am brave enough to do that, but here goes.

Taken with a rather washed out phone. The spaghetti to the right is
alarm and door bell wiring. The 3 terminal combination on the right hand
side of the DIN rail is for the smoke detectors and their interconnecting
line.

Yes there is still an MCB in there, not too sure what to do about that,
it is the feed to the garage, about 3m of internal cable to a 2 way
"garage" CU with RCD and 2 MCBs for lights and power. Ideas please?

There is about a 2" gap behind the CU Don't look too closely at the 2
copper pipes to the right, they are central heating, when it was put to
bed the cabling was cable tied together and away from the pipes.


http://s117.photobucket.com/user/G8IAY/media/rbo_zpsc9d77b32.jpg.html

All thoughts, comments etc. most welcomed, what ever they maybe.



CONGRATULATIONS

It looks rather neat inside the CU and DIN rail box.

Much neater than the cows **** of a job I did on my parents Starbreaker CU
yesterday morning when I fitted a couple of RCBOs and an MCB in 10 minutes
before ****ing off to the pub at 11am and going out on an all day bender
in Bridlington.

You asked for comments. I have only one.

The DIN box and CU need to be IP4X rated.

Did the cables originally run behind some sort of boxing in?


Just checked.

Looks like it did.

http://s117.photobucket.com/user/G8I...6bcf2.jpg.html


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In message , ARW
writes

http://s117.photobucket.com/user/G8IAY/media/rbo_zpsc9d77b32.jpg.html

All thoughts, comments etc. most welcomed, what ever they maybe.



CONGRATULATIONS

It looks rather neat inside the CU and DIN rail box.


Thank you, I was dreading your comments!! :-)


Much neater than the cows **** of a job I did on my parents Starbreaker
CU yesterday morning when I fitted a couple of RCBOs and an MCB in 10
minutes before ****ing off to the pub at 11am and going out on an all
day bender in Bridlington.


Having looked at just replacing the MCBs with RCBOs and no DIN box
interface I can imagine your problems, I tried just one and didn't even
bother with that, yes it would/may have, fitted, but there would have
been no space left for any wires as it is it is a bit tight, but
manageable.



You asked for comments. I have only one.

The DIN box and CU need to be IP4X rated.

Did the cables originally run behind some sort of boxing in? Did your
reference "put to bed" mean that you have now replaced the front of
this boxing in and hidden the cables?. The boxing in may provide the
IP4X rating for the DIN box and CU. If not then it is only a small job
to meet that requirement.


As you commented on later, apart from the front of the CU, everything
else is behind a wooden panel. That is all I need to tidy up, it sort
of matured with age and has two different levels, so when I find my
round tuit I will move the transfer switch forward to be on the same
level as the CU and redo the panel into a few removable sections to
allow access but all as one flat surface. There is a burglar alarm
control box and a reset switch for the smoke alarms mounted there too,
esthetically it could do with a tidy up.


Thank you for posting the photo. It just goes to prove that DIYers can
do a good job.


We try :-)





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Bill
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On 21/04/2014 15:13, Bill wrote:
In message , ARW
writes

A plus point is having a separately fed annexe, some where to run a
lead light from and more importantly, somewhere to boil the kettle!

I did look at just fitting the RCBOs into the CU and not bothering
with the terminals, HA!! not a chance, it is cramped even with just
one single L&N from each RCBO Never again!

Any way, thanks to all for their advice a while back, it was much
appreciated.



Photos please if you could be so kind


I'm not sure that I am brave enough to do that, but here goes.

Taken with a rather washed out phone. The spaghetti to the right is
alarm and door bell wiring. The 3 terminal combination on the right
hand side of the DIN rail is for the smoke detectors and their
interconnecting line.

Yes there is still an MCB in there, not too sure what to do about that,
it is the feed to the garage, about 3m of internal cable to a 2 way
"garage" CU with RCD and 2 MCBs for lights and power. Ideas please?


No requirement (in fact it would actually be a disadvantage) to have RCD
protection at the head (assuming its not a TT install) of a submain to
another CU. Its better discrimination of a leakage situation on a garage
circuit causes a tip there rather than at the house CU.

There is about a 2" gap behind the CU Don't look too closely at the 2
copper pipes to the right, they are central heating, when it was put to
bed the cabling was cable tied together and away from the pipes.


http://s117.photobucket.com/user/G8IAY/media/rbo_zpsc9d77b32.jpg.html

All thoughts, comments etc. most welcomed, what ever they maybe.


All in all very neat and tidy[1]. It can be very difficult with so
little working room using tall RCBOs in many CUs. Assuming the boxing in
will cover the wire entrance to the tops of the tops of the CU/Din rail
box there is no need for additional packing to fill the gaps. Else you
would need something to close off the gaps.


--
Cheers,

John.

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