Screwfix have a BG 12 module CU with 6 RCBOs on offer for £69.99. At that price it is a steal so I am thinking of getting 2, one for the main house CU and I know it is overkill but one for the garage. I do want discrimination in the garage with 2 lighting circuits one for the main garage/workshop and one for the separated mancave, likewise 2 ring mains and all the outside lights will also be run off the garage CU.

The question is connecting the garage CU to the house CU? In the 17th edition wiki article the CU arrangement for a fully RCBO populated CU shows an MCB being used for the garage using SWA. In my case that will not be possible as the cable between CUs will be T&E with approx. 2m run in a wall chase. Is there any reason why the garage circuit cannot be protected by an RCBO at the house CU even though there will be further RCBOs for the separate garage/Mancave circuits?

Richard

On Wednesday, 15 May 2019 17:15:35 UTC+1, Tricky Dicky wrote:
I do want discrimination in the garage ...
Is there any reason why the garage circuit cannot be protected by
an RCBO at the house CU

Yes, discrimination.

AFAICS no time-delay / 100mA RCDs are available as RCBOs, so you'd need to allow for a 2-module time-delay RCD and an MCB for the garage - if they're available in BG.

Also someone will hopefully clarify whether 100mA time-delay is acceptable for protecting buried cable.

Owain

On 15/05/2019 17:15, Tricky Dicky wrote:
Screwfix have a BG 12 module CU

sadly out of stock around here (well, the 6 nearest - I gave up at that
point)

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

On 15/05/2019 17:15, Tricky Dicky wrote:
Screwfix have a BG 12 module CU with 6 RCBOs on offer for £69.99. At
that price it is a steal so I am thinking of getting 2, one for the
main house CU and I know it is overkill but one for the garage. I do
want discrimination in the garage with 2 lighting circuits one for
the main garage/workshop and one for the separated mancave, likewise
2 ring mains and all the outside lights will also be run off the
garage CU.

The question is connecting the garage CU to the house CU? In the 17th
edition wiki article the CU arrangement for a fully RCBO populated CU
shows an MCB being used for the garage using SWA. In my case that
will not be possible as the cable between CUs will be T&E with
approx. 2m run in a wall chase. Is there any reason why the garage
circuit cannot be protected by an RCBO at the house CU even though
there will be further RCBOs for the separate garage/Mancave
circuits?

Richard


If it uses the same sort of RCBO it will probably trip if there is a
fault on one of the garage circuits.

You need one that trips slower and/or higher leakage to avoid this.

On 15/05/2019 17:30, wrote:
On Wednesday, 15 May 2019 17:15:35 UTC+1, Tricky Dicky wrote:
I do want discrimination in the garage ...
Is there any reason why the garage circuit cannot be protected by
an RCBO at the house CU

Yes, discrimination.

AFAICS no time-delay / 100mA RCDs are available as RCBOs, so you'd need to allow for a 2-module time-delay RCD and an MCB for the garage - if they're available in BG.

Also someone will hopefully clarify whether 100mA time-delay is acceptable for protecting buried cable.


It should be 30mA non time delayed.

Or make it a deviation from the regs and don't RCD it.


--
Adam

Just checked the stock at Screwfix and none of the stores have any available so it's back to the drawing board. There is a similar one available at £99.99 with mini RCBOs but it gets a poor review from an electrician.

Richard

On 15/05/2019 17:15, Tricky Dicky wrote:
Screwfix have a BG 12 module CU with 6 RCBOs on offer for £69.99. At
that price it is a steal so I am thinking of getting 2, one for the
main house CU and I know it is overkill but one for the garage. I do
want discrimination in the garage with 2 lighting circuits one for
the main garage/workshop and one for the separated mancave, likewise
2 ring mains and all the outside lights will also be run off the
garage CU.

The question is connecting the garage CU to the house CU? In the 17th
edition wiki article the CU arrangement for a fully RCBO populated CU
shows an MCB being used for the garage using SWA. In my case that
will not be possible as the cable between CUs will be T&E with
approx. 2m run in a wall chase. Is there any reason why the garage
circuit cannot be protected by an RCBO at the house CU even though
there will be further RCBOs for the separate garage/Mancave
circuits?

Yup, you will lose discrimination.


--
Cheers,

John.

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

On Wednesday, 15 May 2019 17:15:35 UTC+1, Tricky Dicky wrote:
Screwfix have a BG 12 module CU with 6 RCBOs on offer for £69.99.
At that price it is a steal

If you don't mind an RCD board (with the option of some high integrity RCBOs) this is better than a steal

https://www.switchgeardirect.co.uk/p...ory/clearance/

16 way dual RCD, your choice of MCBs, £50 inc.

Owain

In article ,
scribeth thus
On Wednesday, 15 May 2019 17:15:35 UTC+1, Tricky Dicky wrote:
Screwfix have a BG 12 module CU with 6 RCBOs on offer for £69.99.
At that price it is a steal

If you don't mind an RCD board (with the option of some high integrity RCBOs)
this is better than a steal

https://www.switchgeardirect.co.uk/p...ory/clearance/

16 way dual RCD, your choice of MCBs, £50 inc.

Owain


Have TLC electrical not got any, we had a couple from them a while ago?


https://www.tlc-direct.co.uk/Main_In...ex/BG_Consumer
_Units/index.html
--
Tony Sayer


Man is least himself when he talks in his own person.

Give him a keyboard, and he will reveal himself.

On Thursday, 16 May 2019 11:43:15 UTC+1, tony sayer wrote:
https://www.switchgeardirect.co.uk/p...ory/clearance/
16 way dual RCD, your choice of MCBs, £50 inc.
Have TLC electrical not got any, we had a couple from them a while ago?

Their 16 way only comes with 12 MCBs, their choice not yours, and is £68 + delivery + VAT.

Owain

On 16/05/2019 08:48, wrote:
On Wednesday, 15 May 2019 17:15:35 UTC+1, Tricky Dicky wrote:
Screwfix have a BG 12 module CU with 6 RCBOs on offer for £69.99.
At that price it is a steal

If you don't mind an RCD board (with the option of some high integrity RCBOs) this is better than a steal

Do you know what (if any) other brands fit Havell's boards? I was told
they have pulled out of the UK market (so replacement MCBs etc might be
hard to source).



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

Apologies for resurecting this thread, but one final question. If I cannot have RCBOs at both ends of the garage supply, if I go for RCBOs in the garage CU and stick with am MCB in the main CU, does that MCB need to be outside of any RCD protected group or can it be RCD protected. There is a possibility that my garage supply cable can be re-routed under the floor and within cupboards or voids where none of it would require burial in a wall rather than the original plan which was to take it through the loft where at least 2m would have to be buried in a wall. I will not know how easy this will be until I lift a few boards and see.

Richard

On Mon, 27 May 2019 01:47:44 -0700 (PDT), Tricky Dicky
wrote:

Apologies for resurecting this thread, but one final question. If I cannot have RCBOs at both ends of the garage supply, if I go for RCBOs in the garage CU and stick with am MCB in the main CU, does that MCB need to be outside of any RCD protected group or can it be RCD protected. There is a possibility that my garage supply cable can be re-routed under the floor and within cupboards or voids where none of it would require burial in a wall rather than the original plan which was to take it through the loft where at least 2m would have to be buried in a wall. I will not know how easy this will be until I lift a few boards and see.

Richard

Yes, No


Any difference between N and L current will trip an RCBO or RCD
AB

On 27/05/2019 09:47, Tricky Dicky wrote:
if I go for RCBOs in the garage CU and stick with am MCB in the main CU, does that MCB need to be outside of any RCD protected group or can it be RCD protected.

My (limited) understanding is that it wouldnt NEED to be RCD protected
but there is no requirement that it is *not* so protected.


--
Socialism is the philosophy of failure, the creed of ignorance and the
gospel of envy.

Its inherent virtue is the equal sharing of misery.

Winston Churchill

On 27/05/2019 09:47, Tricky Dicky wrote:
Apologies for resurecting this thread, but one final question. If I cannot have RCBOs at both ends of the garage supply, if I go for RCBOs in the garage CU and stick with am MCB in the main CU, does that MCB need to be outside of any RCD protected group or can it be RCD protected. There is a possibility that my garage supply cable can be re-routed under the floor and within cupboards or voids where none of it would require burial in a wall rather than the original plan which was to take it through the loft where at least 2m would have to be buried in a wall. I will not know how easy this will be until I lift a few boards and see.

The MCB should have NO RCD protection. Only the garage end should be RCD
protected.

Did you know that if you bury the cable more than 5cm from the finished
surface on the 2m run then it would not need RCD protection?


--
Adam

On 27/05/2019 12:13, ARW wrote:
On 27/05/2019 09:47, Tricky Dicky wrote:
Apologies for resurecting this thread, but one final question. If I
cannot have RCBOs at both ends of the garage supply, if I go for RCBOs
in the garage CU and stick with am MCB in the main CU, does that MCB
need to be outside of any RCD protected group or can it be RCD
protected. There is a possibility that my garage supply cable can be
re-routed under the floor and within cupboards or voids where none of
it would require burial in a wall rather than the original plan which
was to take it through the loft where at least 2m would have to be
buried in a wall. I will not know how easy this will be until I lift a
few boards and see.

The MCB should have NO RCD protection. Only the garage end should be RCD
protected.

Did you know that if you bury the cable more than 5cm from the finished
surface on the 2m run then it would not need RCD protection?



Or mechanical protection applied. steel conduit should require no extra
protection.

On 27/05/2019 12:13, ARW wrote:
On 27/05/2019 09:47, Tricky Dicky wrote:
Apologies for resurecting this thread, but one final question. If I
cannot have RCBOs at both ends of the garage supply, if I go for RCBOs
in the garage CU and stick with am MCB in the main CU, does that MCB
need to be outside of any RCD protected group or can it be RCD
protected. There is a possibility that my garage supply cable can be
re-routed under the floor and within cupboards or voids where none of
it would require burial in a wall rather than the original plan which
was to take it through the loft where at least 2m would have to be
buried in a wall. I will not know how easy this will be until I lift a
few boards and see.

The MCB should have NO RCD protection. Only the garage end should be RCD
protected.

Did you know that if you bury the cable more than 5cm from the finished
surface on the 2m run then it would not need RCD protection?

I thought surface wiring was exempt too on the basis you're unlikely to
poke a nail through a visible cable? Or is that only SWA?

On 27/05/2019 13:40, Fredxx wrote:
On 27/05/2019 12:13, ARW wrote:
On 27/05/2019 09:47, Tricky Dicky wrote:
Apologies for resurecting this thread, but one final question. If I
cannot have RCBOs at both ends of the garage supply, if I go for
RCBOs in the garage CU and stick with am MCB in the main CU, does
that MCB need to be outside of any RCD protected group or can it be
RCD protected. There is a possibility that my garage supply cable can
be re-routed under the floor and within cupboards or voids where none
of it would require burial in a wall rather than the original plan
which was to take it through the loft where at least 2m would have to
be buried in a wall. I will not know how easy this will be until I
lift a few boards and see.

The MCB should have NO RCD protection. Only the garage end should be
RCD protected.

Did you know that if you bury the cable more than 5cm from the
finished surface on the 2m run then it would not need RCD protection?

I thought surface wiring was exempt too on the basis you're unlikely to
poke a nail through a visible cable?

Indeed.

Or is that only SWA?

No, that applies to T&E as well. (and surface wiring in trunking would
also be ok for the same reason)


--
Cheers,

John.

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

On 27/05/2019 10:48, The Natural Philosopher wrote:
On 27/05/2019 09:47, Tricky Dicky wrote:
if I go for RCBOs in the garage CU and stick with am MCB in the main
CU, does that MCB need to be outside of any RCD protected group or can
it be RCD protected.

My (limited) understanding is that it wouldnt NEED to be RCD protected
but there is no requirement that it is *not* so protected.

In this particular case there is, since the OP does not want to lose
discrimination. If you have regular RCDs/RCBOs (i.e. non time delayed
ones) at both head end and final circuit end, then you can't rely on one
tripping in preference to the other.


--
Cheers,

John.

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

On 27/05/2019 15:04, John Rumm wrote:
On 27/05/2019 13:40, Fredxx wrote:
On 27/05/2019 12:13, ARW wrote:
On 27/05/2019 09:47, Tricky Dicky wrote:
Apologies for resurecting this thread, but one final question. If I
cannot have RCBOs at both ends of the garage supply, if I go for
RCBOs in the garage CU and stick with am MCB in the main CU, does
that MCB need to be outside of any RCD protected group or can it be
RCD protected. There is a possibility that my garage supply cable
can be re-routed under the floor and within cupboards or voids where
none of it would require burial in a wall rather than the original
plan which was to take it through the loft where at least 2m would
have to be buried in a wall. I will not know how easy this will be
until I lift a few boards and see.

The MCB should have NO RCD protection. Only the garage end should be
RCD protected.

Did you know that if you bury the cable more than 5cm from the
finished surface on the 2m run then it would not need RCD protection?

I thought surface wiring was exempt too on the basis you're unlikely
to poke a nail through a visible cable?

Indeed.

Or is that only SWA?

No, that applies to T&E as well. (and surface wiring in trunking would
also be ok for the same reason)

That was my understanding but not sure if it changed under 18th ed. Of
course a decorator might just sink the cable into the plaster and cover
with PVC channelling!

On 27/05/2019 12:26, dennis@home wrote:
On 27/05/2019 12:13, ARW wrote:
On 27/05/2019 09:47, Tricky Dicky wrote:
Apologies for resurecting this thread, but one final question. If I
cannot have RCBOs at both ends of the garage supply, if I go for
RCBOs in the garage CU and stick with am MCB in the main CU, does
that MCB need to be outside of any RCD protected group or can it be
RCD protected. There is a possibility that my garage supply cable can
be re-routed under the floor and within cupboards or voids where none
of it would require burial in a wall rather than the original plan
which was to take it through the loft where at least 2m would have to
be buried in a wall. I will not know how easy this will be until I
lift a few boards and see.

The MCB should have NO RCD protection. Only the garage end should be
RCD protected.

Did you know that if you bury the cable more than 5cm from the
finished surface on the 2m run then it would not need RCD protection?



Or mechanical protection applied. steel conduit should require no extra
protection.


A length of steel conduit with the ends made off properly is also fine.

--
Adam

A length of steel conduit with the ends made off properly is also fine.

Even if it is buried below the plaster?

Richard

On 27/05/2019 15:44, Tricky Dicky wrote:
A length of steel conduit with the ends made off properly is also fine.

Even if it is buried below the plaster?


Yes.


--
Adam

On 27/05/2019 15:59, ARW wrote:
On 27/05/2019 15:44, Tricky Dicky wrote:
A length of steel conduit with the ends made off properly is also fine.

Even if it is buried below the plaster?


Yes.

I thought protection had to be more than 3mm of steel and steel conduit
is only 1.6mm

When you say the ends are made properly, do you mean the conduit is earthed?

On 27/05/2019 16:06, Fredxx wrote:
On 27/05/2019 15:59, ARW wrote:
On 27/05/2019 15:44, Tricky Dicky wrote:
A length of steel conduit with the ends made off properly is also fine.

Even if it is buried below the plaster?


Yes.

I thought protection had to be more than 3mm of steel and steel conduit
is only 1.6mm

When you say the ends are made properly, do you mean the conduit is
earthed?


There is actually no specification for the thickness of the steel other
than "3mm is deemed to be adequate".

1.6mm earthed steel conduit will pass.

The NICEIC seem happy for you to just use steel conduit (as long as you
are paying them your subs).

I have always found it easy enough to sink the cables 50mm deep.


--
Adam

On Mon, 27 May 2019 16:42:40 +0100, ARW wrote:

On 27/05/2019 16:06, Fredxx wrote:
On 27/05/2019 15:59, ARW wrote:
On 27/05/2019 15:44, Tricky Dicky wrote:
A length of steel conduit with the ends made off properly is also fine.

Even if it is buried below the plaster?


Yes.

I thought protection had to be more than 3mm of steel and steel conduit
is only 1.6mm

When you say the ends are made properly, do you mean the conduit is
earthed?


There is actually no specification for the thickness of the steel other
than "3mm is deemed to be adequate".

1.6mm earthed steel conduit will pass.

The NICEIC seem happy for you to just use steel conduit (as long as you
are paying them your subs).

I have always found it easy enough to sink the cables 50mm deep.

I considered chasing in some runs, just for neatness*, but how the hell do
you get 50mm from both sides of a 100mm wall? The cable would always be a
bit off-centre and it's more than 0mm thick.
Where the cables are in the wall (historic routes) they're steel capped but
only the thin steel - just enough for a bit of a warning - and open at the
back.
The internal walls are also hollow block - too much cutting...!

*I actually prefer surface trunking - I like to be able to get at cables and
pipes.
--
Peter.
The gods will stay away
whilst religions hold sway

On 28/05/2019 08:20, PeterC wrote:
On Mon, 27 May 2019 16:42:40 +0100, ARW wrote:

On 27/05/2019 16:06, Fredxx wrote:
On 27/05/2019 15:59, ARW wrote:
On 27/05/2019 15:44, Tricky Dicky wrote:
A length of steel conduit with the ends made off properly is also fine.

Even if it is buried below the plaster?


Yes.

I thought protection had to be more than 3mm of steel and steel conduit
is only 1.6mm

When you say the ends are made properly, do you mean the conduit is
earthed?


There is actually no specification for the thickness of the steel other
than "3mm is deemed to be adequate".

1.6mm earthed steel conduit will pass.

The NICEIC seem happy for you to just use steel conduit (as long as you
are paying them your subs).

I have always found it easy enough to sink the cables 50mm deep.

I considered chasing in some runs, just for neatness*, but how the hell do
you get 50mm from both sides of a 100mm wall? The cable would always be a
bit off-centre and it's more than 0mm thick.
Where the cables are in the wall (historic routes) they're steel capped but
only the thin steel - just enough for a bit of a warning - and open at the
back.

Capping is only there to protect it from the plasterer.
It can be plastic.

The internal walls are also hollow block - too much cutting...!

*I actually prefer surface trunking - I like to be able to get at cables and
pipes.

On 28/05/2019 08:20, PeterC wrote:

Where the cables are in the wall (historic routes) they're steel capped but
only the thin steel - just enough for a bit of a warning - and open at the
back.

The metal capping is very soft.

Believe me, if you hammer the pin for a picture hook into the wall and
it goes through a bit of metal capping you will be totally unaware of it
- until the pin hits the line conductor.

As others have said the capping is only for temporary protection against
plasterers.

On Tue, 28 May 2019 11:57:52 +0100, Mike Clarke wrote:

On 28/05/2019 08:20, PeterC wrote:

Where the cables are in the wall (historic routes) they're steel capped but
only the thin steel - just enough for a bit of a warning - and open at the
back.

The metal capping is very soft.

Believe me, if you hammer the pin for a picture hook into the wall and
it goes through a bit of metal capping you will be totally unaware of it
- until the pin hits the line conductor.

As others have said the capping is only for temporary protection against
plasterers.

Yes, a hook's pin will go through it (don't ask...). This house was last
plastered in about 1950.
There's not sufficient wall to get conduit in as it would break into the
hollow.
--
Peter.
The gods will stay away
whilst religions hold sway

On Tuesday, 28 May 2019 08:20:20 UTC+1, PeterC wrote:

I considered chasing in some runs, just for neatness*, but how the hell do
you get 50mm from both sides of a 100mm wall? The cable would always be a
bit off-centre and it's more than 0mm thick.

That's easy. Chase 2" deep, fit cable. Go to other side, chase, adjust position to ensure it's the full 50mm deep Plaster, or should it perchance prove necessary, rebuild wall.


NT

On 28/05/2019 08:20, PeterC wrote:
On Mon, 27 May 2019 16:42:40 +0100, ARW wrote:

On 27/05/2019 16:06, Fredxx wrote:
On 27/05/2019 15:59, ARW wrote:
On 27/05/2019 15:44, Tricky Dicky wrote:
A length of steel conduit with the ends made off properly is also fine.

Even if it is buried below the plaster?


Yes.

I thought protection had to be more than 3mm of steel and steel conduit
is only 1.6mm

When you say the ends are made properly, do you mean the conduit is
earthed?


There is actually no specification for the thickness of the steel other
than "3mm is deemed to be adequate".

1.6mm earthed steel conduit will pass.

The NICEIC seem happy for you to just use steel conduit (as long as you
are paying them your subs).

I have always found it easy enough to sink the cables 50mm deep.

I considered chasing in some runs, just for neatness*, but how the hell do
you get 50mm from both sides of a 100mm wall? The cable would always be a
bit off-centre and it's more than 0mm thick.
Where the cables are in the wall (historic routes) they're steel capped but
only the thin steel - just enough for a bit of a warning - and open at the
back.
The internal walls are also hollow block - too much cutting...!

*I actually prefer surface trunking - I like to be able to get at cables and
pipes.


Generally on the 17th and 18th edition regs then you would use RCD
protection. This was a specific case for Richards man caves to provide
discrimination.

But yes, good point, I never asked how deep his wall was.

--
Adam

The wall where the garage supply cable will be buried in the wall is an exterior cavity wall with the internal wall being cinder type breeze blocks so quite easy to chase out to a depth of 50mm. Elsewhere the cable will run either through trunking or on the surface. I am a little concerned about carving halfway through the blocks for a 2m vertical run and I am not sure if they are already the hollow type, the ones I have had to sink boxes into elsewhere appear solid but you never know?

Richard

On 29/05/2019 11:41, Tricky Dicky wrote:
The wall where the garage supply cable will be buried in the wall is an exterior cavity wall with the internal wall being cinder type breeze blocks so quite easy to chase out to a depth of 50mm. Elsewhere the cable will run either through trunking or on the surface. I am a little concerned about carving halfway through the blocks for a 2m vertical run and I am not sure if they are already the hollow type, the ones I have had to sink boxes into elsewhere appear solid but you never know?


It's 50mm from final finished surface not 50 mm into the blocks.



--
Adam

On Wed, 29 May 2019 21:27:25 +0100, ARW wrote:

On 29/05/2019 11:41, Tricky Dicky wrote:
The wall where the garage supply cable will be buried in the wall is an exterior cavity wall with the internal wall being cinder type breeze blocks so quite easy to chase out to a depth of 50mm. Elsewhere the cable will run either through trunking or on the surface. I am a little concerned about carving halfway through the blocks for a 2m vertical run and I am not sure if they are already the hollow type, the ones I have had to sink boxes into elsewhere appear solid but you never know?

It's 50mm from final finished surface not 50 mm into the blocks.

Just to clarify: if the cable(s) are protected by a 30mA, 30ms RCD or RCBO
do they have to be a) protected b)as far in a 50mm?
It seems that surface-mounted mini-trunking would be OK; what if that were
flush with or just below the surface?
--
Peter.
The gods will stay away
whilst religions hold sway

On Thursday, 30 May 2019 08:19:58 UTC+1, PeterC wrote:
On Wed, 29 May 2019 21:27:25 +0100, ARW wrote:
On 29/05/2019 11:41, Tricky Dicky wrote:

The wall where the garage supply cable will be buried in the wall is an exterior cavity wall with the internal wall being cinder type breeze blocks so quite easy to chase out to a depth of 50mm. Elsewhere the cable will run either through trunking or on the surface. I am a little concerned about carving halfway through the blocks for a 2m vertical run and I am not sure if they are already the hollow type, the ones I have had to sink boxes into elsewhere appear solid but you never know?

It's 50mm from final finished surface not 50 mm into the blocks.

Just to clarify: if the cable(s) are protected by a 30mA, 30ms RCD or RCBO
do they have to be a) protected b)as far in a 50mm?

no, those are alternatives to RCD, at least as far as cable protection is concerned.

It seems that surface-mounted mini-trunking would be OK;

yes

what if that were
flush with or just below the surface?

then it needs RCD to mitigate against the risk of drilling into it.


NT

On 30/05/2019 08:19, PeterC wrote:
On Wed, 29 May 2019 21:27:25 +0100, ARW wrote:

On 29/05/2019 11:41, Tricky Dicky wrote:
The wall where the garage supply cable will be buried in the wall is an exterior cavity wall with the internal wall being cinder type breeze blocks so quite easy to chase out to a depth of 50mm. Elsewhere the cable will run either through trunking or on the surface. I am a little concerned about carving halfway through the blocks for a 2m vertical run and I am not sure if they are already the hollow type, the ones I have had to sink boxes into elsewhere appear solid but you never know?

It's 50mm from final finished surface not 50 mm into the blocks.

Just to clarify: if the cable(s) are protected by a 30mA, 30ms RCD or RCBO
do they have to be a) protected b)as far in a 50mm?
It seems that surface-mounted mini-trunking would be OK; what if that were
flush with or just below the surface?


If the cables are less than 50mm from the final finished surface then
30mA RCD protection is required. They need no further protection other
than to be run in the required zones.

ie

http://wiki.diyfaq.org.uk/index.php/...lectric_cables

The 18th edition now requires RCD protection of domestic lighting no
matter what cable or installation methods you use.

--
Adam

On 30/05/2019 08:19, PeterC wrote:
On Wed, 29 May 2019 21:27:25 +0100, ARW wrote:

On 29/05/2019 11:41, Tricky Dicky wrote:
The wall where the garage supply cable will be buried in the wall is an exterior cavity wall with the internal wall being cinder type breeze blocks so quite easy to chase out to a depth of 50mm. Elsewhere the cable will run either through trunking or on the surface. I am a little concerned about carving halfway through the blocks for a 2m vertical run and I am not sure if they are already the hollow type, the ones I have had to sink boxes into elsewhere appear solid but you never know?

It's 50mm from final finished surface not 50 mm into the blocks.

Just to clarify: if the cable(s) are protected by a 30mA, 30ms RCD or RCBO
do they have to be a) protected

The RCD protection alone is adequate. Its only when RCD protection is
not available, that other remedies may become required.

b)as far in a 50mm?

For a non RCD cable, then its needs:

Surface wired (bare or in trunking), or
To be buried = 50mm from the surface, or
Mechanically protected by earthed metal - be it capping, conduit, armour
etc, or
A deviation from the regs based on the specific circumstances.

It seems that surface-mounted mini-trunking would be OK; what if that were
flush with or just below the surface?

If its visible and obviously a cable, then its fine.


--
Cheers,

John.

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Adam, I have been following this thread with interest as I have a similar situation as the OP.

I have a house consumer unit in the hallway. A cable runs in a straight line from the middle of the back of the consumer unit straight through a double skin wall, then a ceiling - floor void and then a second double skin wall and then it is surface clipped around the garage wall to a secondary consumer unit which will be filled with RCBOs. So from my understanding of this thread I can fit a 45a MCB in the main consumer unit and connect the secondary consumer unit to that?

The cable is currently 6mm2 T&E and is more than 50mm from the floorboards and plasterboard......

If all else fails I think I could use the 6mm2 T&E as a draw wire to pull through some 10mm2 SWA cable but I then need to think about being able to open up the existing holes without damaging other cables that share the same holes....

On Thu, 30 May 2019 17:56:39 +0100, ARW wrote:

On 30/05/2019 08:19, PeterC wrote:
On Wed, 29 May 2019 21:27:25 +0100, ARW wrote:

On 29/05/2019 11:41, Tricky Dicky wrote:
The wall where the garage supply cable will be buried in the wall is an exterior cavity wall with the internal wall being cinder type breeze blocks so quite easy to chase out to a depth of 50mm. Elsewhere the cable will run either through trunking or on the surface. I am a little concerned about carving halfway through the blocks for a 2m vertical run and I am not sure if they are already the hollow type, the ones I have had to sink boxes into elsewhere appear solid but you never know?

It's 50mm from final finished surface not 50 mm into the blocks.

Just to clarify: if the cable(s) are protected by a 30mA, 30ms RCD or RCBO
do they have to be a) protected b)as far in a 50mm?
It seems that surface-mounted mini-trunking would be OK; what if that were
flush with or just below the surface?


If the cables are less than 50mm from the final finished surface then
30mA RCD protection is required. They need no further protection other
than to be run in the required zones.

ie

http://wiki.diyfaq.org.uk/index.php/...lectric_cables

The 18th edition now requires RCD protection of domestic lighting no
matter what cable or installation methods you use.

Thanks for this.
Unfortunately, some of my cables aren't in Safe Zones and I can't go to
50mm, so they'll have to stay on the surface.
ATM the lights are on a 100mA RCD, but I intend to replace the MCBs with
30mA, miniature, RCBOs.
--
Peter.
The gods will stay away
whilst religions hold sway