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Old May 27th 19, 09:47 AM posted to uk.d-i-y
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Default Consumer Units with RCBOs

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
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Old May 27th 19, 09:57 AM posted to uk.d-i-y
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Default Consumer Units with RCBOs

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
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Old May 27th 19, 10:48 AM posted to uk.d-i-y
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Default Consumer Units with RCBOs

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

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Old May 27th 19, 12:13 PM posted to uk.d-i-y
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Default Consumer Units with RCBOs

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


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Old May 27th 19, 12:26 PM posted to uk.d-i-y
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Default Consumer Units with RCBOs

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.

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Old May 27th 19, 01:40 PM posted to uk.d-i-y
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Default Consumer Units with RCBOs

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?


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Old May 27th 19, 03:04 PM posted to uk.d-i-y
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Default Consumer Units with RCBOs

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 |
\================================================= ================/
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Old May 27th 19, 03:07 PM posted to uk.d-i-y
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Default Consumer Units with RCBOs

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 |
\================================================= ================/
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Old May 27th 19, 03:15 PM posted to uk.d-i-y
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Posts: 1,918
Default Consumer Units with RCBOs

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!


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