The Economy 7 supply to our house goes through a small box with a
built-in isolating switch and space for a single MCB[1]. Presumably if
I can find a 20A RCBO of the same width and shape I can just substitute
this for the MCB. But if such a thing does not exist, would it be OK to
use a two pole RCBO mounted alone in a small box with no separate
isolating switch? Space is not very ample.






[1] It is probably a bit dubious now as it serves a single 'radial'
circuit which branches to two sockets (that I have found) and is wired
in 2.5mm^2 cable bundled with other cables and supplied through a 32A
MCB.

--

Roger Hayter

On 10/07/2018 22:35, Roger Hayter wrote:

The Economy 7 supply to our house goes through a small box with a
built-in isolating switch and space for a single MCB[1]. Presumably if
I can find a 20A RCBO of the same width and shape I can just substitute
this for the MCB.

Such things exist - however they are taller, so not all CUs will have
space.

But if such a thing does not exist, would it be OK to
use a two pole RCBO mounted alone in a small box with no separate
isolating switch? Space is not very ample.

Yup that would be fine. Just blank the spare way, or leave the MCB in
place and label it as "spare" or similar.

[1] It is probably a bit dubious now as it serves a single 'radial'
circuit which branches to two sockets (that I have found) and is wired
in 2.5mm^2 cable bundled with other cables and supplied through a 32A
MCB.

If the branch was at the CU that would actually be acceptable anyway.


--
Cheers,

John.

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

John Rumm wrote:

On 10/07/2018 22:35, Roger Hayter wrote:

The Economy 7 supply to our house goes through a small box with a
built-in isolating switch and space for a single MCB[1]. Presumably if
I can find a 20A RCBO of the same width and shape I can just substitute
this for the MCB.

Such things exist - however they are taller, so not all CUs will have
space.

But if such a thing does not exist, would it be OK to
use a two pole RCBO mounted alone in a small box with no separate
isolating switch? Space is not very ample.

Yup that would be fine. Just blank the spare way, or leave the MCB in
place and label it as "spare" or similar.

It would have to be a new enclosure as the existing one has an integral,
non-modular switch and only space for one MCB.



[1] It is probably a bit dubious now as it serves a single 'radial'
circuit which branches to two sockets (that I have found) and is wired
in 2.5mm^2 cable bundled with other cables and supplied through a 32A
MCB.

If the branch was at the CU that would actually be acceptable anyway.

That's because of the limited current demand from one socket outlet? I
haven't actually checked where they branch because we only use one
socket anyway and the other one has duct tape to avoid confusion.

--

Roger Hayter

On 11/07/2018 10:23, Roger Hayter wrote:
John Rumm wrote:

On 10/07/2018 22:35, Roger Hayter wrote:

The Economy 7 supply to our house goes through a small box with a
built-in isolating switch and space for a single MCB[1]. Presumably if
I can find a 20A RCBO of the same width and shape I can just substitute
this for the MCB.

Such things exist - however they are taller, so not all CUs will have
space.

But if such a thing does not exist, would it be OK to
use a two pole RCBO mounted alone in a small box with no separate
isolating switch? Space is not very ample.

Yup that would be fine. Just blank the spare way, or leave the MCB in
place and label it as "spare" or similar.

It would have to be a new enclosure as the existing one has an integral,
non-modular switch and only space for one MCB.

ok, in which case all you can do is check the height of the available
single module RCBOs, and if not swap the box.

[1] It is probably a bit dubious now as it serves a single 'radial'
circuit which branches to two sockets (that I have found) and is wired
in 2.5mm^2 cable bundled with other cables and supplied through a 32A
MCB.

If the branch was at the CU that would actually be acceptable anyway.

That's because of the limited current demand from one socket outlet?

Yup - you are in reality just talking about a spur - just one where its
taken from origin. So the MCB will still provide fault protection for
the single 2.5mm^2 T&E, and the limitation of a single socket will
provide the overload protection. (overload protection does not *have* to
be at the origin of the circuit (although often it is)).

I
haven't actually checked where they branch because we only use one
socket anyway and the other one has duct tape to avoid confusion.

In reality, (and depending a bit on the installation method for the
cable) you would be hard pushed to do much damage with just a pair of
sockets even if the branch was elsewhere.


--
Cheers,

John.

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

On 11/07/2018 12:02, John Rumm wrote:
On 11/07/2018 10:23, Roger Hayter wrote:
John Rumm wrote:

On 10/07/2018 22:35, Roger Hayter wrote:

The Economy 7 supply to our house goes through a small box with a
built-in isolating switch and space for a single MCB[1].
Presumably if
I can find a 20A RCBO of the same width and shape I can just substitute
this for the MCB.

Such things exist - however they are taller, so not all CUs will have
space.

But if such a thing does not exist, would it be OK to
use a two pole RCBO mounted alone in a small box with no separate
isolating switch?Â* Space is not very ample.

Yup that would be fine. Just blank the spare way, or leave the MCB in
place and label it as "spare" or similar.

It would have to be a new enclosure as the existing one has an integral,
non-modular switch and only space for one MCB.

ok, in which case all you can do is check the height of the available
single module RCBOs, and if not swap the box.

[1]Â* It is probably a bit dubious now as it serves a single 'radial'
circuit which branches to two sockets (that I have found) and is wired
in 2.5mm^2 cable bundled with other cables and supplied through a 32A
MCB.

If the branch was at the CU that would actually be acceptable anyway.

That's because of the limited current demand from one socket outlet?

Yup - you are in reality just talking about a spur - just one where its
taken from origin. So the MCB will still provide fault protection for
the single 2.5mm^2 T&E, and the limitation of a single socket will
provide the overload protection. (overload protection does not *have* to
be at the origin of the circuit (although often it is)).

Â*I
haven't actually checked where they branch because we only use one
socket anyway and the other one has duct tape to avoid confusion.

In reality, (and depending a bit on the installation method for the
cable) you would be hard pushed to do much damage with just a pair of
sockets even if the branch was elsewhere.


Since most of these off-peak installations had surface mounted
cables anyway, so surely RCD protection is not needed ?.

On 12/07/2018 14:35, Andrew wrote:
On 11/07/2018 12:02, John Rumm wrote:
On 11/07/2018 10:23, Roger Hayter wrote:
John Rumm wrote:

On 10/07/2018 22:35, Roger Hayter wrote:

The Economy 7 supply to our house goes through a small box with a
built-in isolating switch and space for a single MCB[1]. Presumably if
I can find a 20A RCBO of the same width and shape I can just
substitute
this for the MCB.

Such things exist - however they are taller, so not all CUs will have
space.

But if such a thing does not exist, would it be OK to
use a two pole RCBO mounted alone in a small box with no separate
isolating switch?Â* Space is not very ample.

Yup that would be fine. Just blank the spare way, or leave the MCB in
place and label it as "spare" or similar.

It would have to be a new enclosure as the existing one has an integral,
non-modular switch and only space for one MCB.

ok, in which case all you can do is check the height of the available
single module RCBOs, and if not swap the box.

[1]Â* It is probably a bit dubious now as it serves a single 'radial'
circuit which branches to two sockets (that I have found) and is wired
in 2.5mm^2 cable bundled with other cables and supplied through a 32A
MCB.

If the branch was at the CU that would actually be acceptable anyway.

That's because of the limited current demand from one socket outlet?

Yup - you are in reality just talking about a spur - just one where
its taken from origin. So the MCB will still provide fault protection
for the single 2.5mm^2 T&E, and the limitation of a single socket will
provide the overload protection. (overload protection does not *have*
to be at the origin of the circuit (although often it is)).

Â*I
haven't actually checked where they branch because we only use one
socket anyway and the other one has duct tape to avoid confusion.

In reality, (and depending a bit on the installation method for the
cable) you would be hard pushed to do much damage with just a pair of
sockets even if the branch was elsewhere.


Since most of these off-peak installations had surface mounted
cables anyway, so surely RCD protection is not needed ?.

The man wants RCD protection, otherwise he wouldn't be changing it.

A nice shower/shed consumer unit sounds about right if it fits.

On 12/07/2018 14:35, Andrew wrote:
On 11/07/2018 12:02, John Rumm wrote:
On 11/07/2018 10:23, Roger Hayter wrote:
John Rumm wrote:

On 10/07/2018 22:35, Roger Hayter wrote:

The Economy 7 supply to our house goes through a small box with a
built-in isolating switch and space for a single MCB[1]. Presumably if
I can find a 20A RCBO of the same width and shape I can just
substitute
this for the MCB.

Such things exist - however they are taller, so not all CUs will have
space.

But if such a thing does not exist, would it be OK to
use a two pole RCBO mounted alone in a small box with no separate
isolating switch?Â* Space is not very ample.

Yup that would be fine. Just blank the spare way, or leave the MCB in
place and label it as "spare" or similar.

It would have to be a new enclosure as the existing one has an integral,
non-modular switch and only space for one MCB.

ok, in which case all you can do is check the height of the available
single module RCBOs, and if not swap the box.

[1]Â* It is probably a bit dubious now as it serves a single 'radial'
circuit which branches to two sockets (that I have found) and is wired
in 2.5mm^2 cable bundled with other cables and supplied through a 32A
MCB.

If the branch was at the CU that would actually be acceptable anyway.

That's because of the limited current demand from one socket outlet?

Yup - you are in reality just talking about a spur - just one where
its taken from origin. So the MCB will still provide fault protection
for the single 2.5mm^2 T&E, and the limitation of a single socket will
provide the overload protection. (overload protection does not *have*
to be at the origin of the circuit (although often it is)).

Â*I
haven't actually checked where they branch because we only use one
socket anyway and the other one has duct tape to avoid confusion.

In reality, (and depending a bit on the installation method for the
cable) you would be hard pushed to do much damage with just a pair of
sockets even if the branch was elsewhere.


Since most of these off-peak installations had surface mounted
cables anyway, so surely RCD protection is not needed ?.


But socket outlets are now required to have RCD protection even if the
cable is surface mounted. So the OP would have to install RCD sockets.

--
Adam

On 11/07/2018 10:23, Roger Hayter wrote:
John Rumm wrote:

On 10/07/2018 22:35, Roger Hayter wrote:

The Economy 7 supply to our house goes through a small box with a
built-in isolating switch and space for a single MCB[1]. Presumably if
I can find a 20A RCBO of the same width and shape I can just substitute
this for the MCB.

Such things exist - however they are taller, so not all CUs will have
space.

But if such a thing does not exist, would it be OK to
use a two pole RCBO mounted alone in a small box with no separate
isolating switch? Space is not very ample.

Yup that would be fine. Just blank the spare way, or leave the MCB in
place and label it as "spare" or similar.

It would have to be a new enclosure as the existing one has an integral,
non-modular switch and only space for one MCB.

A photo of the enclose would be nice. I might know of an RCBO that will
fit after looking.

But your suggestion of a double pole RCBO in an enclosure is fine. If
space is tight you may struggle


--
Adam

On 12/07/2018 14:35, Andrew wrote:
On 11/07/2018 12:02, John Rumm wrote:
On 11/07/2018 10:23, Roger Hayter wrote:
John Rumm wrote:


Â*I
haven't actually checked where they branch because we only use one
socket anyway and the other one has duct tape to avoid confusion.

In reality, (and depending a bit on the installation method for the
cable) you would be hard pushed to do much damage with just a pair of
sockets even if the branch was elsewhere.

Since most of these off-peak installations had surface mounted
cables anyway, so surely RCD protection is not needed ?.

It sounds as if the circuit is now supplying sockets and not just fixed
heating equipment. So they would require RCD protection anyway.

--
Cheers,

John.

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

John Rumm wrote:

On 11/07/2018 10:23, Roger Hayter wrote:
John Rumm wrote:

On 10/07/2018 22:35, Roger Hayter wrote:

The Economy 7 supply to our house goes through a small box with a
built-in isolating switch and space for a single MCB[1]. Presumably if
I can find a 20A RCBO of the same width and shape I can just substitute
this for the MCB.

Such things exist - however they are taller, so not all CUs will have
space.

But if such a thing does not exist, would it be OK to
use a two pole RCBO mounted alone in a small box with no separate
isolating switch? Space is not very ample.

Yup that would be fine. Just blank the spare way, or leave the MCB in
place and label it as "spare" or similar.

It would have to be a new enclosure as the existing one has an integral,
non-modular switch and only space for one MCB.

ok, in which case all you can do is check the height of the available
single module RCBOs, and if not swap the box.

[1] It is probably a bit dubious now as it serves a single 'radial'
circuit which branches to two sockets (that I have found) and is wired
in 2.5mm^2 cable bundled with other cables and supplied through a 32A
MCB.

If the branch was at the CU that would actually be acceptable anyway.

That's because of the limited current demand from one socket outlet?

Yup - you are in reality just talking about a spur - just one where its
taken from origin. So the MCB will still provide fault protection for
the single 2.5mm^2 T&E, and the limitation of a single socket will
provide the overload protection. (overload protection does not *have* to
be at the origin of the circuit (although often it is)).

I
haven't actually checked where they branch because we only use one
socket anyway and the other one has duct tape to avoid confusion.

In reality, (and depending a bit on the installation method for the
cable) you would be hard pushed to do much damage with just a pair of
sockets even if the branch was elsewhere.

Thanks for the advice. I'll put it at the bottom of my list of jobs
that need doing. I'm only thinking of interfering with it because it is
the only non-RCD protected circuit in the house.


--

Roger Hayter