The CU is a Wylex from the early '90s ('91 - 2 IIRC). All MCB, 30mA RCD on
rings, cooker, shower etc. and 100mA on lighting circuits.
As I'd need 30mA on the lights for the fitting in the bathroom I thought of
replacing the two MCBs with miniature Wylex RCBOs, so it's 100mA - 30mA.
I rather like the mini-RCBOs as they are 2-pole.
Would this be a valid arrangement (assuming that the RCBOs will actually
fit!)?
--
Peter.
The gods will stay away
whilst religions hold sway

On 19/03/2019 13:39, PeterC wrote:
The CU is a Wylex from the early '90s ('91 - 2 IIRC). All MCB, 30mA RCD on
rings, cooker, shower etc. and 100mA on lighting circuits.
As I'd need 30mA on the lights for the fitting in the bathroom I thought of
replacing the two MCBs with miniature Wylex RCBOs, so it's 100mA - 30mA.
I rather like the mini-RCBOs as they are 2-pole.
Would this be a valid arrangement (assuming that the RCBOs will actually
fit!)?


If the 100mA RCD is time delayed then this is correct.

However even if the 100mA RCD is not time delayed then you not made the
situation worse and complied with the 17th edition on bathroom lighting
circuits.

--
Adam

On 19/03/2019 13:39, PeterC wrote:

The CU is a Wylex from the early '90s ('91 - 2 IIRC). All MCB, 30mA RCD on
rings, cooker, shower etc. and 100mA on lighting circuits.

Is this a TT earthed install? And does the 100mA RCD have a time delay
feature? (often denoted with a s suffix)

As I'd need 30mA on the lights for the fitting in the bathroom I thought of
replacing the two MCBs with miniature Wylex RCBOs, so it's 100mA - 30mA.
I rather like the mini-RCBOs as they are 2-pole.
Would this be a valid arrangement (assuming that the RCBOs will actually
fit!)?

Well it will work, however if the 100mA RCD is not a time delay types,
then in the event of an earth leakage trip, you may trip either one or
both of the RCDs. You may not get any selectivity or "discrimination"
between them.


--
Cheers,

John.

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

On Tue, 19 Mar 2019 23:12:14 +0000, John Rumm wrote:

On 19/03/2019 13:39, PeterC wrote:

The CU is a Wylex from the early '90s ('91 - 2 IIRC). All MCB, 30mA RCD on
rings, cooker, shower etc. and 100mA on lighting circuits.

Is this a TT earthed install? And does the 100mA RCD have a time delay
feature? (often denoted with a s suffix)

As I'd need 30mA on the lights for the fitting in the bathroom I thought of
replacing the two MCBs with miniature Wylex RCBOs, so it's 100mA - 30mA.
I rather like the mini-RCBOs as they are 2-pole.
Would this be a valid arrangement (assuming that the RCBOs will actually
fit!)?

Well it will work, however if the 100mA RCD is not a time delay types,
then in the event of an earth leakage trip, you may trip either one or
both of the RCDs. You may not get any selectivity or "discrimination"
between them.

Thank John and Adam. I haven't looked closely at the RCD but, as it's no
worse and it'll comply I'm happy with it.
--
Peter.
The gods will stay away
whilst religions hold sway

On 20/03/2019 08:30, PeterC wrote:
On Tue, 19 Mar 2019 23:12:14 +0000, John Rumm wrote:

On 19/03/2019 13:39, PeterC wrote:

The CU is a Wylex from the early '90s ('91 - 2 IIRC). All MCB, 30mA RCD on
rings, cooker, shower etc. and 100mA on lighting circuits.

Is this a TT earthed install? And does the 100mA RCD have a time delay
feature? (often denoted with a s suffix)

As I'd need 30mA on the lights for the fitting in the bathroom I thought of
replacing the two MCBs with miniature Wylex RCBOs, so it's 100mA - 30mA.
I rather like the mini-RCBOs as they are 2-pole.
Would this be a valid arrangement (assuming that the RCBOs will actually
fit!)?

Well it will work, however if the 100mA RCD is not a time delay types,
then in the event of an earth leakage trip, you may trip either one or
both of the RCDs. You may not get any selectivity or "discrimination"
between them.

Thank John and Adam. I haven't looked closely at the RCD but, as it's no
worse and it'll comply I'm happy with it.


BTW what now requires YOU to use a 30mA RCD for the bathroom lights? The
regs are not retrospective so swapping a bathroom light should not
require you to install RCD protection.

--
Adam

On Thu, 21 Mar 2019 23:45:40 +0000, ARW wrote:

On 20/03/2019 08:30, PeterC wrote:
On Tue, 19 Mar 2019 23:12:14 +0000, John Rumm wrote:

On 19/03/2019 13:39, PeterC wrote:

The CU is a Wylex from the early '90s ('91 - 2 IIRC). All MCB, 30mA RCD on
rings, cooker, shower etc. and 100mA on lighting circuits.

Is this a TT earthed install? And does the 100mA RCD have a time delay
feature? (often denoted with a s suffix)

As I'd need 30mA on the lights for the fitting in the bathroom I thought of
replacing the two MCBs with miniature Wylex RCBOs, so it's 100mA - 30mA.
I rather like the mini-RCBOs as they are 2-pole.
Would this be a valid arrangement (assuming that the RCBOs will actually
fit!)?

Well it will work, however if the 100mA RCD is not a time delay types,
then in the event of an earth leakage trip, you may trip either one or
both of the RCDs. You may not get any selectivity or "discrimination"
between them.

Thank John and Adam. I haven't looked closely at the RCD but, as it's no
worse and it'll comply I'm happy with it.


BTW what now requires YOU to use a 30mA RCD for the bathroom lights? The
regs are not retrospective so swapping a bathroom light should not
require you to install RCD protection.

Thanks Adam - I didn't know about that. Around 25 quid saved!
--
Peter.
The gods will stay away
whilst religions hold sway

On 21/03/2019 23:45, ARW wrote:
BTW what now requires YOU to use a 30mA RCD for the bathroom lights? The
regs are not retrospective so swapping a bathroom light should not
require you to install RCD protection.

The regs are retrospective to any 'material alteration'

Whether fitting a new bathroom light is 'material alteration' is a moot
point


--
Climate Change: Socialism wearing a lab coat.

On 22/03/2019 08:50, The Natural Philosopher wrote:
On 21/03/2019 23:45, ARW wrote:
BTW what now requires YOU to use a 30mA RCD for the bathroom lights?
The regs are not retrospective so swapping a bathroom light should not
require you to install RCD protection.

The regs are retrospective to any 'material alteration'

Whether fitting a new bathroom light is 'material alteration' is a moot
point

Swapping a light fitting would be a like for like change and not an
alteration to the fixed wiring. Its not notifiable under part P either -
even in a bathroom.


--
Cheers,

John.

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

On 22/03/2019 10:30, John Rumm wrote:
On 22/03/2019 08:50, The Natural Philosopher wrote:
On 21/03/2019 23:45, ARW wrote:
BTW what now requires YOU to use a 30mA RCD for the bathroom lights?
The regs are not retrospective so swapping a bathroom light should
not require you to install RCD protection.

The regs are retrospective to any 'material alteration'

Whether fitting a new bathroom light is 'material alteration' is a
moot point

Swapping a light fitting would be a like for like change and not an
alteration to the fixed wiring. Its not notifiable under part P either -
even in a bathroom.



Moving a light or fitting an additional one in a bathroom would require
30mA protection in a bathroom under the 17th edition.

I'll have to check but I presume that now means in all rooms under the
18th edition.

You could argue that it would be good practice to fit the RCD protection
if the supplementary bonding is not present.




--
Adam

On 22/03/2019 19:19, ARW wrote:
On 22/03/2019 10:30, John Rumm wrote:
On 22/03/2019 08:50, The Natural Philosopher wrote:
On 21/03/2019 23:45, ARW wrote:
BTW what now requires YOU to use a 30mA RCD for the bathroom lights?
The regs are not retrospective so swapping a bathroom light should
not require you to install RCD protection.

The regs are retrospective to any 'material alteration'

Whether fitting a new bathroom light is 'material alteration' is a
moot point

Swapping a light fitting would be a like for like change and not an
alteration to the fixed wiring. Its not notifiable under part P either
- even in a bathroom.



Moving a light or fitting an additional one in a bathroom would require
30mA protection in a bathroom under the 17th edition.

I'll have to check but I presume that now means in all rooms under the
18th edition.

Probably... how much movement counts as moved I wonder?

You could argue that it would be good practice to fit the RCD protection
if the supplementary bonding is not present.

Yup, and main bonding is there and up to current standards.


--
Cheers,

John.

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

On Fri, 22 Mar 2019 19:19:04 +0000, ARW wrote:

On 22/03/2019 10:30, John Rumm wrote:
On 22/03/2019 08:50, The Natural Philosopher wrote:
On 21/03/2019 23:45, ARW wrote:
BTW what now requires YOU to use a 30mA RCD for the bathroom lights?
The regs are not retrospective so swapping a bathroom light should
not require you to install RCD protection.

The regs are retrospective to any 'material alteration'

Whether fitting a new bathroom light is 'material alteration' is a
moot point

Swapping a light fitting would be a like for like change and not an
alteration to the fixed wiring. Its not notifiable under part P either -
even in a bathroom.


Moving a light or fitting an additional one in a bathroom would require
30mA protection in a bathroom under the 17th edition.

I'll have to check but I presume that now means in all rooms under the
18th edition.

You could argue that it would be good practice to fit the RCD protection
if the supplementary bonding is not present.

Interesting points, thanks.
Sopplementary bonding: er, well, there's no way to do that as all of the
water side is plastic and the incoming main is MDPE. CH is copper, but it
seems to me that creating an earth path where there's no earth is pointless.

There's an old spur for the immersion heater. It was redundant so I used it
for a couple of sockets in the loft. As it's on the 100mA RCD I've been
thinking of using a double socket with integral RCD but, for about the same
money I could use an RCBO. I must measure a spare MCB to see if there's
space.
--
Peter.
The gods will stay away
whilst religions hold sway

On 23/03/2019 09:22, PeterC wrote:
On Fri, 22 Mar 2019 19:19:04 +0000, ARW wrote:

On 22/03/2019 10:30, John Rumm wrote:
On 22/03/2019 08:50, The Natural Philosopher wrote:
On 21/03/2019 23:45, ARW wrote:
BTW what now requires YOU to use a 30mA RCD for the bathroom lights?
The regs are not retrospective so swapping a bathroom light should
not require you to install RCD protection.

The regs are retrospective to any 'material alteration'

Whether fitting a new bathroom light is 'material alteration' is a
moot point

Swapping a light fitting would be a like for like change and not an
alteration to the fixed wiring. Its not notifiable under part P either -
even in a bathroom.


Moving a light or fitting an additional one in a bathroom would require
30mA protection in a bathroom under the 17th edition.

I'll have to check but I presume that now means in all rooms under the
18th edition.

You could argue that it would be good practice to fit the RCD protection
if the supplementary bonding is not present.

Interesting points, thanks.
Sopplementary bonding: er, well, there's no way to do that as all of the
water side is plastic and the incoming main is MDPE. CH is copper, but it
seems to me that creating an earth path where there's no earth is pointless.

There's an old spur for the immersion heater. It was redundant so I used it
for a couple of sockets in the loft. As it's on the 100mA RCD I've been
thinking of using a double socket with integral RCD but, for about the same
money I could use an RCBO. I must measure a spare MCB to see if there's
space.


As a note it's worth mentioning that I spent most of a day bonding the
metal sinks at a school the other day. The hot and cold pipes were
already cross bonded and there was no way that a pd could be introduced
to the sink.

Schools must have money to burn.

--
Adam

On 23/03/2019 09:53, ARW wrote:
On 23/03/2019 09:22, PeterC wrote:
On Fri, 22 Mar 2019 19:19:04 +0000, ARW wrote:

On 22/03/2019 10:30, John Rumm wrote:
On 22/03/2019 08:50, The Natural Philosopher wrote:
On 21/03/2019 23:45, ARW wrote:
BTW what now requires YOU to use a 30mA RCD for the bathroom lights?
The regs are not retrospective so swapping a bathroom light should
not require you to install RCD protection.

The regs are retrospective to any 'material alteration'

Whether fitting a new bathroom light is 'material alteration' is a
moot point

Swapping a light fitting would be a like for like change and not an
alteration to the fixed wiring. Its not notifiable under part P
either -
even in a bathroom.


Moving a light or fitting an additional one in a bathroom would require
30mA protection in a bathroom under the 17th edition.

I'll have to check but I presume that now means in all rooms under the
18th edition.

You could argue that it would be good practice to fit the RCD protection
if the supplementary bonding is not present.

Interesting points, thanks.
Sopplementary bonding: er, well, there's no way to do that as all of the
water side is plastic and the incoming main is MDPE. CH is copper, but it
seems to me that creating an earth path where there's no earth is
pointless.

There's an old spur for the immersion heater. It was redundant so I
used it
for a couple of sockets in the loft. As it's on the 100mA RCD I've been
thinking of using a double socket with integral RCD but, for about the
same
money I could use an RCBO. I must measure a spare MCB to see if there's
space.


As a note it's worth mentioning that I spent most of a day bonding the
metal sinks at a school the other day. The hot and cold pipes were
already cross bonded and there was no way that a pd could be introduced
to the sink.

Bonding the metal sinks to what, the hot and cold pipes?

Schools must have money to burn.

I guess they had an inspection and this was an arse covering exercise.
H&S spending trumps teaching.