In message <l2u7ji-j244.ln1@esprimo.zbmc.eu>, at 13:08:21 on Thu, 21 Apr
2022, Chris Green <cl@isbd.net> remarked:
>Roland Perry <roland@perry.co.uk> wrote:
>>
>> >> I discussed that with the electrician, and he's says it's not kosher
>> >>to combine two spurs onto one like that.
>> >
>> >There is nothing (electrically) dodgy about combining two lighting
>> >circuits onto one MCB - assuming the total load does not exceed the
>> >capacity of the MCB.
>>
>> Even if both are spurs? That was the issue my electrician had.
>>
>Lighting circuits are not rings, so they are essentially just lots of
>spurs in a tree.

The issue the electrician had was having the "root" of two of separate
such spurs(/trees) connected into one breaker in the consumer unit.

Maybe he's wrong about the regs, but he did check with a much more
senior colleague.

Meanwhile I've looked at the upstairs landing light switch and it has
three cables.

One is "going down", and is almost certain to be the other end of the
two cores "going up" from the downstairs hall switch.

There's another pair of cores "going up".

And the third is 'straight through', and is probably the spur from the
consumer unit to the upstairs tree.

I don't think allows us to reinstate a conventional two-way switch
(because you'd need three cores between the two floors) but it could
mean that we don't need to rummage around much in the attic to find a
live pair to connect a smart-controller to.

>I suppose you could connect a single feed going from
>fitting to fitting but it's certainly not required and there's
>absolutely nothing wrong with branching as much as you like as long as
>the overall load is OK.

>You're very unlikely to hit loading limits nowadays with mostly LEDs.

There's no disagreement about that.
--
Roland Perry

On 21/04/2022 11:20, Roland Perry wrote:
> In message <t3r9uj$d70$1@dont-email.me>, at 10:59:48 on Thu, 21 Apr
> 2022, John Rumm <see.my.signature@nowhere.null> remarked:
>> On 21/04/2022 06:22, Roland Perry wrote:
>>> In message <t3pmuk$jg6$2@dont-email.me>, at 20:29:25 on Wed, 20 Apr
>>> 2022, ARW <adamwadsworth@blueyonder.co.uk> remarked:
>>>> On 20/04/2022 20:20, Andy Burns wrote:
>>>>> Roland Perry wrote:
>>>>>
>>>>>> Andy Burns remarked:
>>>>>>
>>>>>>> The Quinetic switches don't need batteries, they use energy
>>>>>>> harvesting.
>>>>>>
>>>>>> So I understand. I've looked their site and it's not clear how the
>>>>>> two-way feature would work. Is it as simple as pairing each switch
>>>>>> individually with one controller, and then toggling either one
>>>>>> will toggle the light?
>
>>>>>  Yes.
>>>>
>>>> Or simpler to move both lighting circuits to the same RCD/RCBO.
>
>>>  I discussed that with the electrician, and he's says it's not kosher
>>> to  combine two spurs onto one like that.
>>
>> There is nothing (electrically) dodgy about combining two lighting
>> circuits onto one MCB - assuming the total load does not exceed the
>> capacity of the MCB.
>
> Even if both are spurs? That was the issue my electrician had.

I don't really understand the use of the term "spur" when applied to a
lighting circuit, which is traditionally wired as radial. Hence you can
have as many branches as you like at any point in the circuit.

>> There is a user issue, that a fault on the one now larger circuit will
>> trip all lights rather than just one those on one story.
>
> The main safety risk here is the stairs, and whether they are connected
> to upstairs, downstairs (or both at the same time) one RCD tripping will
> plunge them into darkness anyway.

Yup, and even spread over two circuits there is no guarantee that the
bit you need to navigate safely will be adequately lit - especially if
the stairs change direction at any point.

(Mine do, hence I have non maintained emergency lighting at both top and
bottom!)

>> Sometimes it might be possible to rewire a part of the upstairs
>> circuit to remove the landing light from that circuit entirely, and
>> connect it to the downstairs one instead.
>
> It's gaining the necessary access which is a problem. And I definitely
> don't want to start cutting new channels in the walls. I suppose one

With the upstairs circuit, much of thee wiring is often accessible from
the loft. So it will then come down to how many cables run between
ground and first floors.

> could run a cable up an outside wall, but I usually try to remove
> unsightly outside cables, not install more of them. And that would be a
> third spur, dear liza.

http://wiki.diyfaq.org.uk/index.php/House_Wiring_for_Beginners#Lighting

--
Cheers,

John.

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

On 21/04/2022 17:43, Roland Perry wrote:
> In message <l2u7ji-j244.ln1@esprimo.zbmc.eu>, at 13:08:21 on Thu, 21 Apr
> 2022, Chris Green <cl@isbd.net> remarked:
>> Roland Perry <roland@perry.co.uk> wrote:
>>>
>>> >>  I discussed that with the electrician, and he's says it's not kosher
>>> >>to  combine two spurs onto one like that.
>>> >
>>> >There is nothing (electrically) dodgy about combining two lighting
>>> >circuits onto one MCB - assuming the total load does not exceed the
>>> >capacity of the MCB.
>>>
>>> Even if both are spurs? That was the issue my electrician had.
>>>
>> Lighting circuits are not rings, so they are essentially just lots of
>> spurs in a tree.
>
> The issue the electrician had was having the "root" of two of separate
> such spurs(/trees) connected into one breaker in the consumer unit.

Even with a socket circuit you can legitimately run a spur from the
circuit origin - i.e. three wires connecting to the MCB and other bus
bars. One for each end of a ring, and the third for the spur.

With a lighting circuit, the same applies you can branch wherever you
like, including at the circuit origin.
> Maybe he's wrong about the regs, but he did check with a much more
> senior colleague.

I wonder if there is some communication at crossed purposes happening here?

> Meanwhile I've looked at the upstairs landing light switch and it has
> three cables.
>
> One is "going down", and is almost certain to be the other end of the
> two cores "going up" from the downstairs hall switch.
>
> There's another pair of cores "going up".
>
> And the third is 'straight through', and is probably the spur from the
> consumer unit to the upstairs tree.

You mean there is a cable not connected to the switch?

Yes that could be the power feed from the CU to the upstairs circuit -
probably running straight to a ceiling rose.

> I don't think allows us to reinstate a conventional two-way switch
> (because you'd need three cores between the two floors) but it could
> mean that we don't need to rummage around much in the attic to find a
> live pair to connect a smart-controller to.

If the circuits were merged, then you can do two way with fewer wires:

http://wiki.diyfaq.org.uk/index.php/2_Way_Switching#Alternative_method_of_Two_Way_Switching

--
Cheers,

John.

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

On 21/04/2022 09:34, Roland Perry wrote:
> In message <t3qvn6$3vv$1@dont-email.me>, at 08:05:09 on Thu, 21 Apr
> 2022, Jeff Layman <jmlayman@invalid.invalid> remarked:
>> On 21/04/2022 07:08, Andy Burns wrote:
>>> Roland Perry wrote:
>>>
>>>> I'm not yet sure how two switches paired with one controller
>>>> performs the XOR (rather than OR) function required for two-way
>>>> operation.
>
>>> I doubt the controller remembers* each switches state and XORs them
>>> all to the output, it'll just toggle its output for a trigger from
>>> any switch paired with it.
>
>>> [*] in fact, I don't even think the individual switches even
>>> remember their own state, they are retractive toggle switches, not
>>> up=off/down=on switches.
>>
>> Correct. I've got a dual-gang Quinetic switch to operate wall or
>> ceiling lights. I'm careful to avoid switching both at the same time as
>> one will not work and they will get "out of sync".
>
> Fair enough. So more like a bathroom cord-pull: once for on and another
> for off.

That's how they work.

>> In fact, as Quinetic switches don't look like ordinary light switches
>> anyway, I wonder why they designed them to look, and appear to operate,
>> like the ordinary switches.
>
> The ones I'm looking at are "architrave" fitting, and look normal.
> Although it's the size I'm more interested in.

They should be fine, as they are only available as single switches. No
chance of two getting out-of-sync.

>> They should be either a push-and-return button or spring toggle. Then,
>> if you pushed both by mistake, you'd just have to push the one which
>> hadn't worked.

--

Jeff

John Rumm <see.my.signature@nowhere.null> wrote:
> > The issue the electrician had was having the "root" of two of separate
> > such spurs(/trees) connected into one breaker in the consumer unit.
>
> Even with a socket circuit you can legitimately run a spur from the
> circuit origin - i.e. three wires connecting to the MCB and other bus
> bars. One for each end of a ring, and the third for the spur.
>
Not every 'socket circuit' is a ring of course.

--
Chris Green
·

On 21/04/2022 11:20, Roland Perry wrote:
> In message <t3r9uj$d70$1@dont-email.me>, at 10:59:48 on Thu, 21 Apr
> 2022, John Rumm <see.my.signature@nowhere.null> remarked:
>> On 21/04/2022 06:22, Roland Perry wrote:
>>> In message <t3pmuk$jg6$2@dont-email.me>, at 20:29:25 on Wed, 20 Apr
>>> 2022, ARW <adamwadsworth@blueyonder.co.uk> remarked:
>>>> On 20/04/2022 20:20, Andy Burns wrote:
>>>>> Roland Perry wrote:
>>>>>
>>>>>> Andy Burns remarked:
>>>>>>
>>>>>>> The Quinetic switches don't need batteries, they use energy
>>>>>>> harvesting.
>>>>>>
>>>>>> So I understand. I've looked their site and it's not clear how the
>>>>>> two-way feature would work. Is it as simple as pairing each switch
>>>>>> individually with one controller, and then toggling either one
>>>>>> will toggle the light?
>
>>>>>  Yes.
>>>>
>>>> Or simpler to move both lighting circuits to the same RCD/RCBO.
>
>>>  I discussed that with the electrician, and he's says it's not kosher
>>> to  combine two spurs onto one like that.
>>
>> There is nothing (electrically) dodgy about combining two lighting
>> circuits onto one MCB - assuming the total load does not exceed the
>> capacity of the MCB.
>
> Even if both are spurs? That was the issue my electrician had.

NICEIC had a comment about that when they did one of my inspections. I
had put the smokes on with the upstairs lights to the same MCB (two
cables at the MCB). I was told it was wrong but when asked for a reg
they just said "we do not like it"

>> There is a user issue, that a fault on the one now larger circuit will
>> trip all lights rather than just one those on one story.
>
> The main safety risk here is the stairs, and whether they are connected
> to upstairs, downstairs (or both at the same time) one RCD tripping will
> plunge them into darkness anyway.

No riskier than a power cut. The number of times it has been mentioned
that stairs and lights not working/failing are a risk to life I have
seen on this newsgroup is unbelievable.

The main cause of stair accidents is alcohol and not a lack of lighting.

On 20 Apr 2022 at 19:54:19 BST, "Roland Perry" <roland@perry.co.uk> wrote:

> I've got an upstairs hall light with a shared neutral issue, so after my
> recent consumer unit replacement, the downstairs (half of an original
> two-way installation) switch has been disconnected.
>
> What I need (I think, I really don't want to start chasing the walls for
> new physical wiring) is a light fitting that responds to a pair of
> cordless switches, one to be glued on the wall downstairs, the other
> upstairs. So that pressing either of them turns the light on/off.
>

Ikea do something like that - hubless switches that can control their own
wireless bulbs. I've got a couple on the hall/stairs/landing.

> Despite reservations about cordless gadgets in general, I don't mind if
> the switches have batteries in them, requiring periodic changing.
>

The switch contains the battery - last about 2 years.

> SWMBO has also found a ceiling light with a "night-light" feature, so
> that even if switched off, it glows a little after dark. Hopefully that
> won't complicate things. [At the moment we have a night-light plugged
> into a 13A socket in the upstairs hall, to help prevent us accidentally
> falling down the stairs in the dark]

I've a few Xiaomi LED battery lights with motion sensors dotted about - takes
AA rechargable batteries that need charging every 6 months or so.

--
Cheers, Rob

On 21/04/2022 19:10, John Rumm wrote:

> Even with a socket circuit you can legitimately run a spur from the
> circuit origin - i.e. three wires connecting to the MCB and other bus
> bars. One for each end of a ring, and the third for the spur.

The older MEM MCBs even had a wiring diagram on them telling you on
which order to place the three cables. The cables were terminated behind
a plate and not is a screw clap like modern MCB

In message <t3sdfe$hqh$1@dont-email.me>, at 21:06:07 on Thu, 21 Apr
2022, ARW <adamwadsworth@blueyonder.co.uk> remarked:
>On 21/04/2022 11:20, Roland Perry wrote:
>> In message <t3r9uj$d70$1@dont-email.me>, at 10:59:48 on Thu, 21 Apr
>>2022, John Rumm <see.my.signature@nowhere.null> remarked:
>>> On 21/04/2022 06:22, Roland Perry wrote:
>>>> In message <t3pmuk$jg6$2@dont-email.me>, at 20:29:25 on Wed, 20 Apr
>>>>2022, ARW <adamwadsworth@blueyonder.co.uk> remarked:
>>>>> On 20/04/2022 20:20, Andy Burns wrote:
>>>>>> Roland Perry wrote:
>>>>>>
>>>>>>> Andy Burns remarked:
>>>>>>>
>>>>>>>> The Quinetic switches don't need batteries, they use energy
>>>>>>>>harvesting.
>>>>>>>
>>>>>>> So I understand. I've looked their site and it's not clear how the
>>>>>>> two-way feature would work. Is it as simple as pairing each
>>>>>>>switch individually with one controller, and then toggling
>>>>>>>either one will toggle the light?
>>
>>>>>>  Yes.
>>>>>
>>>>> Or simpler to move both lighting circuits to the same RCD/RCBO.
>>
>>>>  I discussed that with the electrician, and he's says it's not
>>>>kosher to  combine two spurs onto one like that.
>>>
>>> There is nothing (electrically) dodgy about combining two lighting
>>>circuits onto one MCB - assuming the total load does not exceed the
>>>capacity of the MCB.

>> Even if both are spurs? That was the issue my electrician had.
>
>NICEIC had a comment about that when they did one of my inspections. I
>had put the smokes on with the upstairs lights to the same MCB (two
>cables at the MCB). I was told it was wrong but when asked for a reg
>they just said "we do not like it"

That's probably where my installation is at the moment.

>>> There is a user issue, that a fault on the one now larger circuit
>>>will trip all lights rather than just one those on one story.

>> The main safety risk here is the stairs, and whether they are
>>connected to upstairs, downstairs (or both at the same time) one RCD
>>tripping will plunge them into darkness anyway.
>
>No riskier than a power cut.

The first house I had with RCDs, the vast majority of the 'power cuts'
were false alarms by the RCD.

>The number of times it has been mentioned that stairs and lights not
>working/failing are a risk to life I have seen on this newsgroup is
>unbelievable.

It's particularly applicable when the RCD trips in the middle of the
night, the householder is upstairs and the consumer unit is downstairs.

>The main cause of stair accidents is alcohol and not a lack of lighting.

We need to cross each bridge as we come to it. I'm not proposing DIY
brewing as an aspect of this particular thread!
--
Roland Perry

In message <t3s6m3$q12$1@dont-email.me>, at 19:10:11 on Thu, 21 Apr
2022, John Rumm <see.my.signature@nowhere.null> remarked:
>On 21/04/2022 17:43, Roland Perry wrote:
>> In message <l2u7ji-j244.ln1@esprimo.zbmc.eu>, at 13:08:21 on Thu, 21
>>Apr 2022, Chris Green <cl@isbd.net> remarked:
>>> Roland Perry <roland@perry.co.uk> wrote:
>>>>
>>>> >>  I discussed that with the electrician, and he's says it's not kosher
>>>> >>to  combine two spurs onto one like that.
>>>> >
>>>> >There is nothing (electrically) dodgy about combining two lighting
>>>> >circuits onto one MCB - assuming the total load does not exceed the
>>>> >capacity of the MCB.
>>>>
>>>> Even if both are spurs? That was the issue my electrician had.
>>>>
>>> Lighting circuits are not rings, so they are essentially just lots of
>>> spurs in a tree.

>> The issue the electrician had was having the "root" of two of
>>separate such spurs(/trees) connected into one breaker in the
>>consumer unit.
>
>Even with a socket circuit you can legitimately run a spur from the
>circuit origin - i.e. three wires connecting to the MCB and other bus
>bars. One for each end of a ring, and the third for the spur.

Indeed so, that was part of his explanation. However he said two spurs
despite being fewer wires wasn't OK.

>With a lighting circuit, the same applies you can branch wherever you
>like, including at the circuit origin.

>> Maybe he's wrong about the regs, but he did check with a much more
>>senior colleague.
>
>I wonder if there is some communication at crossed purposes happening here?

It's possible they both had "the wrong answer", but they knew what the
question was.

>> Meanwhile I've looked at the upstairs landing light switch and it has
>>three cables.

>> One is "going down", and is almost certain to be the other end of
>>the two cores "going up" from the downstairs hall switch.

>> There's another pair of cores "going up".

>> And the third is 'straight through', and is probably the spur from
>>the consumer unit to the upstairs tree.
>
>You mean there is a cable not connected to the switch?

At the moment none are connected (he capped them off), but yes, not
*originally* connected.

>Yes that could be the power feed from the CU to the upstairs circuit -
>probably running straight to a ceiling rose.

The closest ceiling rose is directly above, and the one whose
arrangements are under discussion.

>> I don't think allows us to reinstate a conventional two-way switch
>>(because you'd need three cores between the two floors) but it could
>>mean that we don't need to rummage around much in the attic to find a
>>live pair to connect a smart-controller to.
>
>If the circuits were merged, then you can do two way with fewer wires:
>
>http://wiki.diyfaq.org.uk/index.php/2_Way_Switching#Alternative_method_o
>f_Two_Way_Switching

Yes, that was what I was expecting the outcome to be (if we can in fact
merge the two lighting circuits). But noting the compatibility issues
with RCDs.

Meanwhile, if it's still OK to use the earth as a third conductor (as in
their "standard two way circuit"), then we have three conductors in each
direction.
--
Roland Perry

In message <t3s4v2$bqn$1@dont-email.me>, at 18:40:50 on Thu, 21 Apr
2022, John Rumm <see.my.signature@nowhere.null> remarked:
>On 21/04/2022 11:20, Roland Perry wrote:
>> In message <t3r9uj$d70$1@dont-email.me>, at 10:59:48 on Thu, 21 Apr
>>2022, John Rumm <see.my.signature@nowhere.null> remarked:
>>> On 21/04/2022 06:22, Roland Perry wrote:
>>>> In message <t3pmuk$jg6$2@dont-email.me>, at 20:29:25 on Wed, 20 Apr
>>>>2022, ARW <adamwadsworth@blueyonder.co.uk> remarked:
>>>>> On 20/04/2022 20:20, Andy Burns wrote:
>>>>>> Roland Perry wrote:
>>>>>>
>>>>>>> Andy Burns remarked:
>>>>>>>
>>>>>>>> The Quinetic switches don't need batteries, they use energy
>>>>>>>>harvesting.
>>>>>>>
>>>>>>> So I understand. I've looked their site and it's not clear how the
>>>>>>> two-way feature would work. Is it as simple as pairing each
>>>>>>>switch individually with one controller, and then toggling
>>>>>>>either one will toggle the light?
>>
>>>>>>  Yes.
>>>>>
>>>>> Or simpler to move both lighting circuits to the same RCD/RCBO.
>>
>>>>  I discussed that with the electrician, and he's says it's not
>>>>kosher to  combine two spurs onto one like that.
>>>
>>> There is nothing (electrically) dodgy about combining two lighting
>>>circuits onto one MCB - assuming the total load does not exceed the
>>>capacity of the MCB.

>> Even if both are spurs? That was the issue my electrician had.
>
>I don't really understand the use of the term "spur" when applied to a
>lighting circuit, which is traditionally wired as radial. Hence you can
>have as many branches as you like at any point in the circuit.

It means one cable being the root of the tree at the consumer unit. Not
a ring.

>>> There is a user issue, that a fault on the one now larger circuit
>>>will trip all lights rather than just one those on one story.

>> The main safety risk here is the stairs, and whether they are
>>connected to upstairs, downstairs (or both at the same time) one RCD
>>tripping will plunge them into darkness anyway.
>
>Yup, and even spread over two circuits there is no guarantee that the
>bit you need to navigate safely will be adequately lit - especially if
>the stairs change direction at any point.
>
>(Mine do, hence I have non maintained emergency lighting at both top
>and bottom!)

In my house the upstairs light illuminates the whole stairway, but the
downstairs light only that half.

>>> Sometimes it might be possible to rewire a part of the upstairs
>>>circuit to remove the landing light from that circuit entirely, and
>>>connect it to the downstairs one instead.

>> It's gaining the necessary access which is a problem. And I
>>definitely don't want to start cutting new channels in the walls. I
>>suppose one
>
>With the upstairs circuit, much of thee wiring is often accessible from
>the loft.

The loft is difficult to access at all, and full of very
hazardous-looking insulation and general detritus. If can find someone
to give me a grant, I'd like (someone - it's beyond my DIY ambitions) to
clear it all out and re-insulate to modern standards.

>So it will then come down to how many cables run between ground and
>first floors.

I've been looking into that.

>> could run a cable up an outside wall, but I usually try to remove
>>unsightly outside cables, not install more of them. And that would be
>>a third spur, dear liza.
>
>http://wiki.diyfaq.org.uk/index.php/House_Wiring_for_Beginners#Lighting
>
>
>
>

--
Roland Perry

On 22/04/2022 06:28, Roland Perry wrote:
> In message <t3sdfe$hqh$1@dont-email.me>, at 21:06:07 on Thu, 21 Apr
> 2022, ARW <adamwadsworth@blueyonder.co.uk> remarked:
>> On 21/04/2022 11:20, Roland Perry wrote:
>>> In message <t3r9uj$d70$1@dont-email.me>, at 10:59:48 on Thu, 21 Apr
>>> 2022, John Rumm <see.my.signature@nowhere.null> remarked:
>>>> On 21/04/2022 06:22, Roland Perry wrote:
>>>>> In message <t3pmuk$jg6$2@dont-email.me>, at 20:29:25 on Wed, 20 Apr
>>>>> 2022, ARW <adamwadsworth@blueyonder.co.uk> remarked:
>>>>>> On 20/04/2022 20:20, Andy Burns wrote:
>>>>>>> Roland Perry wrote:
>>>>>>>
>>>>>>>> Andy Burns remarked:
>>>>>>>>
>>>>>>>>> The Quinetic switches don't need batteries, they use energy
>>>>>>>>> harvesting.
>>>>>>>>
>>>>>>>> So I understand. I've looked their site and it's not clear how the
>>>>>>>> two-way feature would work. Is it as simple as pairing each
>>>>>>>> switch  individually with one controller, and then toggling
>>>>>>>> either one  will toggle the light?
>>>
>>>>>>>  Yes.
>>>>>>
>>>>>> Or simpler to move both lighting circuits to the same RCD/RCBO.
>>>
>>>>>  I discussed that with the electrician, and he's says it's not
>>>>> kosher  to  combine two spurs onto one like that.
>>>>
>>>> There is nothing (electrically) dodgy about combining two lighting
>>>> circuits onto one MCB - assuming the total load does not exceed the
>>>> capacity of the MCB.
>
>>>  Even if both are spurs? That was the issue my electrician had.
>>
>> NICEIC had a comment about that when they did one of my inspections. I
>> had put the smokes on with the upstairs lights to the same MCB (two
>> cables at the MCB). I was told it was wrong but when asked for a reg
>> they just said "we do not like it"
>
> That's probably where my installation is at the moment.
>
>>>> There is a user issue, that a fault on the one now larger circuit
>>>> will  trip all lights rather than just one those on one story.
>
>>>  The main safety risk here is the stairs, and whether they are
>>> connected  to upstairs, downstairs (or both at the same time) one RCD
>>> tripping will  plunge them into darkness anyway.
>>
>> No riskier than a power cut.
>
> The first house I had with RCDs, the vast majority of the 'power cuts'
> were false alarms by the RCD.

I had that - likely due to too many PCs and general gadgets, all with
their own (leaky) filters on the power supplies, pushing it near the
limits, so any tiny disturbance was enough to push it over.

Scrapping the RCD and replacing all the MCBs that it fed with RCBOs
shared the leakage out and we have had no false trips since.

On 22/04/2022 06:22, Roland Perry wrote:
> In message <t3s6m3$q12$1@dont-email.me>, at 19:10:11 on Thu, 21 Apr
> 2022, John Rumm <see.my.signature@nowhere.null> remarked:
>> On 21/04/2022 17:43, Roland Perry wrote:
>>> In message <l2u7ji-j244.ln1@esprimo.zbmc.eu>, at 13:08:21 on Thu, 21
>>> Apr  2022, Chris Green <cl@isbd.net> remarked:
>>>> Roland Perry <roland@perry.co.uk> wrote:
>>>>>
>>>>> >>  I discussed that with the electrician, and he's says it's not
>>>>> kosher
>>>>> >>to  combine two spurs onto one like that.
>>>>> >
>>>>> >There is nothing (electrically) dodgy about combining two lighting
>>>>> >circuits onto one MCB - assuming the total load does not exceed the
>>>>> >capacity of the MCB.
>>>>>
>>>>> Even if both are spurs? That was the issue my electrician had.
>>>>>
>>>> Lighting circuits are not rings, so they are essentially just lots of
>>>> spurs in a tree.
>
>>>  The issue the electrician had was having the "root" of two of
>>> separate  such spurs(/trees) connected into one breaker in the
>>> consumer unit.
>>
>> Even with a socket circuit you can legitimately run a spur from the
>> circuit origin - i.e. three wires connecting to the MCB and other bus
>> bars. One for each end of a ring, and the third for the spur.
>
> Indeed so, that was part of his explanation. However he said two spurs
> despite being fewer wires wasn't OK.

Even that is ok, so long as any overload condition is prevented by the
nature of the loads on the spurs.

Normally the circuit protective device (Fuse/MCB/RCBO) is responsible
for providing both overload current protection, and fault current
protection.

While fault current protection must always be provided at the origin of
the circuit, there are cases where overload protection can be delegated
elsewhere.

The classic example of this is a normal spur from a 32A ring circuit.
The maximum current carrying capacity of a single length of 2.5mm^2 T&E
is less than the trip threshold of the MCB. However the rules for an
unfused spur limit the load to one socket accessory (single or double).
That means there is no way to cause an overload on the spur cable. A
fault current however (say a short at the end of the spur) will cause
the MCB to open, and adequately protect that single spur cable. (you can
prove this if you calculate the maximum prospective fault current and
then put that into the adiabatic equation)

The rules don't change with the location of the spur - so a ring with
two spurs is "ok" (not ideal, and messy in wiring terms, and often
physically difficult to wire), but technically ok. So by extension, two
spurs at origin is ok, and then removing the ring and just leaving the
two spurs is also ok. Now you have in effect made a radial circuit with
a branch at the origin, and delegated the overload protection to the
load end of the circuit.

So for example you have a couple of 13A immersion heaters, you could
wire each in 2.5mm T&E, and connect both cables to the same 32A MCB. The
13A heater can't overload the cable, and a 32A MCB will give adequate
fault protection to the cables, while also being able to supply the
nominal 26A load.

>> With a lighting circuit, the same applies you can branch wherever you
>> like, including at the circuit origin.
>
>>> Maybe he's wrong about the regs, but he did check with a much more
>>> senior colleague.
>>
>> I wonder if there is some communication at crossed purposes happening
>> here?
>
> It's possible they both had "the wrong answer", but they knew what the
> question was.

Or possibly, as Adam commented, the various professional bodies / trade
associations gold plate their own "rules" on top as "best practice", and
hence forbid practices that BS7671 itself deems ok, or is silent about.

>>> Meanwhile I've looked at the upstairs landing light switch and it has
>>> three cables.
>
>>>  One is "going down", and is almost certain to be the other end of
>>> the  two cores "going up" from the downstairs hall switch.
>
>>>  There's another pair of cores "going up".
>
>>>  And the third is 'straight through', and is probably the spur from
>>> the  consumer unit to the upstairs tree.
>>
>> You mean there is a cable not connected to the switch?
>
> At the moment none are connected (he capped them off), but yes, not
> *originally* connected.
>
>> Yes that could be the power feed from the CU to the upstairs circuit -
>> probably running straight to a ceiling rose.
>
> The closest ceiling rose is directly above, and the one whose
> arrangements are under discussion.
>
>>> I don't think allows us to reinstate a conventional two-way switch
>>> (because you'd need three cores between the two floors) but it could
>>> mean that we don't need to rummage around much in the attic to find a
>>> live pair to connect a smart-controller to.
>>
>> If the circuits were merged, then you can do two way with fewer wires:
>>
>> http://wiki.diyfaq.org.uk/index.php/2_Way_Switching#Alternative_method_o
>> f_Two_Way_Switching
>
> Yes, that was what I was expecting the outcome to be (if we can in fact
> merge the two lighting circuits). But noting the compatibility issues
> with RCDs.

If both circuits are merged, they are then served from the same RCD, and
that problem goes away.

> Meanwhile, if it's still OK to use the earth as a third conductor (as in
> their "standard two way circuit"), then we have three conductors in each
> direction.

Does the circuit as a whole have earthing? (pre 1966, lighting circuits
were not required to be earthed).

If it does not[1], then the question is simplified to "is it ever
acceptable to re-purpose a protective conductor as something else?" The
answer to that is a qualified "yes" so long as the conductor is part of
a multi wire cable, and not a loose "single" and that is is correctly
over marked at both ends.

[1] Although note that unearthed lighting circuits bring their own
problems since all accessories and fittings must be either non
conductive or double insulated, and extending the circuit legally
becomes difficult. For the down on dirty on that see:

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

--
Cheers,

John.

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On 22/04/2022 06:44, Roland Perry wrote:
> In message <t3s4v2$bqn$1@dont-email.me>, at 18:40:50 on Thu, 21 Apr
> 2022, John Rumm <see.my.signature@nowhere.null> remarked:
>> On 21/04/2022 11:20, Roland Perry wrote:
>>> In message <t3r9uj$d70$1@dont-email.me>, at 10:59:48 on Thu, 21 Apr
>>> 2022, John Rumm <see.my.signature@nowhere.null> remarked:
>>>> On 21/04/2022 06:22, Roland Perry wrote:
>>>>> In message <t3pmuk$jg6$2@dont-email.me>, at 20:29:25 on Wed, 20 Apr
>>>>> 2022, ARW <adamwadsworth@blueyonder.co.uk> remarked:
>>>>>> On 20/04/2022 20:20, Andy Burns wrote:
>>>>>>> Roland Perry wrote:
>>>>>>>
>>>>>>>> Andy Burns remarked:
>>>>>>>>
>>>>>>>>> The Quinetic switches don't need batteries, they use energy
>>>>>>>>> harvesting.
>>>>>>>>
>>>>>>>> So I understand. I've looked their site and it's not clear how the
>>>>>>>> two-way feature would work. Is it as simple as pairing each
>>>>>>>> switch  individually with one controller, and then toggling
>>>>>>>> either one  will toggle the light?
>>>
>>>>>>>  Yes.
>>>>>>
>>>>>> Or simpler to move both lighting circuits to the same RCD/RCBO.
>>>
>>>>>  I discussed that with the electrician, and he's says it's not
>>>>> kosher  to  combine two spurs onto one like that.
>>>>
>>>> There is nothing (electrically) dodgy about combining two lighting
>>>> circuits onto one MCB - assuming the total load does not exceed the
>>>> capacity of the MCB.
>
>>>  Even if both are spurs? That was the issue my electrician had.
>>
>> I don't really understand the use of the term "spur" when applied to a
>> lighting circuit, which is traditionally wired as radial. Hence you
>> can have as many branches as you like at any point in the circuit.
>
> It means one cable being the root of the tree at the consumer unit. Not
> a ring.

That is not a spur - just a branch in a radial.

The only time you would have a genuine spur on a radial, is where you
run a backbone connection in a larger CSA cable, but then connect loads
to it using a smaller cable. Say a 32A radial wired in 4mm^2 T&E, and
then individual socket drops in 2.5mm^2 T&E. The MCB would then only
provide fault protection for the socket drops, not overload protection.

>
>>>> There is a user issue, that a fault on the one now larger circuit
>>>> will  trip all lights rather than just one those on one story.
>
>>>  The main safety risk here is the stairs, and whether they are
>>> connected  to upstairs, downstairs (or both at the same time) one RCD
>>> tripping will  plunge them into darkness anyway.
>>
>> Yup, and even spread over two circuits there is no guarantee that the
>> bit you need to navigate safely will be adequately lit - especially if
>> the stairs change direction at any point.
>>
>> (Mine do, hence I have non maintained emergency lighting at both top
>> and bottom!)
>
> In my house the upstairs light illuminates the whole stairway, but the
> downstairs light only that half.
>
>>>> Sometimes it might be possible to rewire a part of the upstairs
>>>> circuit to remove the landing light from that circuit entirely, and
>>>> connect it to the downstairs one instead.
>
>>>  It's gaining the necessary access which is a problem. And I
>>> definitely  don't want to start cutting new channels in the walls. I
>>> suppose one
>>
>> With the upstairs circuit, much of thee wiring is often accessible
>> from the loft.
>
> The loft is difficult to access at all, and full of very
> hazardous-looking insulation and general detritus. If can find someone
> to give me a grant, I'd like (someone - it's beyond my DIY ambitions) to
> clear it all out and re-insulate to modern standards.

Fair enough... some lofts become "no go" areas with increasing time, and
decreasing enthusiasm!

>> So it will then come down to how many cables run between ground and
>> first floors.
>
> I've been looking into that.
>
>>> could run a cable up an outside wall, but I usually try to remove
>>> unsightly outside cables, not install more of them. And that would be
>>> a  third spur, dear liza.
>>
>> http://wiki.diyfaq.org.uk/index.php/House_Wiring_for_Beginners#Lighting
>>
>>
>>
>>
>

--
Cheers,

John.

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John Rumm wrote:

> If both circuits are merged, they are then served from the same RCD, and that
> problem goes away.

But then you have the issue that one RCD tripping will lose all lights in the house

In article <jcfo6uFnib3U2@mid.individual.net>, Andy Burns
<usenet@andyburns.uk> wrote:
> John Rumm wrote:

> > If both circuits are merged, they are then served from the same RCD,
> > and that problem goes away.

> But then you have the issue that one RCD tripping will lose all lights in
> the house

and if you have 2, it will be the one that covers the bit of the house you
are that trips.

--
from KT24 in Surrey, England
"I'd rather die of exhaustion than die of boredom" Thomas Carlyle

On 22/04/2022 14:17, Andy Burns wrote:
> John Rumm wrote:
>
>> If both circuits are merged, they are then served from the same RCD,
>> and that problem goes away.
>
> But then you have the issue that one RCD tripping will lose all lights
> in the house

The importance of which rather depends on what else shares the RCD.
Earth leakage trips on lighting circuits are fairly unlikely.

Or if the install has a "whole house" RCD then it also (while far from
ideal) makes it no worse.

--
Cheers,

John.

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\=================================================================/

On 21/04/2022 20:20, Chris Green wrote:
> John Rumm <see.my.signature@nowhere.null> wrote:
>>> The issue the electrician had was having the "root" of two of separate
>>> such spurs(/trees) connected into one breaker in the consumer unit.
>>
>> Even with a socket circuit you can legitimately run a spur from the
>> circuit origin - i.e. three wires connecting to the MCB and other bus
>> bars. One for each end of a ring, and the third for the spur.
>>
> Not every 'socket circuit' is a ring of course.

True, and even there you can have a branch at the CU (although that
might confuse someone seeing two cables and expecting a ring!)

--
Cheers,

John.

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