Hi,
Re: http://www.lightwiring.co.uk/tag/2-way-switch/
Why is the 1st Fig.1 not recommended but you should use the 2nd Fig.1?

The first fig only needs one conductor per switch terminal. The 2nd
requires two instances of 2 conductors in a terminal.

On 14/11/2022 12:58, Grumps wrote:
> Hi,
> Re: http://www.lightwiring.co.uk/tag/2-way-switch/
> Why is the 1st Fig.1 not recommended but you should use the 2nd Fig.1?
>
> The first fig only needs one conductor per switch terminal. The 2nd
> requires two instances of 2 conductors in a terminal.

Its there in the text. the latter means it becomes too easy to take a
neutral from a different circuit to the one that supplies the live.

This is colloquially referred to as a "borrowed" neutral.

Using the 1st reduces the risk of borrowed neutrals.

(A fully populated RCBO CU will in fact detect borrowed neutrals but
MCBS won't. On a twin RCD split load, it depends on whether the
borrowed neutral cones form the same RCD as the live or from the other
RCD. The former won;t trip but the latter will.

On 14/11/2022 12:58, Grumps wrote:
> Hi,
> Re: http://www.lightwiring.co.uk/tag/2-way-switch/
> Why is the 1st Fig.1 not recommended but you should use the 2nd Fig.1?

I thought that they explained it fairly well.

In domestic premises you tend to get such a configuration on the stairs
and if the live feeds at top and bottom of the stairs are on different
lighting circuits as is actually quite common (or at least was back in
the incandescent lamp era).

I found a nasty one in my home when I moved in. Strictly the oil boiler
heating engineer found it when replacing the pump. Someone had provided
a sneaky way of powering the CH pump from a switch on the lighting
circuit from the living room. IOW the CH circuits were not safe to work
on because it was stealing power from the downstairs lighting circuit.

Thank heavens for neon screwdrivers!
>
> The first fig only needs one conductor per switch terminal. The 2nd
> requires two instances of 2 conductors in a terminal.

It depends. If you only have one lighting circuit then it is simple but
if you have more than one things could be dangerous and still live.

--
Regards,
Martin Brown

On 14/11/2022 13:51, Martin Brown wrote:
> On 14/11/2022 12:58, Grumps wrote:
>> Hi,
>> Re: http://www.lightwiring.co.uk/tag/2-way-switch/
>> Why is the 1st Fig.1 not recommended but you should use the 2nd Fig.1?
>
> I thought that they explained it fairly well.
>
> In domestic premises you tend to get such a configuration on the stairs
> and if the live feeds at top and bottom of the stairs are on different
> lighting circuits as is actually quite common (or at least was back in
> the incandescent lamp era).

My hall and landing lights are fed from the upstairs lighting circuit.
This has advantages, such as the time I arrived home in the early hours
of the morning, switched the light on and the bulb blew, tripping the
MCB - it meant that the downstairs circuit had not tripped and pushing
the kitchen door open, allowed me to use that light to see the burglar
alarm buttons and cancel it in time, so avoiding waking all the
neighbours up!

On 14/11/2022 14:00, SteveW wrote:
> On 14/11/2022 13:51, Martin Brown wrote:
>> On 14/11/2022 12:58, Grumps wrote:
>>> Hi,
>>> Re: http://www.lightwiring.co.uk/tag/2-way-switch/
>>> Why is the 1st Fig.1 not recommended but you should use the 2nd Fig.1?
>>
>> I thought that they explained it fairly well.
>>
>> In domestic premises you tend to get such a configuration on the
>> stairs and if the live feeds at top and bottom of the stairs are on
>> different lighting circuits as is actually quite common (or at least
>> was back in the incandescent lamp era).
>
> My hall and landing lights are fed from the upstairs lighting circuit.
> This has advantages, such as the time I arrived home in the early hours
> of the morning, switched the light on and the bulb blew, tripping the
> MCB - it meant that the downstairs circuit had not tripped and pushing
> the kitchen door open, allowed me to use that light to see the burglar
> alarm buttons and cancel it in time, so avoiding waking all the
> neighbours up!
>

My hall light is on d/stairs RCBO and the landing light is on the
Upstairs RCBO.

Both the hall and landing switches are in a 2 gang switch plate at all
doors. So if one circuit trips, i simply turn the other light on and
there is usually enough light for most people to then work with.

On 14/11/2022 13:06, SH wrote:
> On 14/11/2022 12:58, Grumps wrote:
>> Hi,
>> Re: http://www.lightwiring.co.uk/tag/2-way-switch/
>> Why is the 1st Fig.1 not recommended but you should use the 2nd Fig.1?
>>
>> The first fig only needs one conductor per switch terminal. The 2nd
>> requires two instances of 2 conductors in a terminal.
>
>
> Its there in the text. the latter means it becomes too easy to take a
> neutral from a different circuit to the one that supplies the live.

It also says that it's fine when executed correctly.

> This is colloquially referred to as a "borrowed" neutral.
>
> Using the 1st reduces the risk of borrowed neutrals.
>
> (A fully populated RCBO CU will in fact detect borrowed neutrals but
> MCBS won't.  On a twin RCD split load, it depends on whether the
> borrowed neutral cones form the same RCD as the live or from the other
> RCD. The former won;t trip but the latter will.

I'm thinking another problem with the 2-wire control is that there is
T+E from the ceiling rose to the 1st switch, then 3+E cable between the
switches (of which one core is the switched live). The switched live
will have to find its way back to the ceiling rose via the T+E, which
will require a junction.

On 14/11/2022 15:22, Grumps wrote:
> On 14/11/2022 13:06, SH wrote:
>> On 14/11/2022 12:58, Grumps wrote:
>>> Hi,
>>> Re: http://www.lightwiring.co.uk/tag/2-way-switch/
>>> Why is the 1st Fig.1 not recommended but you should use the 2nd Fig.1?
>>>
>>> The first fig only needs one conductor per switch terminal. The 2nd
>>> requires two instances of 2 conductors in a terminal.
>>
>>
>> Its there in the text. the latter means it becomes too easy to take a
>> neutral from a different circuit to the one that supplies the live.
>
> It also says that it's fine when executed correctly.
>
>> This is colloquially referred to as a "borrowed" neutral.
>>
>> Using the 1st reduces the risk of borrowed neutrals.
>>
>> (A fully populated RCBO CU will in fact detect borrowed neutrals but
>> MCBS won't.  On a twin RCD split load, it depends on whether the
>> borrowed neutral cones form the same RCD as the live or from the other
>> RCD. The former won;t trip but the latter will.
>
> I'm thinking another problem with the 2-wire control is that there is
> T+E from the ceiling rose to the 1st switch, then 3+E cable between the
> switches (of which one core is the switched live). The switched live
> will have to find its way back to the ceiling rose via the T+E, which
> will require a junction.

Not the case actually.

One method is:

you use the 3 core to wire the two way switches together so common to
common, L1 to L1, L2 to L2 and earth the back boxes together.

Then your Twin and Earth wire from teh ceiling rose is then wired across
L1 and L2 in one of the switches and teh earth added to the back box.

Another method is put one wire from ceiling rose switch cable into
common terminal of 1st switch.

Then 3 & E cable is used to wire L1 to L1, L2 to L2 and then use the
third remaining conductor to connect to Common of the remote switch and
then to the other wire coming from the ceiling rose at the first switch
via an insulated choc block connector.

On 14/11/2022 15:53, SH wrote:
> On 14/11/2022 15:22, Grumps wrote:
>> On 14/11/2022 13:06, SH wrote:
>>> On 14/11/2022 12:58, Grumps wrote:
>>>> Hi,
>>>> Re: http://www.lightwiring.co.uk/tag/2-way-switch/
>>>> Why is the 1st Fig.1 not recommended but you should use the 2nd Fig.1?
>>>>
>>>> The first fig only needs one conductor per switch terminal. The 2nd
>>>> requires two instances of 2 conductors in a terminal.
>>>
>>>
>>> Its there in the text. the latter means it becomes too easy to take a
>>> neutral from a different circuit to the one that supplies the live.
>>
>> It also says that it's fine when executed correctly.
>>
>>> This is colloquially referred to as a "borrowed" neutral.
>>>
>>> Using the 1st reduces the risk of borrowed neutrals.
>>>
>>> (A fully populated RCBO CU will in fact detect borrowed neutrals but
>>> MCBS won't.  On a twin RCD split load, it depends on whether the
>>> borrowed neutral cones form the same RCD as the live or from the
>>> other RCD. The former won;t trip but the latter will.
>>
>> I'm thinking another problem with the 2-wire control is that there is
>> T+E from the ceiling rose to the 1st switch, then 3+E cable between
>> the switches (of which one core is the switched live). The switched
>> live will have to find its way back to the ceiling rose via the T+E,
>> which will require a junction.
>
>
>
> Not the case actually.
>
> One method is:
>
> you use the 3 core to wire the two way switches together so common to
> common, L1 to L1, L2 to L2 and earth the back boxes together.
>
> Then your Twin and Earth wire from teh ceiling rose is then wired across
> L1 and L2 in one of the switches and teh earth added to the back box.

Yes, that's what that web-site calls 3 wire control.

> Another method is put one wire from ceiling rose switch cable into
> common terminal of 1st switch.
>
> Then 3 & E cable is used to wire L1 to L1, L2 to L2 and then use the
> third remaining conductor to connect to Common of the remote switch and
> then to the other wire coming from the ceiling rose at the first switch
> via an insulated choc block connector.

And that seems to be the 2 wire control.

On 14/11/2022 12:58, Grumps wrote:
> Hi,
> Re: http://www.lightwiring.co.uk/tag/2-way-switch/

> Why is the 1st Fig.1 not recommended but you should use the 2nd Fig.1?

The risk of connecting the live from one circuit to the neutral of
another, which is both dangerous, and also incompatible with RCDs in
some cases.

It it also more likely to cause interference for inductive loop hearing
aid users.

Here is the preferred option:

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

> The first fig only needs one conductor per switch terminal. The 2nd
> requires two instances of 2 conductors in a terminal.

The light and switch wiring are as per normal, and you run one 3&E
between the switches.

--
Cheers,

John.

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

Why, I'd have thought the difference was minimal.
Brian

--

--:
This newsgroup posting comes to you directly from...
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Note this Signature is meaningless.!
"SH" <i.love.spam@spam.com> wrote in message
news:tkteh3$1hp2$1@gioia.aioe.org...
> On 14/11/2022 12:58, Grumps wrote:
>> Hi,
>> Re: http://www.lightwiring.co.uk/tag/2-way-switch/
>> Why is the 1st Fig.1 not recommended but you should use the 2nd Fig.1?
>>
>> The first fig only needs one conductor per switch terminal. The 2nd
>> requires two instances of 2 conductors in a terminal.
>
>
> Its there in the text. the latter means it becomes too easy to take a
> neutral from a different circuit to the one that supplies the live.
>
> This is colloquially referred to as a "borrowed" neutral.
>
> Using the 1st reduces the risk of borrowed neutrals.
>
> (A fully populated RCBO CU will in fact detect borrowed neutrals but MCBS
> won't. On a twin RCD split load, it depends on whether the borrowed
> neutral cones form the same RCD as the live or from the other RCD. The
> former won;t trip but the latter will.

On 15/11/2022 09:15, Brian Gaff wrote:

>> On 14/11/2022 12:58, Grumps wrote:
>>> Hi,
>>> Re:http://www.lightwiring.co.uk/tag/2-way-switch/
>>> Why is the 1st Fig.1 not recommended but you should use the 2nd Fig.1?
>>>
>>> The first fig only needs one conductor per switch terminal. The 2nd
>>> requires two instances of 2 conductors in a terminal.
>>
>> Its there in the text. the latter means it becomes too easy to take a
>> neutral from a different circuit to the one that supplies the live.
>>
>> This is colloquially referred to as a "borrowed" neutral.
>>
>> Using the 1st reduces the risk of borrowed neutrals.
>>
>> (A fully populated RCBO CU will in fact detect borrowed neutrals but MCBS
>> won't. On a twin RCD split load, it depends on whether the borrowed
>> neutral cones form the same RCD as the live or from the other RCD. The
>> former won;t trip but the latter will.

> Why, I'd have thought the difference was minimal.

That much depends on how much you like being electrocuted!

Borrowed neutrals are a serious electrical faults, not just a minor
problem that trips RCDs.

If you isolate a circuit to work on it, it can be very unwelcome to find
that its neutral is now live because it it connected to the live on
another circuit via a lamp.

--
Cheers,

John.

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

On 14/11/2022 12:58, Grumps wrote:
> Hi,
> Re: http://www.lightwiring.co.uk/tag/2-way-switch/
> Why is the 1st Fig.1 not recommended but you should use the 2nd Fig.1?
>
> The first fig only needs one conductor per switch terminal. The 2nd
> requires two instances of 2 conductors in a terminal.

Take a look at this ..... big changes now in how things can be done.
https://www.youtube.com/watch?v=9wnGN4RetJk