Intriguing wiring
 

For anyone who thinks wiring is too easy to be left to the
professionals. In our bathroom the fan permanent live is supplied from
the socket circuit (admittedly from a fused switch unit next to the
sccket in the cupboard under the sink) and the switched live is from the
lighting circuit. I don't suppose this is totally forbidden, but it
seems a bit eccentric to me, especially if one thinks the fan might be
isolated by the (two pole) FSU.


--

Roger Hayter

Intriguing wiring
 

On 11/03/2019 14:41, Roger Hayter wrote:
For anyone who thinks wiring is too easy to be left to the
professionals. In our bathroom the fan permanent live is supplied from
the socket circuit (admittedly from a fused switch unit next to the
sccket in the cupboard under the sink) and the switched live is from the
lighting circuit. I don't suppose this is totally forbidden, but it
seems a bit eccentric to me, especially if one thinks the fan might be
isolated by the (two pole) FSU.



Or not isolated depending on the circuit that switches it on from a
different live source.

I believe you are supposed to have a 3 pole isolator that does both
lives and neutral with a 3mm gap in the switch.

Intriguing wiring
 

dennis@home wrote:

On 11/03/2019 14:41, Roger Hayter wrote:
For anyone who thinks wiring is too easy to be left to the
professionals. In our bathroom the fan permanent live is supplied from
the socket circuit (admittedly from a fused switch unit next to the
sccket in the cupboard under the sink) and the switched live is from the
lighting circuit. I don't suppose this is totally forbidden, but it
seems a bit eccentric to me, especially if one thinks the fan might be
isolated by the (two pole) FSU.



Or not isolated depending on the circuit that switches it on from a
different live source.

I believe you are supposed to have a 3 pole isolator that does both
lives and neutral with a 3mm gap in the switch.

A necessity that only arises if you want the fan to be switched by the
same switch as the light switch.[1] We want a separate switch, but I
think we will have the 3 pole isolator anyway in case a future resident
wants it changed to one switch.


[1] Unless you are happy for the bathroom light to go out when you
isolate the fan, which is considered bad practice for some reason.
--

Roger Hayter

Intriguing wiring
 

On 11/03/2019 15:48, Roger Hayter wrote:

A necessity that only arises if you want the fan to be switched by the
same switch as the light switch.[1] We want a separate switch, but I
think we will have the 3 pole isolator anyway in case a future resident
wants it changed to one switch.


[1] Unless you are happy for the bathroom light to go out when you
isolate the fan, which is considered bad practice for some reason.

Isolating the fan will not turn off the light.

The switched live to the 3 pole isolator comes from the light switch but
the supply to the light is taken off before the isolator.

http://wiki.diyfaq.org.uk/index.php/...h_no_timer.png

Intriguing wiring
 

On Mon, 11 Mar 2019 14:41:24 +0000, Roger Hayter wrote:

For anyone who thinks wiring is too easy to be left to the
professionals. In our bathroom the fan permanent live is supplied from
the socket circuit (admittedly from a fused switch unit next to the
sccket in the cupboard under the sink) and the switched live is from the
lighting circuit. I don't suppose this is totally forbidden,


Yes, it is totally forbidden!
521.8.2 says L +N of each final circuit shall be electrically separate
from those of every other final circuit.

There will be more, but ICBA to look them up now.

Suffice to say, it can be dangerous how yours is, and should be rectified
to make it safer, i.e, get the permanant live from the same circuit as
the switched live.

Intriguing wiring
 

Mike Clarke wrote:

On 11/03/2019 15:48, Roger Hayter wrote:

A necessity that only arises if you want the fan to be switched by the
same switch as the light switch.[1] We want a separate switch, but I
think we will have the 3 pole isolator anyway in case a future resident
wants it changed to one switch.


[1] Unless you are happy for the bathroom light to go out when you
isolate the fan, which is considered bad practice for some reason.

Isolating the fan will not turn off the light.

The switched live to the 3 pole isolator comes from the light switch but
the supply to the light is taken off before the isolator.

http://wiki.diyfaq.org.uk/index.php/...h_no_timer.png

Well, exactly. But you might *choose* to use a two pole isolator
*before* both the light and the fan. That would work fine, except you
would have to work on the fan in the dark or bring your own light. I
was just emphasising *why* you need a three pole isolator.


--

Roger Hayter

Intriguing wiring
 

Alan wrote:

On Mon, 11 Mar 2019 14:41:24 +0000, Roger Hayter wrote:

For anyone who thinks wiring is too easy to be left to the
professionals. In our bathroom the fan permanent live is supplied from
the socket circuit (admittedly from a fused switch unit next to the
sccket in the cupboard under the sink) and the switched live is from the
lighting circuit. I don't suppose this is totally forbidden,


Yes, it is totally forbidden!
521.8.2 says L +N of each final circuit shall be electrically separate
from those of every other final circuit.

There will be more, but ICBA to look them up now.

Suffice to say, it can be dangerous how yours is, and should be rectified
to make it safer, i.e, get the permanant live from the same circuit as
the switched live.

There is no need. Said fan previously discharged into the (almost
except at the eaves) closed space between two rafters and T& G below
and slates above. Now it has Kingspan resting on it and a membrane
under the slates, and I have therefore disconnected it. A work in (not
much) progress as we now have an unconnected ventilator in the roof not
far away.

--

Roger Hayter

Intriguing wiring
 

On 11/03/2019 15:48, Roger Hayter wrote:
dennis@home wrote:

On 11/03/2019 14:41, Roger Hayter wrote:
For anyone who thinks wiring is too easy to be left to the
professionals. In our bathroom the fan permanent live is supplied from
the socket circuit (admittedly from a fused switch unit next to the
sccket in the cupboard under the sink) and the switched live is from the
lighting circuit. I don't suppose this is totally forbidden, but it
seems a bit eccentric to me, especially if one thinks the fan might be
isolated by the (two pole) FSU.



Or not isolated depending on the circuit that switches it on from a
different live source.

I believe you are supposed to have a 3 pole isolator that does both
lives and neutral with a 3mm gap in the switch.

A necessity that only arises if you want the fan to be switched by the
same switch as the light switch.[1] We want a separate switch, but I
think we will have the 3 pole isolator anyway in case a future resident
wants it changed to one switch.


[1] Unless you are happy for the bathroom light to go out when you
isolate the fan, which is considered bad practice for some reason.

I must say I power my fan, loo, and shower light from a single switch,
but there is a separate strip light for the bathroom area which
illuminates both areas well.

Intriguing wiring
 

On Monday, 11 March 2019 20:07:07 UTC, newshound wrote:

I must say I power my fan, loo, and shower light from a single switch,
but there is a separate strip light for the bathroom area which
illuminates both areas well.

I'm wondering why the loo is powered, an electric fencer for those that pee without due care & attention?


NT

Intriguing wiring
 

On 11/03/2019 14:41, Roger Hayter wrote:
For anyone who thinks wiring is too easy to be left to the
professionals. In our bathroom the fan permanent live is supplied from
the socket circuit (admittedly from a fused switch unit next to the
sccket in the cupboard under the sink) and the switched live is from the
lighting circuit. I don't suppose this is totally forbidden,

Er, yes it is!

but it
seems a bit eccentric to me, especially if one thinks the fan might be
isolated by the (two pole) FSU.

A fan with switched and permanent live ought to have a three pole isolator.


--
Cheers,

John.

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