On 03/01/2024 20:44, Alan Lee wrote:
> On 03/01/2024 19:38, Scott wrote:
>> On Wed, 3 Jan 2024 18:41:36 +0000, Alan Lee <alan@darkroom.plus.com>
>> wrote:
>
>>> Just do what 95% of sparkies do, and dont bother with the fused spur.
>>> There really is no need for it.
>>> Or, buy a Greenwood fan, they dont require a 3 amp fuse.
>>
>> What happens next time work is done at the same premises?  I thought
>> there was a 'last man out' rule making each successive electrician
>> responsible for the entire system - or is responsibility restricted to
>> the work done by each individual electrician?  I have never been sure.
>
> Nobody will GAF. There is a good argument that the 3amp fuse is
> spurious, so is ignored, as, really, it does nothing, other than allow a
> way of local isolation (which is not a requirement of the wiring regs.)
>
> If you go to a house to do work, you are only responsible for the work
> you have done, thats why all of the electrical certificates have an
> 'extent of installation covered by this certificate' box, which you fill
> in to show what you have done, e.g. "added fused spur from existing
> circuit 2 to supply single socket in hallway".
> Fill that in, then you cannot be blamed for the socket falling off with
> exposed wires in the bedroom.

There is a little more nuance there though. There are some cases where
you can't ignore what is there. Say you notice that the main
equipotential bonding is missing. You can't sign off your work with it
left in that state. So you would have to insist that the bonding fault
is fixed, or decline the new work.

Likewise, if asked to add a new light to a circuit that is wired with
twin cable and no earth. Then you would not be able to extend that, and
work to the required standards.

--
Cheers,

John.

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

On 04/01/2024 14:21, nothanks@aolbin.com wrote:
> On 03/01/2024 16:48, nothanks@aolbin.com wrote:
>> On 03/01/2024 16:07, Tricky Dicky wrote:
>>>
>>> I am fitting a Manrose MF100T ventilation fan in our bathroom. This will
>>> have a 3 pole isolator outside the bathroom and the plan is to run it in
>>> conjunction with the bathroom light so that the fan comes on when the
>>> light
>>> is operated typical of many windowless bathrooms and en-suites in many
>>> modern houses.
>>>
>>> The issue is that the manufacturer specify’s a 3A max. fuse for live and
>>> switched live and of course the lighting circuit is 6A.
>>>
>>> One option is to fit a fused spur unit into the incoming feed for the
>>> bathroom but that means all lights beyond that point would now be
>>> protected
>>> by a 3A fuse and the issue is that there are at least 3 ceiling fans
>>> in the
>>> rooms beyond that point.
>>>
>>> An alternative is to take 3-core and E cable from the bathroom light as
>>> planned and using two FCU’s
>>> One for live and the other for switched live before running the rest
>>> of the
>>> cable to the 3-pole isolator.
>>>
>>> The trouble is that I have not seen this arrangement anywhere. My
>>> daughters
>>> new build has one bathroom, 2 en-suites and a cloakroom/WC all
>>> windowless
>>> and all with ventilators activated by the light switch and I know all
>>> the
>>> lighting circuits are 6A.
>>>
>>> So what to do?
>>>
>>> I have a link to a similar fan which unlike the instructions for the
>>> MF100T
>>> has a wiring diagram
>>>
>>> https://www.manrose.co.uk/wp-content/uploads/doc/FandWs/496934.pdf
>> Not an answer, but a suggestion: consider having two pull switches,
>> one for the fan and one for the light, rather than having the fan
>> always come on with the light. This means you don't have the fan noise
>> at night time and you can leave the fan on for a while in the morning
>> after a vindaloo supper the night before.
>
> A further thought: you could put a 3A fuse inside the fan enclosure if
> you wanted a fuse but not an FCU.

That can work, but will be limited to fans with only one live connection.

If it has run on, then you would need a fuse protecting its permanent
live and another one on the switched live. Now you have two fuses in
parallel protecting the same device which is not good in a number of ways.

--
Cheers,

John.

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

On 05/01/2024 13:15, John Rumm wrote:
> On 04/01/2024 14:21, nothanks@aolbin.com wrote:
>> On 03/01/2024 16:48, nothanks@aolbin.com wrote:
>>> On 03/01/2024 16:07, Tricky Dicky wrote:
>>>>
>>>> I am fitting a Manrose MF100T ventilation fan in our bathroom. This
>>>> will
>>>> have a 3 pole isolator outside the bathroom and the plan is to run
>>>> it in
>>>> conjunction with the bathroom light so that the fan comes on when
>>>> the light
>>>> is operated typical of many windowless bathrooms and en-suites in many
>>>> modern houses.
>>>>
>>>> The issue is that the manufacturer specify’s a 3A max. fuse for live
>>>> and
>>>> switched live and of course the lighting circuit is 6A.
>>>>
>>>> One option is to fit a fused spur unit into the incoming feed for the
>>>> bathroom but that means all lights beyond that point would now be
>>>> protected
>>>> by a 3A fuse and the issue is that there are at least 3 ceiling fans
>>>> in the
>>>> rooms beyond that point.
>>>>
>>>> An alternative is to take 3-core and E cable from the bathroom light as
>>>> planned and using two FCU’s
>>>> One for live and the other for switched live before running the rest
>>>> of the
>>>> cable to the 3-pole isolator.
>>>>
>>>> The trouble is that I have not seen this arrangement anywhere. My
>>>> daughters
>>>> new build has one bathroom, 2 en-suites and a cloakroom/WC all
>>>> windowless
>>>> and all with ventilators activated by the light switch and I know
>>>> all the
>>>> lighting circuits are 6A.
>>>>
>>>> So what to do?
>>>>
>>>> I have a link to a similar fan which unlike the instructions for the
>>>> MF100T
>>>> has a wiring diagram
>>>>
>>>> https://www.manrose.co.uk/wp-content/uploads/doc/FandWs/496934.pdf
>>> Not an answer, but a suggestion: consider having two pull switches,
>>> one for the fan and one for the light, rather than having the fan
>>> always come on with the light. This means you don't have the fan
>>> noise at night time and you can leave the fan on for a while in the
>>> morning after a vindaloo supper the night before.
>>
>> A further thought: you could put a 3A fuse inside the fan enclosure if
>> you wanted a fuse but not an FCU.
>
> That can work, but will be limited to fans with only one live connection.
>
> If it has run on, then you would need a fuse protecting its permanent
> live and another one on the switched live. Now you have two fuses in
> parallel protecting the same device which is not good in a number of ways.

The Manrose install sheet only requires a fuse on the permanent live.
Why the need for two fuses? The switched live can be treated a signal
wire and I presume doesn't supply any current to the fan.

If that is the case there is perhaps no need for the triple isolation
switch?

If the fuse is fan side of the 3-pole isolation switch then it can be
changed, or altered, whilst being fully isolated without switching the
lighting MCB.

Fredxx <fredxx@spam.invalid> wrote:
> On 05/01/2024 11:41, SH wrote:
>> On 05/01/2024 11:32, SH wrote:
>>> On 05/01/2024 10:51, Andy Burns wrote:
>>>> SteveW wrote:
>>>>
>>>>> 6A seems to be the lowest rated RCBO for my consumer unit.
>>>>
>>>> Plenty of 1A MCBs and even the occasional 0.5A, but smallest RCBO I
>>>> can see is 2A
>>>
>>>
>>> I have a 5 bedroom house and I have literally just counted the number
>>> of bulbs on all of my lighting circuits (I have 4 lighting circuits.)
>>>
>>> The one with the most lamps is the ground floor with 55 lamps, all are
>>> LED lamps or LED Strips. All are at 4 to 6 watts.
>>>
>>> So lets take the highest wattage bulb and multiply by 55. This gives
>>> 330 Watts. There is an extractor fan on the d/stairs toilet fed by
>>> this circuit.
>>>
>>> The one with the highest wattage lamps is the outdoor floodlights
>>> circuit and there are 18 floodlamps with wattages ranging from 4 watts
>>> to 20 watts. Lets take the 20 watts figure as worst case and multiply
>>> by 18 which gives 350 Watts
>>>
>>> A 6A MCB or RCBO supports a continuous current of 1320 Watta at a
>>> supply voltage of 220 watts so 6A is cleary more than adequate.
>>>
>>> Swapping to a 3A MCB or RCBO would support a continuous current of 660
>>> Watts at a supply voltage of 220 watts which is almost double the the
>>> wattage assuming *all* lamps were all on at the same time. In practie
>>> very few of us actually have *all* the lamps on at the same time.
>>>
>>> The main issue with swapping out NCBs/RCBOs/RCDs in a consumer unit is
>>> that it is mandataed somewhere that the consumer unit and the
>>> MCBs/RCBOs/RCDs *should* be from the same manufacturer.
>>>
>>> S.
>>>
>>>
>>
>>
>> Coming back to the original OP's query,
>>
>> It strikces me that there is a possible solution but with a Caveat (*)
>>
>> Put in a dry lining box next to the light fitting.
>>
>> Transfer the Power Loop in and Power loop Out cables from the existing
>> light fitting to the new drylining box.
>>
>> Then wire in some twin and earth cable from the new drylining box and
>> then fit a FCU to this drylining box so that the bathroom light is now
>> on its own 3A supply.
>>
>> It is assumed that the wall switch also runs to the existing rose and
>> that the 3 core & E is also taken from the existing rose to the isolator
>> switch and thence onwards to the fan.
>>
>> (*) you will need to pay attention to the special zones of bathrooms
>> such that (a) the FCU is at a sifficient distance and hieght away from
>> the bath or shower and (b) with it being a humid atmosphere, humidity
>> may get inside teh FCU so it might be prudent to use a IP66 rated FCU
>> enclosure OR extend the power loop in, power loop out and the bridging
>> cable so that teh FCU can be mounted somewhere outside the bathroom.
>>
>> As a side point, putting a 3A fuse into the Live in for the fan does not
>> offer any protection to the switched live wire.
>
> The switched live might be a sensor input rather than supplying power. I
> note the wiring diagram:
> https://www.manrose.co.uk/wp-content/uploads/doc/FandWs/496934.pdf
> allows for a fuse in just the live feed.
>
> Nevertheless I still feel that is an issue and would prefer the light
> and fan on it's own fuse.
>
>> Although you could put a
>> 2nd fuse into teh Switched live, you then could have an unsafe situation
>> where if a fuse opens, unless one is diligent about opening the fan
>> isolator switch, one could be working on a fan thinking its completely
>> dead when in fact either teh permanent Live or switched Live is still Live!
>
> As long as the wires are correctly sleeved, anyone gaining access to the
> terminals ought to be checking to see if a wire is live and remove power
> wherever possible.
>

Look again the diagram for the timer version shows the switched live tapped
off the live connection after the 3A fuse

On 05/01/2024 15:22, Tricky Dicky wrote:
> Fredxx <fredxx@spam.invalid> wrote:
>> On 05/01/2024 11:41, SH wrote:
>>> On 05/01/2024 11:32, SH wrote:
>>>> On 05/01/2024 10:51, Andy Burns wrote:
>>>>> SteveW wrote:
>>>>>
>>>>>> 6A seems to be the lowest rated RCBO for my consumer unit.
>>>>>
>>>>> Plenty of 1A MCBs and even the occasional 0.5A, but smallest RCBO I
>>>>> can see is 2A
>>>>
>>>>
>>>> I have a 5 bedroom house and I have literally just counted the number
>>>> of bulbs on all of my lighting circuits (I have 4 lighting circuits.)
>>>>
>>>> The one with the most lamps is the ground floor with 55 lamps, all are
>>>> LED lamps or LED Strips. All are at 4 to 6 watts.
>>>>
>>>> So lets take the highest wattage bulb and multiply by 55. This gives
>>>> 330 Watts. There is an extractor fan on the d/stairs toilet fed by
>>>> this circuit.
>>>>
>>>> The one with the highest wattage lamps is the outdoor floodlights
>>>> circuit and there are 18 floodlamps with wattages ranging from 4 watts
>>>> to 20 watts. Lets take the 20 watts figure as worst case and multiply
>>>> by 18 which gives 350 Watts
>>>>
>>>> A 6A MCB or RCBO supports a continuous current of 1320 Watta at a
>>>> supply voltage of 220 watts so 6A is cleary more than adequate.
>>>>
>>>> Swapping to a 3A MCB or RCBO would support a continuous current of 660
>>>> Watts at a supply voltage of 220 watts which is almost double the the
>>>> wattage assuming *all* lamps were all on at the same time. In practie
>>>> very few of us actually have *all* the lamps on at the same time.
>>>>
>>>> The main issue with swapping out NCBs/RCBOs/RCDs in a consumer unit is
>>>> that it is mandataed somewhere that the consumer unit and the
>>>> MCBs/RCBOs/RCDs *should* be from the same manufacturer.
>>>>
>>>> S.
>>>>
>>>>
>>>
>>>
>>> Coming back to the original OP's query,
>>>
>>> It strikces me that there is a possible solution but with a Caveat (*)
>>>
>>> Put in a dry lining box next to the light fitting.
>>>
>>> Transfer the Power Loop in and Power loop Out cables from the existing
>>> light fitting to the new drylining box.
>>>
>>> Then wire in some twin and earth cable from the new drylining box and
>>> then fit a FCU to this drylining box so that the bathroom light is now
>>> on its own 3A supply.
>>>
>>> It is assumed that the wall switch also runs to the existing rose and
>>> that the 3 core & E is also taken from the existing rose to the isolator
>>> switch and thence onwards to the fan.
>>>
>>> (*) you will need to pay attention to the special zones of bathrooms
>>> such that (a) the FCU is at a sifficient distance and hieght away from
>>> the bath or shower and (b) with it being a humid atmosphere, humidity
>>> may get inside teh FCU so it might be prudent to use a IP66 rated FCU
>>> enclosure OR extend the power loop in, power loop out and the bridging
>>> cable so that teh FCU can be mounted somewhere outside the bathroom.
>>>
>>> As a side point, putting a 3A fuse into the Live in for the fan does not
>>> offer any protection to the switched live wire.
>>
>> The switched live might be a sensor input rather than supplying power. I
>> note the wiring diagram:
>> https://www.manrose.co.uk/wp-content/uploads/doc/FandWs/496934.pdf
>> allows for a fuse in just the live feed.
>>
>> Nevertheless I still feel that is an issue and would prefer the light
>> and fan on it's own fuse.
>>
>>> Although you could put a
>>> 2nd fuse into teh Switched live, you then could have an unsafe situation
>>> where if a fuse opens, unless one is diligent about opening the fan
>>> isolator switch, one could be working on a fan thinking its completely
>>> dead when in fact either teh permanent Live or switched Live is still Live!
>>
>> As long as the wires are correctly sleeved, anyone gaining access to the
>> terminals ought to be checking to see if a wire is live and remove power
>> wherever possible.
>>
>
> Look again the diagram for the timer version shows the switched live tapped
> off the live connection after the 3A fuse
>

Fig 3 assumes you dont have power loop in and power loop out at the
lighting rose....

The circuit digram would be more complex once the power loop in and
power loop out is added....

On 05/01/2024 13:21, Fredxx wrote:
> On 05/01/2024 13:15, John Rumm wrote:
>> On 04/01/2024 14:21, nothanks@aolbin.com wrote:
>>> On 03/01/2024 16:48, nothanks@aolbin.com wrote:
>>>> On 03/01/2024 16:07, Tricky Dicky wrote:
>>>>>
>>>>> I am fitting a Manrose MF100T ventilation fan in our bathroom. This
>>>>> will
>>>>> have a 3 pole isolator outside the bathroom and the plan is to run
>>>>> it in
>>>>> conjunction with the bathroom light so that the fan comes on when
>>>>> the light
>>>>> is operated typical of many windowless bathrooms and en-suites in many
>>>>> modern houses.
>>>>>
>>>>> The issue is that the manufacturer specify’s a 3A max. fuse for
>>>>> live and
>>>>> switched live and of course the lighting circuit is 6A.
>>>>>
>>>>> One option is to fit a fused spur unit into the incoming feed for the
>>>>> bathroom but that means all lights beyond that point would now be
>>>>> protected
>>>>> by a 3A fuse and the issue is that there are at least 3 ceiling
>>>>> fans in the
>>>>> rooms beyond that point.
>>>>>
>>>>> An alternative is to take 3-core and E cable from the bathroom
>>>>> light as
>>>>> planned and using two FCU’s
>>>>> One for live and the other for switched live before running the
>>>>> rest of the
>>>>> cable to the 3-pole isolator.
>>>>>
>>>>> The trouble is that I have not seen this arrangement anywhere. My
>>>>> daughters
>>>>> new build has one bathroom, 2 en-suites and a cloakroom/WC all
>>>>> windowless
>>>>> and all with ventilators activated by the light switch and I know
>>>>> all the
>>>>> lighting circuits are 6A.
>>>>>
>>>>> So what to do?
>>>>>
>>>>> I have a link to a similar fan which unlike the instructions for
>>>>> the MF100T
>>>>> has a wiring diagram
>>>>>
>>>>> https://www.manrose.co.uk/wp-content/uploads/doc/FandWs/496934.pdf
>>>> Not an answer, but a suggestion: consider having two pull switches,
>>>> one for the fan and one for the light, rather than having the fan
>>>> always come on with the light. This means you don't have the fan
>>>> noise at night time and you can leave the fan on for a while in the
>>>> morning after a vindaloo supper the night before.
>>>
>>> A further thought: you could put a 3A fuse inside the fan enclosure
>>> if you wanted a fuse but not an FCU.
>>
>> That can work, but will be limited to fans with only one live connection.
>>
>> If it has run on, then you would need a fuse protecting its permanent
>> live and another one on the switched live. Now you have two fuses in
>> parallel protecting the same device which is not good in a number of
>> ways.
>
> The Manrose install sheet only requires a fuse on the permanent live.
> Why the need for two fuses? The switched live can be treated a signal
> wire and I presume doesn't supply any current to the fan.

You can't really extrapolate from one fan to all. If you need a 3A fused
supply, then it is better IMHO to run all inputs to the fan from the
same supply.

> If that is the case there is perhaps no need for the triple isolation
> switch?

You need the triple isolator to make sure mains can't reach the fan
while maintaining it. Some fans will run with neutral and a live feed to
the switched live terminal. (they will only need the perm live connected
to "run on")

> If the fuse is fan side of the 3-pole isolation switch then it can be
> changed, or altered, whilst being fully isolated without switching the
> lighting MCB.

Most faceplate installed fuses can be safely changed live anyway - the
fuse carrier inserts and removes it, and the terminals are not (easily)
touchable.

--
Cheers,

John.

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

On 05/01/2024 11:32, SH wrote:
>
<snip>

> The main issue with swapping out NCBs/RCBOs/RCDs in a consumer unit is
> that it is mandataed somewhere that the consumer unit and the
> MCBs/RCBOs/RCDs *should* be from the same manufacturer.

And in my case *HAVE* to be, as it is a Crabtree Starbreaker, with their
own design of busbar and devices that plug directly into it and have no
incoming Live terminal.

On 05/01/2024 13:15, John Rumm wrote:
> On 04/01/2024 14:21, nothanks@aolbin.com wrote:
>> On 03/01/2024 16:48, nothanks@aolbin.com wrote:
>>> On 03/01/2024 16:07, Tricky Dicky wrote:
>>>>
>>>> I am fitting a Manrose MF100T ventilation fan in our bathroom. This
>>>> will
>>>> have a 3 pole isolator outside the bathroom and the plan is to run
>>>> it in
>>>> conjunction with the bathroom light so that the fan comes on when
>>>> the light
>>>> is operated typical of many windowless bathrooms and en-suites in many
>>>> modern houses.
>>>>
>>>> The issue is that the manufacturer specify’s a 3A max. fuse for live
>>>> and
>>>> switched live and of course the lighting circuit is 6A.
>>>>
>>>> One option is to fit a fused spur unit into the incoming feed for the
>>>> bathroom but that means all lights beyond that point would now be
>>>> protected
>>>> by a 3A fuse and the issue is that there are at least 3 ceiling fans
>>>> in the
>>>> rooms beyond that point.
>>>>
>>>> An alternative is to take 3-core and E cable from the bathroom light as
>>>> planned and using two FCU’s
>>>> One for live and the other for switched live before running the rest
>>>> of the
>>>> cable to the 3-pole isolator.
>>>>
>>>> The trouble is that I have not seen this arrangement anywhere. My
>>>> daughters
>>>> new build has one bathroom, 2 en-suites and a cloakroom/WC all
>>>> windowless
>>>> and all with ventilators activated by the light switch and I know
>>>> all the
>>>> lighting circuits are 6A.
>>>>
>>>> So what to do?
>>>>
>>>> I have a link to a similar fan which unlike the instructions for the
>>>> MF100T
>>>> has a wiring diagram
>>>>
>>>> https://www.manrose.co.uk/wp-content/uploads/doc/FandWs/496934.pdf
>>> Not an answer, but a suggestion: consider having two pull switches,
>>> one for the fan and one for the light, rather than having the fan
>>> always come on with the light. This means you don't have the fan
>>> noise at night time and you can leave the fan on for a while in the
>>> morning after a vindaloo supper the night before.
>>
>> A further thought: you could put a 3A fuse inside the fan enclosure if
>> you wanted a fuse but not an FCU.
>
> That can work, but will be limited to fans with only one live connection.
>
> If it has run on, then you would need a fuse protecting its permanent
> live and another one on the switched live. Now you have two fuses in
> parallel protecting the same device which is not good in a number of ways.
>

Agreed. Having multiple, independently isolated, supplies to one device
is a recipe for an unpleasant surprise for someone. My main point is
that being able to directly control the fan has value, especially near a
bedroom.

On 05/01/2024 12:18, Fredxx wrote:
> On 05/01/2024 11:41, SH wrote:
>> On 05/01/2024 11:32, SH wrote:
>>> On 05/01/2024 10:51, Andy Burns wrote:
>>>> SteveW wrote:
>>>>
>>>>> 6A seems to be the lowest rated RCBO for my consumer unit.
>>>>
>>>> Plenty of 1A MCBs and even the occasional 0.5A, but smallest RCBO I
>>>> can see is 2A
>>>
>>>
>>> I have a 5 bedroom house and I have literally just counted the number
>>> of bulbs on all of my lighting circuits (I have 4 lighting circuits.)
>>>
>>> The one with the most lamps is the ground floor with 55 lamps, all
>>> are LED lamps or LED Strips. All are at 4 to 6 watts.
>>>
>>> So lets take the highest wattage bulb and multiply by 55. This gives
>>> 330 Watts. There is an extractor fan on the d/stairs toilet fed by
>>> this circuit.
>>>
>>> The one with the highest wattage lamps is the outdoor floodlights
>>> circuit and there are 18 floodlamps with wattages ranging from 4
>>> watts to 20 watts. Lets take the 20 watts figure as worst case and
>>> multiply by 18 which gives 350 Watts
>>>
>>> A 6A MCB or RCBO supports a continuous current of 1320 Watta at a
>>> supply voltage of 220 watts so 6A is cleary more than adequate.
>>>
>>> Swapping to a 3A MCB or RCBO would support a continuous current of
>>> 660 Watts at a supply voltage of 220 watts which is almost double the
>>> the wattage assuming *all* lamps were all on at the same time. In
>>> practie very few of us actually have *all* the lamps on at the same
>>> time.
>>>
>>> The main issue with swapping out NCBs/RCBOs/RCDs in a consumer unit
>>> is that it is mandataed somewhere that the consumer unit and the
>>> MCBs/RCBOs/RCDs *should* be from the same manufacturer.
>>>
>>> S.
>>>
>>>
>>
>>
>> Coming back to the original OP's query,
>>
>> It strikces me that there is a possible solution but with a Caveat (*)
>>
>> Put in a dry lining box next to the light fitting.
>>
>> Transfer the Power Loop in and Power loop Out cables from the existing
>> light fitting to the new drylining box.
>>
>> Then wire in some twin and earth cable from the new drylining box and
>> then fit a FCU to this drylining box so that the bathroom light is now
>> on its own 3A supply.
>>
>> It is assumed that the wall switch also runs to the existing rose and
>> that the 3 core & E is also taken from the existing rose to the
>> isolator switch and thence onwards to the fan.
>>
>> (*) you will need to pay attention to the special zones of bathrooms
>> such that (a) the FCU is at a sifficient distance and hieght away from
>> the bath or shower and (b) with it being a humid atmosphere, humidity
>> may get inside teh FCU so it might be prudent to use a IP66 rated FCU
>> enclosure OR extend the power loop in, power loop out and the bridging
>> cable so that teh FCU can be mounted somewhere outside the bathroom.
>>
>> As a side point, putting a 3A fuse into the Live in for the fan does
>> not offer any protection to the switched live wire.
>
> The switched live might be a sensor input rather than supplying power. I
> note the wiring diagram:
>   https://www.manrose.co.uk/wp-content/uploads/doc/FandWs/496934.pdf
> allows for a fuse in just the live feed.

Take another look - in particular fig 3. The first two examples are only
for single live feeds.

If you look at fig 3 - the first example with two live connections, you
will note that *both* are derived from the fused supply.

> Nevertheless I still feel that is an issue and would prefer the light
> and fan on it's own fuse.

If the switched live is feeding both the fan and the light, the they
*must* both be fed from the fused supply.

>> Although you could put a 2nd fuse into teh Switched live, you then
>> could have an unsafe situation where if a fuse opens, unless one is
>> diligent about opening the fan isolator switch, one could be working
>> on a fan thinking its completely dead when in fact either teh
>> permanent Live or switched Live is still Live!
>
> As long as the wires are correctly sleeved, anyone gaining access to the
> terminals ought to be checking to see if a wire is live and remove power
> wherever possible.

While true, that is no excuse for dangerous shoddy work.

--
Cheers,

John.

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

On 05/01/2024 15:33, SH wrote:
> On 05/01/2024 15:22, Tricky Dicky wrote:
>> Fredxx <fredxx@spam.invalid> wrote:
>>> On 05/01/2024 11:41, SH wrote:
>>>> On 05/01/2024 11:32, SH wrote:
>>>>> On 05/01/2024 10:51, Andy Burns wrote:
>>>>>> SteveW wrote:
>>>>>>
>>>>>>> 6A seems to be the lowest rated RCBO for my consumer unit.
>>>>>>
>>>>>> Plenty of 1A MCBs and even the occasional 0.5A, but smallest RCBO I
>>>>>> can see is 2A
>>>>>
>>>>>
>>>>> I have a 5 bedroom house and I have literally just counted the number
>>>>> of bulbs on all of my lighting circuits (I have 4 lighting circuits.)
>>>>>
>>>>> The one with the most lamps is the ground floor with 55 lamps, all are
>>>>> LED lamps or LED Strips. All are at 4 to 6 watts.
>>>>>
>>>>> So lets take the highest wattage bulb and multiply by 55. This gives
>>>>> 330 Watts. There is an extractor fan on the d/stairs toilet fed by
>>>>> this circuit.
>>>>>
>>>>> The one with the highest wattage lamps is the outdoor floodlights
>>>>> circuit and there are 18 floodlamps with wattages ranging from 4 watts
>>>>> to 20 watts. Lets take the 20 watts figure as worst case and multiply
>>>>> by 18 which gives 350 Watts
>>>>>
>>>>> A 6A MCB or RCBO supports a continuous current of 1320 Watta at a
>>>>> supply voltage of 220 watts so 6A is cleary more than adequate.
>>>>>
>>>>> Swapping to a 3A MCB or RCBO would support a continuous current of 660
>>>>> Watts at a supply voltage of 220 watts which is almost double the the
>>>>> wattage assuming *all* lamps were all on at the same time. In practie
>>>>> very few of us actually have *all* the lamps on at the same time.
>>>>>
>>>>> The main issue with swapping out NCBs/RCBOs/RCDs in a consumer unit is
>>>>> that it is mandataed somewhere that the consumer unit and the
>>>>> MCBs/RCBOs/RCDs *should* be from the same manufacturer.
>>>>>
>>>>> S.
>>>>>
>>>>>
>>>>
>>>>
>>>> Coming back to the original OP's query,
>>>>
>>>> It strikces me that there is a possible solution but with a Caveat (*)
>>>>
>>>> Put in a dry lining box next to the light fitting.
>>>>
>>>> Transfer the Power Loop in and Power loop Out cables from the existing
>>>> light fitting to the new drylining box.
>>>>
>>>> Then wire in some twin and earth cable from the new drylining box and
>>>> then fit a FCU to this drylining box so that the bathroom light is now
>>>> on its own 3A supply.
>>>>
>>>> It is assumed that the wall switch also runs to the existing rose and
>>>> that the 3 core & E is also taken from the existing rose to the
>>>> isolator
>>>> switch and thence onwards to the fan.
>>>>
>>>> (*) you will need to pay attention to the special zones of bathrooms
>>>> such that (a) the FCU is at a sifficient distance and hieght away from
>>>> the bath or shower and (b) with it being a humid atmosphere, humidity
>>>> may get inside teh FCU so it might be prudent to use a IP66 rated FCU
>>>> enclosure OR extend the power loop in, power loop out and the bridging
>>>> cable so that teh FCU can be mounted somewhere outside the bathroom.
>>>>
>>>> As a side point, putting a 3A fuse into the Live in for the fan does
>>>> not
>>>> offer any protection to the switched live wire.
>>>
>>> The switched live might be a sensor input rather than supplying power. I
>>> note the wiring diagram:
>>>    https://www.manrose.co.uk/wp-content/uploads/doc/FandWs/496934.pdf
>>> allows for a fuse in just the live feed.
>>>
>>> Nevertheless I still feel that is an issue and would prefer the light
>>> and fan on it's own fuse.
>>>
>>>> Although you could put a
>>>> 2nd fuse into teh Switched live, you then could have an unsafe
>>>> situation
>>>> where if a fuse opens, unless one is diligent about opening the fan
>>>> isolator switch, one could be working on a fan thinking its completely
>>>> dead when in fact either teh permanent Live or switched Live is
>>>> still Live!
>>>
>>> As long as the wires are correctly sleeved, anyone gaining access to the
>>> terminals ought to be checking to see if a wire is live and remove power
>>> wherever possible.
>>>
>>
>> Look again the diagram for the timer version shows the switched live
>> tapped
>> off the live connection after the 3A fuse
>>
>
>
> Fig 3 assumes you dont have power loop in and power loop out at the
> lighting rose....
>
> The circuit digram would be more complex once the power loop in and
> power loop out is added....

Here is what you need with loop in wiring:

https://wiki.diyfaq.org.uk/index.php/Extractor_fan_wiring#Simplified_Schematic_Version

That can all be done from a ceiling rose with one additional terminal
required:

https://wiki.diyfaq.org.uk/images/f/f3/CeilingRoseFusedFanConnection.png

--
Cheers,

John.

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

On 06/01/2024 17:49, Graham. wrote:
> That was my thought too. Some 3A MCBs do exist but relatively
> rare.I would have thought the fan would have it's own internal
> fuse, even a non-replaceable one.
>
> All the faulty mains bathroom fans that I have examined have had a
> thermal fuse buried in the winding. I have concluded that it's a
> requirment.

I don't know of any British Standard or other requirement but it is
common for a winding to have some internal thermal protection. It only
takes a shorted turn or similar failure for the device to overheat and
melt a housing, yet not draw sufficient current for a fuse to blow.

I'm therefore sceptical of the enhanced safety using a 3 Amp fuse in the
OP's example as opposed to a 5 or 6 Amp MCB.

I am aware of the control circuitry for a fan with an internal timer,
using discrete ICs and thyristor, but I still don't see the advantage.

Graham. <graham-usenet@mail.com> wrote:
> That was my thought too. Some 3A MCBs do exist but relatively
> rare.I would have thought the fan would have it's own internal
> fuse, even a non-replaceable one.
>
They're not **that** difficult to find. I have a load of 2 amp ones
which were a bit of a nuisance to be honest because they were the only
ones I could find that fitted into the CU on my boat. I kept tripping
them when I tried to run the vacuum cleaner or an electric heater on
those circuits. I have since replaced them with more suitable ratings
(it wasn't totally trivial because they were two pole breakers that
disconnect both live and neutral).

--
Chris Green
·

On 06/01/2024 16:41, John Rumm wrote:
> On 05/01/2024 15:33, SH wrote:
>> On 05/01/2024 15:22, Tricky Dicky wrote:
>>> Fredxx <fredxx@spam.invalid> wrote:
>>>> On 05/01/2024 11:41, SH wrote:
>>>>> On 05/01/2024 11:32, SH wrote:
>>>>>> On 05/01/2024 10:51, Andy Burns wrote:
>>>>>>> SteveW wrote:
>>>>>>>
>>>>>>>> 6A seems to be the lowest rated RCBO for my consumer unit.
>>>>>>>
>>>>>>> Plenty of 1A MCBs and even the occasional 0.5A, but smallest RCBO I
>>>>>>> can see is 2A
>>>>>>
>>>>>>
>>>>>> I have a 5 bedroom house and I have literally just counted the number
>>>>>> of bulbs on all of my lighting circuits (I have 4 lighting circuits.)
>>>>>>
>>>>>> The one with the most lamps is the ground floor with 55 lamps, all
>>>>>> are
>>>>>> LED lamps or LED Strips. All are at 4 to 6 watts.
>>>>>>
>>>>>> So lets take the highest wattage bulb and multiply by 55. This gives
>>>>>> 330 Watts. There is an extractor fan on the d/stairs toilet fed by
>>>>>> this circuit.
>>>>>>
>>>>>> The one with the highest wattage lamps is the outdoor floodlights
>>>>>> circuit and there are 18 floodlamps with wattages ranging from 4
>>>>>> watts
>>>>>> to 20 watts. Lets take the 20 watts figure as worst case and multiply
>>>>>> by 18 which gives 350 Watts
>>>>>>
>>>>>> A 6A MCB or RCBO supports a continuous current of 1320 Watta at a
>>>>>> supply voltage of 220 watts so 6A is cleary more than adequate.
>>>>>>
>>>>>> Swapping to a 3A MCB or RCBO would support a continuous current of
>>>>>> 660
>>>>>> Watts at a supply voltage of 220 watts which is almost double the the
>>>>>> wattage assuming *all* lamps were all on at the same time. In practie
>>>>>> very few of us actually have *all* the lamps on at the same time.
>>>>>>
>>>>>> The main issue with swapping out NCBs/RCBOs/RCDs in a consumer
>>>>>> unit is
>>>>>> that it is mandataed somewhere that the consumer unit and the
>>>>>> MCBs/RCBOs/RCDs *should* be from the same manufacturer.
>>>>>>
>>>>>> S.
>>>>>>
>>>>>>
>>>>>
>>>>>
>>>>> Coming back to the original OP's query,
>>>>>
>>>>> It strikces me that there is a possible solution but with a Caveat (*)
>>>>>
>>>>> Put in a dry lining box next to the light fitting.
>>>>>
>>>>> Transfer the Power Loop in and Power loop Out cables from the existing
>>>>> light fitting to the new drylining box.
>>>>>
>>>>> Then wire in some twin and earth cable from the new drylining box and
>>>>> then fit a FCU to this drylining box so that the bathroom light is now
>>>>> on its own 3A supply.
>>>>>
>>>>> It is assumed that the wall switch also runs to the existing rose and
>>>>> that the 3 core & E is also taken from the existing rose to the
>>>>> isolator
>>>>> switch and thence onwards to the fan.
>>>>>
>>>>> (*) you will need to pay attention to the special zones of bathrooms
>>>>> such that (a) the FCU is at a sifficient distance and hieght away from
>>>>> the bath or shower and (b) with it being a humid atmosphere, humidity
>>>>> may get inside teh FCU so it might be prudent to use a IP66 rated FCU
>>>>> enclosure OR extend the power loop in, power loop out and the bridging
>>>>> cable so that teh FCU can be mounted somewhere outside the bathroom.
>>>>>
>>>>> As a side point, putting a 3A fuse into the Live in for the fan
>>>>> does not
>>>>> offer any protection to the switched live wire.
>>>>
>>>> The switched live might be a sensor input rather than supplying
>>>> power. I
>>>> note the wiring diagram:
>>>>    https://www.manrose.co.uk/wp-content/uploads/doc/FandWs/496934.pdf
>>>> allows for a fuse in just the live feed.
>>>>
>>>> Nevertheless I still feel that is an issue and would prefer the light
>>>> and fan on it's own fuse.
>>>>
>>>>> Although you could put a
>>>>> 2nd fuse into teh Switched live, you then could have an unsafe
>>>>> situation
>>>>> where if a fuse opens, unless one is diligent about opening the fan
>>>>> isolator switch, one could be working on a fan thinking its completely
>>>>> dead when in fact either teh permanent Live or switched Live is
>>>>> still Live!
>>>>
>>>> As long as the wires are correctly sleeved, anyone gaining access to
>>>> the
>>>> terminals ought to be checking to see if a wire is live and remove
>>>> power
>>>> wherever possible.
>>>>
>>>
>>> Look again the diagram for the timer version shows the switched live
>>> tapped
>>> off the live connection after the 3A fuse
>>>
>>
>>
>> Fig 3 assumes you dont have power loop in and power loop out at the
>> lighting rose....
>>
>> The circuit digram would be more complex once the power loop in and
>> power loop out is added....
>
> Here is what you need with loop in wiring:
>
> https://wiki.diyfaq.org.uk/index.php/Extractor_fan_wiring#Simplified_Schematic_Version
>
> That can all be done from a ceiling rose with one additional terminal
> required:
>
> https://wiki.diyfaq.org.uk/images/f/f3/CeilingRoseFusedFanConnection.png
>

One coould in fact use a 3 terminal wago connector provided there was
room in the ceiling rose..

Or alternatively, use a round dry lining box behind the exisiting rose
for more room/

On Friday 5 January 2024 at 13:15:41 UTC, John Rumm wrote:
> On 04/01/2024 14:21, noth...@aolbin.com wrote:
> > On 03/01/2024 16:48, noth...@aolbin.com wrote:
> >> On 03/01/2024 16:07, Tricky Dicky wrote:
> >>>
> >>> I am fitting a Manrose MF100T ventilation fan in our bathroom. This will
> >>> have a 3 pole isolator outside the bathroom and the plan is to run it in
> >>> conjunction with the bathroom light so that the fan comes on when the
> >>> light
> >>> is operated typical of many windowless bathrooms and en-suites in many
> >>> modern houses.
> >>>
> >>> The issue is that the manufacturer specify’s a 3A max. fuse for live and
> >>> switched live and of course the lighting circuit is 6A.
> >>>
> >>> One option is to fit a fused spur unit into the incoming feed for the
> >>> bathroom but that means all lights beyond that point would now be
> >>> protected
> >>> by a 3A fuse and the issue is that there are at least 3 ceiling fans
> >>> in the
> >>> rooms beyond that point.
> >>>
> >>> An alternative is to take 3-core and E cable from the bathroom light as
> >>> planned and using two FCU’s
> >>> One for live and the other for switched live before running the rest
> >>> of the
> >>> cable to the 3-pole isolator.
> >>>
> >>> The trouble is that I have not seen this arrangement anywhere. My
> >>> daughters
> >>> new build has one bathroom, 2 en-suites and a cloakroom/WC all
> >>> windowless
> >>> and all with ventilators activated by the light switch and I know all
> >>> the
> >>> lighting circuits are 6A.
> >>>
> >>> So what to do?
> >>>
> >>> I have a link to a similar fan which unlike the instructions for the
> >>> MF100T
> >>> has a wiring diagram
> >>>
> >>> https://www.manrose.co.uk/wp-content/uploads/doc/FandWs/496934.pdf
> >> Not an answer, but a suggestion: consider having two pull switches,
> >> one for the fan and one for the light, rather than having the fan
> >> always come on with the light. This means you don't have the fan noise
> >> at night time and you can leave the fan on for a while in the morning
> >> after a vindaloo supper the night before.
> >
> > A further thought: you could put a 3A fuse inside the fan enclosure if
> > you wanted a fuse but not an FCU.
> That can work, but will be limited to fans with only one live connection.
>
> If it has run on, then you would need a fuse protecting its permanent
> live and another one on the switched live. Now you have two fuses in
> parallel protecting the same device which is not good in a number of ways..

fusing the neutral would get round that :) (don't)