Discussion:
isolation switch
(too old to reply)
charles
2014-12-17 22:48:00 UTC
Permalink
Should an extractor fan in a kitchen be fitted with an isolation switch?
I've come across one which seems to be wired dirwetly from the power ring
main. I'm unhappy.
--
From KT24

Using a RISC OS computer running v5.18
Adrian
2014-12-17 22:49:20 UTC
Permalink
Post by charles
Should an extractor fan in a kitchen be fitted with an isolation switch?
I've come across one which seems to be wired dirwetly from the power
ring main. I'm unhappy.
I presume there's a switch of _some_ kind...?
Graham.
2014-12-18 02:14:04 UTC
Permalink
On Wed, 17 Dec 2014 22:49:20 +0000 (UTC), Adrian
Post by Adrian
Post by charles
Should an extractor fan in a kitchen be fitted with an isolation switch?
I've come across one which seems to be wired dirwetly from the power
ring main. I'm unhappy.
I presume there's a switch of _some_ kind...?
Xpelair with an integral pull cord perhaps?

I'd be far more concerned about the lack of a fuse than an isolator.
--
Graham.

%Profound_observation%
charles
2014-12-18 07:19:29 UTC
Permalink
Post by Graham.
On Wed, 17 Dec 2014 22:49:20 +0000 (UTC), Adrian
Post by Adrian
Post by charles
Should an extractor fan in a kitchen be fitted with an isolation
switch? I've come across one which seems to be wired dirwetly from the
power ring main. I'm unhappy.
I presume there's a switch of _some_ kind...?
Xpelair with an integral pull cord perhaps?
I'd be far more concerned about the lack of a fuse than an isolator.
my concern about an isolator was that the switch stuck ON when the pull
cord link snapped off. I traced the supply to the ring main, which I had to
turn off. But yes, the wiring that I saw certainly should have been
protected by something less than a 32A MCB
--
From KT24

Using a RISC OS computer running v5.18
Dave Plowman (News)
2014-12-18 11:27:00 UTC
Permalink
Post by charles
Post by Graham.
I'd be far more concerned about the lack of a fuse than an isolator.
my concern about an isolator was that the switch stuck ON when the pull
cord link snapped off. I traced the supply to the ring main, which I had
to turn off. But yes, the wiring that I saw certainly should have been
protected by something less than a 32A MCB
Anything connected to a final ring - other than sockets - should be via an
FCU.
--
*Confession is good for the soul, but bad for your career.

Dave Plowman ***@davenoise.co.uk London SW
To e-mail, change noise into sound.
charles
2014-12-18 11:43:10 UTC
Permalink
Post by Dave Plowman (News)
Post by charles
Post by Graham.
I'd be far more concerned about the lack of a fuse than an isolator.
my concern about an isolator was that the switch stuck ON when the pull
cord link snapped off. I traced the supply to the ring main, which I had
to turn off. But yes, the wiring that I saw certainly should have been
protected by something less than a 32A MCB
Anything connected to a final ring - other than sockets - should be via an
FCU.
That's what I thought, but can you quote the regulation number?
--
From KT24

Using a RISC OS computer running v5.18
s***@gowanhill.com
2014-12-18 12:02:30 UTC
Permalink
Post by charles
Post by Dave Plowman (News)
Anything connected to a final ring - other than sockets - should be via an
FCU.
That's what I thought, but can you quote the regulation number?
14th Edition (1970 Amendment)

A.48 Apparatus permanently connected (i.e. not through a plug and socket-outlet) to a radial or ring final sub-circuit of the type described in Regulation A.43 or A.44 shall be protected locally by a fuse of rating not exceeding 15 amperes and controlled by a switch conforming with the requirements of Regulations A.58-61, or by a circuit-breaker of rating not exceeding 15 amperes.

I don't have any more recent edition of the Regs to hand.

Owain
charles
2014-12-18 12:14:11 UTC
Permalink
Post by s***@gowanhill.com
Post by charles
Post by Dave Plowman (News)
Anything connected to a final ring - other than sockets - should be
via an FCU.
That's what I thought, but can you quote the regulation number?
14th Edition (1970 Amendment)
A.48 Apparatus permanently connected (i.e. not through a plug and
socket-outlet) to a radial or ring final sub-circuit of the type
described in Regulation A.43 or A.44 shall be protected locally by a fuse
of rating not exceeding 15 amperes and controlled by a switch conforming
with the requirements of Regulations A.58-61, or by a circuit-breaker of
rating not exceeding 15 amperes.
Unfortunately I can't quote regulations that were superceded in 1981 to a
contractor who did the work in 2014. But, thanks
--
From KT24

Using a RISC OS computer running v5.18
Roger Mills
2014-12-18 14:05:40 UTC
Permalink
Post by charles
Post by s***@gowanhill.com
Post by charles
Post by Dave Plowman (News)
Anything connected to a final ring - other than sockets - should be
via an FCU.
That's what I thought, but can you quote the regulation number?
14th Edition (1970 Amendment)
A.48 Apparatus permanently connected (i.e. not through a plug and
socket-outlet) to a radial or ring final sub-circuit of the type
described in Regulation A.43 or A.44 shall be protected locally by a fuse
of rating not exceeding 15 amperes and controlled by a switch conforming
with the requirements of Regulations A.58-61, or by a circuit-breaker of
rating not exceeding 15 amperes.
Unfortunately I can't quote regulations that were superceded in 1981 to a
contractor who did the work in 2014. But, thanks
Are you absolutely sure that there isn't an FCU hidden inside a cupboard
somewhere?
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.
charles
2014-12-18 16:32:32 UTC
Permalink
Post by Roger Mills
Post by charles
Post by s***@gowanhill.com
Post by charles
Post by Dave Plowman (News)
Anything connected to a final ring - other than sockets - should be
via an FCU.
That's what I thought, but can you quote the regulation number?
14th Edition (1970 Amendment)
A.48 Apparatus permanently connected (i.e. not through a plug and
socket-outlet) to a radial or ring final sub-circuit of the type
described in Regulation A.43 or A.44 shall be protected locally by a
fuse of rating not exceeding 15 amperes and controlled by a switch
conforming with the requirements of Regulations A.58-61, or by a
circuit-breaker of rating not exceeding 15 amperes.
Unfortunately I can't quote regulations that were superceded in 1981 to
a contractor who did the work in 2014. But, thanks
Are you absolutely sure that there isn't an FCU hidden inside a cupboard
somewhere?
It is possible that he's hung a cupboard over the top of it, but it isn't
visible from inside the cupboards.
--
From KT24

Using a RISC OS computer running v5.18
Graham.
2014-12-18 20:47:44 UTC
Permalink
On Thu, 18 Dec 2014 16:32:32 +0000 (GMT), charles
Post by charles
Post by Roger Mills
Post by charles
Post by s***@gowanhill.com
Post by charles
Post by Dave Plowman (News)
Anything connected to a final ring - other than sockets - should be
via an FCU.
That's what I thought, but can you quote the regulation number?
14th Edition (1970 Amendment)
A.48 Apparatus permanently connected (i.e. not through a plug and
socket-outlet) to a radial or ring final sub-circuit of the type
described in Regulation A.43 or A.44 shall be protected locally by a
fuse of rating not exceeding 15 amperes and controlled by a switch
conforming with the requirements of Regulations A.58-61, or by a
circuit-breaker of rating not exceeding 15 amperes.
Unfortunately I can't quote regulations that were superceded in 1981 to
a contractor who did the work in 2014. But, thanks
Are you absolutely sure that there isn't an FCU hidden inside a cupboard
somewhere?
It is possible that he's hung a cupboard over the top of it, but it isn't
visible from inside the cupboards.
Is it twin & earth cable that's connected to the fan, or is it flex.
If it's flex that's a good indication that there is some sort of
connection nearby.
--
Graham.

%Profound_observation%
charles
2014-12-18 21:32:40 UTC
Permalink
Post by Graham.
On Thu, 18 Dec 2014 16:32:32 +0000 (GMT), charles
Post by charles
Post by Roger Mills
Post by charles
Post by s***@gowanhill.com
Post by charles
Post by Dave Plowman (News)
Anything connected to a final ring - other than sockets - should
be via an FCU.
That's what I thought, but can you quote the regulation number?
14th Edition (1970 Amendment)
A.48 Apparatus permanently connected (i.e. not through a plug and
socket-outlet) to a radial or ring final sub-circuit of the type
described in Regulation A.43 or A.44 shall be protected locally by
a fuse of rating not exceeding 15 amperes and controlled by a
switch conforming with the requirements of Regulations A.58-61, or
by a circuit-breaker of rating not exceeding 15 amperes.
Unfortunately I can't quote regulations that were superceded in 1981
to a contractor who did the work in 2014. But, thanks
Are you absolutely sure that there isn't an FCU hidden inside a
cupboard somewhere?
It is possible that he's hung a cupboard over the top of it, but it
isn't visible from inside the cupboards.
Is it twin & earth cable that's connected to the fan, or is it flex. If
it's flex that's a good indication that there is some sort of connection
nearby.
I'm sure there's a connetcion, but I suspect it's under the plaster.
--
From KT24

Using a RISC OS computer running v5.18
Mike Clarke
2014-12-19 10:55:41 UTC
Permalink
Post by Graham.
Is it twin & earth cable that's connected to the fan, or is it flex.
If it's flex that's a good indication that there is some sort of
connection nearby.
But does not indicate if it's the *right* sort of connection.
--
Mike Clarke
A.Lee
2014-12-18 18:30:50 UTC
Permalink
charles wrote:

Snip - fan directly fed from 32A circuit.
Post by charles
Unfortunately I can't quote regulations that were superceded in 1981 to a
contractor who did the work in 2014. But, thanks
What do the Fan Instructions say?
They are what will determine whether you need a fused spur, or fed via
the 32A circuit.
You already have an isolator - the circuit breaker.
The fan is unlikely to need overload protection, unless called for by
the Manufacturers Instructions.

Of course, it would be good practice to locally switch/fuse it for
maintenance purposes, but it is not required if the Manufacturers
Instructions do not require it - most do BTW.
--
Alan
To reply by mail, change '+' to 'plus'
Graham.
2014-12-18 20:41:30 UTC
Permalink
On Thu, 18 Dec 2014 18:30:50 +0000 (UTC), "A.Lee"
Post by A.Lee
Snip - fan directly fed from 32A circuit.
Post by charles
Unfortunately I can't quote regulations that were superceded in 1981 to a
contractor who did the work in 2014. But, thanks
What do the Fan Instructions say?
They are what will determine whether you need a fused spur, or fed via
the 32A circuit.
You already have an isolator - the circuit breaker.
The fan is unlikely to need overload protection, unless called for by
the Manufacturers Instructions.
Of course, it would be good practice to locally switch/fuse it for
maintenance purposes, but it is not required if the Manufacturers
Instructions do not require it - most do BTW.
Good grief Alan, it's a kitchen fan, not a wind-tunnel at BAE. No way
can he rely just on a 32A MCB.
--
Graham.

%Profound_observation%
A.Lee
2014-12-18 20:56:19 UTC
Permalink
Post by Graham.
On Thu, 18 Dec 2014 18:30:50 +0000 (UTC), "A.Lee"
Post by A.Lee
Snip - fan directly fed from 32A circuit.
Post by charles
Unfortunately I can't quote regulations that were superceded in 1981 to a
contractor who did the work in 2014. But, thanks
What do the Fan Instructions say?
They are what will determine whether you need a fused spur, or fed via
the 32A circuit.
You already have an isolator - the circuit breaker.
The fan is unlikely to need overload protection, unless called for by
the Manufacturers Instructions.
Of course, it would be good practice to locally switch/fuse it for
maintenance purposes, but it is not required if the Manufacturers
Instructions do not require it - most do BTW.
Good grief Alan, it's a kitchen fan, not a wind-tunnel at BAE. No way
can he rely just on a 32A MCB.
Could you please explain why you think that?
I've got a 3 watt (0.0125A) lamp here running on a 10 A circuit breaker.

Why is that safe, when a 0.625A (~150w) fan would not be OK running on a
32A breaker?

The typical 3A fuse used to 'protect' typical fans does not protect the
fan at all, and in most cases would be pretty useless.
The fan is a fixed load (typically), so would not draw more power than
it is rated for, except in fault conditions. Then, you would expect the
circuit breaker to open, as short term loading wil be far more than 32
amps.

The big uncertaintly here, is what make the fan is, and what the
Manufacturer stipulates, as I said above. If they say it should have
a fuse and DP switch, then it should have one.
But dont confuse the fuse as protecting the fan, all it is doing is
protecting the supply cable, even then, it is prety useless.
--
Alan
To reply by mail, change '+' to 'plus'
Dave Plowman (News)
2014-12-19 00:34:41 UTC
Permalink
Post by A.Lee
Post by Graham.
Good grief Alan, it's a kitchen fan, not a wind-tunnel at BAE. No way
can he rely just on a 32A MCB.
Could you please explain why you think that?
I've got a 3 watt (0.0125A) lamp here running on a 10 A circuit breaker.
Then the cable to that lamp should be capable of tripping the breaker
without burning out in event of a short.
Post by A.Lee
Why is that safe, when a 0.625A (~150w) fan would not be OK running on a
32A breaker?
The typical 3A fuse used to 'protect' typical fans does not protect the
fan at all, and in most cases would be pretty useless.
The fan is a fixed load (typically), so would not draw more power than
it is rated for, except in fault conditions. Then, you would expect the
circuit breaker to open, as short term loading wil be far more than 32
amps.
The big uncertaintly here, is what make the fan is, and what the
Manufacturer stipulates, as I said above. If they say it should have
a fuse and DP switch, then it should have one.
But dont confuse the fuse as protecting the fan, all it is doing is
protecting the supply cable, even then, it is prety useless.
That's all the fuse does. If the appliance requires additional protection
for safety reasons, it will have internal fusing of some sort. Quite
likely non replaceable. A thermal fuse in the motor winding, etc.
--
*If only you'd use your powers for good instead of evil.

Dave Plowman ***@davenoise.co.uk London SW
To e-mail, change noise into sound.
John Rumm
2014-12-19 00:21:34 UTC
Permalink
Post by Graham.
On Thu, 18 Dec 2014 18:30:50 +0000 (UTC), "A.Lee"
Post by A.Lee
Snip - fan directly fed from 32A circuit.
Post by charles
Unfortunately I can't quote regulations that were superceded in 1981 to a
contractor who did the work in 2014. But, thanks
What do the Fan Instructions say?
They are what will determine whether you need a fused spur, or fed via
the 32A circuit.
You already have an isolator - the circuit breaker.
The fan is unlikely to need overload protection, unless called for by
the Manufacturers Instructions.
Of course, it would be good practice to locally switch/fuse it for
maintenance purposes, but it is not required if the Manufacturers
Instructions do not require it - most do BTW.
Good grief Alan, it's a kitchen fan, not a wind-tunnel at BAE. No way
can he rely just on a 32A MCB.
To be fair, it depends on the circumstance. If you can argue there is no
way for the fan to cause an overload of its supply cable, then you can
dispense with overload protection altogether. Then the remaining
requirement is for fault protection. Say it were connected via 1.5mm^2
T&E, then that would be adequately fault protected by a B32 MCB.

(however its likely that a fan will stipulate overload protection via a
fuse).
--
Cheers,

John.

/=================================================================\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\=================================================================/
charles
2014-12-19 03:14:00 UTC
Permalink
Post by John Rumm
Post by Graham.
On Thu, 18 Dec 2014 18:30:50 +0000 (UTC), "A.Lee"
Post by A.Lee
Snip - fan directly fed from 32A circuit.
Post by charles
Unfortunately I can't quote regulations that were superceded in 1981 to a
contractor who did the work in 2014. But, thanks
What do the Fan Instructions say?
They are what will determine whether you need a fused spur, or fed via
the 32A circuit.
You already have an isolator - the circuit breaker.
The fan is unlikely to need overload protection, unless called for by
the Manufacturers Instructions.
Of course, it would be good practice to locally switch/fuse it for
maintenance purposes, but it is not required if the Manufacturers
Instructions do not require it - most do BTW.
Good grief Alan, it's a kitchen fan, not a wind-tunnel at BAE. No way
can he rely just on a 32A MCB.
To be fair, it depends on the circumstance. If you can argue there is no
way for the fan to cause an overload of its supply cable, then you can
dispense with overload protection altogether. Then the remaining
requirement is for fault protection. Say it were connected via 1.5mm^2
T&E, then that would be adequately fault protected by a B32 MCB.
whereas the internal wiring that I could see was probably only 0.75mm^2.
--
From KT24

Using a RISC OS computer running v5.18
John Rumm
2014-12-19 12:53:20 UTC
Permalink
Post by charles
Post by John Rumm
Post by Graham.
On Thu, 18 Dec 2014 18:30:50 +0000 (UTC), "A.Lee"
Post by A.Lee
Snip - fan directly fed from 32A circuit.
Post by charles
Unfortunately I can't quote regulations that were superceded in 1981 to a
contractor who did the work in 2014. But, thanks
What do the Fan Instructions say?
They are what will determine whether you need a fused spur, or fed via
the 32A circuit.
You already have an isolator - the circuit breaker.
The fan is unlikely to need overload protection, unless called for by
the Manufacturers Instructions.
Of course, it would be good practice to locally switch/fuse it for
maintenance purposes, but it is not required if the Manufacturers
Instructions do not require it - most do BTW.
Good grief Alan, it's a kitchen fan, not a wind-tunnel at BAE. No way
can he rely just on a 32A MCB.
To be fair, it depends on the circumstance. If you can argue there is no
way for the fan to cause an overload of its supply cable, then you can
dispense with overload protection altogether. Then the remaining
requirement is for fault protection. Say it were connected via 1.5mm^2
T&E, then that would be adequately fault protected by a B32 MCB.
whereas the internal wiring that I could see was probably only 0.75mm^2.
True but not particularly relevant.

This is why you need to keep the concepts of fault and overload
protection separate in your mind. Usually they are both provided by the
same protective device, but not always - the responsibilities can be
separated.

Fault protection must always be present at the origin of the circuit.
Overload protection can be elsewhere, or possibly not present at all and
provided simply by design options limiting or eliminating the
possibility of overload.

A common example would be the 3A drop flex to a pendent fitting on a
lighting circuit. That circuit may be protected by a B6 MCB, which will
not provide overload protection to the drop flex. However the single
lamp holder on the end, and the choice of lamps available does impose a
limit. So additional protection for sustained overload is not needed.
However it would be possible to cause a short circuit at the end of the
drop flex, and that must be accounted for. The way you work out whether
a wire has adequate fault protection is to use the adiabatic calculation:

http://wiki.diyfaq.org.uk/index.php?title=Calculating_A_Cable_Size#Adiabatic_Check

You start by working out the likely fault current - this will be
inversely proportional to the the total circuit impedance at the point
of the fault. The impedance simply being the sum of the resistances of
the cable runs, and the supply and possibly earth impedances. Once you
have this and the k factor for the cable in question you can work out
the minimum cross sectional area of cable required to survive long
enough to clear the fault.

So for example, take your nominal 0.75mm^2 cables in the fan. Say the
loop impedance was 1 ohm at the point of fitting. That gives a potential
fault current of 230A, which will open the B32 MCB in 0.1 secs or less
(i.e. on the magnetic part of its response). If your wires are PVC
insulated we can take K at 115. So that gives us a minimum wire size of:

sqrt( 230^2 x 0.1 ) / 115 = 0.63mm^2

So even if someone sticks a 6" nail through the fan, and manages to
short a couple of those wires, we are still ok ;-)

Now for the avoidance of doubt:

I am not suggesting here that directly connecting fans to 32A ring
circuits is a good idea. In most cases I would expect the manufacturers
instructions (which take precedence) to impose lower limit protection
anyway. Even if they don't it would (IMHO) still be good practice to
include a switched FCU for applications like this.
--
Cheers,

John.

/=================================================================\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\=================================================================/
Graham.
2014-12-19 15:02:26 UTC
Permalink
On Fri, 19 Dec 2014 12:53:20 +0000, John Rumm
Post by John Rumm
Post by charles
Post by John Rumm
Post by Graham.
On Thu, 18 Dec 2014 18:30:50 +0000 (UTC), "A.Lee"
Post by A.Lee
Snip - fan directly fed from 32A circuit.
Post by charles
Unfortunately I can't quote regulations that were superceded in 1981 to a
contractor who did the work in 2014. But, thanks
What do the Fan Instructions say?
They are what will determine whether you need a fused spur, or fed via
the 32A circuit.
You already have an isolator - the circuit breaker.
The fan is unlikely to need overload protection, unless called for by
the Manufacturers Instructions.
Of course, it would be good practice to locally switch/fuse it for
maintenance purposes, but it is not required if the Manufacturers
Instructions do not require it - most do BTW.
Good grief Alan, it's a kitchen fan, not a wind-tunnel at BAE. No way
can he rely just on a 32A MCB.
To be fair, it depends on the circumstance. If you can argue there is no
way for the fan to cause an overload of its supply cable, then you can
dispense with overload protection altogether. Then the remaining
requirement is for fault protection. Say it were connected via 1.5mm^2
T&E, then that would be adequately fault protected by a B32 MCB.
whereas the internal wiring that I could see was probably only 0.75mm^2.
True but not particularly relevant.
This is why you need to keep the concepts of fault and overload
protection separate in your mind. Usually they are both provided by the
same protective device, but not always - the responsibilities can be
separated.
Fault protection must always be present at the origin of the circuit.
Overload protection can be elsewhere, or possibly not present at all and
provided simply by design options limiting or eliminating the
possibility of overload.
A common example would be the 3A drop flex to a pendent fitting on a
lighting circuit. That circuit may be protected by a B6 MCB, which will
not provide overload protection to the drop flex. However the single
lamp holder on the end, and the choice of lamps available does impose a
limit. So additional protection for sustained overload is not needed.
However it would be possible to cause a short circuit at the end of the
drop flex, and that must be accounted for. The way you work out whether
http://wiki.diyfaq.org.uk/index.php?title=Calculating_A_Cable_Size#Adiabatic_Check
You start by working out the likely fault current - this will be
inversely proportional to the the total circuit impedance at the point
of the fault. The impedance simply being the sum of the resistances of
the cable runs, and the supply and possibly earth impedances. Once you
have this and the k factor for the cable in question you can work out
the minimum cross sectional area of cable required to survive long
enough to clear the fault.
So for example, take your nominal 0.75mm^2 cables in the fan. Say the
loop impedance was 1 ohm at the point of fitting. That gives a potential
fault current of 230A, which will open the B32 MCB in 0.1 secs or less
(i.e. on the magnetic part of its response). If your wires are PVC
sqrt( 230^2 x 0.1 ) / 115 = 0.63mm^2
So even if someone sticks a 6" nail through the fan, and manages to
short a couple of those wires, we are still ok ;-)
I am not suggesting here that directly connecting fans to 32A ring
circuits is a good idea. In most cases I would expect the manufacturers
instructions (which take precedence) to impose lower limit protection
anyway. Even if they don't it would (IMHO) still be good practice to
include a switched FCU for applications like this.
Thank goodness for that.

As always, I am pleased to be educated about the wider picture.


When our bathroom was re-done, pre Part P, the fitters insisted in
fitting an unswitched FCU feeding the over mirror lights/isolated
shaver point. This was fed from a 6A lighting MCB.

I couldn't see the point, especially as he left the 13A fuse in it as
supplied.
--
Graham.

%Profound_observation%
charles
2014-12-18 20:57:41 UTC
Permalink
Post by A.Lee
Snip - fan directly fed from 32A circuit.
Post by charles
Unfortunately I can't quote regulations that were superceded in 1981 to
a contractor who did the work in 2014. But, thanks
What do the Fan Instructions say?
No idea never seen them
Post by A.Lee
They are what will determine whether you need a fused spur, or fed via
the 32A circuit.
the internal wiring in the fan wouldn't support 32A/
Post by A.Lee
You already have an isolator - the circuit breaker.
Not in my book
Post by A.Lee
The fan is unlikely to need overload protection, unless called for by
the Manufacturers Instructions.
Of course, it would be good practice to locally switch/fuse it for
maintenance purposes, but it is not required if the Manufacturers
Instructions do not require it - most do BTW.
I've found the relevant reg: 4.33,2.1. "A device for the protection of
overload shall be installed at the point where a reduction in the value of
the current-carrying capacity of the conductors of the installation.

There's also quite a bit in 537.
--
From KT24

Using a RISC OS computer running v5.18
A.Lee
2014-12-18 23:02:27 UTC
Permalink
Post by charles
Post by A.Lee
What do the Fan Instructions say?
No idea never seen them
Google the Make and Model, and you'll be pretty likely to get the
instructions.
If it says "Must be supplied by a double switch and fuse", then he has
no comeback at all, and should change the wiring to suit.
Post by charles
Post by A.Lee
They are what will determine whether you need a fused spur, or fed via
the 32A circuit.
the internal wiring in the fan wouldn't support 32A
No, but it wont need to, it'll only be carrying whatever the motor
draws.
Post by charles
Post by A.Lee
You already have an isolator - the circuit breaker.
Not in my book
But BS7671 says your Circuit Breaker / Fuse can be the Isolator.
Post by charles
Post by A.Lee
The fan is unlikely to need overload protection, unless called for by
the Manufacturers Instructions.
Of course, it would be good practice to locally switch/fuse it for
maintenance purposes, but it is not required if the Manufacturers
Instructions do not require it - most do BTW.
I've found the relevant reg: 4.33,2.1. "A device for the protection of
overload shall be installed at the point where a reduction in the value of
the current-carrying capacity of the conductors of the installation.
There's also quite a bit in 537.
But take into account 433.3.1 (ii)

Anyhow, the point is moot, as you do not know how it is connected.
Ring him to find out?
--
Alan
To reply by mail, change '+' to 'plus'
s***@gowanhill.com
2014-12-19 00:00:41 UTC
Permalink
Post by charles
Post by s***@gowanhill.com
14th Edition (1970 Amendment)
Unfortunately I can't quote regulations that were superceded in 1981 to a
contractor who did the work in 2014. But, thanks
My flat was built in 1968, so I'm still okay working to the 14th ? ;-)

Owain
John Rumm
2014-12-18 02:04:03 UTC
Permalink
Post by charles
Should an extractor fan in a kitchen be fitted with an isolation switch?
I've come across one which seems to be wired dirwetly from the power ring
main. I'm unhappy.
Most fans stipulate they should be fed from a fused outlet of typically
no more than 5A. So a switched fused connection unit is normally the
obvious choice.
--
Cheers,

John.

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