Hi,

In my kitchen I have some unswitched sockets under the counter for the
washing machine and dishwasher. These are switched above the counter
by FCUs. Is there any reason that FCUs are used rather than 20A
switches or is it just whatever they had to hand on the day? Just
curious.

TIA

Fred wrote in
:

Hi,

In my kitchen I have some unswitched sockets under the counter for the
washing machine and dishwasher. These are switched above the counter
by FCUs. Is there any reason that FCUs are used rather than 20A
switches or is it just whatever they had to hand on the day? Just
curious.

TIA

I have the same - built in 1988.

I must confess I have changed some FCUs to sockets so the one below the
worktop is now a spur.

On Sep 18, 8:12*am, Fred wrote:

In my kitchen I have some unswitched sockets under the counter for the
washing machine and dishwasher. These are switched above the counter
by FCUs. Is there any reason that FCUs are used rather than 20A
switches or is it just whatever they had to hand on the day? Just
curious.

The FCUs are specifically designed to be used as part of a ring final
circuit. It is unclear whether the modular 20A switches are rated in
the same way. Certainly they seem to have much smaller terminals.
This would suggest that 20A switches are suitable
for a radial circuit with a 20A circuit breaker, but maybe not for a
connection to a ring.

John

"Fred" wrote in message
...
Hi,

In my kitchen I have some unswitched sockets under the counter for the
washing machine and dishwasher. These are switched above the counter
by FCUs. Is there any reason that FCUs are used rather than 20A
switches or is it just whatever they had to hand on the day? Just
curious.


When I did a kitchen some years ago the advice from this group was that an
unswitched socket under the counter was all you needed - no additional
isolating switch.
If the aim is to be able to isolate the unit for servicing, exchange, or in
the event of a fault, then pulling out the plug should suffice.
I assume this advice still stands.


Cheers

Dave R
--
No plan survives contact with the enemy.
[Not even bunny]

Helmuth von Moltke the Elder

(\__/)
(='.'=)
(")_(")

In article ,
Fred writes:
Hi,

In my kitchen I have some unswitched sockets under the counter for the
washing machine and dishwasher. These are switched above the counter
by FCUs. Is there any reason that FCUs are used rather than 20A
switches or is it just whatever they had to hand on the day? Just
curious.

20A switch would be fine.
May have used FCUs so that a plain flex outlet could be used below
instead of a socket. FCUs may have been cheaper, being more common.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

John Walliker wrote:

On Sep 18, 8:12 am, Fred wrote:

In my kitchen I have some unswitched sockets under the counter for the
washing machine and dishwasher. These are switched above the counter
by FCUs. Is there any reason that FCUs are used rather than 20A
switches or is it just whatever they had to hand on the day? Just
curious.

The FCUs are specifically designed to be used as part of a ring final
circuit. It is unclear whether the modular 20A switches are rated in
the same way. Certainly they seem to have much smaller terminals.
This would suggest that 20A switches are suitable
for a radial circuit with a 20A circuit breaker, but maybe not for a
connection to a ring.

John

They're fine if feeding a single socket with fused plug as the plugtop fuse
provides overload protection to the 20A switch.


--
Tim Watts

On 18/09/2012 08:12, Fred wrote:
Hi,

In my kitchen I have some unswitched sockets under the counter for the
washing machine and dishwasher. These are switched above the counter
by FCUs. Is there any reason that FCUs are used rather than 20A
switches or is it just whatever they had to hand on the day? Just
curious.

TIA

Are they spurs off the ring main, and are there more than one socket on
each spur? If so, the FCUs are to protect the spur. If there's only one
socket on each spur, I don't see the point of the FCUs.
--
Cheers,
Roger
____________
Please reply to Newsgroup. Whilst email address is valid, it is seldom
checked.

"Roger Mills" wrote in message
...

Are they spurs off the ring main, and are there more than one socket on
each spur? If so, the FCUs are to protect the spur. If there's only one
socket on each spur, I don't see the point of the FCUs.

They are probably cheaper than 20A switches.

In article ,
Fred wrote:
In my kitchen I have some unswitched sockets under the counter for the
washing machine and dishwasher. These are switched above the counter
by FCUs. Is there any reason that FCUs are used rather than 20A
switches or is it just whatever they had to hand on the day? Just
curious.

What they had to hand. There is no requirement to fuse a single socket on
a spur. If you had many, there would be.

--
*Why can't women put on mascara with their mouth closed?

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
Tim Watts wrote:
They're fine if feeding a single socket with fused plug as the plugtop
fuse provides overload protection to the 20A switch.

The only function of the plug fuse is to protect the appliance cable.

--
*The man who fell into an upholstery machine is fully recovered*

Dave Plowman London SW
To e-mail, change noise into sound.

On 18/09/2012 10:03 David WE Roberts wrote:

When I did a kitchen some years ago the advice from this group was that
an unswitched socket under the counter was all you needed - no
additional isolating switch.
If the aim is to be able to isolate the unit for servicing, exchange, or
in the event of a fault, then pulling out the plug should suffice.
I assume this advice still stands.

I thought the requirement was that you should be able to turn off the
power to the appliance without having to touch it? With the plug behind
the appliance, that's not possible.

--
F

On Tuesday, September 18, 2012 11:12:56 AM UTC+1, F wrote:
On 18/09/2012 10:03 David WE Roberts wrote:



When I did a kitchen some years ago the advice from this group was that

an unswitched socket under the counter was all you needed - no

additional isolating switch.

If the aim is to be able to isolate the unit for servicing, exchange, or

in the event of a fault, then pulling out the plug should suffice.

I assume this advice still stands.



I thought the requirement was that you should be able to turn off the

power to the appliance without having to touch it? With the plug behind

the appliance, that's not possible.


Yes, if you use that method, the plug should not be behind the appliance !
I like others have fitted a socket in the adjacent cabinet, and cut an opening so the socket can be passed through and plugged in.
However, for the oven, I am fitting a fused cooker isolator, since this is hard wired and does not have a plug.
I had enough sockets and things above the worktop without any more FCUs.
If you are not careful you can have more sockets and switches than tiles.

Simon.

On 2012-09-18, David WE Roberts wrote:


"Fred" wrote in message
...
Hi,

In my kitchen I have some unswitched sockets under the counter for the
washing machine and dishwasher. These are switched above the counter
by FCUs. Is there any reason that FCUs are used rather than 20A
switches or is it just whatever they had to hand on the day? Just
curious.


When I did a kitchen some years ago the advice from this group was that an
unswitched socket under the counter was all you needed - no additional
isolating switch.
If the aim is to be able to isolate the unit for servicing, exchange, or in
the event of a fault, then pulling out the plug should suffice.
I assume this advice still stands.

Doesn't it depend on whether the plugs & sockets are accessible
without moving the appliance?

On Sep 18, 10:33*am, Tim Watts wrote:
John Walliker wrote:
On Sep 18, 8:12 am, Fred wrote:

In my kitchen I have some unswitched sockets under the counter for the
washing machine and dishwasher. These are switched above the counter
by FCUs. Is there any reason that FCUs are used rather than 20A
switches or is it just whatever they had to hand on the day? Just
curious.

The FCUs are specifically designed to be used as part of a ring final
circuit. *It is unclear whether the modular 20A switches are rated in
the same way. *Certainly they seem to have much smaller terminals.
This would suggest that 20A switches are suitable
for a radial circuit with a 20A circuit breaker, but maybe not for a
connection to a ring.

John

They're fine if feeding a single socket with fused plug as the plugtop fuse
provides overload protection to the 20A switch.

Only if the overload is downstream of the plug.

MBQ

Dave Plowman (News) wrote:

In article ,
Tim Watts wrote:
They're fine if feeding a single socket with fused plug as the plugtop
fuse provides overload protection to the 20A switch.

The only function of the plug fuse is to protect the appliance cable.


That may be the primary reason - but it is inherent that the fuse will also
protect the feeder cable from overloads (but not faults[1]) up until the
first junction with other loads - so in this case, the switch suuply
terminals if that is on the ring or before if it is a spur.

Either way, the design specification of the branch circuit the switch is
controlling is 13A max so a switch capable of switching that current should
be adequate.

[1] It could be argued that a fault downstream of the switch but before the
plugtop fuse may provide sufficient energy to damage the contacts, I doubt
whether a 20A switch is in much jeapody compared to a 32A switch.

It's exactly what I am doing and I'm quite happy with the idea.

--
Tim Watts

In article ,
Tim Watts wrote:
The only function of the plug fuse is to protect the appliance cable.


That may be the primary reason - but it is inherent that the fuse will
also protect the feeder cable from overloads (but not faults[1]) up
until the first junction with other loads - so in this case, the switch
suuply terminals if that is on the ring or before if it is a spur.

In which case it would be perfectly ok to have unlimited sockets on a
spur. All the plug fuses would protect it. ;-)

Either way, the design specification of the branch circuit the switch is
controlling is 13A max so a switch capable of switching that current
should be adequate.

Where do you get the '13 amp max'? The spur circuit must be capable of
tripping the 32 amp protection in the CU in event of a fault.

[1] It could be argued that a fault downstream of the switch but before
the plugtop fuse may provide sufficient energy to damage the contacts,
I doubt whether a 20A switch is in much jeapody compared to a 32A
switch.

It's exactly what I am doing and I'm quite happy with the idea.

--
*Reality? Is that where the pizza delivery guy comes from?

Dave Plowman London SW
To e-mail, change noise into sound.

In message , Adam Funk
writes


When I did a kitchen some years ago the advice from this group was that an
unswitched socket under the counter was all you needed - no additional
isolating switch.
If the aim is to be able to isolate the unit for servicing, exchange, or in
the event of a fault, then pulling out the plug should suffice.
I assume this advice still stands.

Doesn't it depend on whether the plugs & sockets are accessible
without moving the appliance?

Certainly a very important point if the appliance is going up in flames
or sparking every where at the time :-)

--
Bill

On 2012-09-18, Bill wrote:

In message , Adam Funk
writes


When I did a kitchen some years ago the advice from this group was that an
unswitched socket under the counter was all you needed - no additional
isolating switch.
If the aim is to be able to isolate the unit for servicing, exchange, or in
the event of a fault, then pulling out the plug should suffice.
I assume this advice still stands.

Doesn't it depend on whether the plugs & sockets are accessible
without moving the appliance?

Certainly a very important point if the appliance is going up in flames
or sparking every where at the time :-)

Exactly, those problems make it hard to pull the machine out!

In article ,
Bill wrote:
Doesn't it depend on whether the plugs & sockets are accessible
without moving the appliance?

Certainly a very important point if the appliance is going up in flames
or sparking every where at the time :-)

If the switch were close by I'd not go near that either. I'd turn off at
the CU.

--
*Save the whale - I'll have it for my supper*

Dave Plowman London SW
To e-mail, change noise into sound.

Dave Plowman (News) wrote:

In article ,
Tim Watts wrote:
The only function of the plug fuse is to protect the appliance cable.


That may be the primary reason - but it is inherent that the fuse will
also protect the feeder cable from overloads (but not faults[1]) up
until the first junction with other loads - so in this case, the switch
suuply terminals if that is on the ring or before if it is a spur.

In which case it would be perfectly ok to have unlimited sockets on a
spur. All the plug fuses would protect it. ;-)

I don't get the presumed joke there??

Either way, the design specification of the branch circuit the switch is
controlling is 13A max so a switch capable of switching that current
should be adequate.

Where do you get the '13 amp max'? The spur circuit must be capable of
tripping the 32 amp protection in the CU in event of a fault.

13A max design current due to a single fused plugtop downstream. The switch
can exceed its design current in normal use irrespective of the fact it is
protected upstream by a 32A device.

Tripping is another issue which will be unaffected by whether the switch is
20A or 32A. Either way, fault currents can get into 100's of amps for mS as
I'm aware you know - the only debate is whether a 20A switch would be
damaged by the I2t let through, and I would propose that it is highly
unlikely unless it was closed onto a downstream fault - in which case that
could cause damage to 32A switch's contacts too.

[1] It could be argued that a fault downstream of the switch but before
the plugtop fuse may provide sufficient energy to damage the contacts,
I doubt whether a 20A switch is in much jeapody compared to a 32A
switch.

It's exactly what I am doing and I'm quite happy with the idea.

--
Tim Watts

Tim Watts wrote:

Dave Plowman (News) wrote:

In article ,
Tim Watts wrote:
The only function of the plug fuse is to protect the appliance cable.


That may be the primary reason - but it is inherent that the fuse will
also protect the feeder cable from overloads (but not faults[1]) up
until the first junction with other loads - so in this case, the switch
suuply terminals if that is on the ring or before if it is a spur.

In which case it would be perfectly ok to have unlimited sockets on a
spur. All the plug fuses would protect it. ;-)

I don't get the presumed joke there??

Either way, the design specification of the branch circuit the switch is
controlling is 13A max so a switch capable of switching that current
should be adequate.

Where do you get the '13 amp max'? The spur circuit must be capable of
tripping the 32 amp protection in the CU in event of a fault.

13A max design current due to a single fused plugtop downstream. The
switch can exceed its design current in normal use irrespective of the

^^^^ cannot


fact it is protected upstream by a 32A device.

Tripping is another issue which will be unaffected by whether the switch
is 20A or 32A. Either way, fault currents can get into 100's of amps for
mS as I'm aware you know - the only debate is whether a 20A switch would
be damaged by the I2t let through, and I would propose that it is highly
unlikely unless it was closed onto a downstream fault - in which case that
could cause damage to 32A switch's contacts too.

[1] It could be argued that a fault downstream of the switch but before
the plugtop fuse may provide sufficient energy to damage the contacts,
I doubt whether a 20A switch is in much jeapody compared to a 32A
switch.

It's exactly what I am doing and I'm quite happy with the idea.

--
Tim Watts

"Adam Funk" wrote in message
...
On 2012-09-18, David WE Roberts wrote:


"Fred" wrote in message
...
Hi,

In my kitchen I have some unswitched sockets under the counter for the
washing machine and dishwasher. These are switched above the counter
by FCUs. Is there any reason that FCUs are used rather than 20A
switches or is it just whatever they had to hand on the day? Just
curious.


When I did a kitchen some years ago the advice from this group was that
an
unswitched socket under the counter was all you needed - no additional
isolating switch.
If the aim is to be able to isolate the unit for servicing, exchange, or
in
the event of a fault, then pulling out the plug should suffice.
I assume this advice still stands.

Doesn't it depend on whether the plugs & sockets are accessible
without moving the appliance?

Yes - socket in adjacent unit so you can get at it without touching the
appliance.

--
No plan survives contact with the enemy.
[Not even bunny]

Helmuth von Moltke the Elder

(\__/)
(='.'=)
(")_(")

In article ,
Tim Watts wrote:
Where do you get the '13 amp max'? The spur circuit must be capable of
tripping the 32 amp protection in the CU in event of a fault.

13A max design current due to a single fused plugtop downstream. The
switch can exceed its design current in normal use irrespective of the
fact it is protected upstream by a 32A device.

The 'design' current is for a reasonable life switching that current.
So I'm not clear how you think a 13 amp fuse downstream of this will stop
it being exceeded? If the appliance shorts, the fuse will blow. A switch
with its contacts made will handle rather more than its rated spec.

Tripping is another issue which will be unaffected by whether the switch
is 20A or 32A. Either way, fault currents can get into 100's of amps
for mS as I'm aware you know - the only debate is whether a 20A switch
would be damaged by the I2t let through, and I would propose that it is
highly unlikely unless it was closed onto a downstream fault - in which
case that could cause damage to 32A switch's contacts too.

The MCB contacts get damaged when it trips?

--
*If a parsley farmer is sued, can they garnish his wages?

Dave Plowman London SW
To e-mail, change noise into sound.

Dave Plowman (News) wrote:

In article ,
Tim Watts wrote:
Where do you get the '13 amp max'? The spur circuit must be capable of
tripping the 32 amp protection in the CU in event of a fault.

13A max design current due to a single fused plugtop downstream. The
switch can exceed its design current in normal use irrespective of the
fact it is protected upstream by a 32A device.

The 'design' current is for a reasonable life switching that current.
So I'm not clear how you think a 13 amp fuse downstream of this will stop
it being exceeded? If the appliance shorts, the fuse will blow. A switch
with its contacts made will handle rather more than its rated spec.

Tripping is another issue which will be unaffected by whether the switch
is 20A or 32A. Either way, fault currents can get into 100's of amps
for mS as I'm aware you know - the only debate is whether a 20A switch
would be damaged by the I2t let through, and I would propose that it is
highly unlikely unless it was closed onto a downstream fault - in which
case that could cause damage to 32A switch's contacts too.

The MCB contacts get damaged when it trips?


No - the 32A isolator that would be used in place of teh 20A that you think
is inadequate.
--
Tim Watts

On 18/09/2012 08:12, Fred wrote:
Hi,

In my kitchen I have some unswitched sockets under the counter for the
washing machine and dishwasher. These are switched above the counter
by FCUs. Is there any reason that FCUs are used rather than 20A
switches or is it just whatever they had to hand on the day? Just
curious.

Its most likely what they had available at the time. There is no reason
that a single socket wired as a spur (switched or otherwise) needs
another fuse.


--
Cheers,

John.

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

On 18/09/2012 10:33, Tim Watts wrote:
John Walliker wrote:

On Sep 18, 8:12 am, Fred wrote:

In my kitchen I have some unswitched sockets under the counter for the
washing machine and dishwasher. These are switched above the counter
by FCUs. Is there any reason that FCUs are used rather than 20A
switches or is it just whatever they had to hand on the day? Just
curious.

The FCUs are specifically designed to be used as part of a ring final
circuit. It is unclear whether the modular 20A switches are rated in
the same way. Certainly they seem to have much smaller terminals.
This would suggest that 20A switches are suitable
for a radial circuit with a 20A circuit breaker, but maybe not for a
connection to a ring.

John

They're fine if feeding a single socket with fused plug as the plugtop fuse
provides overload protection to the 20A switch.

The design current for an unfused spur is 20A anyway (single or double
socket) - so still adequate.

(obviously a double socket might not be a good design choice in that
circumstance)


--
Cheers,

John.

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

F wrote:
On 18/09/2012 10:03 David WE Roberts wrote:

When I did a kitchen some years ago the advice from this group was
that an unswitched socket under the counter was all you needed - no
additional isolating switch.
If the aim is to be able to isolate the unit for servicing,
exchange, or in the event of a fault, then pulling out the plug
should suffice. I assume this advice still stands.

I thought the requirement was that you should be able to turn off the
power to the appliance without having to touch it? With the plug
behind the appliance, that's not possible.

That is not a requirement. Washing machines and dishwashers do not need
emergency switching.

A push in dishwasher or washing machine can be supplied from an unswitched
socket behind it and requires no other isolation.

--
Adam

Andrew Gabriel wrote:
In article ,
Fred writes:
Hi,

In my kitchen I have some unswitched sockets under the counter for
the washing machine and dishwasher. These are switched above the
counter by FCUs. Is there any reason that FCUs are used rather than
20A switches or is it just whatever they had to hand on the day?
Just curious.

20A switch would be fine.
May have used FCUs so that a plain flex outlet could be used below
instead of a socket. FCUs may have been cheaper, being more common.

There is a benefit to using the 20A switch for local authorities and
landlords. If the washer blows a fuse then it is the fuse in the washers
plug top that blows and not the fuse in the fused spur. It saves a calling
out an electrician. The tenant is told on the phone to remove the washer
and try some other appliance in the single socket. If the other appliance
works then you need not send an electrician

--
Adam

John Rumm wrote:
On 18/09/2012 10:33, Tim Watts wrote:
John Walliker wrote:

On Sep 18, 8:12 am, Fred wrote:

In my kitchen I have some unswitched sockets under the counter
for the washing machine and dishwasher. These are switched
above the counter by FCUs. Is there any reason that FCUs are
used rather than 20A switches or is it just whatever they had
to hand on the day? Just curious.

The FCUs are specifically designed to be used as part of a ring
final circuit. It is unclear whether the modular 20A switches
are rated in the same way. Certainly they seem to have much
smaller terminals. This would suggest that 20A switches are
suitable for a radial circuit with a 20A circuit breaker, but maybe
not
for a connection to a ring.

John

They're fine if feeding a single socket with fused plug as the
plugtop fuse provides overload protection to the 20A switch.

The design current for an unfused spur is 20A anyway (single or double
socket) - so still adequate.

(obviously a double socket might not be a good design choice in that
circumstance)

I suspect that you could melt an overloaded double socket before a BS1362
13A fuse trips given the right set up:-)

--
Adam

On 18/09/2012 10:03, David WE Roberts wrote:
When I did a kitchen some years ago the advice from this group was that
an unswitched socket under the counter was all you needed - no
additional isolating switch.
If the aim is to be able to isolate the unit for servicing, exchange, or
in the event of a fault, then pulling out the plug should suffice.
I assume this advice still stands.

We've just had the dishwasher catching fire thread. Personally I like
the idea of pulling the power without having to move a smoking machine...

Andy

Andy Champ wrote:
On 18/09/2012 10:03, David WE Roberts wrote:
When I did a kitchen some years ago the advice from this group was
that an unswitched socket under the counter was all you needed - no
additional isolating switch.
If the aim is to be able to isolate the unit for servicing,
exchange, or in the event of a fault, then pulling out the plug
should suffice. I assume this advice still stands.

We've just had the dishwasher catching fire thread. Personally I like
the idea of pulling the power without having to move a smoking
machine...


So where is the isolator for your TV? TVs catch fire.

--
Adam

On 18/09/2012 18:57 ARW wrote:

F wrote:
On 18/09/2012 10:03 David WE Roberts wrote:

When I did a kitchen some years ago the advice from this group was
that an unswitched socket under the counter was all you needed - no
additional isolating switch.
If the aim is to be able to isolate the unit for servicing,
exchange, or in the event of a fault, then pulling out the plug
should suffice. I assume this advice still stands.

I thought the requirement was that you should be able to turn off the
power to the appliance without having to touch it? With the plug
behind the appliance, that's not possible.

That is not a requirement. Washing machines and dishwashers do not need
emergency switching.

A push in dishwasher or washing machine can be supplied from an unswitched
socket behind it and requires no other isolation.

Thanks: I stand corrected! Wish I had known that a few years ago...

--
F

In article ,
Tim Watts wrote:
The MCB contacts get damaged when it trips?


No - the 32A isolator that would be used in place of teh 20A that you
think is inadequate.

What are you on about?

--
*Don't sweat the petty things and don't pet the sweaty things.

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
Andy Champ wrote:
We've just had the dishwasher catching fire thread. Personally I like
the idea of pulling the power without having to move a smoking machine..

Then the socket needs to be some way from the machine. All the
installations I've seen with isolating switches seem to site the switch
above the machine. So you'd have to lean over the fire to switch it off...

--
*There are 3 kinds of people: those who can count & those who can't.

Dave Plowman London SW
To e-mail, change noise into sound.

On 9/18/2012 3:27 PM, Andy Champ wrote:
On 18/09/2012 10:03, David WE Roberts wrote:
When I did a kitchen some years ago the advice from this group was that
an unswitched socket under the counter was all you needed - no
additional isolating switch.
If the aim is to be able to isolate the unit for servicing, exchange, or
in the event of a fault, then pulling out the plug should suffice.
I assume this advice still stands.

We've just had the dishwasher catching fire thread. Personally I like
the idea of pulling the power without having to move a smoking machine...

An acquaintance had to redo much of her kitchen earlier this year, after
her dishwasher caught fire.
I made sure to have an over-the-counter switch for mine...

In article ,
S Viemeister wrote:
An acquaintance had to redo much of her kitchen earlier this year, after
her dishwasher caught fire.

If my dishwasher caught fire, I'd need an ambulance, not new kitchen.

--
*The problem with the gene pool is that there is no lifeguard *

Dave Plowman London SW
To e-mail, change noise into sound.

Dave Plowman (News) wrote:

In article ,
Tim Watts wrote:
The MCB contacts get damaged when it trips?


No - the 32A isolator that would be used in place of teh 20A that you
think is inadequate.

What are you on about?


I might counter with the same!

Shall we start again - why did you mention the MCB - I'm only discussing the
isolator switch.

You *seem* to be claiming a 20A on a circuit with a 32A protective device is
not adequate.

*I* am claiming it is, on the basis that the design current (ie the max
possible load) cannot exceed 13A, because of the 13A (max) fuse that can be
in the single plugtop that that leg feeds.

Problems with that??
--
Tim Watts

In article ,
Tim Watts wrote:
Dave Plowman (News) wrote:

In article ,
Tim Watts wrote:
The MCB contacts get damaged when it trips?


No - the 32A isolator that would be used in place of teh 20A that you
think is inadequate.

What are you on about?


I might counter with the same!

Shall we start again - why did you mention the MCB - I'm only discussing
the isolator switch.

I was discussing your incorrect statement that a 13 amp plug fuse in some
way protected the permanent wiring. Which is not its purpose.

You *seem* to be claiming a 20A on a circuit with a 32A protective
device is not adequate.

Not so.

*I* am claiming it is, on the basis that the design current (ie the max
possible load) cannot exceed 13A, because of the 13A (max) fuse that can
be in the single plugtop that that leg feeds.

Problems with that??

You are allowed a double socket on a spur.

The plug fuse protects the appliance cable. The CU MCB or whatever
protects the permanent wiring.

--
*You! Off my planet!

Dave Plowman London SW
To e-mail, change noise into sound.

Dave Plowman (News) wrote:

In article ,
Tim Watts wrote:
Dave Plowman (News) wrote:

In article ,
Tim Watts wrote:
The MCB contacts get damaged when it trips?


No - the 32A isolator that would be used in place of teh 20A that you
think is inadequate.

What are you on about?


I might counter with the same!

Shall we start again - why did you mention the MCB - I'm only discussing
the isolator switch.

I was discussing your incorrect statement that a 13 amp plug fuse in some
way protected the permanent wiring. Which is not its purpose.


It may not be its original purpose, but by the laws of physics it does
protect the upstream single cable (that after the tee off from the ring)
from *overload*.

I believe it is also accepted as valid practise to make that assumption.

If the cable that the 20A isolator is controlling *cannot exceed* 13A by
design (because there is a single socket/fused plugtop downstream) then the
20A isolator can never be subjected to an overload outside of its design
limits.

Noone ever suggested a double socket on the end of this spur - the original
discussion was IIRC regarding a single appliance socket being fed by an
isolator that did not contain a fuse as part of the isolator.

That's overload scenarios covered.

Fault scenarios I covered previously.
--
Tim Watts

Tim Watts wrote:

Dave Plowman (News) wrote:

In article ,
Tim Watts wrote:
Dave Plowman (News) wrote:

In article ,
Tim Watts wrote:
The MCB contacts get damaged when it trips?


No - the 32A isolator that would be used in place of teh 20A that you
think is inadequate.

What are you on about?


I might counter with the same!

Shall we start again - why did you mention the MCB - I'm only discussing
the isolator switch.

I was discussing your incorrect statement that a 13 amp plug fuse in some
way protected the permanent wiring. Which is not its purpose.


It may not be its original purpose, but by the laws of physics it does
protect the upstream single cable (that after the tee off from the ring)
from *overload*.

I believe it is also accepted as valid practise to make that assumption.

If the cable that the 20A isolator is controlling *cannot exceed* 13A by
design (because there is a single socket/fused plugtop downstream) then
the 20A isolator can never be subjected to an overload outside of its
design limits.

Noone ever suggested a double socket on the end of this spur - the
original discussion was IIRC regarding a single appliance socket being fed
by an isolator that did not contain a fuse as part of the isolator.

That's overload scenarios covered.

Fault scenarios I covered previously.

For an interesting read, see he

http://www.theiet.org/forums/forum/m...eadid=%2042570

It is not 100% conclusive, but the statement "Isn't it like 2.5mm² not being
rated for 32A either - but we still use it on ring circuits & unfused spurs"

distilled it for me.

Look at some light fittings - may be fitted to a 10A lighting circuit, but
have a tiny 5A button/pullcord. However, in the same way, the current
through the switch cannot exceed some fraction of an amp by design (max
wattage lamp the fitting will take). Same logic.

--
Tim Watts