House of Horrors

Bill Wright wrote:

What's the thing about the rating of a fuse versus the actual current needed
to blow it immediately? There's some sort of standard about this I believe.

One of the things that surprises many is just how much current is
required to blow a fuse. If you take the example of a rewireable 5A fuse
of the type you find in older consumer units (aka fusebox), you can see
from:

http://www.internode.co.uk/temp/fuse.pdf

That it will carry 9A indefinitely, it takes 13A to get it to blow in
five seconds, or 45A to get it to go "instantly" (i.e. 0.1 sec or less)

--
Cheers,

John.

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

"Prometheus" wrote in message
...
a 'protection' that would allow about 700 W to be dissipated under a
fault condition is no protection at all.


However the purpose of the fuse is to protect the cable to the device not
the device.

A lot of devices in fault mode may well not consume any more power than
in correct operation, while through the fault, a fire hazard.

Hopefully the design of a device includes safe failure and perhaps a
competant rigger will install amplifiers in low fire risk locations.

In article , buddenbrooks
writes

"Prometheus" wrote in message
...
a 'protection' that would allow about 700 W to be dissipated under a
fault condition is no protection at all.


However the purpose of the fuse is to protect the cable to the device not
the device.

Perfectly true, hence I also stated "All very true, but there should be
a much lower rated protection device in the DA (or its PSU)," a comment
which quite inexplicably you deleted from the quote when you replied.

A lot of devices in fault mode may well not consume any more power than
in correct operation, while through the fault, a fire hazard.

All perfectly true, the designer will have considered this originally,
although most components are a low risk in them selves.

Hopefully the design of a device includes safe failure and perhaps a
competant rigger will install amplifiers in low fire risk locations.

Whilst the installer does need to consider that the risk inherent in the
location the design should be safe for a normal domestic environment.
--
Ian G8ILZ
There are always two people in every pictu the photographer and the viewer.
~Ansel Adams

"buddenbrooks" wrote in message

"Prometheus" wrote in message
...
a 'protection' that would allow about 700 W to be dissipated under a
fault condition is no protection at all.


However the purpose of the fuse is to protect the cable to the
device not the device.

I thought it was to protect the ring main.

Does anyone know why we don't have fused sockets, rather than fused plugs?

That would seem to be much more logical, and would protect against people
plugging lots of high consumption appliances into a single socket with an
unfused adapter.

--
Max Demian

Max Demian wrote:

"buddenbrooks" wrote in message

"Prometheus" wrote in message
...
a 'protection' that would allow about 700 W to be dissipated under a
fault condition is no protection at all.


However the purpose of the fuse is to protect the cable to the
device not the device.

I thought it was to protect the ring main.

Does anyone know why we don't have fused sockets, rather than fused plugs?

How is the wall socket to know what's plugged into it? Your table lamp
needs at most a 3A fuse, your electric fire needs a 13A fuse. Or do you
want to revert back to 5A sockets and 15A sockets?

That would seem to be much more logical, and would protect against people
plugging lots of high consumption appliances into a single socket with an
unfused adapter.

I've never seen an unfused adaptor. They'd almost certainly be illegal
to sell.

--

Immunity is better than innoculation.

Peter

In article , Max Demian
writes
"buddenbrooks" wrote in message

"Prometheus" wrote in message
...
a 'protection' that would allow about 700 W to be dissipated under a
fault condition is no protection at all.


However the purpose of the fuse is to protect the cable to the
device not the device.

I thought it was to protect the ring main.

The ring main is rated at over 30A, hence it has a 30A fuse.

Does anyone know why we don't have fused sockets, rather than fused plugs?

Since that would necessitate using 13A fuses in each socket it would not
offer much protection for lower current appliance that are connected
with smaller cables, you would not really want 13A cable on small
handheld equipment. Of course we could return to using 2, 5 and 15 amp
sockets on a radial system with appropriate fuses for each spar in the
consumer unit.

That would seem to be much more logical, and would protect against people
plugging lots of high consumption appliances into a single socket with an
unfused adapter.

A 13A socket can pass far more than 13A without a problem, the ratting
is for making and unmaking the connection.

--
Ian G8ILZ
There are always two people in every pictu the photographer and the viewer.
~Ansel Adams

In article ,
Max Demian wrote:
"buddenbrooks" wrote in message

"Prometheus" wrote in message
...
a 'protection' that would allow about 700 W to be dissipated under a
fault condition is no protection at all.


However the purpose of the fuse is to protect the cable to the
device not the device.

I thought it was to protect the ring main.

Does anyone know why we don't have fused sockets, rather than fused plugs?

To make an easier, simpler installation. Just consider the size of the
distribution board (consumer unit) if every socket outlet had its own
fuse/circuit breaker. [My kitchen alone has 7 double outlets plus 3
built-in appliances as well as hob & oven.]



That would seem to be much more logical, and would protect against people
plugging lots of high consumption appliances into a single socket with an
unfused adapter.

Have you ever come across an "unfused adaptor"?

--
From KT24 - in "Leafy Surrey"

Using a RISC OS computer running v5.11

In article ,
Prometheus wrote:


A 13A socket can pass far more than 13A without a problem,

That assumes a decent connection between the pins of the plug and the walls
of the socket. Many combinations only touch at one or two points,
especially if the springs on the socket have been forced apart with
"childproof devices". I had to replace a socket at our village hall where
this had happened since a 1kW load was causing overheating at this point.

Not for nothing was the brand name "MulkiKontact" (MK) created,

--
From KT24 - in "Leafy Surrey"

Using a RISC OS computer running v5.11

charles wrote:

A 13A socket can pass far more than 13A without a problem,

That assumes a decent connection between the pins of the plug and the walls
of the socket. Many combinations only touch at one or two points,
especially if the springs on the socket have been forced apart with
"childproof devices". I had to replace a socket at our village hall where
this had happened since a 1kW load was causing overheating at this point.

Not for nothing was the brand name "MulkiKontact" (MK) created,

Ah !! I didn't know that.

If you think 13 Amps is pushing your luck through a UK socket, try 16 Amps
(the max rated current) through your average Euro Shuko plug and socket !


--
Mark
Please replace invalid and invalid with gmx and net to reply.

In article ,
Max Demian wrote:
However the purpose of the fuse is to protect the cable to the device
not the device.

I thought it was to protect the ring main.

The final ring circuit is protected in the consumer unit.

Does anyone know why we don't have fused sockets, rather than fused
plugs?

Because you use - or should do - the correct fuse in the plug for the
appliance in question. Ie 13 amp for a heater, etc, 5 for a low current
appliance.

That would seem to be much more logical, and would protect against
people plugging lots of high consumption appliances into a single
socket with an unfused adapter.

You'd be back to the old days of effectively different sized sockets for
different uses. One of the things the 13 amp system replaced.

Easier to ban the sale of unfused adaptors.

--
*If you lived in your car, you'd be home by now *

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