Hi,

About ten years ago I bought an extension lead from Wickes. Not
knowing any better at the time, I bought a long one, thinking that a
long one could be used when long or short lengths were required,
whereas a short one could only be used for short lengths.

Then I came and read here and I learnt that long leads had
disadvantages. I can't remember now whether this was because of
voltage drop or fault currents, or may be both. Can someone remind me?

Anyway, some of my tools have started switching on and off
intermittently when plugged into the lead, and I can only assume that
over the years the contacts in the extension socket have been worn and
are not making a good connection to the plug.

So it is time to buy a new lead or leads. I seem to remember reading
that 1.5mm^2 cores could only be used safely up to 15m and 2.5mm^2
cores (in a caravan power lead) could be used up to 25m. Is there any
advantage to buying a short "caravan hook-up" cable to use for lengths
under 25m?

Otherwise I'm thinking I could use the cable from the Wickes lead, or
possibly use arctic flex as an improvement, to make some short leads.

TIA

Some of those older sockets were amenable to being taken apart and resprung
to make them work again. I found those four way ones tended to have a
problem where they connected to the bus bars. its all by pressure and over
the years things relax and get tarnished.
Brian

--
Brian Gaff -
Note:- In order to reduce spam, any email without 'Brian Gaff'
in the display name may be lost.
Blind user, so no pictures please!
"Fred" wrote in message
...
Hi,

About ten years ago I bought an extension lead from Wickes. Not
knowing any better at the time, I bought a long one, thinking that a
long one could be used when long or short lengths were required,
whereas a short one could only be used for short lengths.

Then I came and read here and I learnt that long leads had
disadvantages. I can't remember now whether this was because of
voltage drop or fault currents, or may be both. Can someone remind me?

Anyway, some of my tools have started switching on and off
intermittently when plugged into the lead, and I can only assume that
over the years the contacts in the extension socket have been worn and
are not making a good connection to the plug.

So it is time to buy a new lead or leads. I seem to remember reading
that 1.5mm^2 cores could only be used safely up to 15m and 2.5mm^2
cores (in a caravan power lead) could be used up to 25m. Is there any
advantage to buying a short "caravan hook-up" cable to use for lengths
under 25m?

Otherwise I'm thinking I could use the cable from the Wickes lead, or
possibly use arctic flex as an improvement, to make some short leads.

TIA

Fred wrote:
Hi,

About ten years ago I bought an extension lead from Wickes. Not
knowing any better at the time, I bought a long one, thinking that a
long one could be used when long or short lengths were required,
whereas a short one could only be used for short lengths.

Then I came and read here and I learnt that long leads had
disadvantages. I can't remember now whether this was because of
voltage drop or fault currents, or may be both. Can someone remind me?

Anyway, some of my tools have started switching on and off
intermittently when plugged into the lead, and I can only assume that
over the years the contacts in the extension socket have been worn and
are not making a good connection to the plug.

So it is time to buy a new lead or leads. I seem to remember reading
that 1.5mm^2 cores could only be used safely up to 15m and 2.5mm^2
cores (in a caravan power lead) could be used up to 25m. Is there any
advantage to buying a short "caravan hook-up" cable to use for lengths
under 25m?

Otherwise I'm thinking I could use the cable from the Wickes lead, or
possibly use arctic flex as an improvement, to make some short leads.

TIA
Replace the sockets instead of buying new leads if they are structurally
sound.

On Thu, 15 Mar 2012 13:42:47 -0000, Fred
wrote:

Hi,

About ten years ago I bought an extension lead from Wickes. Not
knowing any better at the time, I bought a long one, thinking that a
long one could be used when long or short lengths were required,
whereas a short one could only be used for short lengths.

Then I came and read here and I learnt that long leads had
disadvantages. I can't remember now whether this was because of
voltage drop or fault currents, or may be both. Can someone remind me?

Anyway, some of my tools have started switching on and off
intermittently when plugged into the lead, and I can only assume that
over the years the contacts in the extension socket have been worn and
are not making a good connection to the plug.

So it is time to buy a new lead or leads. I seem to remember reading
that 1.5mm^2 cores could only be used safely up to 15m and 2.5mm^2
cores (in a caravan power lead) could be used up to 25m. Is there any
advantage to buying a short "caravan hook-up" cable to use for lengths
under 25m?

Otherwise I'm thinking I could use the cable from the Wickes lead, or
possibly use arctic flex as an improvement, to make some short leads.

TIA

Biggest problem with modern long leads is that if you use much power you
have to unwind the whole lot to prevent overheating. If you use thicker
cable you add to the size and weight. Intermittently used power tools are
probably not a problem but our wallpaper steamer is.

On 15/03/2012 15:27, Hugh - Was Invisible wrote:
On Thu, 15 Mar 2012 13:42:47 -0000, Fred
wrote:

About ten years ago I bought an extension lead from Wickes. Not
knowing any better at the time, I bought a long one, thinking that a
long one could be used when long or short lengths were required,
whereas a short one could only be used for short lengths.

Biggest problem with modern long leads is that if you use much power you
have to unwind the whole lot to prevent overheating. If you use thicker
cable you add to the size and weight. Intermittently used power tools
are probably not a problem but our wallpaper steamer is.

Or in the case of our local church fete a pair of 3kW kettles on a
mostly rolled up mad hot extension lead plugged into the wall. They did
it last year as well completely melting the inside of the reel. *SCARY*

I am inclined to the view now that they should include a thermal cutout!
The clear warning on the reel has little or no effect on most folk

--
Regards,
Martin Brown

On 15/03/2012 15:36, Martin Brown wrote:
On 15/03/2012 15:27, Hugh - Was Invisible wrote:
On Thu, 15 Mar 2012 13:42:47 -0000, Fred
wrote:

About ten years ago I bought an extension lead from Wickes. Not
knowing any better at the time, I bought a long one, thinking that a
long one could be used when long or short lengths were required,
whereas a short one could only be used for short lengths.

Biggest problem with modern long leads is that if you use much power you
have to unwind the whole lot to prevent overheating. If you use thicker
cable you add to the size and weight. Intermittently used power tools
are probably not a problem but our wallpaper steamer is.

Or in the case of our local church fete a pair of 3kW kettles on a
mostly rolled up mad hot extension lead plugged into the wall. They did
it last year as well completely melting the inside of the reel. *SCARY*

I am inclined to the view now that they should include a thermal cutout!
The clear warning on the reel has little or no effect on most folk

The modern 50m JoJo ones do include the cutout these days... presumable
for this sort of reason.


--
Cheers,

John.

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

On 15/03/2012 13:42, Fred wrote:
Hi,

About ten years ago I bought an extension lead from Wickes. Not
knowing any better at the time, I bought a long one, thinking that a
long one could be used when long or short lengths were required,
whereas a short one could only be used for short lengths.

Then I came and read here and I learnt that long leads had
disadvantages. I can't remember now whether this was because of
voltage drop or fault currents, or may be both. Can someone remind me?

The answer is both, and also "heat"...

The longer the lead then the more voltage drop. May not be a huge
problem for many tools (power tools run a bit slower and with a bit less
oomph), but some kit may get upset (things with induction motors that
may stall on startup, or run but attempt to compensate for lack of volts
by drawing more current, and then overheating)

The second issue is fault current, or to be more accurate lack of it.
Long leads will have a higher earth loop impedance, and also a lower
prospective short circuit current. So when something goes pair shaped
the fuse in the lead takes longer to operate, or in the worst case, does
not operate at all in a sensible time. Making sure its fed from a RCD
protected socket is obviously a "good thing" (tm).

Lastly, heat. Long leads can only take a small proportion of their full
load when wound. Hence for big loads at moderate distances, you may find
yourself having to unwind a rats nest of cable to use it safely.

Anyway, some of my tools have started switching on and off
intermittently when plugged into the lead, and I can only assume that
over the years the contacts in the extension socket have been worn and
are not making a good connection to the plug.

Either that, or the flex has broken and gone intermittent at the ends
where it bends a lot.

The socket terminals might allow a bit of cleaning and bending to get a
better grip. The flex can have the first and last metre cut off and be
re-terminated to get rid of the dodgy bits.

So it is time to buy a new lead or leads. I seem to remember reading
that 1.5mm^2 cores could only be used safely up to 15m and 2.5mm^2
cores (in a caravan power lead) could be used up to 25m. Is there any
advantage to buying a short "caravan hook-up" cable to use for lengths
under 25m?

Depends on the loads you need to run partly. If you are doing big ones
at moderate distance, or ones for which voltage drop is going to be a
problem, then it may be worth it.

Otherwise I'm thinking I could use the cable from the Wickes lead, or
possibly use arctic flex as an improvement, to make some short leads.



--
Cheers,

John.

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

On Thu, 15 Mar 2012 13:42:47 +0000, Fred wrote:

Then I came and read here and I learnt that long leads had
disadvantages. I can't remember now whether this was because of
voltage drop or fault currents, or may be both. Can someone remind me?

Both but as others have said volt drop won't upset many things a
great deal. Fault currents could be an issue but as you will always
be running the extension via an RCD (won't you...) that isn't such a
problem either.

So it is time to buy a new lead or leads.

If the cable is in otherwise good condition just replace the socket
and if the plug isn't an RCD one replace that as well. You may say
that all your 13A sockets are RCD protected but what if you use it
elsewhere?

I seem to remember reading that 1.5mm^2 cores could only be used safely
up to 15m and 2.5mm^2 cores (in a caravan power lead) could be used up
to 25m.

A little bell jingles that the length limits are something like that
so as not to have too much (FSVO "too much") volt drop at full load.

Is there any advantage to buying a short "caravan hook-up" cable to use
for lengths under 25m?

I have a couple of 25m "caravan hook up" cables, for several reasons:

The cable is bright orange.
The cable is nice and flexible and coils nicely.
They are 2.5mm^2 cross section.

It is quite chunky stuff to have a 13A plug attached, so I have 16A
IEE connectors and adapters to 13A, primary use is from the generator
but as the IEE's are bit more water resistant than a 13A the pressure
washer has an IEE plug on it.

Unless you are working outside in winter I wouldn't bother with
arctic flex, the caravan hook stuff handles well and doesn't fight
back a great deal even when near freezing.

--
Cheers
Dave.

In article ,
Martin Brown wrote:
Or in the case of our local church fete a pair of 3kW kettles on a
mostly rolled up mad hot extension lead plugged into the wall. They did
it last year as well completely melting the inside of the reel. *SCARY*

Two 3 Kw kettles on the same extension should have blown the plug fuse and
quickly.

--
*Why is it considered necessary to screw down the lid of a coffin?

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

Dave Plowman (News) wrote:

Two 3 Kw kettles on the same extension should have blown the plug fuse and
quickly.

A 13A fuse is required to carry 1.6x the rated current without blowing,
and only required to blow within 30 minutes for 1.9x rated current, so
whether, or how quickly it should blow, depends on the duty cycle of the
two kettles ...

John Rumm wrote:
On 15/03/2012 15:36, Martin Brown wrote:
On 15/03/2012 15:27, Hugh - Was Invisible wrote:
On Thu, 15 Mar 2012 13:42:47 -0000, Fred
wrote:

About ten years ago I bought an extension lead from Wickes. Not
knowing any better at the time, I bought a long one, thinking
that a long one could be used when long or short lengths were
required, whereas a short one could only be used for short
lengths.
Biggest problem with modern long leads is that if you use much
power you have to unwind the whole lot to prevent overheating. If
you use thicker cable you add to the size and weight.
Intermittently used power tools are probably not a problem but
our wallpaper steamer is.

Or in the case of our local church fete a pair of 3kW kettles on a
mostly rolled up mad hot extension lead plugged into the wall. They
did it last year as well completely melting the inside of the reel.
*SCARY* I am inclined to the view now that they should include a thermal
cutout! The clear warning on the reel has little or no effect on
most folk

The modern 50m JoJo ones do include the cutout these days...
presumable for this sort of reason.

The extension lead Geoff gave me has a thermal cut out and it has operated
twice.

Once when a pillock plugged in a 2kW heater without unwinding it (he was
told not to) and then again when another pillock decided to charge up two
cherry pickers without unwinding it (without asking to use it).

I was suprised at how long it took to reset the trip/cool down even after I
had unwound the lead.


--
Adam

On Mar 15, 1:42*pm, Fred wrote:
Anyway, some of my tools have started switching on and off
intermittently when plugged into the lead

If the cable is ok & 1.25mm^2 you could just replace the rest...
- Check the plug & strain relief are ok
- Remove any reel, they invite coiled use to avoid a trip hazard only
to overheat
- Fit a new duraplug or generic rubber 2-way or 4-way socket strip

If the cable is not ok...
- Buy or make up a short lead (10m) and long lead (20m)
- Do not go so short you need to daisychain leads, that invites other
problems

Cable sizing...
- For 13A load IEE guidelines are 1.5mm^2 to 15m, 2.5mm^2 to 25m.
- The aim is to prevent sufficient voltage drop that operation of
equipment at the end of the lead is impeded (motor does not start,
sits there cooking) or a short circuit does not permit sufficient
current flow to blow a fuse (cable sits there melting, cable becomes
the fuse)
- Real world is it depends on what you are going to stick on the end
of it.

Fridge-freezer.
- A long extension lead may cause sufficient voltage drop to prevent
the compressor starting, ruining food or creating a fire hazard.
- However, 25m of 2.5mm^2 flex from a CU is no different to 25m of
2.5mm^2 flat-twin-&-earth from a CU. (The CPC is actually larger in
the former, but not my point).

Tumble dryer.
- A 3kW load that melts solid extension leads not fully unwound, or
equally just dumped on the floor.

Pressure washer with beefy 1.7kW induction motor.
- Despite the spec, 25m on 1.5mm^2 is fine because it is only a 7A
load and the motor is not likely to stall.

Battery charger & light, soldering iron 50m away in shed.
- Gets more interesting when you add a 3kW fan heater or big induction
motor saw.
- Reality is the longer the cable, the more permanent its
installation, the greater the risk of damage occurring.

Never forget the RCD and test it. Avoid reels, they seem to induce
people to keep cable wound up to avoid a trip hazard yet can create an
overheating risk. Not all extension reels have thermal cutouts and
quality of stuff these days is a bit hit n miss. Warranty claim after
the carpet has a reel shaped burn in it is not going to go down
well :-)

On Mar 15, 1:42*pm, Fred wrote:
Hi,

About ten years ago I bought an extension lead from Wickes. Not
knowing any better at the time, I bought a long one, thinking that a
long one could be used when long or short lengths were required,
whereas a short one could only be used for short lengths.

Then I came and read here and I learnt that long leads had
disadvantages. I can't remember now whether this was because of
voltage drop or fault currents, or may be both. Can someone remind me?

Anyway, some of my tools have started switching on and off
intermittently when plugged into the lead, and I can only assume that
over the years the contacts in the extension socket have been worn and
are not making a good connection to the plug.

So it is time to buy a new lead or leads. I seem to remember reading
that 1.5mm^2 cores could only be used safely up to 15m and 2.5mm^2
cores (in a caravan power lead) could be used up to 25m. Is there any
advantage to buying a short "caravan hook-up" cable to use for lengths
under 25m?

Otherwise I'm thinking I could use the cable from the Wickes lead, or
possibly use arctic flex as an improvement, to make some short leads.

TIA

The downsides of long leads are outweighed by the upsides, and both
are minor issues anyway. Just fix whatever's broken on your lead.

If you replace plug or socket, cut 6" of flex off that end.


NT

On Thu, 15 Mar 2012 15:36:30 +0000, Martin Brown
wrote:

On 15/03/2012 15:27, Hugh - Was Invisible wrote:
On Thu, 15 Mar 2012 13:42:47 -0000, Fred
wrote:

About ten years ago I bought an extension lead from Wickes. Not
knowing any better at the time, I bought a long one, thinking that a
long one could be used when long or short lengths were required,
whereas a short one could only be used for short lengths.

Biggest problem with modern long leads is that if you use much power you
have to unwind the whole lot to prevent overheating. If you use thicker
cable you add to the size and weight. Intermittently used power tools
are probably not a problem but our wallpaper steamer is.

Or in the case of our local church fete a pair of 3kW kettles on a
mostly rolled up mad hot extension lead plugged into the wall. They did
it last year as well completely melting the inside of the reel. *SCARY*

I am inclined to the view now that they should include a thermal cutout!
The clear warning on the reel has little or no effect on most folk

Similar story, this time a conveyer type toaster in the breakfast room
of a Premier Inn. Wound-up extention cable under table geting
noticably hot.

I told the maître d’hôtel (joke) that it was dangerous and needed
unwinding, and that I was an electrical engineer (a lie) and knew
about such things.

It was still there the next morning.





--
Graham.
%Profound_observation%

On 15/03/2012 18:07, ARWadsworth wrote:
John Rumm wrote:
On 15/03/2012 15:36, Martin Brown wrote:
On 15/03/2012 15:27, Hugh - Was Invisible wrote:
On Thu, 15 Mar 2012 13:42:47 -0000, Fred
wrote:

Or in the case of our local church fete a pair of 3kW kettles on a
mostly rolled up mad hot extension lead plugged into the wall. They
did it last year as well completely melting the inside of the reel.
*SCARY* I am inclined to the view now that they should include a thermal
cutout! The clear warning on the reel has little or no effect on
most folk

The modern 50m JoJo ones do include the cutout these days...
presumable for this sort of reason.

Had a look, but would want a 10m one or maybe 20m and they don't seem to
have thermal protect at least according to the summary at Farnell.

The extension lead Geoff gave me has a thermal cut out and it has operated
twice.

Once when a pillock plugged in a 2kW heater without unwinding it (he was
told not to) and then again when another pillock decided to charge up two
cherry pickers without unwinding it (without asking to use it).

I was suprised at how long it took to reset the trip/cool down even after I
had unwound the lead.

Still preferable to ending up with a molten mess of plastic and cable
all gummed up together. I was amazed the previous one didn't catch fire!

I also reckon they should be aggressively limited to no more than 20A
for 10s to avoid other obvious stupidity like 2 kettles which is an
overload condition on a 13A socket even with the cable unwound.

--
Regards,
Martin Brown

On 15/03/2012 17:45, Dave Plowman (News) wrote:
In ,
Martin wrote:

Or in the case of our local church fete a pair of 3kW kettles on a
mostly rolled up mad hot extension lead plugged into the wall. They did
it last year as well completely melting the inside of the reel. *SCARY*

Two 3 Kw kettles on the same extension should have blown the plug fuse and
quickly.

Not quickly enough! About 10 minutes continuous use I would guess and
kettles tend to get used with only a small amount of overlap apart from
at the beginning when they boil both to get started. I can assure you
the 13A plug fuse did not blow in the time the water took to boil.

The fuse also recovers from thermal stress much faster than the bulky
reel of wound up and increasingly hotter cable.

I suspect part of the problem *IS* that people think the fuse will
always protect them if they are doing something wrong.

--
Regards,
Martin Brown

Martin Brown wrote:
On 15/03/2012 17:45, Dave Plowman (News) wrote:
In ,
Martin wrote:

Or in the case of our local church fete a pair of 3kW kettles on a
mostly rolled up mad hot extension lead plugged into the wall. They did
it last year as well completely melting the inside of the reel. *SCARY*

Two 3 Kw kettles on the same extension should have blown the plug fuse
and
quickly.

Not quickly enough! About 10 minutes continuous use I would guess and
kettles tend to get used with only a small amount of overlap apart from
at the beginning when they boil both to get started. I can assure you
the 13A plug fuse did not blow in the time the water took to boil.

The fuse also recovers from thermal stress much faster than the bulky
reel of wound up and increasingly hotter cable.

I suspect part of the problem *IS* that people think the fuse will
always protect them if they are doing something wrong.

Its very easy to melt a coiled up reel of cable at less than 13A.
Most of them say exactly that.


--
To people who know nothing, anything is possible.
To people who know too much, it is a sad fact
that they know how little is really possible -
and how hard it is to achieve it.

On Mar 16, 11:40*am, Martin Brown
wrote:
I suspect part of the problem *IS* that people think the fuse will
always protect them if they are doing something wrong.

I am surprised at how many people think a 13A fuse blows immediately
you go above it.

Equally, many do not understand the thermal insulation effect of a
rug, cushion or curtains on an extension lead. One reason I changed
all leads to 1.5mm H07RNF and 10A fuses, the rubber purely because it
is a little more robust to objects dropped on it (and at the time
cheap whereas now I notice it has jumped in price).

No idea if a fridge/freezer inrush mandates 13A over 10A or 7A;
standard fuse sizes are 3A 5A 13A. A lot of cheap consumer products
seem to be using internal components as the fuse :-)

Cheapest is education.

On Mar 16, 1:06*pm, "js.b1" wrote:
On Mar 16, 11:40*am, Martin Brown
wrote:

I suspect part of the problem *IS* that people think the fuse will
always protect them if they are doing something wrong.

I am surprised at how many people think a 13A fuse blows immediately
you go above it.

Equally, many do not understand the thermal insulation effect of a
rug, cushion or curtains on an extension lead. One reason I changed
all leads to 1.5mm H07RNF and 10A fuses, the rubber purely because it
is a little more robust to objects dropped on it (and at the time
cheap whereas now I notice it has jumped in price).

No idea if a fridge/freezer inrush mandates 13A over 10A or 7A;
standard fuse sizes are 3A 5A 13A. A lot of cheap consumer products
seem to be using internal components as the fuse :-)

Cheapest is education.

Inrush of around 3x running current would give in the region of an amp
on a modern domestic appliance. Plug fuses don't seem to fussed about
motor startup current in practice, perhaps partly because these fuses
are mostly rated at well above motor rated i anyway.


NT

On 16/03/2012 11:33, Martin Brown wrote:
On 15/03/2012 18:07, ARWadsworth wrote:
John Rumm wrote:
On 15/03/2012 15:36, Martin Brown wrote:
On 15/03/2012 15:27, Hugh - Was Invisible wrote:
On Thu, 15 Mar 2012 13:42:47 -0000, Fred
wrote:

Or in the case of our local church fete a pair of 3kW kettles on a
mostly rolled up mad hot extension lead plugged into the wall. They
did it last year as well completely melting the inside of the reel.
*SCARY* I am inclined to the view now that they should include a
thermal
cutout! The clear warning on the reel has little or no effect on
most folk

The modern 50m JoJo ones do include the cutout these days...
presumable for this sort of reason.

Had a look, but would want a 10m one or maybe 20m and they don't seem to
have thermal protect at least according to the summary at Farnell.

Although less common on the shorter leads, there are some by the looks
of it:

http://cpc.farnell.com/jojo/706724/c...10m/dp/PL08818

The extension lead Geoff gave me has a thermal cut out and it has
operated
twice.

Once when a pillock plugged in a 2kW heater without unwinding it (he was
told not to) and then again when another pillock decided to charge up two
cherry pickers without unwinding it (without asking to use it).

I was suprised at how long it took to reset the trip/cool down even
after I
had unwound the lead.

Still preferable to ending up with a molten mess of plastic and cable
all gummed up together. I was amazed the previous one didn't catch fire!

I also reckon they should be aggressively limited to no more than 20A
for 10s to avoid other obvious stupidity like 2 kettles which is an
overload condition on a 13A socket even with the cable unwound.

Two 3kW kettles probably would take out the plug fuse in under a minute.



--
Cheers,

John.

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

On Mar 16, 1:06*pm, "js.b1" wrote:
On Mar 16, 11:40*am, Martin Brown
wrote:

I suspect part of the problem *IS* that people think the fuse will
always protect them if they are doing something wrong.

I am surprised at how many people think a 13A fuse blows immediately
you go above it.

And how many think the fuse is to protect the equipment rather than
the lead .


Equally, many do not understand the thermal insulation effect of a
rug, cushion or curtains on an extension lead. One reason I changed
all leads to 1.5mm H07RNF and 10A fuses, the rubber purely because it
is a little more robust to objects dropped on it (and at the time
cheap whereas now I notice it has jumped in price).

Isn;t there a problem with 10a fuses getting hot in teh plug if
someone uses that lead
for a 3kw kettle.


No idea if a fridge/freezer inrush mandates 13A over 10A or 7A;
standard fuse sizes are 3A 5A 13A. A lot of cheap consumer products
seem to be using internal components as the fuse :-)

Cheapest is education.

Are you saying we use students as cheap fuses ;-)

On 16/03/2012 11:40, Martin Brown wrote:
On 15/03/2012 17:45, Dave Plowman (News) wrote:
In ,
Martin wrote:

Or in the case of our local church fete a pair of 3kW kettles on a
mostly rolled up mad hot extension lead plugged into the wall. They did
it last year as well completely melting the inside of the reel. *SCARY*

Two 3 Kw kettles on the same extension should have blown the plug fuse
and
quickly.

Not quickly enough! About 10 minutes continuous use I would guess and
kettles tend to get used with only a small amount of overlap apart from
at the beginning when they boil both to get started. I can assure you
the 13A plug fuse did not blow in the time the water took to boil.

If there is only a small overlap in use then you would not really expect
the fuse to blow. That is diversity in action for you ;-)

The fuse also recovers from thermal stress much faster than the bulky
reel of wound up and increasingly hotter cable.

Its reaction is also as fast as its recovery though...

However the cable heating aspect is not really something you can expect
a fuse to do anything about, since it needs to be sized to provide
adequate fault protection for the cable in the first place, and overload
protection for the *maximum* rating of the cable in the second place.
However with a fully or partially wound lead you will not get anywhere
close to the maximum load before it overheats. You ideally need an
additional thermal protection mechanism in the drum of the lead itself
to cope with this.

I suspect part of the problem *IS* that people think the fuse will
always protect them if they are doing something wrong.

Possibly... many don't understand that its there primarily for fault
protection any not overload. The first its very good at, the second its
"ok" at in severe cases, but a bit patchy in the moderate cases.

--
Cheers,

John.

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

On Mar 16, 1:51*pm, NT wrote:
No idea if a fridge/freezer inrush mandates 13A over 10A or 7A;
standard fuse sizes are 3A 5A 13A. A lot of cheap consumer products
seem to be using internal components as the fuse :-)

Inrush of around 3x running current would give in the region of an amp
on a modern domestic appliance. Plug fuses don't seem to fussed about
motor startup current in practice, perhaps partly because these fuses
are mostly rated at well above motor rated i anyway.

Is it that low on all of them?

I did blow a 5A fuse on a modern Bosch larder freezer.
The fuse was in a 1.2m 1.5mm extension lead used to supply it
overnight, and it blew sometime the following morning. The manual does
warn to only use a 13A fuse, so perhaps significant stall is expected
at some point. The 5A fuse might had been bouncing in boxes of screws
for a couple of decades.

On Mar 16, 2:08*pm, whisky-dave wrote:
On Mar 16, 1:06*pm, "js.b1" wrote:
Isn;t there a problem with 10a fuses getting hot in teh plug if
someone uses that lead for a 3kw kettle.

No, a fuse dissipates 1W at rated current.

For a 10A fuse (data from Coopers)...
- 1 * In (10A) for min of 1000hrs continuous.
- 1.6 * In (16A) for min of 30min continuous.
- 1.9 * In (19A) for MAX of 30min continuous.

So even with a 10A fuse you can still pull 16A for 30min continuously.


Cheapest is education.

Are you saying we use students as cheap fuses ;-)

Some lecturers could be, only time they would ever be a bright spark...

In message
,
whisky-dave writes
On Mar 16, 1:06*pm, "js.b1" wrote:
On Mar 16, 11:40*am, Martin Brown
wrote:

I suspect part of the problem *IS* that people think the fuse will
always protect them if they are doing something wrong.

I am surprised at how many people think a 13A fuse blows immediately
you go above it.

And how many think the fuse is to protect the equipment rather than
the lead .


Equally, many do not understand the thermal insulation effect of a
rug, cushion or curtains on an extension lead. One reason I changed
all leads to 1.5mm H07RNF and 10A fuses, the rubber purely because it
is a little more robust to objects dropped on it (and at the time
cheap whereas now I notice it has jumped in price).

Isn;t there a problem with 10a fuses getting hot in teh plug if
someone uses that lead
for a 3kw kettle.


No idea if a fridge/freezer inrush mandates 13A over 10A or 7A;
standard fuse sizes are 3A 5A 13A. A lot of cheap consumer products
seem to be using internal components as the fuse :-)

Cheapest is education.

Are you saying we use students as cheap fuses ;-)



Perhaps NEETS would be socially more acceptable.
--
hugh

On Fri, 16 Mar 2012 14:02:12 +0000, John Rumm wrote:

Two 3kW kettles probably would take out the plug fuse in under a minute.

Thats not quite a 100% overload. I think the average BSwhatever
plug top fuse would last longer than that(*). Wether the plug top
could take the heat generated is another matter...

(*) Wonkypeida says for a 13A fuse 1-400s @ 30A (6.9kW). My
experience of urns and kettles on the same 13A plugtop is that it
take quite a number of minutes for the fuse to blow and the plug top
melts as well.

--
Cheers
Dave.

On Mar 16, 5:17*pm, "Dave Liquorice"
wrote:
On Fri, 16 Mar 2012 14:02:12 +0000, John Rumm wrote:
Two 3kW kettles probably would take out the plug fuse in under a minute..

Thats not quite a 100% overload. I think the average BSwhatever
plug top fuse would last longer than that(*). Wether the plug top
could take the heat generated is another matter...

A strictly 3kW kettle, 3000W, is 12.5A at 240V.
I think most are quoted as a range such as 2960-3180W etc.

Coopers BS1362...
- 1.6*In (20.8A) MIN of 30min - 5000W
- 1.9*In (24.7A) MAX of 30min - 6000W.

In article o.uk,
Dave Liquorice wrote:
On Fri, 16 Mar 2012 14:02:12 +0000, John Rumm wrote:

Two 3kW kettles probably would take out the plug fuse in under a
minute.

Thats not quite a 100% overload. I think the average BSwhatever
plug top fuse would last longer than that(*). Wether the plug top
could take the heat generated is another matter...

(*) Wonkypeida says for a 13A fuse 1-400s @ 30A (6.9kW). My
experience of urns and kettles on the same 13A plugtop is that it
take quite a number of minutes for the fuse to blow and the plug top
melts as well.

Assuming it's not the first time this has been done, the fuse could well
be rather weaker than spec.

--
*It's o.k. to laugh during sexŒ.Œ.just don't point!

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

When I was looking for some suitably rated Arctic cable for my arc
welder I came across this site: http://essentialsupplies.co.uk/

In it I found this statement:

"Arctic cable is only designed for outdoor use at 110v, we recommend
using HO7 RN-F rubber cable for temporary 230v outdoor use including
marquees."


Any thoughts?


Richard

On Fri, 16 Mar 2012 10:50:26 -0700 (PDT), js.b1 wrote:

I think most are quoted as a range such as 2960-3180W etc.

As kettles are, essentially, purely resistive the power is
proportional to the applied volts. Stuff is speced with a volatge
range so the lower power coresponds with the lower voltage and vice
versa. I've never done the maths to see if the calculated resistance
is the same (within reason).

--
Cheers
Dave.

On Mar 16, 6:43*pm, RJS wrote:
"Arctic cable is only designed for outdoor use at 110v, we recommend
using HO7 RN-F rubber cable for temporary 230v outdoor use including
marquees."

No it is not.

It is a PVC cable, 300/500V rated, a bit skimpy for a rough industrial
environment where it may be subjected to not only clumsy feet, high
heels and mineral oils. It does however use colour coding to match the
assumed BS4343 connectors, for example yellow indicates 110V and blue
indicates 230V and black indicates you are using it in a theatre :-)
There are white, orange, yellow, green, blue, purple etc.

H07RNF is chosen for rough industrial environments because it is oil
resistant, thicker sheath & insulation, and in particular "07" means
500/700V rated. The higher voltage rating is important if you have a 3
phase supply (generators or commercial hookup) to a BS4343
distribution board consisting of lots of blue 1 phase sockets. It can
be used at any voltage re 110V, 230V, 415VAC. N is Neoprene which is
UV/Rot resistant unlike R which is not.

If a cable is going to get a lot of abuse, it is worth considering
H07RNF.

Unfortunately a few years ago whilst Arctic was 43-47p/m & H07RNF just
59-62p/m, the price difference now is much greater. I think H07RNF is
about double if not triple the price of Arctic, so I would prefer to
put the money on a spare plug in RCD - or just limit H07RNF to where
it is either needed or could be useful. An example is I would put
H07RNF on an often left outdoor extension lead, but a casual "vacuum
cleaner extension" could be Arctic.

A note is H07RNF does vary around the world, the cheap Asian cables
can be rigid as hell because the rubber compound assumes a warmer
climate (I think). The UK stuff such as Drakaflex is extremely
flexible even at freezing conditions.

On Mar 16, 7:00*pm, "Dave Liquorice"
wrote:
As kettles are, essentially, purely resistive the power is
proportional to the applied volts. Stuff is speced with a volatge
range so the lower power coresponds with the lower voltage and vice
versa. I've never done the maths to see if the calculated resistance
is the same (within reason).

The variation probably covers resistance variation as well - it is
only a kettle.

For example of the four otherwise identical 700W heaters I have had,
the element wattage measured by plug in energy meter vary from 707W to
823W. The precise figure may be wrong, but as a resistive load there
is clearly quite a variation.

I think I remember a 600W kettle once... it might be boiled by now,
must find it!

js.b1 wrote:
On Mar 16, 6:43 pm, RJS wrote:
"Arctic cable is only designed for outdoor use at 110v, we recommend
using HO7 RN-F rubber cable for temporary 230v outdoor use including
marquees."

No it is not.

It is a PVC cable, 300/500V rated, a bit skimpy for a rough industrial
environment where it may be subjected to not only clumsy feet, high
heels and mineral oils. It does however use colour coding to match the
assumed BS4343 connectors, for example yellow indicates 110V and blue
indicates 230V and black indicates you are using it in a theatre :-)
There are white, orange, yellow, green, blue, purple etc.

H07RNF is chosen for rough industrial environments because it is oil
resistant, thicker sheath & insulation, and in particular "07" means
500/700V rated. The higher voltage rating is important if you have a 3
phase supply (generators or commercial hookup) to a BS4343
distribution board consisting of lots of blue 1 phase sockets. It can
be used at any voltage re 110V, 230V, 415VAC. N is Neoprene which is
UV/Rot resistant unlike R which is not.

If a cable is going to get a lot of abuse, it is worth considering
H07RNF.

Unfortunately a few years ago whilst Arctic was 43-47p/m & H07RNF just
59-62p/m, the price difference now is much greater. I think H07RNF is
about double if not triple the price of Arctic, so I would prefer to
put the money on a spare plug in RCD - or just limit H07RNF to where
it is either needed or could be useful. An example is I would put
H07RNF on an often left outdoor extension lead, but a casual "vacuum
cleaner extension" could be Arctic.

A note is H07RNF does vary around the world, the cheap Asian cables
can be rigid as hell because the rubber compound assumes a warmer
climate (I think). The UK stuff such as Drakaflex is extremely
flexible even at freezing conditions.

You could warm it up by running 2 kettles of it:-)

--
Adam

On Mar 16, 8:40*pm, "ARWadsworth"
wrote:
js.b1 wrote:
A note is H07RNF does vary around the world, the cheap Asian cables
can be rigid as hell because the rubber compound assumes a warmer
climate (I think). The UK stuff such as Drakaflex is extremely
flexible even at freezing conditions.

You could warm it up by running 2 kettles of it:-)

Leave it outside, powered up, and the neighbours will soon warm it
up...

On Mar 16, 3:54*pm, "js.b1" wrote:
On Mar 16, 1:51*pm, NT wrote:

No idea if a fridge/freezer inrush mandates 13A over 10A or 7A;
standard fuse sizes are 3A 5A 13A. A lot of cheap consumer products
seem to be using internal components as the fuse :-)

Inrush of around 3x running current would give in the region of an amp
on a modern domestic appliance. Plug fuses don't seem to fussed about
motor startup current in practice, perhaps partly because these fuses
are mostly rated at well above motor rated i anyway.

Is it that low on all of them?

I really dont know, I gather thats fairly typical for induction
motors. I've done more work with other types, which have much higher
startup current.


I did blow a 5A fuse on a modern Bosch larder freezer.
The fuse was in a 1.2m 1.5mm extension lead used to supply it
overnight, and it blew sometime the following morning. The manual does
warn to only use a 13A fuse, so perhaps significant stall is expected
at some point. The 5A fuse might had been bouncing in boxes of screws
for a couple of decades.

who knows, too many possible reasons why.


NT

On 15/03/2012 15:36, Martin Brown wrote:
On 15/03/2012 15:27, Hugh - Was Invisible wrote:
On Thu, 15 Mar 2012 13:42:47 -0000, Fred
wrote:

About ten years ago I bought an extension lead from Wickes. Not
knowing any better at the time, I bought a long one, thinking that a
long one could be used when long or short lengths were required,
whereas a short one could only be used for short lengths.

Biggest problem with modern long leads is that if you use much power you
have to unwind the whole lot to prevent overheating. If you use thicker
cable you add to the size and weight. Intermittently used power tools
are probably not a problem but our wallpaper steamer is.

Or in the case of our local church fete a pair of 3kW kettles on a
mostly rolled up mad hot extension lead plugged into the wall. They did
it last year as well completely melting the inside of the reel. *SCARY*

Unfortunately your average lay person has no clue about the different
current consumptions of different appliances, and the significance thereof.

Even if they (often only vaguely) understand that a 3-bar electric fire
is more expensive to run than a 100mA phone charger, they have no
concept of what the different currents involved actually mean, and what
the safety implications are.

David

On 16/03/2012 17:17, Dave Liquorice wrote:
On Fri, 16 Mar 2012 14:02:12 +0000, John Rumm wrote:

Two 3kW kettles probably would take out the plug fuse in under a minute.

Thats not quite a 100% overload. I think the average BSwhatever
plug top fuse would last longer than that(*). Wether the plug top
could take the heat generated is another matter...

(*) Wonkypeida says for a 13A fuse 1-400s @ 30A (6.9kW). My
experience of urns and kettles on the same 13A plugtop is that it
take quite a number of minutes for the fuse to blow and the plug top
melts as well.

I was going from the graph in BS1362:

http://wiki.diyfaq.org.uk/images/d/d...FusingTime.png

However to be fair that is the lower limit of the range of possible
values, so it may well last longer depending on the fuse.

Also worth keeping in mind that with low resistance items like notional
3kW heaters, they are often quoted as 3kW at 240V (which suggests an
element resistance of 12.5 ohms) but that is only 2875W at 230V. So
small shifts in voltage make a noticeable difference. Factor in the
effect of the load on the actual voltage drop on the lead and you can
get quite substantial amount of load shedding.

Say its a 1.5mm^2 flex and assume 24mOhm/m round trip resistance. Try
and draw 20A through 20m of that, and you have just dropped another 600W
of load.


--
Cheers,

John.

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

On 16/03/2012 15:54, js.b1 wrote:
On Mar 16, 1:51 pm, wrote:
No idea if a fridge/freezer inrush mandates 13A over 10A or 7A;
standard fuse sizes are 3A 5A 13A. A lot of cheap consumer products
seem to be using internal components as the fuse :-)

Inrush of around 3x running current would give in the region of an amp
on a modern domestic appliance. Plug fuses don't seem to fussed about
motor startup current in practice, perhaps partly because these fuses
are mostly rated at well above motor rated i anyway.

Is it that low on all of them?

I would have expected it to be much larger on a fridge due to the
induction motor in the compressor. 5 to 9 times nominal is the range for
inrush on that sort of motor IIRC.

So even a couple amp normal draw, could suck 18A on startup.

I did blow a 5A fuse on a modern Bosch larder freezer.
The fuse was in a 1.2m 1.5mm extension lead used to supply it
overnight, and it blew sometime the following morning. The manual does
warn to only use a 13A fuse, so perhaps significant stall is expected
at some point. The 5A fuse might had been bouncing in boxes of screws
for a couple of decades.


--
Cheers,

John.

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

On 16/03/2012 20:13, js.b1 wrote:

It is a PVC cable, 300/500V rated, a bit skimpy for a rough industrial
environment where it may be subjected to not only clumsy feet, high
heels and mineral oils. It does however use colour coding to match the
assumed BS4343 connectors, for example yellow indicates 110V and blue
indicates 230V and black indicates you are using it in a theatre :-)
There are white, orange, yellow, green, blue, purple etc.

H07RNF is chosen for rough industrial environments because it is oil
resistant, thicker sheath& insulation, and in particular "07" means
500/700V rated. The higher voltage rating is important if you have a 3

as an aside, I added some details to the end of the flex article the
other day for breaking down those harmonised codings:

http://wiki.diyfaq.org.uk/index.php?..._Cabl e_Codes


(still needs some work to make it a bit easier!)

--
Cheers,

John.

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

On 16/03/2012 18:43, RJS wrote:

[...]
"Arctic cable is only designed for outdoor use at 110v, we recommend
using HO7 RN-F rubber cable for temporary 230v outdoor use including
marquees."

Any thoughts?

It's correct. You might like to read the two articles about this that
were published in the IET's /Wiring Matters/ fairly recently.

Firstly:
http://electrical.theiet.org/wiring-...s.cfm?type=pdf

and the follow-up:
http://electrical.theiet.org/wiring-...s.cfm?type=pdf

To summarise:

- 3183A 'arctic' cable made to BS 7919 Table 44 is suitable for handling
down to -25 deg. C, but is only intended for use on 110 V ('reduced low
voltage') systems. This cable type is explicitly described as not
suitable for outdoor use at "standard voltages" (meaning 230/400 V), nor
for use in industrial or agricultural buildings. [Ref. BS 7540-3 Guide
to use ...]

- The 'blue stuff' is not actually an arctic cable at all. It's an
ordinary duty cord to BS 6500, i.e. 3183Y or H05VV-F. It's fine for 230
V but shouldn't be handled at temperatures below +5 deg. C. It is not a
heavy duty cable.

- For heavy duty, use H07RN-F, as already mentioned.

--
Andy