Extension leads

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Fred

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Oct 22, 2010, 12:45:51 PM10/22/10
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Hello,

In a recent pressure washer thread THM mentioned that you shouldn't
use "mickey mouse" leads with induction motors, only I wasn't quite
sure what makes a lead become "mickey mouse" category.

Are all tools with induction motors affected or is it only a problem
for hungry, high-watts motors, like those in pressure washers?

I was thinking 1.25mm^2 CSA flex is rated for 13A, so you might think
it would be ok for any 13A appliance but is it the case that once the
lead is so long, you have to upgrade the CSA to avoid a voltage drop?

Is this like the "taking electricity outdoors" considerations where a
long cable results in voltage drop? Is it the voltage that upsets the
induction motor, or is it something else all together?

Is another problem that above a certain CSA you cannot fit the lead
into a plug? Other threads have suggested using "caravan leads" with
the big round blue plugs (sorry I don't remember the real name for
these) but OTOH don't these have to have a standard plug on one end,
so you'll still come up against the same problem eventually.

TIA

Tabby

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Oct 22, 2010, 1:42:30 PM10/22/10
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Induction motors and extension leads arent a particular issue unless
the motor is running a compressor, such as in a fridge, and the
extension lead is very long and thin. Yes, there's a lot more could be
written on this.


NT

m...@privacy.net

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Oct 22, 2010, 2:17:23 PM10/22/10
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On 22 Oct,
Fred <fr...@no-email.here.invalid> wrote:

> Is another problem that above a certain CSA you cannot fit the lead
> into a plug? Other threads have suggested using "caravan leads" with
> the big round blue plugs (sorry I don't remember the real name for
> these) but OTOH don't these have to have a standard plug on one end,
> so you'll still come up against the same problem eventually.

My extension lead uses 2.5mm^2 arctic flex in blue. It was a job to
terminate. I had to take one of the teeth out of the MK safetyplug to get the
cable in, but the flexgrip is still 100% solid. Other brands may vary.

--
B Thumbs
Change lycos to yahoo to reply

js.b1

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Oct 22, 2010, 2:28:34 PM10/22/10
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On Oct 22, 5:45 pm, Fred <f...@no-email.here.invalid> wrote:
> I was thinking 1.25mm^2 CSA flex is rated for 13A, so you might think
> it would be ok for any 13A appliance but is it the case that once the
> lead is so long, you have to upgrade the CSA to avoid a voltage drop?

Domestic plugs are generally limited to 1.5mm CSA. You can get a few
plugs that take 2.5mm CSA, but unless you plan on some vast length
with 3120W it is simply unnecessary.

> the big round blue plugs

Ceeform, BS4343, 16A 32A 63A 125A.

Beware these have certain min cable size restrictions for sealing - a
thin PVC flex on an appliance may not seal at the cord grip so whilst
the plug may be IP44 or IP67, water running back down the flex might
be somewhat shocking :-) Under BS7671 a 16A BS4343 should use 2.5mm
flex, which has a rather substantial overall diameter compared to most
appliance flex which has very small overall diameter 1.0mm flex.

Arctic flex is not actually made to a BS-number, most heavy duty
extension leads are based around H0RNF (often miss-named HO7RNF on
Ebay) which is commonly available in 1.5mm quite cheaply (64-77p/metre
including VAT). www.10outof10.co.uk carry H07RNF and www.ebay.co.uk
has many listings for HO7RNF (lots of cut lengths, no connection just
used a couple of the sellers and the cable is very good). Trading
Depot do 1.5mm Arctic flex quite cheaply in cut lengths (41p/m) and
postage is quite low. Many other suppliers out there, TLC Direct do
various black rubber cables, Screwfix probably do "something cheap" on
a 25m reel with free shipping possible if you want other stuff.

Most IP rated sockets do have screw-holes in a separate compartment to
the electrical components, so can be used "loose", but a common
problem is they may not close over a moulded-on plug.

You can pickup ready made IPx4+ rated extension leads in orange, the
socket does close over a moulded in plug and everything is moulded,
pre-tested etc. I think Homebase did some, also Wickes. Can not recall
the brand name.

harry

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Oct 22, 2010, 2:44:17 PM10/22/10
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Onr thing to bear in mind is that if using a heating appliance on an
extention lead, be sure to unwind all of it. They can overheat if
left coiled up on a reel and actually melt the insulation.

The Medway Handyman

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Oct 22, 2010, 2:54:09 PM10/22/10
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Tabby wrote:
> On Oct 22, 5:45 pm, Fred <f...@no-email.here.invalid> wrote:
>> Hello,
>>
>> In a recent pressure washer thread THM mentioned that you shouldn't
>> use "mickey mouse" leads with induction motors, only I wasn't quite
>> sure what makes a lead become "mickey mouse" category.
>>
>> Are all tools with induction motors affected or is it only a problem
>> for hungry, high-watts motors, like those in pressure washers?

A large commercial pressure washer could have a 3.1kw induction motor, so is
right in the limit for a 13 amp fuse.

>>
>> I was thinking 1.25mm^2 CSA flex is rated for 13A, so you might think
>> it would be ok for any 13A appliance but is it the case that once the
>> lead is so long, you have to upgrade the CSA to avoid a voltage drop?

IME yes, long leads cause fuses to blow and TOL's to trip. Coiled leads do
it as well.

Someone will be along in a minute with the technical bits.

Strange, having been brought up on pressure washers, I now look on extension
leads from that viewpoint. Nearly didn't buy one recently because it would
only handle 10 amps - more than enough for any power tool I own - but not
much good for a HPC.


--
Dave - The Medway Handyman
www.medwayhandyman.co.uk


A.Lee

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Oct 22, 2010, 3:46:03 PM10/22/10
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The Medway Handyman <davidno-...@blueyonder.co.uk> wrote:

> Tabby wrote:
> > On Oct 22, 5:45 pm, Fred <f...@no-email.here.invalid> wrote:
> >> Hello,
> >>
> >> In a recent pressure washer thread THM mentioned that you shouldn't
> >> use "mickey mouse" leads with induction motors, only I wasn't quite
> >> sure what makes a lead become "mickey mouse" category.
> >>
> >> Are all tools with induction motors affected or is it only a problem
> >> for hungry, high-watts motors, like those in pressure washers?

> A large commercial pressure washer could have a 3.1kw induction motor, so is
> right in the limit for a 13 amp fuse.

Ahh, but a 13 amp fuse doesnt blow until around 26A.

> >> I was thinking 1.25mm^2 CSA flex is rated for 13A, so you might think
> >> it would be ok for any 13A appliance but is it the case that once the
> >> lead is so long, you have to upgrade the CSA to avoid a voltage drop?
>
> IME yes, long leads cause fuses to blow and TOL's to trip. Coiled leads do
> it as well.
> Someone will be along in a minute with the technical bits.

Voltage drop will cause a bigger amperage to be drawn. If it is on the
limit at 13 amps at the plug, going 25 or 30 metres away to the socket
will likely give a 10 volts or so voltage drop. Amps x volts = watts.
The motor will always want (say) 2850w, that equates to 12.4A at 230V.
With a 10v voltage drop, the current will be going up to 12.95A, so
pretty close to the rated limit of the cable.
At that amperage, the cable will be getting warm, as although they are
supposedly passed for 13A, I'd say the majority of extension leads were
not made compliant to the ones sent for testing, so I'd always err on
the safe side, and take 10% off of the rated current limit to stay safe.

I've not got the details for flex, but for 3 core cable, 1.5mm sq can
carry up to 22A if in free air.
The voltage drop for this cable will be 29mV/A/m .
If using a 25m extension lead, that'd be .029x12.4Ax25 = 8.99v Voltage
drop.
For fixed wiring, this would be acceptable - 5% limit on voltage drop,
8.99v is around 4% drop.
I have not got any details on flexible connectors, so cannot comment if
this is acceptable.
I know putting 4 appliances into a 50metre socket is not a good idea,
unless they are low current drawers.

Alan.


--
To reply by e-mail, change the ' + ' to 'plus'.

John Rumm

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Oct 22, 2010, 4:08:27 PM10/22/10
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On 22/10/2010 17:45, Fred wrote:
> Hello,
>
> In a recent pressure washer thread THM mentioned that you shouldn't
> use "mickey mouse" leads with induction motors, only I wasn't quite
> sure what makes a lead become "mickey mouse" category.
>
> Are all tools with induction motors affected or is it only a problem
> for hungry, high-watts motors, like those in pressure washers?

Its the high currents that matter more. Some of the top end domestic
pressure washers will be right on the 13A limit.

> I was thinking 1.25mm^2 CSA flex is rated for 13A, so you might think
> it would be ok for any 13A appliance but is it the case that once the
> lead is so long, you have to upgrade the CSA to avoid a voltage drop?
>
> Is this like the "taking electricity outdoors" considerations where a
> long cable results in voltage drop? Is it the voltage that upsets the
> induction motor, or is it something else all together?

Yup, induction motors are a little unusual in the sense that if you drop
the voltage, let them spin up and then apply maximum mechanical load
(i.e. much like a pressure washer), they will try and develop the same
output power regardless. This means at reduced volts they suck more
amps. More amps means more heat to dissipate in the motor windings and
can result in damage to the motor. (it also obviously heats the cable
more, raises its resistance further and it then drops more volts)

> Is another problem that above a certain CSA you cannot fit the lead
> into a plug? Other threads have suggested using "caravan leads" with
> the big round blue plugs (sorry I don't remember the real name for
> these) but OTOH don't these have to have a standard plug on one end,
> so you'll still come up against the same problem eventually.

What distance and what size motor are we talking about here?


--
Cheers,

John.

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

Tabby

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Oct 22, 2010, 5:18:15 PM10/22/10
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On Oct 22, 8:46 pm, a...@darkroom.+.com (A.Lee) wrote:


5% and 13A is all no problem. Today's mains motors are desgined to run
at much lower voltage and still be in spec.

13A is a continuous rating at which all marketed goods are legally
required to be safe. 13A is in no way a problem - though of course
there are plugs that cant do 13A, but nor can they do 12.5.

If theres a problem it lies elsewhere,


NT

Dave Osborne

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Oct 22, 2010, 6:23:16 PM10/22/10
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You should have bought a CEEform plug/connector and terminated the
2.5mm2 on the CEEform plug. You should then have made a short 13A plug
to CEEform connector with a piece of 1.25mm2 or 1.5mm2 flex.

13A plugs are not designed to take 2.5mm2 flex and you shouldn't really
try to force the issue. Strictly "bush-league" as they say ;-)

HTH.

Dave Osborne

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Oct 22, 2010, 6:51:36 PM10/22/10
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js.b1 wrote:
> On Oct 22, 5:45 pm, Fred <f...@no-email.here.invalid> wrote:
>> I was thinking 1.25mm^2 CSA flex is rated for 13A, so you might think
>> it would be ok for any 13A appliance but is it the case that once the
>> lead is so long, you have to upgrade the CSA to avoid a voltage drop?
>
> Domestic plugs are generally limited to 1.5mm CSA. You can get a few
> plugs that take 2.5mm CSA,

Never seen one. Can you provide a reference?

but unless you plan on some vast length
> with 3120W it is simply unnecessary.
>
>> the big round blue plugs
>
> Ceeform, BS4343, 16A 32A 63A 125A.
>
> Beware these have certain min cable size restrictions for sealing - a
> thin PVC flex on an appliance may not seal at the cord grip

Only if it's a crap old-style design. Most decent modern brands of 16A
Ceeforms either have a clutch strain relief or (if they have the older
style with two bits of plastic and two screws) will clamp down on 1.5mm2
cable no problem. Even if you have an old style Ceeform that is too
small for 1.5mm2, you can always use a bit of extra cable sheath to pack
out the cord grip.

so whilst
> the plug may be IP44 or IP67, water running back down the flex might
> be somewhat shocking :-) Under BS7671 a 16A BS4343 should use 2.5mm
> flex,

Only for caravan connections afaics. Do you have any other references,
apart from table 721?

Table 4F3A rates 1.5mm2 at 16A and the entertainment industry routinely
uses Ceeform extensions made up with 1.5mm2 cable.


which has a rather substantial overall diameter compared to most
> appliance flex which has very small overall diameter 1.0mm flex.
>
> Arctic flex is not actually made to a BS-number,

BS6500?

http://www.bs6500.co.uk/

most heavy duty
> extension leads are based around H0RNF

Que? Is this a typo?

H07RN-F is the correct designation. The "0" is a zero.

js.b1

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Oct 22, 2010, 9:02:22 PM10/22/10
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On Oct 22, 11:51 pm, Dave Osborne <DaveyO...@SPAMymail.com> wrote:

> js.b1 wrote:
> > Domestic plugs are generally limited to 1.5mm CSA. You can get a few
> > plugs that take 2.5mm CSA,
>
> Never seen one. Can you provide a reference?

Clipsal 56 series 56P313 with suffix GY for Grey or OR for chemical
resistant ORange.

BS1363/A "tough duty" plug terminals may take 2.5mm conductors, but
the cord grip will rarely accommodate a 2.5mm cable's outer diameter.
You might get Arctic 2.5mm to clamp satisfactory, but 2.5mm H07RNF has
quite a wide outer diameter range and may prove impossible with most
cord grip designs.

Conversely the Clipsal 56 series plug has a rear cable entry based
around an M20 cable gland - so even 2.5mm H07RNF can be accommodated
(although I recall quite a bit more tightening is required to get the
gland's O-ring to bottom and seal). Unfortunately a downside of the
design is that it imposes quite a large min cable diameter, 1.0mm
cable typically used on hedge-trimmers & mid-range pressure washers
will not seal adequately (7.2-8.5mm). A clipsal compatible solution
for small appliance cables is to use the older PDL series plugs -
their double-grommet seal on the plug will tolerate very small
diameter cable, but at the expense of not accepting anything above
1.0mm 2-core H07RNF.


> Even if you have an old style Ceeform that is too small for 1.5mm2,
> you can always use a bit of extra cable sheath to pack out the cord grip.

That is unlikely to seal sufficiently.
Geweiss Ceeform IP67 will not seal on 1.0mm 2-core or 1.0mm 3-core PVC
cable (that is to say 7-8mm o.d. cable), there were two other equally
nasty makes at the bargain basement end of the market.


>> Under BS7671 a 16A BS4343 should use 2.5mm flex
>

> Only for caravan connections afaics. Do you have any other references,
> apart from table 721?

"Should" was too strong a word. BS7671 regulation reference is indeed
721 & specific to caravans, there was a HSE article recommending
2.5mm, although that may be typo, error or journalistic licence (they
do not have to pay for the cable).


> Table 4F3A rates 1.5mm2 at 16A and the entertainment industry routinely
> uses Ceeform extensions made up with 1.5mm2 cable.

Indeed, the installed base is vast - 1.25mm routinely 13A, 1.50mm
routinely 16A.


> > Arctic flex is not actually made to a BS-number,
>
> BS6500?
> http://www.bs6500.co.uk/

Yes and no.
Firstly it may be generally made to, but not tested to, which are
quite different things.
Secondly as I was typing I was trying to recall Cole's article, HSE
comments, Prysmian comments and a comment from one committee report.

Found it.
If you go the IET forum and search under "Flexible cable type H07RN-F
(BS 7919)" you can read responses to Mark Cole's article.

BS6500 is for domestic & similar environments, down to +5oC. BS7919 is
for industrial environments, down to -25oC. The problem centres around
mechanical robustness of Arctic PVC in commercial environments at LV.
It is true that there is a bias to phase out PVC (that I know that
from one Prysmian engineer and one AEI engineer), probably because no-
one is making enough profit on it (ooops, typo!).

Quite a few yellow arctic cables have had no BS number and are more
blue-brown than yellow along their length as the sheath is so thin,
there is quite a lot of variation. Stuff branded is a different matter
and seems fine.


> Que? Is this a typo? H07RN-F is the correct designation. The "0" is a zero.

Deliberately :-)
If you Google use H07RN (zero, re "07").
If you Ebay use HO7 (letter O, incorrectly).

Ironically people miss-searching for HO7 may have forced sellers to
list as HO7 as well as H07 via Ebay's "keyword auto-suggestion" :-)
Seen the same thing on part numbers, special characters and miss-
spellings which can often work in your favour. Ebay used to miss 16mm2
where the 2 was proper superscript for example, not checked if it
still does; meant you could pick up 100m of 16mm 6491X for 99p plus
£8.50 delivery or similar nonsense.

If assembling a lead for pressure-washer applications, just make sure
the cable glands do in fact seal - make up, hose spray whilst dead,
diss-assemble and examine for water ingress. I found a lot did not
seal properly. A pressure washer creates a water jet way up the IP
scale, such that moulded extension leads may be preferable. I found
very deep embossed lettering on a cable sheath situated under a cable
gland can cause water migration under simple hose spraying. To survive
a direct blast from a pressure washer is probably IPx8 rating due to
the pressures involved.

Rick Hughes

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Oct 23, 2010, 5:00:01 AM10/23/10
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"A.Lee" <alan@darkroom.+.com> wrote in message
news:1jqs5zy.1w11jor417kvoN%alan@darkroom.+.com...

> Voltage drop will cause a bigger amperage to be drawn. If it is on the
> limit at 13 amps at the plug, going 25 or 30 metres away to the socket
> will likely give a 10 volts or so voltage drop. Amps x volts = watts.
> The motor will always want (say) 2850w, that equates to 12.4A at 230V.
> With a 10v voltage drop, the current will be going up to 12.95A, so
> pretty close to the rated limit of the cable.
> At that amperage, the cable will be getting warm, as although they are
> supposedly passed for 13A, I'd say the majority of extension leads were
> not made compliant to the ones sent for testing, so I'd always err on
> the safe side, and take 10% off of the rated current limit to stay safe.

Bricklayer was using his cement mixer & angle grinder off one of those
plastic wind up extension lead cases. .... later in day noticed case was so
hot it had all melted and deformed ....... obviously did not believe the
label that said unwind fully before use.

Dave Osborne

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Oct 23, 2010, 6:42:44 AM10/23/10
to
js.b1 wrote:
> On Oct 22, 11:51 pm, Dave Osborne <DaveyO...@SPAMymail.com> wrote:
>> js.b1 wrote:
>>> Domestic plugs are generally limited to 1.5mm CSA. You can get a few
>>> plugs that take 2.5mm CSA,
>> Never seen one. Can you provide a reference?
>
> Clipsal 56 series 56P313 with suffix GY for Grey or OR for chemical
> resistant ORange.

OK, that's part of a proprietary waterproof plug/socket/connector
system. I was thinking of an ordinary 13A plug. I dare say you could
squeeze 2.5mm2 into a Lewden weathertight plug as well.

>> Even if you have an old style Ceeform that is too small for 1.5mm2,
>> you can always use a bit of extra cable sheath to pack out the cord grip.
>
> That is unlikely to seal sufficiently.

OK, I was thinking more about strain relief than weather sealing. I
think I see a pattern here...

Andy Dingley

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Oct 23, 2010, 9:56:50 AM10/23/10
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On 22 Oct, 23:23, Dave Osborne <DaveyO...@SPAMymail.com> wrote:


> 13A plugs are not designed to take 2.5mm2 flex and you shouldn't really
> try to force the issue. Strictly "bush-league" as they say ;-)

MK "Safetyplugs" with the captive nut clamp, rather than the tiny
little screw, used to be really useful for doing this. They also
loosen less if there is any heating of the clamp screw.

js.b1

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Oct 23, 2010, 10:05:08 AM10/23/10
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On Oct 23, 11:42 am, Dave Osborne <DaveyO...@SPAMymail.com> wrote:
> I dare say you could squeeze 2.5mm2 into
> a Lewden weathertight plug as well.

Lewden are somewhat better built than Clipsal too.
I think Clipsal might have revised their plug rear gland design in
Australia to ensure better sealing over a wider cable range (pretty
much like the recent BS4343 connectors as you point out).

The benefit of Clipsal 56 series is their modular approach - you just
choose how many backbox ways you want re 1-9 and populate with
sockets, lids, switches, RCD enclosures, anything. Price can be
outrageous of course.

MK Masterseal tried to be "modular" with their box-couplers, but on
uneven walls the very short couplers can simply pull out - requiring a
levelled backplate or conduit fittings. Masterseal lacked a 1G+1G or 1G
+1G+1G moulded backbox, although that would still require levelling of
the screws or the thinwall polycarbonate boxes can distort possibly
compromising the seals. Masterseal Compact might solve the problem of
plugs with moulded cord grips (eg, pressure washer) not fitting
sockets, but I have never checked.


> OK, I was thinking more about strain relief than weather sealing

Pressure washers are unique in producing very high pressure directed
spray, which defeats many conventional seals at close quarters.
Moulded waterproof extension leads actually might have the edge over
DIY if they can handle the moulded cord grip.

Andrew Gabriel

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Oct 23, 2010, 11:31:03 AM10/23/10
to
In article <nff3c6t05netis04k...@4ax.com>,

Fred <fr...@no-email.here.invalid> writes:
> Hello,
>
> In a recent pressure washer thread THM mentioned that you shouldn't
> use "mickey mouse" leads with induction motors, only I wasn't quite
> sure what makes a lead become "mickey mouse" category.
>
> Are all tools with induction motors affected or is it only a problem
> for hungry, high-watts motors, like those in pressure washers?
>
> I was thinking 1.25mm^2 CSA flex is rated for 13A, so you might think
> it would be ok for any 13A appliance but is it the case that once the
> lead is so long, you have to upgrade the CSA to avoid a voltage drop?

Yes, but before voltage drop becomes a problem, the fault current
loop resistance becomes a problem.

For a 13A extension leads, you should stick to the following
max lengths based on CSA, and never daisy-chain multiple leads:

1.25mm� - 12m
1.5mm� - 15m
2.5mm� - 25m (cable won't normally fit in 13A plugs)
Spot the pattern - it's easy to remember.

You can increase the length proportionally with a reduction in the
fuse in the extension lead plug, so with a 5A fuse, 1.25mm� lead
can be 12*13/5 = 31m long.

In theory you could increase the lengths if you know the lead is
always going to be RCD protected, but you can't really know that
to be the case, give that extension leads are inherently portable.

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

Tabby

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Oct 23, 2010, 3:13:02 PM10/23/10
to
On Oct 23, 4:31 pm, and...@cucumber.demon.co.uk (Andrew Gabriel)
wrote:
> In article <nff3c6t05netis04kcljmpto8dbers7...@4ax.com>,


Now I'm wondering what this definition of a problem is based on.
15m of 1.5mm² will drop 4.4v at 13A and have a PSCC of 700A.
700A opens even a D type breaker in 0.001-2 seconds, well within 17th
edn socket disconnection times.


NT

Dave

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Oct 23, 2010, 4:24:22 PM10/23/10
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On 22/10/2010 17:45, Fred wrote:

There are 13 Amp cables that can take the current intermittently and
those that can take it 24/7. I have one of each, but if I am using my
arc welder, I chose the thicker one.

If the cable is on a reel then totally uncoil it, or it will melt.

Dave

Andy Wade

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Oct 23, 2010, 6:14:13 PM10/23/10
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On 23/10/2010 20:13, Tabby wrote:

> Now I'm wondering what this definition of a problem is based on.

The figures Andrew quoted are in the IET code of practice for in-service
inspection and testing ('PAT testing' if you must call it that).

> 15m of 1.5mm² will drop 4.4v at 13A

That's an optimistic figure. It's more like 5.6 V at 70 deg. conductor
temp.

> and have a PSCC of 700A.

Bzzt - only for zero source impedance at the feeding end! In reality
you can have an ohm or more of Zs at the socket that the extension is
plugged into - and possibly over 2 ohms if it's on a 20 A radial
circuit. The 15 m extension adds another 0.4 ohm or so, giving a
worst-case overall Zs nearer to 2.7 ohms (85 A fault current).

> 700A opens even a D type breaker in 0.001-2 seconds, well within 17th
> edn socket disconnection times.

The operating time of the 13 A plug fuse is more relevant. Looking at
BS 1362, about 90 A is required to clear a 13 A fuse in 0.4 s.
Convinced now?

--
Andy

Tabby

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Oct 23, 2010, 7:37:25 PM10/23/10
to
On Oct 23, 11:14 pm, Andy Wade <spambuc...@maxwell.myzen.co.uk> wrote:
> On 23/10/2010 20:13, Tabby wrote:
>
> > Now I'm wondering what this definition of a problem is based on.
>
> The figures Andrew quoted are in the IET code of practice for in-service
> inspection and testing ('PAT testing' if you must call it that).

Exactly, a code of practice does not equal a problem.


> > 15m of 1.5mm² will drop 4.4v at 13A
>
> That's an optimistic figure.  It's more like 5.6 V at 70 deg. conductor
> temp.
>
> > and have a PSCC of 700A.
>
> Bzzt - only for zero source impedance at the feeding end!

Sure, I was being a bit handwavey there.

> In reality
> you can have an ohm or more of Zs at the socket that the extension is
> plugged into - and possibly over 2 ohms if it's on a 20 A radial
> circuit.  The 15 m extension adds another 0.4 ohm or so, giving a
> worst-case overall Zs nearer to 2.7 ohms (85 A fault current).
>
> > 700A opens even a D type breaker in 0.001-2 seconds, well within 17th
> > edn socket disconnection times.
>
> The operating time of the 13 A plug fuse is more relevant.  Looking at
> BS 1362, about 90 A is required to clear a 13 A fuse in 0.4 s.
> Convinced now?

I dont see 0.4s clearance in worst case scenario as being a genuine
problem. 1-30 seconds clearance for type B 32A breaker would be, but
as you point out the 13A fuse would go first in this case.


NT

Fred

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Oct 24, 2010, 2:48:57 PM10/24/10
to
On Fri, 22 Oct 2010 23:23:16 +0100, Dave Osborne
<Dave...@SPAMymail.com> wrote:

>You should have bought a CEEform plug/connector and terminated the
>2.5mm2 on the CEEform plug. You should then have made a short 13A plug
>to CEEform connector with a piece of 1.25mm2 or 1.5mm2 flex.

Thanks. I wasn't sure whether you could do this or whether you needed
2.5mm^2 for the whole length of the extension lead. I'm guessing it is
permissible to use the 1.5mm to fit the plug because you are just
using a short length, so not long enough to drop voltage or limit
currents? Is that right?

On the subject of these plugs, I've often wondered about fitting one
of these wall inlets onto my house wall:
http://cpc.farnell.com/pro-elec/is1023r/wall-mount-inlet-16a-240v-2p-e/dp/PL09779
or
http://cpc.farnell.com/pro-power/pe1663smb/wall-mount-inlet-240v/dp/PL08949

On the other side I would connect it to a socket and if I had a power
cut plug the boiler in one side and a cheap 2 stroke generator into
the other. I've never got round to it because, touch wood, we've not
had a power cut for a couple of years (cue a cut tomorrow).

I'm sure CPC describe these as IP44. Now according to this:
http://www.baseefa.com/filelib/IP%20Ratings.pdf

the x4 means protection from water sprayed from all directions. I
can't see how this is possible when the pins are exposed. Or does it
only have ip44 protection when in use and coupled?

Fred

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Oct 24, 2010, 2:54:09 PM10/24/10
to
On Sat, 23 Oct 2010 15:31:03 +0000 (UTC), and...@cucumber.demon.co.uk
(Andrew Gabriel) wrote:

>Yes, but before voltage drop becomes a problem, the fault current
>loop resistance becomes a problem.
>
>For a 13A extension leads, you should stick to the following
>max lengths based on CSA, and never daisy-chain multiple leads:
>
>1.25mm� - 12m
>1.5mm� - 15m
>2.5mm� - 25m (cable won't normally fit in 13A plugs)

Thank you, that's taught me a lot.

>Spot the pattern - it's easy to remember.

CSA x 10

I have a 25m lead from Wickes and IIRC it is 1.25mm^2, possibly
1.5mm^2 (it's cold and dark outside so I'm not going to check ;)). It
certainly is not 2.5mm^2 because as other posters have said, it
wouldn't fit a plug.

FIL has a massive 50m lead from Argos. Made by Masterplug possibly?
The cable is fat but I'm sure it's not that fat. Even if it was,
according to your table, even 2.5mm^2 would be too small anyway.

I saw some 2.5mm^2 flex in B&Q. I was surprised how wide it was and
also that they sold it. I can't imagine anyone who shops at B&Q
needing to buy some. Since it won't fit plugs, I guess it must be used
for fixed appliances. What would they be: cookers? I thought many now
just used 13A plugs.

Thanks again.

js.b1

unread,
Oct 24, 2010, 3:31:14 PM10/24/10
to
Consumer extension leads have often been very long and often a bit
"skimpy".

The reason is they expect people to use them on a hedge trimmer
(500-950W) or lawn mower or drill (900W), but pressure washers can be
quite a beefy load at the higher end of the market (1.7kW induction).

Welders on the other hand use the thickest cable they can afford.

For an IP44 inlet with a shield, search for "16A inlet" on www.ebay.co.uk
- there is a picture of a Mennekes with a spring loaded shutter to
keep rubbish out when not in use. Obviously, never ever connect an
inlet connector in such a manner that it can become live (just a
general comment).

Dave Osborne

unread,
Oct 25, 2010, 7:31:25 PM10/25/10
to
Fred wrote:
> On Fri, 22 Oct 2010 23:23:16 +0100, Dave Osborne
> <Dave...@SPAMymail.com> wrote:
>
>> You should have bought a CEEform plug/connector and terminated the
>> 2.5mm2 on the CEEform plug. You should then have made a short 13A plug
>> to CEEform connector with a piece of 1.25mm2 or 1.5mm2 flex.
>
> Thanks. I wasn't sure whether you could do this or whether you needed
> 2.5mm^2 for the whole length of the extension lead. I'm guessing it is
> permissible to use the 1.5mm to fit the plug because you are just
> using a short length, so not long enough to drop voltage or limit
> currents? Is that right?

Well the amount of voltage drop is a function of the current and the
length and is measured in V/A/m or voltes-per-amp-per-metre. So, if your
1.25mm2 or 1.5mm2 cable is very short, it's not going to drop much
voltage, even at max current.

>
> On the subject of these plugs, I've often wondered about fitting one
> of these wall inlets onto my house wall:
> http://cpc.farnell.com/pro-elec/is1023r/wall-mount-inlet-16a-240v-2p-e/dp/PL09779
> or
> http://cpc.farnell.com/pro-power/pe1663smb/wall-mount-inlet-240v/dp/PL08949
>
> On the other side I would connect it to a socket and if I had a power
> cut plug the boiler in one side and a cheap 2 stroke generator into
> the other. I've never got round to it because, touch wood, we've not
> had a power cut for a couple of years (cue a cut tomorrow).
>
> I'm sure CPC describe these as IP44. Now according to this:
> http://www.baseefa.com/filelib/IP%20Ratings.pdf
>
> the x4 means protection from water sprayed from all directions. I
> can't see how this is possible when the pins are exposed. Or does it
> only have ip44 protection when in use and coupled?

Only IP44 when in use and coupled, but as they're not live when they're
not connected, they don't need a lid (although you can get them with
lids): -

http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=3153236

Fred

unread,
Oct 31, 2010, 2:59:49 PM10/31/10
to
On Tue, 26 Oct 2010 00:31:25 +0100, Dave Osborne
<Dave...@SPAMymail.com> wrote:

>Well the amount of voltage drop is a function of the current and the
>length and is measured in V/A/m or voltes-per-amp-per-metre. So, if your
> 1.25mm2 or 1.5mm2 cable is very short, it's not going to drop much
>voltage, even at max current.


Thanks, I thought the short length was the key factor here. Andrew
Gabriel was talking about fault current, does the fact that you have
used 1.5, even for a tiny length, affect fault current and the maximum
length of flex?

If you have a very long lead such that you are concerned about fault
currents, is there any way to make things safer (other than use a
fatter cable or install a permanent socket)? Would plugging an RCD in
the distant end of the lead, i.e. where you are using the tool, help?

>Only IP44 when in use and coupled, but as they're not live when they're
>not connected, they don't need a lid (although you can get them with
>lids): -

Thanks, that explains it. I'm not sure I'll ever get round to it
because I couldn't put a genny the other side of the boiler because
that would be in the car port and though one side is open, I imagine
it would accumulate deadly exhaust fumes, so I'd have to move it
further away and then we come back to issues of cable length and
earthing and all these complications and us not having many power cuts
are the reason I haven't done it yet!

Thanks again.

Tabby

unread,
Oct 31, 2010, 3:34:00 PM10/31/10
to
On Oct 31, 6:59 pm, Fred <f...@no-email.here.invalid> wrote:
> On Tue, 26 Oct 2010 00:31:25 +0100, Dave Osborne
>
> <DaveyO...@SPAMymail.com> wrote:
> >Well the amount of voltage drop is a function of the current and the
> >length and is measured in V/A/m or voltes-per-amp-per-metre. So, if your
> >  1.25mm2 or 1.5mm2 cable is very short, it's not going to drop much
> >voltage, even at max current.
>
> Thanks, I thought the short length was the key factor here. Andrew
> Gabriel was talking about fault current, does the fact that you have
> used 1.5, even for a tiny length, affect fault current and the maximum
> length of flex?
>
> If you have a very long lead such that you are concerned about fault
> currents, is there any way to make things safer (other than use a
> fatter cable or install a permanent socket)? Would plugging an RCD in
> the distant end of the lead, i.e. where you are using the tool, help?

yes against L-E faults, but not against L-N faults.


> >Only IP44 when in use and coupled, but as they're not live when they're
> >not connected, they don't need a lid (although you can get them with
> >lids): -
>
> Thanks, that explains it. I'm not sure I'll ever get round to it
> because I couldn't put a genny the other side of the boiler because
> that would be in the car port and though one side is open, I imagine
> it would accumulate deadly exhaust fumes, so I'd have to move it
> further away and then we come back to issues of cable length and
> earthing and all these complications and us not having many power cuts
> are the reason I haven't done it yet!
>
> Thanks again.


I dont recall you giving details of length, load etc, maybe you did.

Picking/designing your overload protection to suit the lead can make
all the difference.


NT

Fred

unread,
Nov 1, 2010, 4:58:05 AM11/1/10
to
On Sun, 31 Oct 2010 12:34:00 -0700 (PDT), Tabby <meow...@care2.com>
wrote:


>I dont recall you giving details of length, load etc, maybe you did.

No, I didn't. I don't have a particular application in mind. I only
have a small garden so I don't really need to worry about cable
length. I'm guessing I'd wouldn't need anything over 5m, if that,
here. I just found comments on another thread interesting and wanted
to learn more, which thanks to the replies here, I have. Thanks again.

Dave Osborne

unread,
Nov 1, 2010, 2:47:54 PM11/1/10
to
Fred wrote:
> On Tue, 26 Oct 2010 00:31:25 +0100, Dave Osborne
> <Dave...@SPAMymail.com> wrote:
>
>> Well the amount of voltage drop is a function of the current and the
>> length and is measured in V/A/m or voltes-per-amp-per-metre. So, if your
>> 1.25mm2 or 1.5mm2 cable is very short, it's not going to drop much
>> voltage, even at max current.
>
>
> Thanks, I thought the short length was the key factor here. Andrew
> Gabriel was talking about fault current, does the fact that you have
> used 1.5, even for a tiny length, affect fault current and the maximum
> length of flex?
>

Not really.

Table 4F3B of the wiring regs gives the following voltage drops for
flexible cords:

CSA (mm2) Volt Drop (mV/A/m)

1.25 37
1.5 32
2.5 19
4.0 12

Let's say your load current is 5 Amps.

The volt drop of 25m of 1.5 is 32mV/A/m x 5A x 25m = 4000mV or 4V.
The volt drop of 25m of 2.5 is 19mV/A/m x 5A x 25m = 2375mV or 2.375V

Now, if we make up the 2.5 extension in industrial connectors and have a
0.5m adapter cable in 1.5mm2 the volt drop is increased by only 80mV.

32 x 5 x 0.5 = 80mV = 0.08V

Giving a total volt drop of 2.375V + 0.08V = 2.455V.

So you see a short length of 1.5 makes hardly any difference.

Fred

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Nov 10, 2010, 4:34:23 AM11/10/10
to
On Mon, 01 Nov 2010 18:47:54 +0000, Dave Osborne
<Dave...@SPAMymail.com> wrote:

>
>So you see a short length of 1.5 makes hardly any difference.

Thanks very much.

Dave Plowman (News)

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Nov 10, 2010, 5:10:25 AM11/10/10
to
In article <5serc6lv264ntr0q3...@4ax.com>,

Fred <fr...@no-email.here.invalid> wrote:
> If you have a very long lead such that you are concerned about fault
> currents, is there any way to make things safer (other than use a
> fatter cable or install a permanent socket)? Would plugging an RCD in
> the distant end of the lead, i.e. where you are using the tool, help?

The way it's done for location filming where you're getting power from
normal 13 amp sockets in say a house for lighting etc, is to use a short
13 amp to 16 amp tail (with RCD) using 1.5mm TRS, and then a 2.5mm TRS
extension lead. With a 16 amp to 13 amp tail at the other end if needed.
I can't remember how long that main extension can be and still comply, but
it's probably enough for most things. On a large rig you'd use a
generator, and run out distribution points.

--
*Who is this General Failure chap anyway - and why is he reading my HD? *

Dave Plowman da...@davenoise.co.uk London SW
To e-mail, change noise into sound.

Fred

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Nov 14, 2010, 3:09:17 PM11/14/10
to
On Wed, 10 Nov 2010 10:10:25 +0000 (GMT), "Dave Plowman (News)"
<da...@davenoise.co.uk> wrote:

>The way it's done for location filming

Thanks. That sounds an exciting way to make a living, how did you get
into that? I thought it was hard to get into film and tv, or is that
only if you want to be the other side of the camera?

Dave Plowman (News)

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Nov 14, 2010, 6:20:18 PM11/14/10
to
In article <jdg0e6dtarbddnhtg...@4ax.com>,

Like any job you find out about it first. Plenty of low paid jobs around
to start with - but not everyone's cup of tea because the hours can be
long and anti-social.

It may sound exciting but in practice it tend to be lots of hanging around
followed by periods of frenzied activity.

I did enjoy my career, though. Not sure I'd go into it these days. The
salad days were when TV was made by enthusiasts at all levels - not just
another business controlled by accountants.

--
*In "Casablanca", Humphrey Bogart never said "Play it again, Sam" *

Fred

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Nov 20, 2010, 11:20:17 AM11/20/10
to
On Sun, 14 Nov 2010 23:20:18 +0000 (GMT), "Dave Plowman (News)"
<da...@davenoise.co.uk> wrote:

>It may sound exciting but in practice it tend to be lots of hanging around
>followed by periods of frenzied activity.

I guess even brain surgeons get bored of doing the same thing every
day though.

>I did enjoy my career, though. Not sure I'd go into it these days. The
>salad days were when TV was made by enthusiasts at all levels - not just
>another business controlled by accountants.

Too true. Too many "talent" shows now where the accountants are more
interested in the money they can make from the phone lines that the
channel's output.

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