On internet, where can I find a table that lists the current,
in ampers, that given flex wire can carry ? Specifically, I'm
interested in amps rating for 2x1.5 sq.mm. and 2x2.5 sq.mm
(220V). I tried to google no luck so far.
There's many such ratings and you'll have to determine what you want.
Google for "fusing current" to find one extreme.
Actual current in an application depends on ambient temperature,
conduit and another conductors in the conduit, wire insulation,
insulation type, desired life of insulation, etc.
If the wire is wound into coils (like for a motor or resistor or
inductor) then geometry becomes crucial.
1.5sq mm wire seems to be about like 22 gauge which is sometimes
optimistically rated for 5 amps (it will be getting warm at that
As Tim says,there are many ratings for any given cable - see section 4
However for a rule of thumb in domestic installation, cables burried in
plaster or clipped to joists and not covered by insulation 1.0sq is
rated at 15amps, 1.5sq at 20 amps and 2.5 at 27 amps.
Standard radial circuits usually fuse 1.0 at 5 or 6amps ,1.5 at 10 or
15 amps and 2.5 at 20amps. Ring circuits in 2.5 are usually fused at
Contrary to Tim's post 1.5sq is a litttle larger than 16swg.
Also, in the case of an extension cable, beware of max length
due to earth fault loop impedance. In the case of an extension
cable fused at 13A, that is 15m for 1.5 mm² and 25m for 2.5 mm².
Any longer than these values and you need to ensure the cable
is protected by an RCD, or reduce the value of the fuse
protecting the cable proportionally below 13A.
And the larger sizes of cable won't go in a 13A plug anyway (unless you
terminate the sheath short of the plug, a naughty wicked sinful and
depraved technique used only by hacksaw-wielding plantpots and building
Oh dear. Does that mean that the 30m extension lead that I made
for the electric lawn mower has significant electrical risks? Naturally
I used a properly sealed connector to "puddle-proof" the joint between
the cables (I can't remember the IP rating of the connector, but it was
suitable for regular immersion to a couple of metres, but not for
diving with. I'd have to cultivate an ROV technician to obtain higher
ratings. Which could be done.). The cost of a 30 or 50m reel of mains
flex at B+Q was considerably higher (as in, times several) than the
cost of 2 X 15m extension leads.
The risk is what? That in the event of a fault at the remote
socket, current travelling back down the earth line will raise the
potential of the remote end of the earth (Ohms Law), which leaves the
person at the remote end holding something live while standing in a
90% of the time I remember to plug the extension lead into an
RCD through-plug before I take the lawn mower out of the cellar. Maybe
I'd better tie-wrap or gaffer-tape the extension lead and RCD together
to make it 100% (including when the wife/ daughter does the lawn while
Possibly -- it depends on a lot of things.
Also, quite apart from the earthing problems with long cables,
you might be dropping a significant proportion of the mains
voltage across the cable when the mower is running. Most electric
mowers use cheap universal motors which won't mind this too much,
but better quality mowers use induction motors, which don't like
running at reduced voltage on-load (could overheat).
Yep -- you would do better at an electrical wholesaler for that.
(Conversely, they'll charge much more for the extension leads;-).
Yes. Also the resistance of the long conductors will reduce the
fault current which flows so it takes significantly longer to
blow the fuse (or in really bad cases, might not blow the fuse
Better still, mount an RCD-protected socket outside, so you are
always going to use an RCD protected supply outdoors. (I would
suggest using a separate RCD and socket, with the RCD mounted
inside in the dry, and a plain waterproof socket outdoors. That
way, if moisture does get into the outdoor part which it often
does eventually, you don't also write off an expensive outdoor
But in the lawnmower context, (a) the mower will almost certainly be a
Class 2 (double insulated) appliance so it won't rely on earthing, and
its metal frame won't rise in voltage relative to the ground during a an
earth fault should you mow through the 3-core cable: (b) the extension
lead should be plugged into an RCD-protected socket, so the earth fault
loop impedance issue becomes largely irrelevant, provided that the earth
isn't completely o/c. If the house electrical installation is old and
doesn't have RCD-protected sockets then use an plug-in RCD adaptor, as
We don't know what cable size was used - but 30 m of 1.0 mm^2 flex will
only be just over 1 ohm and I can't see that causing too much in the way
of problems. In 0.75 mm^2 though things will be getting rather marginal.
I don't remember if the B+Q tags said what the conductor size was.
But Mr Multi-meter says the conductors are 0.5, 0.7 and 0.8 ohms, so I'd
guess it's 1mm.sq.
Where's my roll of gaffer tape? Well, it wouldn't pass muster for
offshore use, but it's a good enough fix for me.
Electrical sockets outside the house are a total insanity here.
If they didn't get stolen they'd get broken as punishment for not being
I plug the RCD into an internal socket and put the extension
lead out the window to the garden. If the weather is too bad to have
the lead running out of the window, then it's too bad for drilling
burglar alarms into the wall or mowing the lawn. Can't think of any
other credible reason for wanting power out in the garden.
If I were to get permission from SWMBO for a greenhouse/ shed,
then I'd provide it with a trenched power supply from an RCD at the
consumer unit. KISS.
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