30m long mains extension cable trips fuse

[Kleinstein]

Induction motors may draw more current when the voltage drops. As an additional effect the motor may not even start proper. Especially compressors have this problem with a long extension cord.

[Monkeh]

Shoving 10A down a 30m lead is asking for trouble. A 13A socket can't necessarily provide 13A safely, see makers advice.

Then it's not BS1363 compliant and can't be on the market. Stop buying garbage from the poundshop.

from the 30m long extension cable, only 10m cable is extended from the base, and the rest of the cable is in wound state.

Don't do that. If you don't need the 30m, just don't use it.

[vinlove]

British ring main wiring!  The BS1363 plugs have max. 13A fuses but the ring main feeding the sockets is typically fused (nowadays with a breaker) at 32A.  Its also possible to have radial circuits fused (breakered) at 16A feeding BS1363 sockets, but they are far less common.  However both are rated for more than a BS1362 13A fuse, which is *supposed* to provide discrimination such that the distribution panel fuse doesn't blow if an appliance shorts out.  Nowadays with circuit breakers in the panel, discrimination is much less reliable and near non-existant on 16A circuits, though admittedly its much less of a PITA to reset a breaker rather than having to replace a fuse cartridge or rewire a fuse.

yes, I seem seeing it now with some parts to delve into more.  The most wall mains sockets in UK residential properties are rated at 32A I think especially for the electric cookers, storage heaters and even washing machines. So they will never blow fuses. They don't even have fuses.  They can trip the breaker when installed with the breakers.

[bingo600]

I have a 25m rool/spool of 230v extension cable.

When using with high power utils (1000+ Watt)  - I always make sure to unrool all of it.
Was once told about possible inductive kickback, if not doing that.

I'm no EE or Electrician , but i can run my devices wo. fuse blowing (10A).
I think 1800W is the max i have loaded it with.

[vinlove]

I have a 25m rool/spool of 230v extension cable.

When using with high power utils (1000+ Watt)  - I always make sure to unrool all of it.
Was once told about possible inductive kickback, if not doing that.

I'm no EE or Electrician , but i can run my devices wo. fuse blowing (10A).
I think 1800W is the max i have loaded it with.

Yes, I was suspicious of this effect of the rolled cable inductance play up when used with high current device pulling lots of currents through it.
I was not sure how it affects, and why in theory.

[themadhippy]

  Its also possible to have radial circuits fused (breakered) at 16A feeding BS1363 sockets, but they are far less common.

Ring finals are slowly going out of favor with  A2 (4mm cable and  32A breaker )and A3 (2.5mm 20A) becoming more popular.A3 especially so for low demand areas  like bedroom and living area  sockets ,and keeping the ring for kitchens with its higher demand also no need  to buy a drum of 4mm.

The most wall mains sockets in UK residential properties are rated at 32A

A standard BS1363  double socket to is only designed for maximum load of 20A

[Zero999]

I have a 25m rool/spool of 230v extension cable.

When using with high power utils (1000+ Watt)  - I always make sure to unrool all of it.
Was once told about possible inductive kickback, if not doing that.

I'm no EE or Electrician , but i can run my devices wo. fuse blowing (10A).
I think 1800W is the max i have loaded it with.

Yes, I was suspicious of this effect of the rolled cable inductance play up when used with high current device pulling lots of currents through it.
I was not sure how it affects, and why in theory.

The cable should be unwound before using, especially to the full rating, but I repeat: it's got nothing to do with the inductance. As I said before, the currents in the neighbouring conductors flow in opposite directions, thus causing the magnetic fields to cancel each other out. Even if you put the live through one extension lead and the neutral through another (don't do this, it's a bad idea, it's just a thought experiment), so the fields don't cancel, the inductance would have a similar effect at 50 to 60Hz, as the resistance of the cable: a couple of mH inductance will have an impedance of just under an Ohm, similar to the DC resistance. The reason for this is because there's no magnetic core. This is why all transformers and inductors designed to work at mains frequencies have magnetic cores. Also note that inductance doesn't result an any power dissipation.

The reason for unwinding the cable is purely thermal. A tightly wound coil concentrates the power dissipated due to I²R losses in the cable, into a small space. The cable in the middle of the coil, doesn't have air circulating around it to provide convective cooling and any radiated heat is absorbed by a neighbouring turns, causing them to heat up more. When the cable is unwound, the heat can escape more easily due to better air circulation and the heat is able to radiate out into space more easily.

The bottom line is, a tightly coiled cable will heat much more, than an unwound cable, given everything else (current, length, conductor size) being equal. The temperature rating of the insulation will be exceeded, if it's not designed to work at full power, when coiled up, which is the case for all extension leads made.

Suppose the total resistance of the cable is 1 Ohm* and the current is 12A, P = I²R, so that's a power dissipation of 144W, more than an old school 60W light bulb and a bit more than a slow cooker. Imagine the difference in temperature rise, when that heat is concentrated in a small area, compared to spread out over a large one.

*Based on 60m (the total length of the live + neutral in a 30m run) of 1.25mm² cable rounded up, given it's specified at 20^oC and the cable will get heat up.
http://www.farnell.com/datasheets/1805062.pdf