3 x Twin & Earth In 20mm Conduit

[JohnD]

I suppose you use conduit for neatness and slight impact protection?

If you decide the conduit is too tight, look at mini-trunking. It's neat and much easier to install, because the top cover clips on and off. You can have one run for each cable, so no bunching.

As you can easily open it for access, it's simple to add an extra socket or something part way along.

 

[ericmark]

Eric, there is no mention 20amps anwhere. It's fed from a 32A MCB. I think you know that a 32A type B MCB will pass 46A continuously without tripping.


each cable is still passing that current though and due to its resistance will dissipate heat. So the currents DO add. If they didn't, then a coiled extension lead with a 3kW fan heater on the end would never burst into flames.

That said, I see nothing wrong with what he has either.

You are looking at induction linking or transformer effect with a coiled extension lead, since a 10.5 kW shower at 230 volts will draw 45.66 amp if what you say is correct it would never trip a 32 amp MCB, but they do in fullness of time, it will not trip straight away, but will trip when a woman is washing her hair.

What I have questioned is what reduces the 32 amp supply to a supply below the capacity of 2.5 mm² cables? Some thing is missing, garage CU, FCU, larger than 2.5 mm² to garage, and if latter how is lighting supply reduced to 16 amp?

 

[davelx]

45.66 amp if what you say is correct it would never trip a 32 amp MCB, but they do in fullness of time, it will not trip straight away, but will trip when a woman is washing her hair.

Fig 3A4 PAGE 370. Read the curves.

 

[ericmark]

10,000 seconds is 2.8 hours so yes a long time, maybe women don't wash hair for quite that long, but I know with 16 amp MCB when the load was 20 amp they did trip, I made a mistake, 25 x 60 watt fluorescent at 110 volt I though 13.63 amps, however in real terms it was around 20 to 21 amps. And the lighting in the tunnels tripped. OK not straight away, but it did trip, and the basic idea is the trip will open before the cable over heats, and cable also takes time to heat up, so it trips before cable is damaged if correctly selected.

 

[ScubaCollie]

Hi All thank you very much for all your input much appreciated.

There's a lot of information and figures in the above, however it appears that what I've done is OK and I can leave as is and don't need to do anything else to it?

Or should I be ripping all the cable out of the conduit and strip the outside protective sheath and reinstall the wires as individual?