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larger than 100sqm main circuit

Postby wildtypitch » Fri Dec 28, 2007 10:08 am

Thanks for all the advice I've read so far, a great help.

I want to install a mains circuit in a room 250sqm large. Idealy i want sockets running down each long side (18m each). I would get a qualified electrician in but for one thing. I'm a brit in China, the wiring and electricians here are completely untrustworthy.
It's 220v over here like the UK but plugs do not come with fuses, so I guess that means I can't use ring mains circuits safely. Will two radial circuits the larger being 30-40m in length (across two sides of the space due to CU location) be safe with 4sqmm wiring with a 20 amp mcb ?
The space is a workshop so I will be using some demmanding equipment.
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Postby ericmark » Fri Dec 28, 2007 4:21 pm

Since you are in China rules may be different but safety wise you can't fuse over the size of plugs and sockets if they do not have fuses in them so if 16 amp then max fuse size is 16 amp. Also volt drop is the main problem with long runs 16th edition has tables giving this for example 2.5mm single phase is 19mV/A/m so at 16 Amp and 9.2 Volt drop (UK Limit) gives about 30 meters of cable max. 4mm is 12mV/A/m so that will allow 48 meters. Earths abroad can be a big problem depending on ground and rainfall etc. Don't know what type of workshop but power track with fuses in plugs on ceiling may be worth looking at? It may also reduce trip hazards? I know Hong Kong had a complete mixture of systems I expect the rest of China is the same. China light and power even checked our systems so I expect they may also test yours so may be better with local advice.

All best Eric

Postby sparx » Mon Dec 31, 2007 7:41 pm

Hi, as previously stated other parts of the world work to differing standards but a 4mm @ 20A load over say 40m would drop 8.8volts, just in for UK, & we do go a bit OTT on side of safety here.....
regards SPARX
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