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Bob UK
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Posted on Friday, 16 January, 2015 - 11:09 am:   Edit PostDelete PostView Post/Check IP

30amp at 240v is 7.2kW. This is ample. My supply comes direct from my house fuse board. It has a dedicated 30amp fuse. The cable is 6mm square twin and earth intended for electric cookers.

In the work shop is a 4 way fuse box with an earth leakage circuit breaker and main switch.

The cable earth is bonded to a copper Water pipe. Then the earth goes to the earth bar in the fuse box.

The first fuse is lights and 5amp the switch is a double and 4 x 40w tubes on each switch. 8 tubes total. Not 60w as I first thought.

Second fuse is 10amp compressor.
third is lathe and pedestal drill.

Fourth is the ring main for wall sockets. The fuse is 20 amp, this goes to a contactor, then to the wall sockets then back to the contactor. The sockets are fed from both ends. Plus a spur can be added with one double only. This is safe up to 45 amps, and is fused at 20amps. The contactor has a big red button which turns off all sockets.
The plugs used in the wall sockets are fused. I fit the lowest possible fuse. A soldering iron has a 1 amp fuse. Small hand drill 3 amp.

To fix the wiring and sockets I put a 3" wide 3/4 thick pine at 4.5 ft from the floor along the walls. This also supports a 4" wide shelf. The wiring is clipped underneath the shelf with the sockets which gives protection.

Wire gauge for lights 1mm square twin and earth. The rest is 2.5mm squared twin and earth. All the earths are connected together in the fuse box.

The wood is easy to clip to and screw sockets to. Two double sockets on each wall. Socket not in correct place? Just fit another.
The idea is that most of the sockets will not be used at the same time so you can fit more without it being unsafe.

This allows stuff to be moved and wired in safely and quickly.

In the UK doing the above is legal but it must be check by a sparks who sign it off.

So when doing this work it's important that you follow code. The code is straight forward for single phase man cave and obvious.

If the code says 12" for clips then 12" it is. It's that simple.
The code changes often. It is not applied retrospectively. Once installed to the current code ( pun intended) that's it. So Google the code. I only check when I need to so I forget details. The main thing sparks like to see is logical tidy straight wiring runs. Not a plate ful of spaghetti hanging out of the fuse box. They don't like diagonal runs. Also label fuses and use plastic yellow green sleeve on all earth wires and fit safety earth tags. All cheap stuff.

The cooker cable contactor and fuse box aren't cheap. A contactor is about 50 and fuse box 100. The rest is cheap, double light switch is 3 a double socket 4. I get trade packs. Second hand fluorescent fittings turn up regular in surplus shops. I got 5 4ft fittings with tubes and starters for 20. For a double garage budget 300 for the system.

The fuse board is near the door and simply pull main switch on the fuse box. So whatever has been forgotten is now dead and can't set a fire.
(The Cutty Sark fire was caused by a vacuum cleaner left running all week end.)

All available on the web.

Note if you hide the wiring it looks neat but is extremely difficult if alterations are needed and very disruptive.

It a man cave not a lounge.

Earth leakage circuit breaker.
This monitors the amps in the neutral line and live line. The amps should be the same if the neutral amps is lower then some of the amps is leaking to earth.

The earth could be a person. The breaker will drop out instantly often before anybody touches anything. They reckon that if I touch a live in my cave the breaker will drop before I get a shock. I am not going to try it out.

My breaker cost 80 extra but they are now cheaper.

Incidently on electric cars the battery is around 300 volts. The battery isn't earthed to the car. This means the 300v is floating. This means that one can touch the positive terminal without feeling a thing. However if even a slightest hint of the negative terminal earthing to the ground and you get a shock.

Please don't try it.

In the OZ outback they had a single line supply at 20kv no earth or neutral. The return is the actual ground one stands on.

Just out side Town is a substation. The transformer drops the volts down to plus 120 and minus 120v with a neutral at 0v. Houses get 120v single phase and factories get 240 two phase. The two phases are 180 apart. The houses and factories return is the neutral and there's a safety earth to the substation. The substation earth is a big copper spike buried in potash.
The primary windings of the transformer are connect to the 20kv And the earth spike. The secondary windings which supply the customers has a centre tap, this is connected to the earth spike. This is both earth and neutral. Each end of the secondary windings is the two phases. The volts in the primary is single phase. I believe the USA has a similarity system in houses. For heavy loads they grab the minus 120v line and go 240v for dryers etc. This has advantages because a kid mucking with a table lamp get a nasty bite not thrown across the room on 240v.

It you stand to close to the substation you can get a mild shock. It you spread your feet very wide the shocks worse.
This is because the ground has resistance and the potential difference is greater the further the ground contact points are apart. So if on awalkabout don't ignore the danger high voltage keep back signs.

Its perfectly safe just keep away. Especially in wet weather.
This system is a cost effective way of transmitting power to remote places.
Very clever electrical design.
Wikipedia explains it better.

(Message approved by david_gore)

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