Workshop wiring
- Thread starter RichD1
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You can have as many sockets as you like ON a radial circuit.
Thats like asking "how fast can a car go?"
You can have 500 sockets if you like, but what you really need to know is how much current you can draw in total from the sockets if they were all being used for things.
The amount you can draw in total will be limited by the protective device protecting the sockets circuit in the outhouse, and the protective device protecting the cable that connects the house to outbuilding.
I guess that there is a consumer unit in the outbuilding and another in the house?
What is the value of the protective devices in each relating to this circuit?
You can have 500 sockets if you like, but what you really need to know is how much current you can draw in total from the sockets if they were all being used for things.
The amount you can draw in total will be limited by the protective device protecting the sockets circuit in the outhouse, and the protective device protecting the cable that connects the house to outbuilding.
I guess that there is a consumer unit in the outbuilding and another in the house?
What is the value of the protective devices in each relating to this circuit?
40A MCB in the house and intending to have 2 x 32A in the workshop, each running a radial, down each side wall. Probably with 4 x double sockets on each radial.
Though this might appear to be likely to create an overload situation, I can only use one piece of woodworking equipment at a time. I've worked out that using my biggest machine a table saw and dust extractor, some lighting and a 1.5kW heater, max current draw will be around 21 amps.
Richard
Though this might appear to be likely to create an overload situation, I can only use one piece of woodworking equipment at a time. I've worked out that using my biggest machine a table saw and dust extractor, some lighting and a 1.5kW heater, max current draw will be around 21 amps.
Richard
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The MCB/fuse/RCBO has to match the cable and device supplied so using 4mm² cable clipped direct feeding 13A sockets from a B32 MCB is OK but using 2.5mm² cable it would not be permitted or feeding a 15A socket it would not be permitted.
Also volt drop and earth loop impedance also need considering a B32 MCB should have am ELI better than 1.44Ω use a C32 MCB then half that value 0.72Ω however with a RCD could raise to 200Ω so selecting is not that easy.
The ring has an advantage of reducing the ELI and allowing smaller cable which fits our 13A sockets with ease. In the main with radials we reduce the MCB size to 20A which in turn allows use of 2.5mm² cable and increases the ELI to 2.3Ω.
I think you have looked at it too simply and have not taken all into consideration. You can have as many 13A sockets as you wish if the protective device is correct size.
Also volt drop and earth loop impedance also need considering a B32 MCB should have am ELI better than 1.44Ω use a C32 MCB then half that value 0.72Ω however with a RCD could raise to 200Ω so selecting is not that easy.
The ring has an advantage of reducing the ELI and allowing smaller cable which fits our 13A sockets with ease. In the main with radials we reduce the MCB size to 20A which in turn allows use of 2.5mm² cable and increases the ELI to 2.3Ω.
I think you have looked at it too simply and have not taken all into consideration. You can have as many 13A sockets as you wish if the protective device is correct size.
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Although historically there have been restrictions as to the floor area covered by the circuit.
50 square metres: 20A
75 square metres: 30/32A
And this will ultimately limit the final number.
50 square metres: 20A
75 square metres: 30/32A
And this will ultimately limit the final number.
I was intending to use C32 as there are induction motors on table saw and planer/thicknesser. Wiring to be 2.5 T&E.
Are you saying this would not be OK? Better to make a ring?
The feed from the house is 6mm T&E. Only RCD will be in the main house CSU.
Richard
Are you saying this would not be OK? Better to make a ring?
The feed from the house is 6mm T&E. Only RCD will be in the main house CSU.
Richard
You need an electrician to design and install this properly for you.
What you are proposing is all wrong.
What you are proposing is all wrong.
If you are using 2.5mm T&E on a 32A breaker then it must be a ring final. It's not a case of "better".
Personally I would not have the RCD in the house as a fault will trip the house including your freezer, computer, boiler, etc. Better to have the 40A on a non RCD part of the house CU and have an RCD as the main switch in the outbuilding.
Better not to have an RCD main switch in the outbuilding as a trip will knock out the lighting instantly but power tools will still be spinning down.
Owain, the same would occur anywhere that an RCD is used, in this scenario.
The only way to avoid the situation that you envisage would be to use RCBOs on every circuit in the outbuilding.
The only way to avoid the situation that you envisage would be to use RCBOs on every circuit in the outbuilding.
Or fit some EM lighting in the garage
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