Workshop Wiring - Circuit advice

[M@tt]

Right i'll be rebuilding my shed/carport into a garage/workshop shortly. I'm aware of Part P and all that guff so we don't need to get into that this is purely a circuit design question.

The shed curently has power run to it wired from the house CU on a 40amp breaker it's run by some chunky T+E through some plastic tubing buried in the ground but i'm going to replace that with some proper SWA. I believe 3 core 4mm will be sufficient for my needs out there. (rated at 42 Amps according to http://www.tlc-direct.co.uk/Products/SW4slash3.html)

The bit i could do with some advice is regarding the circuit ratings. I've currently got a 2 way CU in the shed again witha 40amp main RCD??(can never remember the right acronym) then a 16 amp MCB for sockets and a 6amp MCB for lighting.
I'm running a compressor, a welder (Clarke 160) and various power tools. On occasions the compressor will cause the 16 amp circuit to trip if other stuff is on at the same time when it tries to fire up.

I'm thinking i should prehaps fit a new CU (4way) in the workshop with a dedicated 16amp/32amp? circuit for the welder, another 16amp/32amp for the compressor and then the rest of the wall sockets on a 16amp breaker and the lights again on a 6amp.

I was going to fit 2x16amp wall sockets 1 for the welder and 1 for the compressor and replace their current 13amp plugs with the blue 16amp jobbies.

What do you reckon??

Cheers

 

[brightspark]

run the armoured from the house in 6.0mm cable to 4 way db in garage . use 1 circuit for lighting 6 amp . run some 4.omm cable to a 30 amp socket fed from a 30 amp fuse .run some 2.5 cable to a 16 amp socket fed from 16 amp fuse .then a few of 13 amp sockets fed of a 2.5mm cable radial suply of either a 16 amp fuse or a 20 amp max.. if the welder or the comp is run at over 16 amp eg at 20 amp the 30 amp sockets must be used

 

[GrahamGKD]

Matt,
I see Brightspark has got in before me - you have to be quick around here!

Posting this anyway since I've already composed it....

Fist off - I'm not a sparky - I have researched some of this stuff though! Your plan sounds OK to me.

Presumably you have used the calculator on the TLC site and have taken account of the length of cable run for the SWA? If it comes out marginal I would tend to err on the heavier side to reduce the voltage drop.

My understanding is that it is permissible to run a string of 16A sockets on 2.5mm cable (probably depends on cable run length) back to a 16A MCB.

You don't specifically include this in your proposal but my understanding is that each of the bigger 32A sockets have to be on their own circuit and back to a separate 32A MCB. Again depending on cable length, you would need 4mm cable for this.

You might want to think about the slower tripping 'C curve' MCBs for the 16A circuits.

Hope this helps.

Graham.

 

[brightspark]

Matt,
I see Brightspark has got in before me - you have to be quick around here!

Posting this anyway since I've already composed it....

Fist off - I'm not a sparky - I have researched some of this stuff though! Your plan sounds OK to me.

Presumably you have used the calculator on the TLC site and have taken account of the length of cable run for the SWA? If it comes out marginal I would tend to err on the heavier side to reduce the voltage drop.

My understanding is that it is permissible to run a string of 16A sockets on 2.5mm cable (probably depends on cable run length) back to a 16A MCB.

You don't specifically include this in your proposal but my understanding is that each of the bigger 32A sockets have to be on their own circuit and back to a separate 32A MCB. Again depending on cable length, you would need 4mm cable for this.

You might want to think about the slower tripping 'C curve' MCBs for the 16A circuits.

Hope this helps.

Graham.

right 1st time dont run on the borderline go the next size up hardly any difrence in price

 

[GrahamGKD]

Thanks Brightspark - always good to know I'm not talking b*ll*cks!

 

[M@tt]

cheers gents!!

My Clarke 160TM says in the manual (http://www.clarkeservice.co.uk/manuals/mig_welders/mig160tm.pdf) its primary power is 16amps so i'm guessing a 16A socket is good for it, along with a 16A MCB (is it best to go for B or C type breaker??)

My SIP Airstream 3hp compresso r(http://www.alexander-mills.co.uk/sip/compressors/airstream1.jpg) says its 15amp so again i'm guessing a 16A socket and dedicated circuit with 16A breaker is the way to go (with probably a C type breaker to allow for startup surge??)

i'll get up Newey and Eyre this lunchtime then

 

[GrahamGKD]

...personally, I'd choose the 'C' MCB for both.

 

[M@tt]

oh another thing

i've just thought if i wanted to fit several 16A sockets on the welder circuit down either side of the workshop so that i can move the welder around as needs be without running a long extension lead would the circuit need to be a ring or just a normal daisy chained effort? The welder will only ever be plugged into 1 of them at a time

 

[GrahamGKD]

Matt,
The info I found on this (which may not have been the latest 17th edition regs) suggested that a string of sockets or spur is the way to go, as opposed to a ring.

Reasoning this out - when you use a ring for normal 13A sockets the circuit is protected by a 32A MCB and the current draw from any one socket is limited to 13A. In your case, with the 16A sockets, there is no fuse in the plug/socket but you can only draw a total of 16A from the circuit because the circuit is back to a 16A MCB.

Graham.

 

[M@tt]

brilliant cheers Graham

I've just been out at lunch and picked up 25m of 6mm 3core SWA (£1.95+vat/m) from a place just up the raod although it was cheaper from Newey & Aire (£1.79+vat/m) but they were quite a bit further away (thought it might be useful if other people are searching to see what prices are available)

I also got 6x 16A IP44 wall sockets from Toolstation £3.98(here)

 

[seriesonewelder]

Matt,
The info I found on this (which may not have been the latest 17th edition regs) suggested that a string of sockets or spur is the way to go, as opposed to a ring.

Reasoning this out - when you use a ring for normal 13A sockets the circuit is protected by a 32A MCB and the current draw from any one socket is limited to 13A. In your case, with the 16A sockets, there is no fuse in the plug/socket but you can only draw a total of 16A from the circuit because the circuit is back to a 16A MCB.

Graham.

As I understand it (I'm currently re-wiring my garage) a seperate breaker/circiut is required for each 16amp socket. Can a pro' sparky confirm Please.

 

[brightspark]

As I understand it (I'm currently re-wiring my garage) a seperate breaker/circiut is required for each 16amp socket. Can a pro' sparky confirm Please.

3 or 4 sockets can be run on a radial using 2.5mm cable using a 16 amp mcb. the cable is rated to 20 amp so not a problem so even if a few were being used at once it would only trip the breaker and not damage anything else

 

[seriesonewelder]

3 or 4 sockets can be run on a radial using 2.5mm cable using a 16 amp mcb. the cable is rated to 20 amp so not a problem so even if a few were being used at once it would only trip the breaker and not damage anything else

Thank You

 

[M@tt]

legend!!

cheers BS & Graham