Wiring up home workshop

[Sideways]

You probably know that if the extension comes on a reel, uncoil every inch of it and spread it about a bit if using anywhere near its rated power

Especially if you are providing the extension reel so your granny can sit on the sofa with a 3kW electric fire at her feet.
The worst offenders of them all are high power long duration appliances like heaters. Rolled up extension leads get stinking hot, soft and floppy if you forget to unroll them.

 

[Dabop]

Weird, your UK standards allows a higher current from a standard wall outlet/powerpoint than the AU/NZ ones (13A against only 10A) and yet restricts the cable size to only 1.5mm against our 2.5mm (or larger- Au/MZ has no size restrictions on the cable so if you could get a 3mm or larger cable that physically fits and is properly rated and secured, then alls good, go for it lol)

:-O

In fact heaters and other 'long duration' loads like that- it is a VERY common thing for warnings to say to AVOID such small cables as 1.0mm or 1.5mm as being dangerous and prone to overheating, always use a 'heavy duty' extension cord....

 

[Sachakins]

Weird, your UK standards allows a higher current from a standard wall outlet/powerpoint than the AU/NZ ones (13A against only 10A) and yet restricts the cable size to only 1.5mm against our 2.5mm (or larger- Au/MZ has no size restrictions on the cable so if you could get a 3mm or larger cable that physically fits and is properly rated and secured, then alls good, go for it lol)

:-O

1.5mm is only for lighting vircuits over here. Sockets are 2.5mm T&E minimum for 13 amp. Electric cookers and some electric showers are 4mm or 6mm.

Just had a EV 7.6kw charger fitted, at 6mm cable.

 

[Dabop]

1.5mm is only for lighting vircuits over here. Sockets are 2.5mm T&E minimum for 13 amp. Electric cookers and some electric showers are 4mm or 6mm.

Just had a EV 7.6kw charger fitted, at 6mm cable.

Same here for fixed wiring, but 'extension cords' are different-1mm is ok for 'light duty/7.5A rated cords, 1.5mm for normal duty 10A cords (which apparently is the limit on UK cords/plugs) but for heavy duty ones 2.5mm is the norm here (apparently not allowed on a UK plug... despite having a higher current/wattage limit than our 10A)

 

[Dabop]

Another aspect with MCB (circuit breakers) is that you can have different 'current curves' for the same current limit- eg in Australia, it is common to find B (older houses) or C curve breakers (newer ones), while the UK tends to use A or B curve breakers...
(there are several other ratings as well- all with the same 'Amps limit' but different 'current curves') usually an electrician will spec up a B curve breaker but fit a C curve breaker of the same current limit for 'troublesome loads' like electrical motors or lots of inductive loads (LED lights, switchmode power supplies etc)... while heavy motors might even have a D rated breaker fitted on the outlets circuit like the workshop at my stepdads place with a metalworking lathe hanging off it lol
(note they all have the same cable requirements, just different 'tripping' characteristics...)

Look for the letter in front of the amps rating- here are my ones in the fusebox at the old house- C10 on the lighting (10A), C20 on the two power circuits, and C25 on the garage 'combined lighting/power' circuit (detached garage)

A UK consumer unit with B curve MCB's

MCB current curve characteristics

If the workshop is on its own cable, it might be worth having a sparky test and fit a different class rated MCB to it...

 

[Scruples]

So, I've read that on start up the planer can draw 1-2x the wattage - that would be up to 4400w. Using an amperage calculator, this converts to 18.3amps which is well above a 13amp fuse. Also would 2.5mm cable be suitable for this current?

A 13A plug top fuse is rated as a coarse protection device which means it can take up to 3x the rated current instantaneously and may carry that current for up to 4 hours before blowing. It is not a cartridge fuse.

A 2.5mm² will carry 22A under the right circumstances, e,g, cable length and installed environmental conditions, all of which are defined in the regs.

 

[Scruples]

4mm radials are run from a 32 amp protective device and rings are just historical, I would not contemplate using a ring these days.

I ran a 2.5 ring in my workshop which means a 5mm² effectively around the walls. It also allows for later additions to the workshop without too much additional work and cable. Call me old-fashioned, but logical. I would, however, spec a professional workshop differently where machines may be run simultaneously.

 

[Phil Pascoe]

Especially if you are providing the extension reel so your granny can sit on the sofa with a 3kW electric fire at her feet.
The worst offenders of them all are high power long duration appliances like heaters. Rolled up extension leads get stinking hot, soft and floppy if you forget to unroll them.

I lost count of the number of 5a reels I threw out at work melted solid from being overloaded and used nearly fully wound.

 

[Skeety]

If you are doing it then get a spark in.

The only time I have seen 2.5mm flex used for extension leads is blue arctic cable terminated into commando plugs\sockets. Definitely not mains 13A plugs.

I have just done my workshop with similar loads to yours. It's probably way overkill but that has 16mm2 SWA supply, could have got away with 10mm2 but close on voltage drops etc. As i was doing the grunt work of burying it in ducting, clipping to the wall i went with 16 as the cost was negligable.

That is terminated into a 10 way consumer unit with SPD. 3 Radials (20A RCBO Type B) 2 lighting circuits (LED with 200W transformers) on 10A RCBO Type C and a 32A interlocked command socket on a 32A MCB.

Way more diversity\complexity and cost than needed but it's done. If i get air con in there or have a hot tub then the supply will be more than enough!

 

[Spectric]

I ran a 2.5 ring in my workshop which means a 5mm² effectively around the walls.

You have highlighted one of the issues with the ring, it only takes a break in one of the wires and you now have a 2.5mm cable protected by a 32 amp device.

It also allows for later additions to the workshop

For that you really needed singles in trunking and conduit drops, with a radial you get to the last socket and that's it, with a ring you now have to get a cable back to the board.

The other issue is the time it can take to fully test a ring main, if someone has been playing and bridged the ring with another socket some where it can be a right nightmare to find and I have seen a few.

The ring main harks back to the post war years and copper shortages, the original concept was the ring only provided power to supply a kettle and two electric heaters because that is all they thought the house holder needed, there was a radial to a cooker and one lighting circuit for the whole house.

That concept did not change for decades except we used a ring upstairs and a ring downstairs whilst spliting the lighting the same and all from a single RCD board. The big changes have come about because of our demand for more and more electrical appliances and our increased awareness of safety, now we have to put a lot more time into the design of an installation and with far more circuits, 18 and 27 way distribution boards being readily available.

 

[Dabop]

Ring circuits never really took off anywhere but the UK- and they can (as you noted) cause all sorts of headaches when the ring breaks, or is modified in ways it shouldn't have been with add-ons
:-(
A broken ring (and from what I have seen, it is far from uncommon in EICR's to find a broken ring) can leave your wiring heavily overloaded, with only one leg of the ring shouldering the entire load... (up to 32A on a 2.5mm single!!!) depending on the wirings surroundings, that can mean its running at over two times the maximum rated current for a 2.5mm^2 buried in plaster for example (13A maximum in that case because of thermal derating...)

From Au/NZ wiring calculator Showing the ratings for various sizes for a 'plastered in the wall' cable (common in older plaster walls), a 2.5 is massively overloaded in this case (the first cable that can carry the 32A load allowed by the breaker is a 16mm^2 one!!!

A 'slot and conduit' as is more common in newer installations is even worse- that 'single 2.5mm^2' leg of the broken ring is down to only 12A!!!

12A current limit- on a 32A breaker!!!!

 

[Swannie61]

I would suggest running a 4mm 2 core SWA cable from the dist board, from an RCD rated around 40a 30mA, to the shed/garage and have a garage dist board fitted. You could then have 2 circuits, lighting and a radial circuit for a few sockets.
You could run the cable yourself, even fit the board where required, but get an Electrician to connect everything. Part P is only required for the compliance check, the Electrian doesn't need to be Pt.P registered, only the person doing the check. However, its usually easier to have a Pt. P sparky carry out all the connection work. Hope that helps

 

[Spectric]

I would suggest running a 4mm 2 core SWA cable from the dist board, from an RCD rated around 40a 30mA, to the shed/garage and have a garage dist board fitted.

You then need an earthing rod at the shed / garage end to provide the means of earthing which is often the best way to do it because then you do not have to worry about extraneous conductive parts which can mean with a PEN supply to the property that the supply cable would need to be 10mm to the outbuilding.
For the price you would use at least 6mm cable but this depends upon the length of the run which has a direct input to the volt drop and also future proofs the job.

 

[Scruples]

You have highlighted one of the issues with the ring, it only takes a break in one of the wires and you now have a 2.5mm cable protected by a 32 amp device.


For that you really needed singles in trunking and conduit drops, with a radial you get to the last socket and that's it, with a ring you now have to get a cable back to the board.

The other issue is the time it can take to fully test a ring main, if someone has been playing and bridged the ring with another socket some where it can be a right nightmare to find and I have seen a few.

The ring main harks back to the post war years and copper shortages, the original concept was the ring only provided power to supply a kettle and two electric heaters because that is all they thought the house holder needed, there was a radial to a cooker and one lighting circuit for the whole house.

That concept did not change for decades except we used a ring upstairs and a ring downstairs whilst spliting the lighting the same and all from a single RCD board. The big changes have come about because of our demand for more and more electrical appliances and our increased awareness of safety, now we have to put a lot more time into the design of an installation and with far more circuits, 18 and 27 way distribution boards being readily available.

You have highlighted one of the issues with the ring, it only takes a break in one of the wires and you now have a 2.5mm cable protected by a 32 amp device.


For that you really needed singles in trunking and conduit drops, with a radial you get to the last socket and that's it, with a ring you now have to get a cable back to the board.

The other issue is the time it can take to fully test a ring main, if someone has been playing and bridged the ring with another socket some where it can be a right nightmare to find and I have seen a few.

The ring main harks back to the post war years and copper shortages, the original concept was the ring only provided power to supply a kettle and two electric heaters because that is all they thought the house holder needed, there was a radial to a cooker and one lighting circuit for the whole house.

That concept did not change for decades except we used a ring upstairs and a ring downstairs whilst spliting the lighting the same and all from a single RCD board. The big changes have come about because of our demand for more and more electrical appliances and our increased awareness of safety, now we have to put a lot more time into the design of an installation and with far more circuits, 18 and 27 way distribution boards being readily available.

No, I ran 2.5 TWE around the walls in 4x2 plastic trunking protected by a 16A breaker and RCD. The connections are all good, so there's no risk of a disconnected core. The flexibility of this method speaks for itself. In all my years as an electrician the faults on a ring were few and far between and always caused by bodgers.

Electric demand and appliances have changed a lot over the years and we're safer these days than ever before.

 

[Spectric]

always caused by bodgers

How many bodgers have you met that actually admit to being a bodger or to undertaking the bodge job ! They always seem to think it is the electrician just trying to rip them off.

Electric demand and appliances have changed a lot over the years and we're safer these days than ever before.

Yes and no, residual protective devices have make things much safer for people, maybe had the use of AFDD's been added to the 18th then extra protection could have been added for buildings themselves but on the flip side we now have lithium batteries and many iffy asian chargers and such with property burning as a result. We also have issues with so called " fake cable" which is finding its way into the supply chain which uses poor quality copper that is less ductile and in some cases has higher impedance per metre.