Wiring up home workshop

[fireflyar]

Hello to everyone. This is my first post.

I'd like to ask for some advice regarding running power to my home workshop/shed.

Basically, I have about a 15 - 20m distance from the nearest socket in the house. Up until now I've been using a 10w extension to run a vac plus any of my tools or small machines This has worked fine, I do realise it's not the best solution but is a temporary fix. I recently bought a 2200w planer thicknesser and a small 550w extractor. Upon starting the planer the fuse in the extension blew.

I've done a bit of reading and understand generally why this happened. I don't fully comprehend the requirements of running these machines, in terms of distance, cable type, ampage, etc, though.

I'm considering putting some sockets into the shed and am just wondering what the specs would be for cable size and where to source the power from (socket or consumer unit - a slightly bigger job!)

Or is there an extension that would run these machines safely, a higher ampage or something? At least until I can afford to do the job properly.

My knowledge of electrics is limited so I would appreciate this in simple terms, if possible, please.

Thanks in advance.

 

[MF1000]

Running both at the same time you will draw just under 12amps . On start up they will pull more on an initial surge, at this point I’m guessing your 13amp fuse blew.

A quick fix is to start them up separately and see if your fuse holds ….after that it’s moving to better wiring and a dedicated supply to the shed with much more expense etc.

unless your plaining/thicknessing lots if material you could run the planer alone and then vac up the resultant chips etc afterwards.

 

[Spectric]

My knowledge of electrics is limited

You need to get a proper electrician to undertake this work, you cannot run a workshop from an extension lead and you can damage the motors in your machines if they are under voltage. Add to this your safety and the possibility of a thermal event plus adding circuits is a notifiable job to your local BC who may want to see a small works cert as well.

A quick fix is to start them up separately and see if your fuse holds

Running on the limit is not a safe thing to do, protective devices are there for your safety and not something to overcome and please do not suggest wrapping the fuse in foil !!

 

[Terry - Somerset]

I am in the process of doing the electrics in my new garage/workshop.

It is being done on the principles used in my previous workshop which worked fine for 10 years. Plug from existing socket on ring main to a double pole fused switch. 1.5mm cable to a number of sockets on a spur. It is probably overkill to have a 13A fuse in both the plug and switch.

I run several machines - largest is a thicknesser drawing about 1500W. Used in conjunction with the dust extractor (1000W) they are comfortably within the capability of cable and fuse.

Fortunately it is just me in the workshop - were I to run the other bits of kit at the same time I would no doubt have a problem.

 

[MF1000]

You need to get a proper electrician to undertake this work, you cannot run a workshop from an extension lead and you can damage the motors in your machines if they are under voltage. Add to this your safety and the possibility of a thermal event plus adding circuits is a notifiable job to your local BC who may want to see a small works cert as well.



Running on the limit is not a safe thing to do, protective devices are there for your safety and not something to overcome and please do not suggest wrapping the fuse in foil !!

My suggestion was not encouraging to act in an unsafe way, merely a coping strategy whilst as I suggested a better supply was found

 

[MarkAW]

1.5mm cable

Do you mean 2.5? I've only ever come across 1.5 used for lighting circuits

 

[fireflyar]

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?

 

[ChaiLatte]

Or is there an extension that would run these machines safely, a higher ampage or something?

The maximum cable size the regulations permit to be wired into a standard UK 3 pin plug is 1.5mm^2. This means no one will sell an extension lead with a thicker cable.

It is possible to buy 2.5mm^2 cable, a plug and trailing socket and make your own extension. It will not comply with any regulations. It is possible to fit 4mm^2 cable into a UK plug, but again, is strictly without of any regulations. If you go this route, remember the first rule of Fight Club.

In the short term, why not buy two more extension leads and use one for each machine, plugged into a different socket in your house? In other words do not plug two shed extensions into each side of the same double socket in the house. If your kitchen is on one breaker, your downstairs sockets on another and your upstairs sockets on a third, you are sharing the load ath the house end.

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.

 

[ChaiLatte]

...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?

That is why fuses (and breakers) have a tripping curve, which is time-related. A simplistic way of looking at it is that a 13A fuse will withstand a continuous current of 13A. A short term overload above that current into a cold fuse will not cause it to blow.

Think of how a fuse works - it heats up and melts. If the huge current that causes it to melt is only applied for a very short time, it will not overheat. You can pick up a hot saucepan and drop it into the sink with only a small display of Riverdancing. Even Michael Flatley could not carry it upstairs and drop it in the bath.

Cable capacities are governed by a lot of factors, so it is not sensible to attempt a yes or no answer to your question without knowing those factors. Cleveland Cable have a reasonable calculator which both lists and takes into account those factors in the answers it gives.

 

[Sideways]

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.

This is the danger.

"So I've read...."
The internet is not a reliable source of information.
In fact startup surges are far greater. Typically 5x rated power, even 7-8x.
I've measured a 1500W PT at 56 Amps on a 13A fuse, but this only lasts for less than a second and fuses need a moment to heat up before they melt.

"Converts to 18.3A"
No it doesn't. You have efficiencies and power factors to take into consideration that may add another 50% to your calculation.

@Terry - Somerset above will be closer to the limit of his supply than he realises, not comfortably within it. Just that most of us outside an industrial setting don't run a PT at full load for long enough or have the test gear to measure the current while they are doing it.

Get an electrician to do it properly.

 

[MikeJhn]

Any new circuit being wired into your consumer unit is notifiable to Local Building Control under the Part P regulations, you need an electrician who is registered as a "competent person" Competent Persons Register | Home

 

[HamsterJam]

I had a similar situation and got an electrician to run a 10mm armoured cable from a 45A RCBO in my house consumer unit to a separate consumer unit in the workshop, feeding lights and sockets. This is not the cheapest but by far the best way.
Note you can reduce the cost of the job by running in the armoured cable yourself and leaving the electrician to connect it.

 

[Terry - Somerset]

@Terry - Somerset above will be closer to the limit of his supply than he realises, not comfortably within it. Just that most of us outside an industrial setting don't run a PT at full load for long enough or have the test gear to measure the current while they are doing it.

Get an electrician to do it properly.

I have noted this, read some of the other comments in the thread, and done some further simplistic research. Probably familiar to some but a surprise to me - and possibly to others!

BS1362 deals with characteristics of fuses. A 13A plug top fuse should carry a minimum of 150A on start up, reducing to 40A after 1 second, and carry 20A indefinitely. PAT testing

On start up current can be up 20 times (assume 10) the motor rating for half a cycle falling to 4-8 times (assume 6) for a couple of seconds. For my thicknesser (1500W) means a start up current of ~60A, falling almost immediately to ~ 35A. Both within BS1362 characteristics.

Although on reflection it is blindingly obvious, the current drawn depends on the load on the motor. So although my thicknesser may be rated at 1500W, at partial rather than full loads it will draw proportionately less.

Conclusions - I may have inadvertently operated close to the limit at times but unknowingly mitigated the risk as:

• total start up loads would be limited as machines would be started sequentially not simultaneously
• I rarely/never tend to operate machines at their full load - eg: more likely to take 0.5mm than 2.0mm at a time on the thicknesser

Interestingly I have recently had the house electrics upgraded, a new consumer unit fitted and the wiring tested. Mostly I am aware of my own limitations and the advice to get an electrician to do the job properly (or at least check my work) is noted!!!

 

[Spectric]

There is often a difference in the theory and what happens in practice, the startup current also depends upon the power factor and efficiency. My 2200 watt P/T had to be on a 16 amp supply as the original 13 amp fuse blew so fast there was no sign of life from the P/T .

The max inrush current can be twenty times the FLA for 10mS which means in theory my P/T could pull over 200 amps, but for only hundreths of a second but enough to take out a 13 amp fuse.

If you think motors have high inrush currents then look at the LED, at T0 the input impedance of an LED is 0 which is a dead short but for only microseconds. The motors excuse is inductance but the LED is capacitance.

 

[ChaiLatte]

...the original 13 amp fuse blew so fast there was no sign of life from the P/T .

Something I stumbled across the other day is what is described as a 13A slow blow (machine) fuse.

https://forest-master.com/time-delay-fuses-x2/
Must be a modern development of the KitKat wrapper my grandad used to use.

 

[Spectric]

I have used slow acting fuses but only within electrical / electronic equipment where they were glass and the fuse itself was a coil. These look like something this company is selling to allow customers to just plug in their products without the hassle of people complaining about fuses blowing. When you look at the products they have 2200 & 2300 watt motors . As they say

" Our time-delay fuses are compatible with all Forest Master Electric Motors. "

The issue is that the circuit is having to handle above design currents for longer and suffering extra stress. I wonder if the issue is just startup current or it is also load spikes as they split logs.

 

[trvlr]

2.5mm is minimum for power cable distribution to sockets; be it radial (a long "string" of cable with sockets on it), or in a ring circuit. If the former then a 20amp breaker (or fuse if still on the olde wired type) or 30/32 amp if on a ring circuit. And there must be an rcd somewhere in that feed. Nothing to stop you using 4mm cable for a radial, other than cost...; and it might allow a slightly higher rated breaker too?

Running a long extension reel regardless of its specs. is not the way to go - except in emergencies; and then it ought to be fully wound out if/when carrying a load close to its cable capacity.

However I feel you'd be better getting off/wiser a local (and reliable, non rip off) electrician to give you hand.

 

[Spectric]

Nothing to stop you using 4mm cable for a radial, other than cost...; and it might allow a slightly higher rated breaker too?

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

 

[Dabop]

The maximum cable size the regulations permit to be wired into a standard UK 3 pin plug is 1.5mm^2. This means no one will sell an extension lead with a thicker cable.

It is possible to buy 2.5mm^2 cable, a plug and trailing socket and make your own extension. It will not comply with any regulations. It is possible to fit 4mm^2 cable into a UK plug, but again, is strictly without of any regulations. If you go this route, remember the first rule of Fight Club.

In the short term, why not buy two more extension leads and use one for each machine, plugged into a different socket in your house? In other words do not plug two shed extensions into each side of the same double socket in the house. If your kitchen is on one breaker, your downstairs sockets on another and your upstairs sockets on a third, you are sharing the load ath the house end.

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.

Um- you sure about that???
BS and Au/NZ3000 regs are 'compatible' (ie a device approved to BS is acceptable under Au/NZ regs
2.5mm^2 is used extensively in '10A heavy duty' and '15A caravan' power cords here

Ironically, Deta is a UK based company lol

 

[Sideways]

Um- you sure about that???

Gotta give the man credit. He's dead right.
I had never had reason to read it but BS1363 part one, 1995 states so clearly, twice over. And this aspect isn't changed in the latest revision.
Captive cable or rewireable plug, the range of cables they are to work with are 0.5mm2 x 2 core through to 1.5mm2 x 3 core (LNE).
I wire up my own 2.5mm2 3 core cables for durability and low loss, but BS1363 plugs are not specified for the purpose. The meaningful part is that they must be able to grip the cable and withstand various detailed pulling and twisting forces. If a plug can meet these specs with a larger cable fitted, then great. If it cannot because you have fed it too large a flex, then the plug is being misused and the user is at fault, not the manufacturers of the individual components going into such a power cable.