Workshop Electrics

[J_Ashley]

I’m planning a new workshop that is to be built and am trying to make sure I have given due consideration to everything. I have very little experience with electrics, and although I’m not building the workshop ultimately I need to give directions/advice and so I need to be sure of myself first.

My woodworking so far has been limited to hand tools and the occasional power tool, so nothing that a normal house plug socket wouldn’t handle. However, in the new workshop I’m planning on kitting myself out with a couple of pieces of machinery and also the necessary dust extraction, so I imagine that things could get power intensive at times.

The highest powered machine I would probably run would be the sander at just over 1kW. However, at the same time the chip extractor will need to be running, which is another 1.5kw. Again, there may then be a host of other things on in the background, e.g. lights, heater, dehumidifier. I think this should represent the peak power usage. If it’s worth mentioning, no piece of kit should require 3 phase power.

The workshop will be at the bottom of the garden, and most people talk about just installing electrics that run from the house. However, I really have no idea as to what that means in terms of the options it gives me. Probably somewhat naively, I’m fearing that I accidently end up with some glorified extension lead installed!

Any advice of what I should be getting installed would be much appreciated.

 

[MikeG.]

Firstly, it is a requirement of the Building Regulations that you get new electrics in an outbuilding certified by an electrician. As you say you aren't confident that you can do this yourself anyway, then you can simply hand the whole thing over to him. You will need an armoured cable out to the new building from your house, which should be buried in the ground below spade depth, and marked with sand and a warning tape. This bit you can do yourself, but get your electrician to supply the cable. He will need to calculate its size according the the length of the run. He will also need to do the connection both ends.

In the workshop you will need a consumer unit, and this will have at least 2 "ways".....one for lighting, one for power.

 

[Sideways]

My tip is to think about the layout of your new shop so that you can ask your electrician to give you enough sockets and in convenient places so that you don't need to run extension cords around once it's done. You always need more sockets than you think - chargers, extra lights, greenhouse heaters to keep the damp at bay, etc.
This is an opportunity to have a 16 Amp circuit with a blue CE (aka "commando") socket fitted if you think you might ever want to run a bigger extractor. Some extractors of say 1.5kW and above will blow 13A fuses because they draw extra current for a few seconds while starting up.
To help the electrician calculate the right size or cable etc think about the biggest load that you may need to run and how long for (minutes or hours ?).
Your largest machine plus dust extractor and lights, or most powerful tool plus shop vac, and maybe for winter working add 2 or 3kW for an electric heater ?
For what it's worth, in a workshop or shed, I'd be tempted to have the wires run in plastic tube conduit fastened to the surface of the walls and "metal clad" sockets. These are durable and you will always know where the wires are so no danger of putting a screw into a cable when you start fitting the place out with storage afterwards. It's not industrial so no need for the strength of metal conduit (cheap enough but takes longer to cut and fit).
And you may want a weatherproof socket on the outside of the shed to give you a convenient place to plug garden tools into.

 

[Glynne]

The reply from Sideways could have been mine (except for the 16 amp which I don't have - but is a good idea anyway).
You will probably not have that many things running at once (machine, extractor, lights etc) but the ability to have things plugged in ready for use is invaluable.
My workshop is ~ 5m x 4m (so not large) and I have 14 double sockets at worktop height, 1 in the ceiling for an ambient extractor and 1 at floor level for a small compressor. I also have a double outside socket for garden stuff. My workshop is also wired for 4 double fluorescent lights (but seriously go for LEDs) and one outside security light. All wiring is surface mounted in plastic conduit - I have previously drilled through water pipes in the house....!
I got a professionally qualified mate to do the wiring, but I managed to cut costs by burying the armoured cable and by mounting the wall sockets where I wanted them wired.
I must look up some of Sideways' posts because he seems really knowledgeable.......!

 

[xy mosian]

If your workshop is large, and you can reach the roof structure from the floor. Then I would suggest a power socket, for hand held power tools, in the centre of the 'shop mounted in the ceiling. This can make using Routers etc. easy than having trailing cables.
xy

 

[J_Ashley]

Thank for the advice all.

The workshop probably won’t be built until later in the summer, but I’m trying to get everything considered in advance. I appreciate there’s some things you can’t find out until later, but it’s probably the only opportunity I’ll have to build a new workshop so I want to get it at right as possible.

Wires - I hand´t previously considered running the wires in a conduit, but that sounds like a cheap and easy way of avoiding a future mishap!

Sockets - I already know what machinery I’m after and I’ve had some great advice about extraction in a different thread, so I think I should be able to come up with a decent plan for an accurate layout and power requirements. This should help me determine the placement and number of sockets, plus I should add a few extra by the sounds of it

16A - seems like a sensible future proofing investment.

Ceiling socket - I had’t considered a ceiling socket, but the roof will be fairly low (need to keep max height to below 2.5m) and so that sounds like a good option. However, at only 3.5m width I’ll never be too far away from a wall either.

Installation - I think I’ll let the electrician do everything, but thanks to all the advice I’ll know more what to ask for. I’ll happily dig my own trench though - don’t mind a bit of manual labour to save a few pennies!

 

[flying haggis]

re ceiling mounted sockets one of these is good

https://www.amazon.co.uk/Brennenstuhl-h ... B00HW06JVK

 

[Roland]

Last month I had an electrician visit to discuss converting an old barn to a workshop. The building will need dry lining. The electrician recommended running conduit around the top of the wall, on the surface of the plasterboard, with Tees down to socket points. Probably two switched double sockets at each point. I’d also run conduit along the main beams, and have sockets above head height. Lighting will be on a second circuit from the consumer board. If I decide to add 16A then it would be a third circuit from the board, in separate conduit, probably star wired.

He also advised that I could run the internal cables myself. He would then check and certify before connecting the consumer unit to the supply.

 

[Mrs C]

Having just finished our garage, as per the above, lots (and lots more) sockets plus 16amp.

Also think about a master power switch so you can switch off and walk out without worrying at the end of the day (with machines on NVR switches where appropriate).

 

[Paul200]

I've nothing to add to the already sound advice given but will add my vote for a ceiling socket and a master switch by the door. I've got the ceiling socket but the number of times I leave the flipping heater switched on ....... :evil:

 

[flying haggis]

Last month I had an electrician visit to discuss converting an old barn to a workshop. The building will need dry lining. The electrician recommended running conduit around the top of the wall, on the surface of the plasterboard, with Tees down to socket points. Probably two switched double sockets at each point. I’d also run conduit along the main beams, and have sockets above head height. Lighting will be on a second circuit from the consumer board. If I decide to add 16A then it would be a third circuit from the board, in separate conduit, probably star wired.

He also advised that I could run the internal cables myself. He would then check and certify before connecting the consumer unit to the supply.

a better idea would be to run square or rectangular trunking round the top of the wall and then have drops to each socket position. doing it this way means you could add circuits or amend them, and the wiring could be done using single core cables of appropiate size for the circuit
ie
https://www.tlc-direct.co.uk/Products/MTMX32.html

 

[Sideways]

(Just note that single core cables are standard practice in round as well as rectangular conduit...)

 

[n0legs]

Squareline guttering makes a great dado system. Great for later upgrades or expansion.

 

[cammy9r]

I had these switches fitted at the door. When I leave I turn them off and it kills all sockets. Also handy in a panic if something goes wrong. Not long ago while cutting down a sheet of mdf on the tablesaw things went sideways resulting in a blade stall. Size of the sheet meant I could not reach the off switch on the saw but I very quickly got to the master kill switch for the bigger machines, switched off and sorted the issue. In my opinion worth having them installed.

 

[Sideways]

I had these switches fitted at the door. When I leave I turn them off and it kills all sockets. Also handy in a panic if something goes wrong. Not long ago while cutting down a sheet of mdf on the tablesaw things went sideways resulting in a blade stall. Size of the sheet meant I could not reach the off switch on the saw but I very quickly got to the master kill switch for the bigger machines, switched off and sorted the issue. In my opinion worth having them installed.

A point to note is that this style of switch is an "isolator". It's purpose is to allow you to lock a circuit off for maintenance. Isolators in general are not designed or rated to break a flowing current anywhere near the rating of the switch. Example a 25 Amp rated isolator may only be rated to break 6 Amps. This is because they are meant to be used to "isolate" a circuit where the load(s) have already been switched off.
You can get a variant isolator - disconnector that is rated to break higher currents. If you intend to use the isolator switch as a "kill switch", then explain this to your sparky so that he can find the correct type of switch for the job. I think the extra cost is minimal.
This is not difficult it's just a slightly non standard application where there's a small risk of confusion.
Be aware also that in a commercial setting, the "kill switch" function is a emergency stop or "e-stop". There are a bunch of rules that apply to these. I haven't checked the regulations recently but I don't think an isolator/ disconnect would be an acceptable solution.

 

[cammy9r]

Thanks Sideways certainly a point to be noted. I only needed isolators to switch everything off before i left. They are not used to disconnect running machines all the time only in an emergency which luckily is almost never.