Electrics in Shed

[Gary S]

Morning all,

I've just had a 12 x 6 shed built in my garden - it's going to be storage for all the gardening stuff plus golf clubs, bikes etc, but also a bit of an overflow from the Workshop (a.k.a. Garage!). Just don't tell SWMBO... :wink:

I am going to put a workbench in there and use it for some of the smaller tools - sanding, drill press etc. I'll still use the garage for the bigger, noisier, messier stuff!

My question (yes, I will get there eventually...) is what electrics should I put into the shed? I was thinking of having quite a few power points (including at least one double socket in the ceiling which may be handy). What lighting would people best recommend - halogen type downlights or strip flourescent lighting or something else?

Also, do you think it would be worth fitting an extractor (such as the ones you have in a bathroom)? I may use the shed to store some of my seasoned timber - would an extractor help to keep a bit of airflow going or is it not the recommended thing to do?

I'm going to insulate the shed with polystyrene and then clad the walls so it would be good to get the electrics all sorted before I do that. Obviously everything will be check fully by a qualified electrician... :roll:

Any help / advice / experiences gratefully received!!

Gary

 

[Adam]

I'm going to insulate the shed with polystyrene and then clad the walls so it would be good to get the electrics all sorted before I do that. Obviously everything will be check fully by a qualified electrician... :roll:

So I guess you know its notifiable under Building regulations.... anyway. Remember that electric cable and polystyrene do not mix. You get transfer of something (ions?) from the PVC cable to the polystyrene leaving the cable brittle. It really does happen - I made that mistake in my first workshop. In the end, I opened up each wall, and cut narrow strips of roofing felt (I had some handy) and laid the cable on that to stop it touching the polystyrene.

Adam

 

[Gary S]

Remember that electric cable and polystyrene do not mix. You get transfer of something (ions?) from the PVC cable to the polystyrene leaving the cable brittle. It really does happen - I made that mistake in my first workshop. In the end, I opened up each wall, and cut narrow strips of roofing felt (I had some handy) and laid the cable on that to stop it touching the polystyrene.

Adam

Fantastic advice - I had no idea...

How about if I wrap duck tape around the cable, would that work?

 

[Adam]

Fantastic advice - I had no idea...How about if I wrap duck tape around the cable, would that work?

Whats tape made of? Plastic? Err, no, I think you need something else. You can easily do it by tacking the cable somewhere tidy, and not filling the void entirely with insulation - leave an inch or two near to the cable. Or make a wooden "tray" to carry the cable and hold back the 'styrene.

And I'm sure you read our resident firefighters opinion on polystyrene sheets recently?

https://www.ukworkshop.co.uk/forums/view ... hp?t=15847

Adam

Quote below...

It's much, much more flammable than the wood and will give off some of the worst kind of combustion products you can imagine. Thick, black, toxic smoke; laden with isocyantes and cyanide for starters.
If you want to use it for insulation, make sure it is well covered with non-combustible linings that do not have an air gap behind them. Otherwise, get rid of it!
Great for a packing material but should never have been considered for a building product IMHO.
AFAIK it is not readily recycleable.
Sorry to sound so down on the stuff, though.
Cheers.

SF

 

[Gary S]

Unfortunately I hadn't read that (otherwise I probably wouldn't have bought it!). I will be lining the inside of the shed with DPM before I put in the polystyrene - not sure if that is great either or whether that is a problem with 'plastic on plastic'?!

I will certainly do something with the cabling - I'm even now considering running it in trunking on top of the internal cladding to keep it well away from the polystyrene.

So, moving on... ... any thoughts on the other questions?!

 

[Adam]

So, moving on... ... any thoughts on the other questions?!

Trunking is better - easily reconfigurable. Also, it will punch less layers in your DPM. In fairness, I lined my previous workshop polystyrene - as I also didn't know about its problems. I think if it caught fire you'd be out the door in a shot. Maybe lining with something like chipboard - doesn't that have fire retardent* properties?

Adam

Not sure, you'd have to check. Plasterboard does for sure.

 

[lurker]

What Adam meant was that Polystyrene leaches the plastizers out of the sheathing.
Duct tape is even worst! I had to do a major rewire on my Volvo electrics after making this mistake.

Also Polystyrene makes a very poisonous fire.

Suggest you go for MMMF ( fibreglass) - still fire hazard though.

 

[PowerTool]

Trunking is a good idea,regardless of what type of insulation.
As for lighting,I have a couple of ordinary tungsten lights for "instant" light,fluorescents over bench/work areas,and a couple of portable halogens if I need supplementary light anywhere.
Works for me

Andrew

 

[Gary S]

Any thoughts on an extractor from anyone?

Since I plan to use the shed to store some timber I'd like to do it as well as I can - if an extractor helps / hinders this it would be go to know to avoid making a mistake.

Thanks, as always...

Gary

 

[davy_owen_88]

Firstly, don't even consider downlights. They don't spread their light very well and are terribly inefficient. Go with fluorescent strip lights or CFLs - or both.

As mentioned electric cables can have their plastisiser leached out by various materials and this makes them brittle and prone to damage. Putting the cable in trunking or conduit will solve this problem but introduce another... which is reduced current carrying capacity. You must make sure the cables are suitable for their intended use and that the protective device (MCB's/fuses) are suitably protecting that cable.

I get the impression that you don't intend on notifying this work, which is entirely your choice, but remember to stick to the regs because if you do get caught out, by the BCO, insurance, annoyed neighbours etc, then you don't want to have to put things right when they are fining you every day the work doesn't meet the standards.

Regarding the extractor. If you are going to be making dust in the shed consider fitting some form of filter over the intake side to prevent dust build up which over time will totally knacker the fan. Another option is a suitably rated extractor fan, IP6X is dust tight, but standard bathroom/kitchen extractors are nowhere near this rating.

When deciding on the size of the supply cable make sure you leave room for expansion later, a few extra quid is well spent on larger cable when you consider the time and money involved in doing the whole lot a second time. Machines don't like voltage drop so make sure the cables can cope with the high inrush currents and the subsequent drop in voltage caused. Oh and there is earthing to consider which varies with earthing type at the intake.

 

[shockingmoment]

Good advice from davy_owen_88

All external electrical work does fall under part p now. If there was a fire, would your insurance cover loss / damage if you couldn't demonstrate comliance. You can still do the donkey work and get someone in to finish off / certify.

Anyway - some things to consider - surface mount cable / sockets (suitably mechanically protected). As the 'shop develops, you may want to move things around. This is easier if sockets / cabling are accessible. Dado trunking is good for this, but can be expensive.

A 16A supply may be needed for some tools - P/T, table saw. A BS4343 industrial socket is good for this.

Suggest installing a small consumer unit in the w/s.

And most important - make sure you have an RCD fitted. If you don't know what this is - get a pro in!