Workshop electrics

[Alparkinsonpm]

Hello,
I am planning to install power to. New workshop in the garden. It will have 6 double sockets and some fluorescent lighting.
I am right to think I should run 2.5mm twin and earth from a spare way on the house consumer unit to the workshop?
I am thinking of installing a separate IP20 garage unit with 1x 6amp and 1x 16amp mcb for lights and sockets respectively. does this sound correct?
If I have the separate box in the workshop do I return the ring cable to that box or does it need to go all the way back to the house?
Also, is 1.5mm cable suitable for lighting?

Thanks

 

[DetlefSchmitz]

How far away from the house is this workshop? Unless it joins the main house you will need Steel Wire Armoured cable buried about half a metre deep.

 

[Alparkinsonpm]

It's about 10m from the house. The cable will be buried in PVC conduit and protected by paving stones and warning tape and then buried. It's not in a prime digging position anyway.

 

[Tronjob]

Unless it joins the main house you will need Steel Wire Armoured cable buried about half a metre deep.

This really isn't a DIY job. Find yourself a local electrician who can come and give you a quote to do it. Whilst you'll probably be able to save some lonely by doing the labouring (digging the trench etc), this is something that you'll have to confirm with him.

 

[PrenticeBoyofDerry]

Hello,
I am planning to install power to.

And what plans are now in place? Design calcs and install method, compliance to regs and notification to building controls, would be an excellent start.

New workshop in the garden. It will have 6 double sockets and some fluorescent lighting.
I am right to think I should run 2.5mm twin and earth from a spare way on the house consumer unit to the workshop?

No that would not be right to think that, you need to calculate it by using the expected load demand, method of installation and distance of distribution cable.

I am thinking of installing a separate IP20 garage unit with 1x 6amp and A1x 16amp mcb for lights and sockets respectively. does this sound correct?

That would depend on what was to be loaded on to the sockets, if nothing above a 16A load at one time, then sounds feasible. The sockets will require 30mA RCD protection, as will any buried cable less than 50mm within walls that are not correctly mechanically protected.

If I have the separate box in the workshop do I return the ring cable to that box or does it need to go all the way back to the house?

I would stick to a radial circuit rather than a ring final one, so no need to return the loop.

Also, is 1.5mm cable suitable for lighting?

By cable do you mean twin and earth? If using T&E 1.00mm2 will be fine as will 1.5mm2.

 

[PrenticeBoyofDerry]

A 10m run with a 5060W(16A+6A) load will only require 2.5mm2 SWA, I would personally increase that to a least 4.00mm, trench at about 600mm and use a duct rather than conduit.

 

[bernardgreen]

And a second duct for services such as data cables. telephone, alarm, door bell etc etc.

 

[winston1]

Hello,
I am planning to install power to. New workshop in the garden. It will have 6 double sockets and some fluorescent lighting.
I am right to think I should run 2.5mm twin and earth from a spare way on the house consumer unit to the workshop?
I am thinking of installing a separate IP20 garage unit with 1x 6amp and 1x 16amp mcb for lights and sockets respectively. does this sound correct?
If I have the separate box in the workshop do I return the ring cable to that box or does it need to go all the way back to the house?
Also, is 1.5mm cable suitable for lighting?

Thanks

It should be run from a 20A MCB in the house consumer unit. You don't need a separate garage unit. Run the sockets direct and the lights from a switched fused connection unit with a 5 amp fuse. You don't need a ring in the workshop just wire the sockets radially. You don't need 1.5mm cable for lighting 1.0mm is perfectly adequate.

 

[bernardgreen]

Consider what happens if there is an overload on the socket circuit in the work shop while working. If there is just one MCB in the house protecting the work shop electrics then the lights will go out as well as the power.

Having two MCBs in the workshop 16 amp and 6 amp and a slow acting 20 amp MCB in the house will allow the lights in the work shop to stay on. Which could be essential if the power tripped as a result of an accident.

It is not 100% certain that the lights will remain on, a massive overload or dead short on the socket circuit may take out both the 16 amp in the work shop and the 20 amp in the house.

 

[ericmark]

Hello,
I am planning to install power to. New workshop in the garden. It will have 6 double sockets and some fluorescent lighting.

There is a big jump with 13A supply and 20A supply number of sockets does not say what power is required.

I am right to think I should run 2.5mm twin and earth from a spare way on the house consumer unit to the workshop?

No twin and earth is rated in doors only some other type of cable will be required.

I am thinking of installing a separate IP20 garage unit with 1x 6amp and 1x 16amp mcb for lights and sockets respectively. does this sound correct?

Will depend where fed from no point in having a 16A MCB fed from 13A fuse. If fed from a 20A supply then seems OK but there are other considerations like RCD protection and earthing arrangements.

If I have the separate box in the workshop do I return the ring cable to that box or does it need to go all the way back to the house?

A ring final is normally 32A and for a shed normally you would have a 16A or less supply to sockets so no ring in the shed circuit.

Also, is 1.5mm cable suitable for lighting?

Yes

Thanks

I think you are trying to over simplify the job. Question 1 is where is the supply coming from? It is common where shed has light use to use a simple FCU in house with 13A fuse and a switched FCU in shed with 3A fuse which doubles as light switch. So maximum draw is 13A. It can be debated if this can be supplied from the house ring final but with light use unlikely to be a problem. If no RCD already in house the using a RCD FCU will ensure shed complies.

Once you leave this simple method then in England Part P raises it head as it will require a new circuit from house consumer unit. In Wales Part P is a problem even with the FCU method.

In real terms once Part P is involved just not worth doing as a DIY job.

 

[winston1]

Consider what happens if there is an overload on the socket circuit in the work shop while working. If there is just one MCB in the house protecting the work shop electrics then the lights will go out as well as the power.

I have and hopefully a fault will take out the plug fuse only.

I have had my garage workshop wired like this for years and never had that scenario. I did one had an earth leakage fault which took out the garage RCD including lights, but you have not suggested having separate RCSs.

 

[JohnW2]

Consider what happens if there is an overload on the socket circuit in the work shop while working. If there is just one MCB in the house protecting the work shop electrics then the lights will go out as well as the power.

As I'm always saying, if loss of light is considered to be a danger (e.g. because power tools may be 'spinning down'), the only safe option to be considering is to have (battery backed-up) 'emergency lighting', since there are scenarios (such as a power cut) that will cause mains-powered lighting to be lost, no matter what 'clever' circuit design one might adopt.

Having two MCBs in the workshop 16 amp and 6 amp and a slow acting 20 amp MCB in the house will allow the lights in the work shop to stay on. Which could be essential if the power tripped as a result of an accident.

I have to say that I'm not familiar with a 'slow acting MCB' (time-delayed RCDs, yes, but 'slow acting MCBs, no) - can you enlighten me?

Kind Regards, John

 

[securespark]

I have to say that I'm not familiar with a 'slow acting MCB' (time-delayed RCDs, yes, but 'slow acting MCBs, no) - can you enlighten me?

Any BS3871-1: 1965 circuit breaker should suffice.

At that age, they should all be slow-acting.

Good job they were superseded by the whippersnapper 60898, although they themselves are now well past the age of majority...