Question about...... my shed!!

[SeanT]

OK, so my shed is built on the back of my outbuilding - ie. it's a temporary wooden structure with three sides that is screwed to said outbuilding (and would probably stay up if the outbuilding came down due to sheer amount of timber....)

If I want to put a socket in the shed, which is actually on the outside wall of the outbuilding (but enclosed by said shed), as an extension of the 13a sfs protected radial circuit that is already in the outbuilding, am I allowed to do this? I assume that as the whole house is on an old fashioned fusewire board (albeit with decent wiring, solid core everywhere, rewired sometime in the last 15 years by the look of things) it would be a good idea to make said socket (which I would consider, strictly speaking, to be an extension of an existing circuit which is suitably protected by a 13a fuse and is just adding one socket to a radial, which seems fine using strict tests of the wording) an RCD protected socket, as it is likely (indeed certain) that garden tools etc. will be run from it - this doesn't seem to be completely compulsory - as it's just another socket outside of part p - but a modicum of common sense says to do it. Is this ok with the current legislation that attempts to prevent me from doing something nice and easy and obvious like this?

Further to this, if I want to take out the 13a fused spur, leaving the 2.5mm existing cable feeding the outbuilding (on a 20 amp fuse methinks), I pretty obviously need to protect the lighting circuit (currently just joined to it) with a fuse, ie. fit a mini fusebox with 16 and 6 amp breakers - I'm guessing that ironically I am not allowed to do this? It really hacks me off that I can't make the installation safer and more up to date overall without spending money, but I guess that one day it'll need to be able to draw more than 13 amp (this wonderous 13 amp fuse already does for a freezer, cold fill washer and tumble dryer somehow and has not blown in the year that I have lived here....) - is there any way that I can do this without involving ££££? Might aswell just leave it as it is really and draw as much power as possible without blowing this fuse and carry on being blinkered like half the uk

 

[jotto]

RCD protected socket as a minimum!

If you still have rewireable fuses, chance are the installation is over 15yrs old.

Check out what size earthing conductors you have leaving the main distribution board....I know its all £££ but it sounds like an update may be needed. What price for your safety.

 

[SeanT]

OK, so maybe over 15 years, but more recent than 1989 anyway (wylex fuseboard has BS5486 part 13 written on it) - earth is 4mm on a 60 amp board - not too concerned with the safety of the current installation, apart from the shoddy bits I sort out now and then (ie. the odd loose screw in a socket when decorating, and the chump that didn't earth my cooker switch properly at some point...)

 

[ban-all-sheds]

If I want to put a socket in the shed, which is actually on the outside wall of the outbuilding (but enclosed by said shed), as an extension of the 13a sfs protected radial circuit that is already in the outbuilding, am I allowed to do this?

Yup.

You are in fact allowed to do whatever you like, as long as it's safe.

I assume that as the whole house is on an old fashioned fusewire board (albeit with decent wiring, solid core everywhere, rewired sometime in the last 15 years by the look of things) it would be a good idea to make said socket (which I would consider, strictly speaking, to be an extension of an existing circuit which is suitably protected by a 13a fuse and is just adding one socket to a radial, which seems fine using strict tests of the wording) an RCD protected socket, as it is likely (indeed certain) that garden tools etc. will be run from it - this doesn't seem to be completely compulsory - as it's just another socket outside of part p

Now there's a thing. It is not "outside of Part P". It is not notifiable, but it still has to comply with P1, so I'd say an RCD socket was compulsory.

Is this ok with the current legislation that attempts to prevent me from doing something nice and easy and obvious like this?

No such legislation exists.

Further to this, if I want to take out the 13a fused spur, leaving the 2.5mm existing cable feeding the outbuilding (on a 20 amp fuse methinks), I pretty obviously need to protect the lighting circuit (currently just joined to it) with a fuse, ie. fit a mini fusebox with 16 and 6 amp breakers - I'm guessing that ironically I am not allowed to do this?

Yes you are allowed to do this, but it would be notifiable.

Removing the FCU is not notifiable. Are you sure it's a 20A radial, and not too long for a 20A load? You don't really need the CU - you could just go straight to the sockets with the 2.5mm² and add an FCU for the lights.

And talking of lights - sounds like they are currently on the 13A FCU. What cable are they wired in?

 

[SeanT]

The cable feeding the outbuilding is a 2.5mm T&E in some sort of buried armoured whatsit and is about 6m total length to where I would put the new box / fused spur for the lighting circuit - 4m of this is from the CU to the outside of the house - ie. 27 amp derated to about 20 for safety margin.
I'll fit an RCD socket as a matter of course, as said socket will primarily be feeding a flymo so it'd be stupid not to - although is it ok to fit an RCD socket and then a double standard socket, in the expectation that the rcd would be for outside use? If not it'll be a four way lead on screws after the first double RCD socket - or can one get an RCD protected fused spur from somewhere? Trying to avoid puttiing the freezer on any kind of trip really obviously....
Lights look like they are wired in 1mm, ie. should have some sort of protection.
There is water out there too, but hot and cold to the outbuilding are both run in plastic, and the water to the outside loo (not "exposed" anyway") is straight from the main (in lead...) - the plastic from the house changes back to copper once it's in the outbuilding, but as it's all existing I guess I can just ignore it for the time being.
I guess fitting the fused spur for the lights is the way to go as regards compliance vs. safety then!

 

[ban-all-sheds]

is it ok to fit an RCD socket and then a double standard socket, in the expectation that the rcd would be for outside use?

Not the easiest of things to argue with sockets in outbuildings/sheds..

or can one get an RCD protected fused spur from somewhere?

Yes.

Trying to avoid puttiing the freezer on any kind of trip really obviously....

Where is the freezer?

the plastic from the house changes back to copper once it's in the outbuilding, but as it's all existing I guess I can just ignore it for the time being.

No you can't, not if you have a PME supply - read this.

I guess fitting the fused spur for the lights is the way to go as regards compliance vs. safety then!

Yup.

 

[SeanT]

OK, so I've taken a look at everything and started nothing sofar.
I have found:

The current installation runs from a 15a wired fuse (soon to be changed for an MCB, either 16 or 20, read on), through a 13 amp fused spur, and from there via 2.5mm cable out to the outbuilding (presumably through some sort of protective buried sheath, don't really care by now TBH, it's already in place and supplying plenty of current for years without failing)
It is all joined together as a radial circuit, with each light being drawn off then a choc block on the neutral and normal (10A!) lightswitch jobby - all in 2.5mm including all the lighting - it feeds two sockets and the two lights. The plan is to extend the radial to feed two more sockets and two more lights (well, two light fittings from one switch)

Changes to existing installation - fit switched fused spurs to each light switch position - they are already under-rated for the 13 amp circuit they are connected to - remove 13 amp switched fuse spur by the distro board in the house and change fuse for a 16 or 20 amp mcb (the rest of the board is going mcb at the same time) - the reason for this is to more accurately reflect the loading which is a washer, dryer, freezer and two light fittings, and then some additional stuff to be added in the shed - total theoretical maximum load around 5kW so will probably use the 20 amp breaker (and leave the kitchen on a 16...) Installation is TN-S so extra bonding may or may not be required - tempted to leave it as is and deny all knowledge tbh but will look into supp. bonding when we take the sink unit out and replace it (as it's about to fall over) - should be over the summer anyway.

New installation in the shed - extend radial from second in line socket in outbuilding - RCD protected fused spur as the first device - couple of metalclad sockets - another switched fused spur for lights.

Have I messed anything up massively?

 

[SeanT]

Bump for ban

 

[ban-all-sheds]

(presumably through some sort of protective buried sheath, don't really care by now TBH,

If you just assume that the existing cable is OK, can you be absolutely sure that it will be OK on a 16/20A breaker? If you don't hoick it out or replace it, can you be absolutely sure that some of the run isn't in 1mm²?

Changes to existing installation - fit switched fused spurs to each light switch position - they are already under-rated for the 13 amp circuit they are connected to

Yup.

remove 13 amp switched fuse spur by the distro board in the house and change fuse for a 16 or 20 amp mcb (the rest of the board is going mcb at the same time) - the reason for this is to more accurately reflect the loading which is a washer, dryer, freezer and two light fittings, and then some additional stuff to be added in the shed - total theoretical maximum load around 5kW so will probably use the 20 amp breaker

How do you plan to test the circuit to confirm that the fault loop value is OK for a 20A breaker?

(and leave the kitchen on a 16...) Installation is TN-S so extra bonding may or may not be required - tempted to leave it as is and deny all knowledge tbh but will look into supp. bonding when we take the sink unit out and replace it (as it's about to fall over) - should be over the summer anyway.

No supplementary bonding req'd in kitchens.

New installation in the shed - extend radial from second in line socket in outbuilding - RCD protected fused spur as the first device - couple of metalclad sockets - another switched fused spur for lights.

So that will leave some sockets in the outbuilding without RCD protection?

Why not have a small CU in the outbuilding rather than all these FCUs?

 

[SeanT]

I will fit a small cu in the outbuilding sooner or later, but as you say, it's notifiable. Thanks for clearing up the randomness!
I won a box of ten switched fused spurs on ebay when I only actually needed one, so it makes sense to use a couple up rather than going out and splashing money on a cu.
Ultimately, I intend to leave it safer than it already is, upsizing the breaker because 20 amps is already being drawn out there by the wife on a daily basis, through the 13 and 15 amp fuses, and removing the components that are not already rated for 13 amps - plus the 2.5mm seems to join in the ceiling somewhere and will be a pain to replace in the correct manner - this will however be done when we remove the massive water storage tank and possible asbestos roof on the top of the outbuilding - hence being unwilling to tamper for now up there.
I can see where the cable leaves the house, and where it enters the outbuilding, I know it's a calculated risk, but the distance underground is around 1 metre and it's the same brand of cable either side - it'd have to change twice underground within the space of a metre - fair point though, for all I know someone tagged onto an old cable either side, but it doesn't look that way.
I know I'm just trying to justify doing something that isn't strictly 100% correct, but I'm still allowed to retain the non-rcd protected sockets out there under one of the current versions of the wiring regs (don't see me going round the whole ground floor of the house changing outlets or shelling out on a new cu either....) - plus I really don't want all my food defrosting, as that'd just make the "upgrade" even more expensive - the wife leaves the freezer door open often enough anyway!!