Supply to shed

[Horace]

Hi hope someone can help. Some years ago I run a supply to my shed (two sockets and two lights) and all is still in place and operating as usual. My issue is that I may not have installed it up to scratch according to regs and I want to clarify.

The sheds supply is spurred from the house ring main (RCD protected at the DB) via a sfcu, the spur goes through the wall to an outside socket, it continues down steel conduit into an adaptable box (under patio) where it connects (via crimps) to an SWA that runs the length of the garden (buried) to the shed. In the shed the SWA is terminated to a DP sfcu where the load side goes to an adaptable box (it is accessible) to feed BOTH the socket and light circuits wired in 2.5 and 1.5 respectively.

 In hidsight I could/should I have put in a second fcu (next to the last socket) to supply/protect the lights and account for cable size reduction; however the supply is already protected by the sfcu where the SWA comes in at 13a, so is this necessary ? 

The joint under the patio is inaccessible but if its filled with resin thats alright isnt it ?

BTW ive got C&G 2360 pt's 1 & 2, never did the NVQ 3 thou and tbh dont think I ever will.

 

[Doc Hudson]

 In hidsight I could/should I have put in a second fcu (next to the last socket) to supply/protect the lights and account for cable size reduction; however the supply is already protected by the sfcu where the SWA comes in at 13a, so is this necessary ? 

The current capacity guidance for 1.5mm T&E ranges from 10A, 13A, 14.5A, 16A to 20A depending upon how much of it is buried in insulation through to clipped direct. Your couple of lights are very unlikely to start any overloading issues on what is a short run of 1.5mm. If you did happen to put a dead short across the L&N I would think your 13A FCU will pop before the shed burns down from the lighting cable fault. If you are really worried put a 10A fuse in your house FCU. https://www.tlc-direct.co.uk/Main_Index/Necessities_Index/Plug_Top_Fuses/index.html This would still give you enough power for your sockets  for occasional garden tools etc.

Doc H.    

 

[Rob_the_rich]

 In hidsight I could/should I have put in a second fcu (next to the last socket) to supply/protect the lights and account for cable size reduction; however the supply is already protected by the sfcu where the SWA comes in at 13a, so is this necessary ? 

1.5mm can carry 13A, depending on the installation method, but I seem to remember lighting circuits being limited to max 10A ocpd. Probably something to do with the size of the terminals in the fittings.

We have a patio expert on this site, I am sure he will be along shortly.

 

[doormatt26]

Also may need to check the rating of the accessories as some are only rated at 6/10a for lighting. (as per manufactures instructions)

 

[Horace]

Thanks for the responses, will have to look up the ocpd for my specific lights/circuit, if it is 10a then a fuse at that size in the fcu would solve it, and bring it up to regs.

 

[Evans Electric]

Hi Horace ,   a second spur in the shed would have been good but not the end of the world  .  

I don't like that galvo adaptable box being buried under the patio though although its a bit late now .  Is it a three core SWA or are you using the armouring as earth ?    Just feel the galvo box will  start to break down over time . 

 

[Horace]

Hi Horace ,   a second spur in the shed would have been good but not the end of the world  .  

I don't like that galvo adaptable box being buried under the patio though although its a bit late now .  Is it a three core SWA or are you using the armouring as earth ?    Just feel the galvo box will  start to break down over time . 

Hi Evans, it is a 3 core, i used 1 core for earth aswell as the armour (banjos at fly lead at each end). The adaptable box under the patio is galvanised but it is concreted in and filled with gel. My concern about this install stems from the possibility of getting a scam assessor round to inspect a new cu I installed in the house, if he enquires about the supply to the shed I want to be able to ensure that its up to scratch as is reasonably possible, would a comment on the EIC suffice ?

In regards to the rating of the two lights, the connector blocks in them are at least 15a size, definitely not the smallest 5a ones, I do not have the makers box or leaflet that may have stated the max values.

So in a nutshell I want to make good (where absolutely necessary), for the assessor; could I get away with it  ?:| , as it is now ? 

 

[Evans Electric]

Ah !   Right then , just show him the consumer unit , the shed thing is'nt that bad really but if it arises can you say it was already there .?   Otherwise just show him, have the Zs at the shed ready and the RCD trip times down. 

Don't worry , you 'll be enlisted anyway as long as the cheque hasn't bounced.  Unless he considers you a total Bozo .

Do a good job of the consumer, he will ask some stock questions which help them to assess if you have a working knowledge of the profession , the Regs, testing .   Memorise the maximum Ze values :

TN-S       0.8 Ohms

TN-C-S   0.35 Ohms

TT           21Ohms     (And read up on it becoming unstable )

Which scam are you going with ?  

 

[Horace]

Which scam are you going with ?  

Not sure yet but leaning towards Elesca

 

[Rob_the_rich]

Are there any extraneous metal bits in the shed that might need bonding?

If so, what size SWA? What size/type is the cable from the ring to the galvanised box?

What type of earthing system is the installation?

I am thinking that the earthed box in the ground could have a different earth potential to the earth around the shed,.

 

[Evans Electric]

Not sure yet but leaning towards Elesca

I'm with ELECSA  which is basically the NICEIC now , but not so picky I think .

STROMA are 1/2 the cost by the way.

Picking up on Rob's post , if theres extraneous metal in the shed  bond it .   And tell you assessor you did it some years ago , you'll be fine as long you are confident that you know what you're doing ,  not up with modern qualies , you'll need the  C&G 2382 though (17th edition Regs) And of course , all the required stuff ,  testers , Insurance, etc   they send you a list to comply with .

Let us know how it all goes.

 

[Horace]

Are there any extraneous metal bits in the shed that might need bonding?

If so, what size SWA? What size/type is the cable from the ring to the galvanised box?

What type of earthing system is the installation?

I am thinking that the earthed box in the ground could have a different earth potential to the earth around the shed,.

Hi Rob, Its a TN-S system, no extraneous conductive parts in the shed (other than the door handle), the shed is wooden, has a wooden floor on joists resting on concrete footings. The box in the ground is concreted in behind a retaining wall with footings, about 10m from the shed. 

2.5mm from the house to the shed.

 

[Horace]

Thanks for the responses guys, most helpful.

 

[Rob_the_rich]

Thanks for the responses guys, most helpful.

Best of luck with your assessment, choccy biccies and real coffee might help.

 

[Risteard]

1.5mm can carry 13A, depending on the installation method, but I seem to remember lighting circuits being limited to max 10A ocpd. Probably something to do with the size of the terminals in the fittings.

We have a patio expert on this site, I am sure he will be along shortly.

No. BS 7671 has a maximum of 16A (if pendants are on the circuit from memory).

 

[Sidewinder]

No. BS 7671 has a maximum of 16A (if pendants are on the circuit from memory).

 559.5.1.204, so UK only, and yes 16A when B15, B22, E14, E27 or E40 lamp holders are connected to the circuit.

 

[Rob_the_rich]

 559.5.1.204, so UK only, and yes 16A when B15, B22, E14, E27 or E40 lamp holders are connected to the circuit.

I was looking for the 10A limit and couldn't find any in byb or osg, perhaps something to do with standard circuit or cable sizes, dunno, can't find it, my bad.

But the ceiling roses and the switches in domestic are usually rated at 6A aren't they? I know it depends on the loads downstream of the fittings, if you were switching more than 6A alarm bells might ring, but in the first ceiling rose of a lighting circuit, the loop terminals could get a roasting if 16A were going through it.

There wouldn't be any through wiring in the terminals of B15, B22 etc lamp holders (unless it is designed for it 559.5.3.1), so the 16A must just be part of the standard for those fittings.

 

[Andy™]

TT           21Ohms     (And read up on it becoming unstable )

200 Deke, the 21 ohms is for something else

 

[Sidewinder]

I was looking for the 10A limit and couldn't find any in byb or osg, perhaps something to do with standard circuit or cable sizes, dunno, can't find it, my bad.

But the ceiling roses and the switches in domestic are usually rated at 6A aren't they? I know it depends on the loads downstream of the fittings, if you were switching more than 6A alarm bells might ring, but in the first ceiling rose of a lighting circuit, the loop terminals could get a roasting if 16A were going through it.

There wouldn't be any through wiring in the terminals of B15, B22 etc lamp holders (unless it is designed for it 559.5.3.1), so the 16A must just be part of the standard for those fittings.

Domestic switches are often only 6 or 10A rated, some mind, are 20A rated, but, remember that the lamp holders listed are also used in industrial & commercial installations so may even be contactor switched.

I think it is in the product standard for lamp holders that they are limited to 16A, but, I've not checked.

The fact remains that 559.5.1.204 gives this value as a max for any circuit with those lamp holders any where.

There are other things such as those you suggest that may require a lower max breaker current as it were.

 

[Evans Electric]

200 Deke, the 21 ohms is for something else

I thought  21 was a  stated  figure from the DNO , at their transformer,  and then, as you say, over 200 is said to become unstable .