Replacing existing catenary wiring to Garden Shed.

Wavey75

I currently have a semi detached house with a garden shed roughly 2-3 metres from the main house.
Currently, a 2.5mm twin & earth runs along a catenary wire to deliver a fused spur to the shed.

I am not happy with this as it means I may be overloading the existing house ring main and I would prefer that I have a separate ring to the main house as I plan to use more power tools in my DIY, which may cause problems for the electrics in the main house.

I am undecided about how to achieve this, but I am an experienced builder with no certificates in electrical wiring, but I would prefer to complete the labour myself and call a certified electrician into to verify the work and connect it to the main RCB in the house and certify it, this will cost me significantly less but I would prefer to do the labour myself as I can take my time and do things with an attention to detail.

I do not think that a SWA (Steel Wired Armoured) is necessary for this installation. Would it be even better to run a 4mm twin inside a metal 25mm or 32mm conduit, but not buried, instead running around the edge of my property and into the shed, right into a 2 way fuse board of some sort?

I plan to add another garden building (a greenhouse) that most likely will require power for things like moisture and heat as I hope to grow food that will not naturally grow in the country.

What problems will I come up against?

I do not think this is part p because I am replacing what is already there, just more safely and up to code, plus I would really love to get rid of this awful catenary.

I think that using metal conduit of SWA is better then burying an SWA, especially as everywhere is concrete on the ground.

I would be grateful for any advice, suggestions and guidance on this upcoming project.

BigBopper

If you're in the building game then get one of your sparks to pop round and have a look.

Jonesya

New circuits do fall under Part P so would need notifying.

Before you decide what to do, total up how much load you expect in the shed, because we don't know whether you're talking about a 6X4 and some hand tools, or a workshop. how many tools running at once, whats the highest rating, then the rest - shop VAC? Lights? You may find that a 13A spur off an FCU is sufficient.

Will you have a heater - that makes a big difference, if you're out there in the winter with a fan heater, that's 10A just for the heating.

http://www.planningportal.gov.uk/uploads/br/BR_PDF_AD_P_2013.pdf

Wavey75

Hi Guys,
Contacting a sparks from work is not an option.
If it's replacing an existing circuit it's not a new circuit, it's a replacement and replacements are not covered under part p, unless I am mistaken?

I have an 8 x 10 metal shed. It will be my hobby shed with a workbench so I can use a table saw, a mitres saw, maybe a phone charge, some lights and a radio or something like that. I may or may not need a heater as I am thinking of insulating it and then covering the insulation with a cheaper alternative to plasterboard, some cheap OSB sheets or something, or maybe nothing at all, haven't decided yet as I need to first install the replacement electrics.

However, I do plan to include power from my shed to my new greenhouse next to it, so whatever equipment goes into a greenhouse to grow stuff will also need to be taken into account, but I will wire the supply from the main house to the shed and run conduit from the shed to my new greenhouse (but this will be built next year) ready to be added to the RCB in the shed board later.

I am thinking 6mm to a 4 way board that will have 2 LED lights and up to 2 13amp double electrical outlets.
The greenhouse I think will have 2 more electrical outlets, but they will be added to the circuit in the shed.

I may ( a few years down the line) want to add a 30 or 32 amp isolated supply for an outdoor hot tub, so the installation now must allow for that possibility.

With this new information, I think the recommended cable would probably be overkill with 10mm to the shed, but finding out the correct cabling to use from the regulations requires a subscription, which I don't have.

phill99

All the sparks I work with won't certificate other peoples work or undertake final connection. They become responsible for the whole of the curcuit and need to verify it in its entirety. Therefore they wont accept 'unknowns' undertaking their own cable routing etc.

Ectophile

Wavey75 wrote: »

Hi Guys,
If it's replacing an existing circuit it's not a new circuit, it's a replacement and replacements are not covered under part p, unless I am mistaken?

I think you're pushing the definition of "replacement" somewhat. What you are proposing is a completely new circuit connected back to the consumer unit. It has a different origin and different capacity.

zax47

Ectophile wrote: »

I think you're pushing the definition of "replacement" somewhat. What you are proposing is a completely new circuit connected back to the consumer unit. It has a different origin and different capacity.

I agree, if he were to take the existing spur off the ring main and just change the cable and routing then that's "replacement", albeit tenuous. If you change the origin of the circuit to be the CU then that's a new circuit and comes under Part P. MOST of the Part P schemes won't allow us to certify anothers work but I believe NAPIT make some exception if you've been involved in the design and final testing.

OP, you say it's a metal shed, so have you considered how to safely export the earth beyond the equipotential zone? You really do need proper advice, if nothing else, from a sparky.

zax47

Wavey75 wrote: »

With this new information, I think the recommended cable would probably be overkill with 10mm to the shed, but finding out the correct cabling to use from the regulations requires a subscription, which I don't have.

Lots of free cable size & capacity calculators online - like this one;

https://www.tlc-direct.co.uk/Technical/Charts/VoltageDrop.html

Myself I'd run SWA, cleated to wall as low possible - you don't have to bury SWA...

Wavey75

Good to know re: SWA not needing to be buried.

I think I will just rip out the existing spur altogether and not bother with upgrading as described above. If I need electricity for a saw or a drill, I'll run an extension lead from the house and then reel it up again when done, just like I do now for hoovering the car.

I'm not going to spend £300 on a part p plan before I've even bought a 13 amp socket, which will increase the project overall costs up near £1,000 either.

I may invest in a 12v solar lighting system (roughly £30 on eBay), but a 240v solar system (to the best of my limited knowledge) will run into the £1,000's, plus may also require part p.

No point doing anything else for a rented house, even if I do plan to stay in it forever.