Electrics to shed - option review opinions

[wizbongre]

Hi All,

Following my original thread //www.diynot.com/forums/electrics/swa-for-new-shed.408691/ I've now (finally!) spoken to a few sparks to get ideas of cost and what they would do. This has led to 2 general camps in terms of design, both of which seem ok to my amateur understanding so I wondered what the consensus on here might be...

Option 1
Junction box adjacent to existing main CU into MCB (none RCD protected) then suitably sized SWA from there along outside of house (kitchen extension) under patio and garden and into a junction box adjacent to a new mini-CU in the new shed. 6mm 3-core SWA but could go for 10mm for future-proof as cost difference of materials isn't massive compared to hassle of replacing.

Option 2
T&E from MCB in main CU, along inside of house through kitchen extension into junction box on inside wall. SWA from there, under patio and garden to shed mini-CU as above. Option to use 4-core SWA and have a two-way switch in kitchen to remotely switch garden lighting.

Based on initial estimates, the overall costs aren't that different as the increased costs of the longer SWA run for option 1 are balanced out by increased labour costs to run the internal cable for option 2 (would involve underfloor fishing due to solid & wooden floors and some channeling.) I assume the T&E would be equivalent size to the SWA for option 2 but haven't asked.

In my mind, option 1 would be easier in terms of installation however option 2 seems more attractive in terms of convenience for me, as although 2-way switching for remote lights isn't on my radar at the moment it would be a nice to have in future.

Anyway, I wondered if anyone on here has an opinion or preference on the two options? (Of course, of the 4 sparks I've discussed this with there are more details they've considered and probably others I've missed off but I think I've covered off the main points here.) For what its worth, the existing setup to our garage is essentially option 1, with 4mm SWA and a 32amp MCB in the main CU. In the main CU there is a spare 20amp MCB ready and waiting for the shed to be cabled up (assume the spark who originally re-wired the house put it there long ago.)

Any comments welcome. The sparks I have spoken to all appear to know what they are doing and as mentioned, costs aren't massively varying so I'm just wondering it there is something I should be making the decision on that I'm missing?

 

[AndyPRK]

I think its up to you really.

1) Do you want the unsightly cable outside
or
2) Do you want the risk/mess of them ripping up your kitchen ?


You could always use 4 core for option 1 and have the garden light switch next to the CU ?
May not be the best place to have the switch, but better than having to unlock a shed to turn the lights on. (or turn off at the end of the evening)

 

[wizbongre]

Thanks Andy. I was hoping it would come down to personal preference and not end up depending on some technical issue.

We plan on re-tiling the kitchen and replacing the worktops in the near future, so a bit of mess now isn't the end of the world.

I think that is decision made - option 2 is favourite

 

[ban-all-sheds]

Option 1
Junction box adjacent to existing main CU into MCB (none RCD protected) then suitably sized SWA from there along outside of house (kitchen extension) under patio and garden and into a junction box adjacent to a new mini-CU in the new shed. 6mm 3-core SWA but could go for 10mm for future-proof as cost difference of materials isn't massive compared to hassle of replacing.

Option 2
T&E from MCB in main CU, along inside of house through kitchen extension into junction box on inside wall. SWA from there, under patio and garden to shed mini-CU as above. Option to use 4-core SWA and have a two-way switch in kitchen to remotely switch garden lighting.

Option 1 every time - completely separate it from the house CU.

A switchfuse rather than an MCB would be the norm.

You could still use multi-core SWA if you want, but remember that the cores will be large. Wireless switching might be preferable.

 

[wizbongre]

Thanks bas.

I'd originally planned to use a remote switch (as have some spare) for the lights until someone suggested the two way switching. That would be cheaper overall as it'd drop the cost of the SWA.

Think I need a follow up conversation with the spark(s)...