Wiring to a micro-brewery in outside shed with a water supply.

[Sightblinder]

Apologies if I'm repeating stuff that's been covered, I did have a look and couldn't find clear answers, especially as there is a water supply involved.

I want to replace the existing wiring in an outside shed with a dedicated feed from the house CU. Currently sockets and lighting in the shed are run from a 13 amp fused spur from the ground floor ring in the house, but this wont have the capacity to run the kit I want to install for a micro-brewery - Brew kettle, water heater, chiller etc that will need around 28 Amps between them at full chat. It's all standard 240v single phase stuff. No 3 phase commercial kit.

Having done some reading I have an idea of what needs doing but wanted a sanity check on the approach and to get some advice on the grounding requirements as there is a water supply in the shed, i.e. extraneous conductive parts if I have the terminology right. The shed is about 25 meters from the house CU. The water supply is fed from the main household supply (feeds taken from the hot and cold water pipes under the kitchen sink) which already has earth bonding on it.

The plan is to do most of the heavy lifting myself and get a local electrician to make the final live connection and inspect / certify afterwards.

Current thinking is to run a 10mm Twin and Earth SWA from a 40 Amp MCB in the house CU, I have an RCD protected spare way in the CU that can be used. Terminate this in a 2 way garage CU in the shed, with RCD, a 6 Amp MCB for the lights and a 32 Amp MCB for the sockets to feed the brew kit.

SWA will be cleated to the outside wall for most of the run and to timber joists for a section where it goes under some decking.

I'll use weatherproof junction boxes with appropriate glands for the SWA on the outside of the house and shed outbound and inbound respectively.

If this makes sense my main question is about the earthing requirements. Can I rely on the earth in the house CU or do I need additional bonding in the shed to the water pipes, or a separate earth spike?

I've tried to get my head around the IET regs but I'm struggling to make sense of it. I've also read https://electrical.theiet.org/media...tdoors-a-supply-to-a-detached-outbuilding.pdf but still not clear on what's needed.

 

[Murdochcat]

Best locate a local spark to discuss this with and agree who does what.

Local eyes on site trumps random internet advice

 

[ETAF]

thought i should just flag
Will this just be for home consumption , just thought i would mention, may be an impact on mortgage and / or home insurance and various other utilities etc

as far as the electrician as said, you need to discuss with them, I have been in the electrical and electronics game and highly qualified - BUT I dont have the paperwork to sign off electrical work - so i spoke to some electricians locally in 2018 when we needed to look at rewiring / new consumer unit - all straight forward stuff - which i have also done before on a few houses , back in 70's 80's - not one of the 5 i spoke to was interested in signing off or discussing my doing any of the work...
BUT in the end i paid for 2 electricians to various parts of the work, 2 because the kitchen fitters / bathroom fitters would only use there preferred electricians and not the one i had to change the consumer unit - to be honest along with covid and getting hold of anyone it was a real pain.

 

[EFLImpudence]

Outside power is not really a DIY job so - as above.

A few points, though.

Having done some reading I have an idea of what needs doing but wanted a sanity check on the approach and to get some advice on the grounding requirements as there is a water supply in the shed, i.e. extraneous conductive parts if I have the terminology right. The shed is about 25 meters from the house CU.

Yes, most likely extraneous-c-ps and as such should be bonded already if using the house earth. It should have bonding with a 10mm² conductor which you will have in the 10mm² SWA.

Your new work will not make any difference.

The plan is to do most of the heavy lifting myself and get a local electrician to make the final live connection and inspect / certify afterwards.

It doesn't work like that.
You need a registered electrician to supervise throughout in order to be able to Inspect, certify and notify the local authority; otherwise you must notify the local authority before the work commences - and see what they say..

Current thinking is to run a 10mm Twin and Earth SWA from a 40 Amp MCB in the house CU,

Twin and earth is the normal household wiring. SWA will be called three-core.

I have an RCD protected spare way in the CU that can be used.

You don't require or want an RCD in the house on SWA; that's why it is used.

Terminate this in a 2 way garage CU in the shed, with RCD, a 6 Amp MCB for the lights and a 32 Amp MCB for the sockets to feed the brew kit.
SWA will be cleated to the outside wall for most of the run and to timber joists for a section where it goes under some decking.

I'll use weatherproof junction boxes with appropriate glands for the SWA on the outside of the house and shed outbound and inbound respectively.

Up to the electrician how you do it.

If this makes sense my main question is about the earthing requirements. Can I rely on the earth in the house CU or do I need additional bonding in the shed to the water pipes, or a separate earth spike?

As I said, it should be bonded already but you can use the SWA when fitted.
People use spikes to avoid having to run a 10mm² bonding conductor back to the house but your SWA is that size anyway.

I've tried to get my head around the IET regs but I'm struggling to make sense of it. I've also read https://electrical.theiet.org/media...tdoors-a-supply-to-a-detached-outbuilding.pdf but still not clear on what's needed.

I haven't read all that

 

[Sightblinder]

Outside power is not really a DIY job so - as above.

A few points, though.


Yes, most likely extraneous-c-ps and as such should be bonded already if using the house earth. It should have bonding with a 10mm² conductor which you will have in the 10mm² SWA.

Your new work will not make any difference.


It doesn't work like that.
You need a registered electrician to supervise throughout in order to be able to Inspect, certify and notify the local authority; otherwise you must notify the local authority before the work commences - and see what they say..


Twin and earth is the normal household wiring. SWA will be called three-core.


You don't require or want an RCD in the house on SWA; that's why it is used.


Up to the electrician how you do it.


As I said, it should be bonded already but you can use the SWA when fitted.
People use spikes to avoid having to run a 10mm² bonding conductor back to the house but your SWA is that size anyway.


I haven't read all that

Thanks for taking the time to reply. You're info on the bonding was really helpful, thanks.

Apologies, I wasn't clear on the original. I don't intend to do it all and then rock up to a local electrician and ask them to sign it it off. I'm trying to get as much together as I can in advance before asking them to look at what I propose, agree what I can and can't do, and go from there. I'm happy to pay for their time to do that, I just can't afford the £5-600 it's likely to cost for the full job because of the labour involved in running the cables. It can't just be buried because it's concrete pretty much all the way between the CU and the shed.

 

[Sightblinder]

thought i should just flag
Will this just be for home consumption , just thought i would mention, may be an impact on mortgage and / or home insurance and various other utilities etc

as far as the electrician as said, you need to discuss with them, I have been in the electrical and electronics game and highly qualified - BUT I dont have the paperwork to sign off electrical work - so i spoke to some electricians locally in 2018 when we needed to look at rewiring / new consumer unit - all straight forward stuff - which i have also done before on a few houses , back in 70's 80's - not one of the 5 i spoke to was interested in signing off or discussing my doing any of the work...
BUT in the end i paid for 2 electricians to various parts of the work, 2 because the kitchen fitters / bathroom fitters would only use there preferred electricians and not the one i had to change the consumer unit - to be honest along with covid and getting hold of anyone it was a real pain.

Yeah, home consumption only, not planning on selling it any time soon although it's been suggested I should

 

[flameport]

or do I need additional bonding in the shed to the water pipes,

Use plastic pipes, then bonding is irrelevant.

 

[ericmark]

I will not repeat good advice already given. You will need some cooling, and refrigeration plant is very dependent on voltage. So start point is the loop impedance or prospective short circuit current.

So looking at design.

As to earthing, this is complex, and I would want to survey the site before deciding how to go, but as long as not a metallic shed should not be any real problem.

As to RCD personally would not use one in the main house, which means no real option supply will be SWA.