Power to a play barn/hut

[paul_in_luton]

Hi All.
Apologies but I've just joined and couldn't post this in the DIY section where it should be.

I've seen other threads on this forum dealing with almost the same problem but I thought I'd try it anyway, so here goes. I have built a play barn/hut at the bottom of the garden for my teenage kids. Currently, when they want to go down there to play pool, table tennis, listen to music etc, they open a window in the conservatory, pass and plug in an extension lead that winds its way down the garden to the hut and off they go. Not ideal to say the least and probably illegal.
I’ve already cabled up two ring mains – 4 double sockets on each, one spur plug on the mezzanine and 6 separate lighting circuits. The only reason for having eight double sockets is that no matter where you put them, they always seem to be in the wrong place. The only stuff that’ll be running down there is a stereo, a small electric fan heater and the lights. Nothing too heavy.
I now want to make this safer so I’m thinking of taking a 50m length of 10mm 3-core SWA out of the back of the consumer unit in the house, burying it 500mm deep, complete with warning tape, instead of the extension lead. The SWA will then go through the concrete wall into the hut, via a metal junction box and on into a Crabtree 410/2B Starbreaker insulated 10 way consumer unit with switch disconnector isolator 100A. Then have two Crabtree 61/B13230 Starbreakers 1 module single pole type B RCBO 32A 6kA 30mA for the ring mains, one 61/B11630 for the spur and six 61/B10630 for the lights.
How does this sound? Comments would be much appreciated.

 

[Marvo]

Welcome to the forum Paul. I've put your thread in the DIY section as suggested and you should now have permissions to post there.

 

[Andy78]

Hi Paul.
What you are proposing is a new circuit and is therefore notifiable to local building control in accordance with part P of the building regs. You can read a bit about it here Elecsa - Part P - What it Means

While there is practically not much wrong with what you suggest, this will need testing with appropriate equipment by a trained individual, a certificate producing, and notifying to building control. This is a job for a local sparky. You should contact a few and seek their advice. They may be willing to let you do the trench work then make the final connections and do the testing, but that would be at their discretion.

A sparky will also be able to look at your existing system in the house, check it is up to standard, and perform cable calculations to make sure everything is fine for your proposed use. These are necessary steps and should not be skipped.

Cheers
Andy

 

[Badged01]

Getting rid of that extension lead and putting in fixed wiring is the safest way to go without a doubt and what you are suggesting seems feasible with a few tweeks.! However, I agree with Andy and my advice would be that you are undertaking a complex task here that involves testing beyond the DIY scope so you really should be getting a “Part P” approved electrician to complete this for you.

Work in the garden is also reportable under Part P of the building regs -- In Wales it is but if you are in Luton (England) then it isnt.

But to answer your question as this is what the DIY forum is for. Ideally you want your SWA run from a non-RCD protected way in the consumer unit then the consumer unit in the shed providing RCD protection to the circuits there. If you have an RCD at the front end of the SWA (house) and in the shed CU you run the risk of both tripping together for a fault in the shed --- i.e. you will loose house circuits if the shed ‘pops’.

For the 10mm SWA cable to meet the 3% voltage drop reqt the SWA should only be pulling 32A which again means you only want two circuit breakers in the shed – 20A or 25A for the sockets and 6A for the lights. (Not RCBO’s.) 25+6=31A

You shouldn’t be having 6 separate lighting circuits on breakers and 3(?) separate socket circuits on breakers as you will potentially be drawing more than the 32A for the VD requirement -- even though the actual cable can handle around 60A.

You will also need to ensure any exposed extraneous metal parts (water pipes?) in the shed are bonded to the consumer unit.

The physical doing of the work is fairly easy but the skill is in the design then the testing and confirming of the electrical safety afterwards. Ive only scrapped the surface here which is why I would strongly recommend you get a professional in to do it for you --- most will be happy for you to do the donkey work if you discuss with them beforehand what they will accept you doing.

 

[HandySparks]

OK, I haven't seen the job, but I'm puzzled as to why you're proposing to use nine final circuits for an outbuilding. RCBOs are a good way to go, but I would have one 20A or 32A for the sockets and one or two 6A lighting circuits. You'll save an awful lot of cash on RCBOs without losing any real functionality or safety.

 

[Andy78]

Getting rid of that extension lead and putting in fixed wiring is the safest way to go without a doubt and what you are suggesting seems feasible with a few tweeks.! However, I agree with Andy and my advice would be that you are undertaking a complex task here that involves testing beyond the DIY scope so you really should be getting a “Part P” approved electrician to complete this for you.

Work in the garden is also reportable under Part P of the building regs -- In Wales it is but if you are in Luton (England) then it isnt.

But to answer your question as this is what the DIY forum is for. Ideally you want your SWA run from a non-RCD protected way in the consumer unit then the consumer unit in the shed providing RCD protection to the circuits there. If you have an RCD at the front end of the SWA (house) and in the shed CU you run the risk of both tripping together for a fault in the shed --- i.e. you will loose house circuits if the shed ‘pops’.

For the 10mm SWA cable to meet the 3% voltage drop reqt the SWA should only be pulling 32A which again means you only want two circuit breakers in the shed – 20A or 25A for the sockets and 6A for the lights. (Not RCBO’s.) 25+6=31A

You shouldn’t be having 6 separate lighting circuits on breakers and 3(?) separate socket circuits on breakers as you will potentially be drawing more than the 32A for the VD requirement -- even though the actual cable can handle around 60A.

You will also need to ensure any exposed extraneous metal parts (water pipes?) in the shed are bonded to the consumer unit.

The physical doing of the work is fairly easy but the skill is in the design then the testing and confirming of the electrical safety afterwards. Ive only scrapped the surface here which is why I would strongly recommend you get a professional in to do it for you --- most will be happy for you to do the donkey work if you discuss with them beforehand what they will accept you doing.

Any new circuit is notifiable. It's only minor works not requiring an EIC within a garden that would not be notifiable.

 

[Badged01]

Any new circuit is notifiable.

I stand corrected! Overlooked that point, for some reason was thinking it was tapped off a existing socket even though it was a 'new' circuit from the CU. Another reason to get a "professional" in to eye-ball the job and design it correctly!