supplying garden shed

[rins]

customer wants 3 sockets plus light in garden shed which is ten metres away from house, checked main cu and it has no spare ways supply is tn. is the best way to do this possibly to split meter tails into a henley block add a small cu with a main switch and 32a breaker run swa cable 6mm from this to a 2nd small cu in shed which would have 30ma rcd 20a (possibly 16a)breaker for sockets and 6a breaker for light.

also which ways best to earth the circuit would i bring an earth cable from main board across to small cu in house and attach this to earth terminal in small cu then bring another one from there to swa gland never used swa did some glanding off at college a while ago just unsure as this is my first trip into shed supply lol

any thoughts would be great thanks

 

[steptoe]

is it TN-S or TN-C-S ?

 

[rins]

Hi steptoe

its a tns supply thanks

 

[Ash]

Why 6mm?

 

[Evans Electric]

is it TN-S or TN-C-S ?

Why did I know this was coming !!!

 

[Manator]

Swa is the better cable choice but why put two CU,s in when one will do? A fused isolator near the board, then a small CU in the shed.

6mm will give you a lot of power for a shed!

 

[jameseye12]

What about Part P?

 

[unphased]

Have you considered installing an 13A unswitched spur on to house sockets and using that for the shed supply? You can still use SWA but 2.5mm2 will be adequate. Much cheaper than installing all the CUs.

 

[batty]

Have you considered installing an 13A unswitched spur on to house sockets and using that for the shed supply? You can still use SWA but 2.5mm2 will be adequate. Much cheaper than installing all the CUs.

Why unswitched I would think a switched spur would be more appropriate especially if sockets in house have RCD protection. I personally like to treat sheds as separate installs so would rather have one or two way consumer unit just to feed shed that way if it blows away in the wind its easy to isolate the electrical supply.

 

[steptoe]

if it blows away in the wind

like a paper shop? :|

 

[batty]

like a paper shop? :|

Just saying steps they can suffer with felt blowing off and the like at least if it has its own consumer unit customer can easily isolate it in an emergency.

 

[steptoe]

it was a joke batty,

yes, a totally separate supply is for me the ideal way too.

 

[batty]

I can never tell with you steps it must be your straight face.

 

[Manator]

Batty he is always joking unless at work.

 

[shed69]

like a paper shop? :|

My dad USED to have a paper shop.... Until the bad storms in 2001.... When it blew away ..... Are you having that Batty!!!! Blew away.....!! Somebody stop me!!!!

 

[batty]

If you don't stop telling bad jokes I will tell you some of mine you will regret it.

 

[AK-UK]

I think that a separated supply, with an isolator in the house and then supply to the shed with armoured to the mini CU.

I just wondered what you guys think, the same situation but there is a free slot in the house CU, 4mm2 armoured to a mini CU in the shed with 3 RCBOs (I always use a supply cable that is a bit bigger than what is required at the time of installation because there is always someone who will add something on the load side.... The home CU does not have RCD (pre 16th) would anyone of you put in the home CU RCD to protect the supply cable (to the shed) or you think that it is not necessary and MCB will be enough?

 

[unphased]

Why unswitched I would think a switched spur would be more appropriate especially if sockets in house have RCD protection. I personally like to treat sheds as separate installs so would rather have one or two way consumer unit just to feed shed that way if it blows away in the wind its easy to isolate the electrical supply.

IMHO electrical installations are first and foremost electrically safe. A 13A unswitched fused spur, or even a switched one, it doesn't really matter, on an RCD protected circuit supplying a shed is safe. Personal preference is just that. Personal preference for a separate supply costs the customer more money. We are not concerning ourselves, are we, whether the shed might blow down when designing an electrically safe installation. The house might catch fire. The shed might catch fire. The house might get flooded, a lorry might smash through the wall out of control. Do you get my point? IMHO electricians consider too many situations outside of their remit. Safety is the primary consideration. Personal preference is just that.

Edit: In fact , the main fuseboard in the house is going to serve the same function as a separate one if you need a point to turn off a circuit. Inconvenient yes, but unsafe, no. Guinness

 

[PC Electrics]

If the CU and shed are co-positioned such that a run from the CU to the shed is convenient, then how about this:

Take a spur from a suitable circuit MCB in the CU, down to a high quality (MK perhaps) DPSwFCU. Use this to feed a 2.5 or 4mm (depending on your volt drop calculations) SWA to the shed. At the shed split the incoming supply in a suitable enclosure to feed the sockets directly (overload protection from the FCU in the house) and another SwFCU with a 3A fuse for lights.

You give no indication of the expected loading or the size of the shed, but this will provide plenty enough capacity for most domestic sheds.

# If you take your spur from an existing socket circuit that is already RCD protected, then no need for any more RCDs. If there is a circuit you can use on the non RCD side then add an RCD in an enclosure in the shed just for the sockets.

# in the event of a fault outside, the DPSwFCU can be used to isolate the shed supply from the house untill the fault is fixed.

# the solution is cost effective, no need for mini CUs and MCBs. Keep it simple.

# If you've read up on the ESCs concern regarding overloading of multi gang extensions and have looked at the current / time curve for a 13A 1362, you will know that a 13A 1362 will pass 20A indefinately. So you have effectively provided the client with a 20A supply. Because of this I recommend designing the supply as 20A and using a high quality FCU to be able to cope with this potential overload.

# True, if there is a fault outside it will knock out the house sockets too. But this is a minor inconvenience in the domestic environment and with the DPSwFCU you've taken measures to limit the inconvenience.

# Use the switch on the lights FCU - no extra light switch required (cost effective).

# if this is a "workshop" and there may be rotating machinery, fit HF light fittings.

---------- Post Auto-Merged at 09:54 ---------- Previous post was made at 09:44 ----------

No need to provide the client with a Rolls Royce solution if all he wants or needs is a Mini. You'll just end up pricing yourself out of getting the work.

---------- Post Auto-Merged at 09:56 ---------- Previous post was made at 09:54 ----------

Note that I mentioned using a DPSwFCU - not all FCUs are DP. In fact most (cheaper) are SP. It's a common misunderstanding.

 

[chrisg1979]

For just 3 sockets and a light then I can't see a problem with a fcu (switched or unswitched).

If the existing circuit is RCD protected then great, if not an RCD fcu would be fine.

Important to test the circuit your spuring off, and check all other relevant factors (bonding etc) but presuming it is just a shed and not a workshop/garage then a dedicated supply may be unnecessary.