Correct way to install two electric sockets into shed

[emilne82]

Good Day Folks,
The wife is nagging at me to move the tumble dryer itno the shed to free up some space in the kitchen. However their is no electric in the shed at the moment. From what i have read the best way to do this is to run a radial circuit from the main consumer unit, burry the cable under ground in some sort of sheath then bring it up through the floor of the shed and install a RCB where the dryer will plug into. Instead of connecting the cable to the CU can i just add a spur of a socket in the kitch wih an RCB or is this not good practice?

 

[breezer]

Good Day Folks,
The wife is nagging at me to move the tumble dryer itno the shed to free up some space in the kitchen. However their is no electric in the shed at the moment. From what i have read the best way to do this is to run a radial circuit from the main consumer unit, burry the cable under ground in some sort of sheath then bring it up through the floor of the shed and install a RCB where the dryer will plug into. Instead of connecting the cable to the CU can i just add a spur of a socket in the kitch wih an RCB or is this not good practice?

but you also said

From what i have read the best way to do this is to run a radial circuit from the main consumer unit, burry the cable under ground in some sort of sheath then bring it up through the floor of the shed and install a RCB where the dryer will plug into.

you have answered your own question

 

[securespark]

But there's more to it than that. You have to design the circuit, choose the correct cable type & size (taking voltage drop into account), along with the correct protective device(s), bury it in the correct manner, etc etc.....

Can you do that?

 

[Steve]

you also have to notify your local building control and pay a fee for them to test it - new circuits are notifiable, as is any new stuff in a kitchen.

To power a tumble dryer and a couple of lights, I would run a 20A radial in 4mm² armoured cable to an RCD CU in the shed. But you need to take into account voltage drop on the distance of cable, and any future demands in or around the shed.

I ran a 32A radial in 6mm² armoured cable to my shed, and slapped in a 32A ring main and a 6 amp lighting circuit. Dont need the 32A, but you never know what you're going to put in there, and you dont want to dig that trench twice. big cable is cheap, labour is expensive!

You need to know how to terminate armoured cable properly, we have seen some quite disastrous examples on this forum. see here

RCD protection can either be at the house (if you have an RCD in the consumer unit), but it is normal to run the cable from the non-RCD side of the house CU (if its split load) and have a seperate RCD at the shed - this stops any nuisance trips taking out the whole house or part of it. You only need one RCD along the line.

 

[HDRW]

you also have to notify your local building control and pay a fee for them to test it - new circuits are notifiable, as is any new stuff in a kitchen.

To power a tumble dryer and a couple of lights, I would run a 20A radial in 4mm² armoured cable to an RCD CU in the shed. But you need to take into account voltage drop on the distance of cable, and any future demands in or around the shed.

I ran a 32A radial in 6mm² armoured cable to my shed, and slapped in a 32A ring main and a 6 amp lighting circuit. Dont need the 32A, but you never know what you're going to put in there, and you dont want to dig that trench twice. big cable is cheap, labour is expensive!

I'm thinking of doing this, but it's a bit more awkward because I need to dig through the concrete patio (it's cracked and knackered anyway!) - can I just lay the new concrete around the SWA "naked", or should there be some sort of pipe running through with the SWA inside that? If the latter, what sort shoud it be?

RCD protection can either be at the house (if you have an RCD in the consumer unit), but it is normal to run the cable from the non-RCD side of the house CU (if its split load) and have a seperate RCD at the shed - this stops any nuisance trips taking out the whole house or part of it. You only need one RCD along the line.

I was going to use an RCBO in the house (I have one handy! ) to protect anyone violent enough to dig through the SWA, and also an RCD in the shed's mini-CU so it's handy to reset if it trips - is this a Bad Thing? I presume the one in the house needs to be rated higher than the one in the shed so they don't both trip together (say 30 & 10mA, or 100 & 30mA)?

Cheers,

Howard

 

[Steve]

You seem to know your stuff about RCDs. Although there is no need What So Ever to protect the cable. Its protection comes from the armoured sheath. If someone cuts through the cable, there will be a guaranteed direct short to earth through the sheath, and the MCB will trip instantly.

You shouldn't be running the SWA through concrete - if you ever need to dig it up or re-route it will be a PITA. Also the cable needs to be 18 inches deep. Thats one thick slab! It wont hurt the cable to run through a couple of inches of concrete though.