RCD Breaker for shed

[cakeman]

Hi

I need some advice on safety for my outside shed
i have had it for 2 years so far with no issues, but i would like to make it proper safe
it is large and designed to store plates & equipment in


but i also have 5 fridges & 1 freezer in there
1 dishwasher
also a socket for extension cables for mowing or using a drill etc
also 5 low energy light bulbs for lighting

what size RCD breaker should i use to be safe and any other suggestions

the fuse box in the house has an excellent set up system of RCD's that work very well. Will these be sufficient enough anyway

thanks in advance

 

[Chri5]

Does the feed to the shed go direct or is it a sub board of the main house CU ?

 

[cakeman]

The feed to the shed is via a junction box in the loft which is on one of the socket cicuits in the house

 

[Steve]

What do you keep in the fridges / freezer? Say an RCD tripped and everything thawed out overnight, would it cause you great hardship?

If so, you'll need to keep those appliances off an RCD by hardwiring them to FCUs, and using surface wiring or steel conduit or SWA all the way from the meter in the house (This isn't normally a problem for most shed installs since the bulk of the run to the shed should be SWA anyway)

What I did in my shed was to use an RCBO (MCB and RCD in one) for the socket circuit, the rest of the installation is non-RCD protected. This leaves me with reliable lighting if the RCBO should trip. Then you'd run another circuit for your fridges and freezers, a 32A radial would suffice if they are domestic appliances (not these:

)

 

[Steve]

The feed to the shed is via a junction box in the loft which is on one of the socket cicuits in the house

Then where does the cable go? Describe its route, distance, and any accessories en-route to the sockets in the shed. And what size is it?

This could get expensive, depending on the answer to that btw.

 

[cakeman]

all fridges are domestic, nothing commercial.
there is a junction box in the loft ( house is a bungalow) which is on one of the sockets circuits , from which goes a wire to the shed .
approx 6metres long. the wire is thicker than normal domestic wiring, not sure of the exact spec but is quite a stiff flex
then at the shed it meets another junction box

1 circuit goes directly to a multi socket adapter thing which is fused and feeds 4 fridges on it

the other has a double socket which does 2 fridges , lights & a spare socket to plug in the occasional tool

like i said in a previous post everything seems to be working well but i am not sure if this is safe or not
wiring never feels warm and the last 2 years or so has been touble free

 

[Steve]

It sounds like a bit of a lashup to be honest with you. And I'm not at all sure its safe. What is written on the MCB/fuse at the house which isolates all this? Is there an RCD protecting this as well? Could you post some pictures up of the things you describe? ("thicker than normal wiring" doesn't tell us anything I'm afraid)

 

[cakeman]

it is connected to an RCD circuit , which does its job well

i'll put up some pics tomorrow when its light

MCB has
240v
50Hz
80A
100mA trip
CAT WEM 80/2

thanks for help so far

1 further piece of info, the dishwasher had a fault last year and had a leak which tripped the whole house electric immediately. i think that means its doing some sort of a good job

 

[Steve]

1 further piece of info, the dishwasher had a fault last year and had a leak which tripped the whole house electric immediately. i think that means its doing some sort of a good job

Yeah but its no good for your cake stuff in the shed. And 100mA is too high trip current. It only takes 50mA to kill a man. Thats why RCDs for sockets etc are 30mA.

 

[333rocky333]

For 6 fridges, Rcd sockets may be a better option, these would be 30ma rated.

The 100ma on your supply suggests the supply may be a TT system.
Is your supply overhead with two wires from a pole to the house.

 

[cakeman]

thanks steve 30mA RCD seem to be the way to go
the fuse box has individual breakers too, not sure on there rating though

333rocky333 . yes it is a 2 wire system from a pole outside the house
what does TT system mean

 

[ricicle]

what does TT system mean

TT is an earthing system where the Electricity Company does not provide an earth. Your building's earth is through an earth rod which is your responsibility. This usually makes the earth fault path high resistance so that earth fault current is lower and mcbs and fuses cannot clear the fault in time - if at all. An RCD must be used to achieve safe disconnection for all circuits in this instance and even then the external earth fault loop impedance must not exceed certain values to ensure that it is reliable and not likely to become too high with changing ground conditions

 

[ban-all-sheds]

what does TT system mean

It means that you are spared at least one worry, which would be the export of a TN-C-S earth to an outbuilding which contains extraneous-conductive-parts.

See http://www.iee.org/Publish/WireRegs...matters_electrical_installations_outdoors.pdf