Connecting 6mm SWA to 2.5mm T&E in an FCU

[EFLImpudence]

1. Why is connecting outside power in the way I’ve proposed in the original post not something a DIY’er should do?

Because you don't know what you don't know - and would have to be told everything.

2. When an outdoor FCU says it has a terminal capacity of 3 x 2.5mm², 2 x 4mm² or 1 x 6mm² cables, will it accommodate a supply of 2.5mm and a load of 6mm?

Well, arithmetically: no but the manufacturer's statements are usually not accurate.
You will see that 3x2.5=7.5; 2x4=8 and 1x6=6.

(I think the answer is yes as the FCU will have separate terminals for the load and supply so therefore the stated terminal capacity applies to each terminal?)

Of course it applies to each.

What Flameport posted was what you had; not the size of the terminals.

The 6mm² and 2.5mm² would be in different terminals - 2.5mm² for the supply and 6mm² for the load.

Do you see the problem with DIYers not knowing what they don't know?

 

[iaredarren]

@EFLImpudence Thanks for clarifying those points on the terminal capacity and the manufacturers arithmetic.

Appreciate your opinion on what I should and shouldn’t be doing DIY. I’ve done the internal wiring on the garden office already, which includes installing an 3amp FCU for the lighting circuit. I’ve also installed an external plug socket before by spurring off a socket in the kitchen. But I’ve never laid SWA and will certainly need to look how to do this and gland it off safely. I’ve also never worked with 6mm cable before, hence my worries about the terminal capacity’s.

But I’ll give what you say some thought and see about getting a qualified electrician in to do this for me. Thanks again

 

[bernardgreen]

the run will be 75 meters

metres

To run mains power over that distance from house to shed requires a careful and informed decision about the safety of exporting the Earth from house to shed. it may be that you will need to export a TT supply ( only Live and Neutral ) to the shed and provide the Earth for the shed from a ground electrode.

 

[SUNRAY]

Thank you

1. Why is connecting outside power in the way I’ve proposed in the original post not something a DIY’er should do?

outdoors electrics are a special location and in particular the earthing arrangements differ considerably from indoor systems, in fact class 1 equipment powered from an incorrectly designed installation can be potentially life threatening

2. When an outdoor FCU says it has a terminal capacity of 3 x 2.5mm², 2 x 4mm² or 1 x 6mm² cables, will it accommodate a supply of 2.5mm and a load of 6mm? (I think the answer is yes as the FCU will have separate terminals for the load and supply so therefore the stated terminal capacity applies to each terminal?)

The answer is yes and if done with care some of those accessories will accomodate 4x 2.5mm², 3x 4mm² or possibly 2x 6mm². It is likely it will be beneficial to double over the 2.5mm² supply (fold the end of the incoming supply cable back on it'self to fill more of the terminal)

 

[iaredarren]

Thanks for clarifying those points on the terminal capacity and the manufacturers arithmetic.

Appreciate your opinion on what I should and shouldn’t be doing DIY. I’ve done the internal wiring on the garden office already, which includes installing an 3amp FCU for the lighting circuit. I’ve also installed an external plug socket before by spurring off a socket in the kitchen. But I’ve never laid SWA and will certainly need to look how to do this and gland it off safely. I’ve also never worked with 6mm cable before, hence my worries about the terminal capacity’s.

But I’ll give what you say some thought and see about getting a qualified electrician in to do this for me. Thanks again

metres

To run mains power over that distance from house to shed requires a careful and informed decision about the safety of exporting the Earth from house to shed. it may be that you will need to export a TT supply ( only Live and Neutral ) to the shed and provide the Earth for the shed from a ground electrode.

Thanks very much I will definitely look into this