Csa of cable for Outside shed CCU

[FoxySparky]

Lads and ladies!
Clear up something for me please.
The old man has asked me to provide some power for his outside wooden shed, by means of a CCU and breakers for the lighting and power.
He will be running various power tools for fixing bits and pieces, and mowing the garden, while also having a floodlight and inside lights for the shed.
A radial for the sockets run off 20amp
While power is off 6amp, is what I will be doing.

What size cable should I run to the CCU from the main Board?

I reckon a 4mm would be sufficient. the old man (not electrically trained) reckons I need at least 6mm.
What do you guys think?

 

[Pete999]

Lads and ladies!
Clear up something for me please.
The old man has asked me to provide some power for his outside wooden shed, by means of a CCU and breakers for the lighting and power.
He will be running various power tools for fixing bits and pieces, and mowing the garden, while also having a floodlight and inside lights for the shed.
A radial for the sockets run off 20amp
While power is off 6amp, is what I will be doing.

What size cable should I run to the CCU from the main Board?

I reckon a 4mm would be sufficient. the old man (not electrically trained) reckons I need at least 6mm.
What do you guys think?

You need to calculate the volt drop using the appropriate VD calculation VD = (mV/A/m)z *L*Ip divided by 1000. as per BS7671

 

[Strima]

What does your design say?

Earthing arrangements?

PFC at source?

Length of run?

Installation method?

Max demand?

etc etc etc...

 

[ipf]

What does your design say?

Earthing arrangements?

PFC at source?

Length of run?

Installation method?

Max demand?

Bonding required?

etc etc etc...

...expand it, Pete.

 

[Charlie_]

I would never go as low as 4mm for this type of job

 

[The Ghost]

How far is the shed from the supply point? I used 4mm² swa for a 25m run checked out in calcs ok.

 

[ackbarthestar]

As others have said, follow the general rule from 433.1.1
Ib < In < Iz.
You'll probably find that a 4mm2 SWA will be sufficient. However, it depends what the maximum loading will be and what method of earthing is already in the house and how you'll be able make the necessary adjustments

 

[Charlie_]

I only say I wouldn’t use 4mm to allow for future load increase

 

[Pete999]

Lads and ladies!
Clear up something for me please.
The old man has asked me to provide some power for his outside wooden shed, by means of a CCU and breakers for the lighting and power.
He will be running various power tools for fixing bits and pieces, and mowing the garden, while also having a floodlight and inside lights for the shed.
A radial for the sockets run off 20amp
While power is off 6amp, is what I will be doing.

What size cable should I run to the CCU from the main Board?

I reckon a 4mm would be sufficient. the old man (not electrically trained) reckons I need at least 6mm.
What do you guys think?

Depends on the length of the cable run and other things as others have eluded to

 

[Andy78]

He will be running various power tools for fixing bits and pieces, and mowing the garden

If he has that many arms you could probably rule out any diversity you have factored in.

If you stop reckoning and start calculating you'll find the answer to your question.

 

[The Ghost]

Yes I do understand caution with using 4mm² re future loads. I have put in a 16a mcb and 6a mcb with two led strips, one socket literally to run a few power tools. If I ever sold the house the workshop I have would be converted to a garage for parking almost certainly, as parking is terrible around where I live. I mostly use hand tools where I can as I dislike using power tools when making things. Like this...

 

[Deleted member 9648]

Just to muddy the waters....my shed runs from a 13a FCU spurred off the RFC in the garage, sockets for small power tools,shed lights,garden lighting,LED floodlights. Ample power. If it's just small power tools and lighting a 13a supply straight to sockets will be adequate with a 3/5a FCU in the shed covering lighting. Start adding freezers and other appliances and it wont.

 

[FoxySparky]

If he has that many arms you could probably rule out any diversity you have factored in.

If you stop reckoning and start calculating you'll find the answer to your question.

Just to clear up Things, I had done calculation of PFC and Volt Drop. And it came back at 4mm sufficient. But just wanted to ask you guys, if you would personally up rate it?

 

[Octopus]

Just to clear up Things, I had done calculation of PFC and Volt Drop. And it came back at 4mm sufficient. But just wanted to ask you guys, if you would personally up rate it?

If the client is happy to pay for 6mm , then put 6mm in

Normally they want 1.5mm but need 10mm!