Man shed wiring

[limey]

Have recently built a 6M*4M man shed in my back garden for me and my 10 year old son. And I am now at the wiring stage of the shed and have been getting conflicting information as to what is the best method for connecting the power.

4mm armoured cabling is to be run from the house to the shed distance of 25-30 metres.

There will be a ring main and 2 lighting circuits (one inside and one out) I would also like to run a seperate spur for the outside pond.

Plan is to install a garage duel Rcd consumer unit in the shed mainly for ease of turning power on and off.

The question and conflicting info I am getting is to how to connect to main house power source.

1) first electrician say's to connect to main consumer unit
2) 2nd electrician says to install another garage consumer unit next to the main consumer unit?

Which is the better and more preferred method?

Currently we have a 13-Way Dual RCD High Integrity Consumer Unit, supplied by a 100amp fuse. There are currently no free rcd's but it would be easy achieved to double up on a lighting circuit for the loft and upstairs lights to free up a slot in the main board.

There is also already Henley blocks installed so installing a 2nd consumer unit would also be easily achieved.

Would be grateful of any advice

Regards
Mark

 

[SaladFingers]

Connect to main consumer unit, using a plastic enclosure with knock outs to terminate the SWA and earth the glanding kit (which may have been why he suggested another CU, possibly thinking of a metalclad).

However, there's no need to have another one next to the source of distribution.

 

[ban-all-sheds]

4mm armoured cabling is to be run from the house to the shed distance of 25-30 metres.

Will that be enough for any possible loads you might have in the shed & garden at any time in the future? Do you like digging trenches? Or will it be running through ducting in case of future changes? Will you be putting in a 2nd duct for comms cables?

There will be a ring main and 2 lighting circuits (one inside and one out) I would also like to run a seperate spur for the outside pond.

Why do you want a ring final in the shed?

Why do you not want the pond on its own circuit?

Plan is to install a garage duel Rcd consumer unit in the shed mainly for ease of turning power on and off.

Why 2 RCDs and not RCBOs?

Which is the better and more preferred method?

Neither.

Find an electrician who will use the Henley blocks to supply a switchfuse, and who will do a better job of discussing SWA size and advising on final circuits.

I assume that you are going to have the electrician do the job, not just give you advice?

 

[ban-all-sheds]

Connect to main consumer unit

And then any earth faults from there onwards, in the outbuilding, associated with the pond etc, will take out half the house circuits.

Not good.

Keep it off the house CU, and have the RCD protection local to the shed etc.

 

[SaladFingers]

Connect to main consumer unit

And then any earth faults from there onwards, in the outbuilding, associated with the pond etc, will take out half the house circuits.

Not good.

Keep it off the house CU, and have the RCD protection local to the shed etc.

Well, it's as bad as saying to connect an extension to a new CU, simply because any earth faults there will trip the rest of the house out.

I'd say at worst, it could be a nusience, rather than a blanket 'not good'.

 

[sparkwright]

Since it's a high integrity board, perhaps space could be found on the non-protected side. An RCBO could be used.

Obviously it could be a pain going into the house if the shed should trip.

Is the whole cable run going to be in SWA?

 

[ban-all-sheds]

Not really the same.

There's a higher probability of earth faults on the circuits at the end of the sub-main than ones in an extension, and as well as the nuisance to the people in the house it would also be a nuisance to the people in the shed if they had to go back to the house to reset. And the nuisance to the people in the house could be significant if one rainy night their RCD tripped because of a fault which they needed to turn out to the shed to clear before they could reset it.

Given that there are already service connector blocks in place, it would be pretty easy to put a switchfuse in.

 

[SaladFingers]

Not really the same.

There's a higher probability of earth faults on the circuits at the end of the sub-main than ones in an extension, and as well as the nuisance to the people in the house it would also be a nuisance to the people in the shed if they had to go back to the house to reset. And the nuisance to the people in the house could be significant if one rainy night their RCD tripped because of a fault which they needed to turn out to the shed to clear before they could reset it.

Given that there are already service connector blocks in place, it would be pretty easy to put a switchfuse in.

Well if there's already a henley block then why not indeed.

 

[limey]

Since it's a high integrity board, perhaps space could be found on the non-protected side. An RCBO could be used.

Obviously it could be a pain going into the house if the shed should trip.

Is the whole cable run going to be in SWA?

The whole cable run is going to be SWA partially through a conduit and partially underground. This is what one of the electrician has suggested doing fitting a breaker to the non protective side

 

[limey]

4mm armoured cabling is to be run from the house to the shed distance of 25-30 metres.

Will that be enough for any possible loads you might have in the shed & garden at any time in the future? Do you like digging trenches? Or will it be running through ducting in case of future changes? Will you be putting in a 2nd duct for comms cables?

Unless he is going to start a rock band 4mm should be more than adequat for the distance in question, allowing for a 5% voltage drop a current draw of 32 plus amps should be adequate would be having a 24 amp trip rather than 32 especially if it is going into main consumer unit.

There will be a ring main and 2 lighting circuits (one inside and one out) I would also like to run a seperate spur for the outside pond.

Why do you want a ring final in the shed?

Why do you not want the pond on its own circuit?

expensive filtration system having a separate circuit will reduce the chances of the power being switched of causing the healthy bacteria to die,

Plan is to install a garage duel Rcd consumer unit in the shed mainly for ease of turning power on and off.

Why 2 RCDs and not RCBOs?

sorry should have said it will have a mcb

Which is the better and more preferred method?

Neither.

Find an electrician who will use the Henley blocks to supply a switchfuse, and who will do a better job of discussing SWA size and advising on final circuits.

what amperage switch fuse would be concerned of having to high an amperage would rather it tripped easy than not at all if some on managed to damage the SWA.?


I assume that you are going to have the electrician do the job, not just give you advice?

yes, i may be daft but not stupid just trying to figure out what's best, and also don't want to waste money if not neccersary.

 

[333rocky333]

Connect to main consumer unit, using a plastic enclosure with knock outs to terminate the SWA and earth .

Why plastic

 

[SaladFingers]

Connect to main consumer unit, using a plastic enclosure with knock outs to terminate the SWA and earth .

Why plastic

Why not? Can use a metal one if you wish.

 

[333rocky333]

earth the glanding kit .

Ok, sorry,still a bit

 

[SaladFingers]

earth the glanding kit .

Ok, sorry,still a bit

Ok, well, thread poster mentioned using armoured. There are gland kits for armoured cable with a 'banjo' shaped washer for connecting to earth as the armour needs to be earthed. The purpose of the glanding kit is to aid with cable entry to enclosures.

 

[333rocky333]

Oh i get it, the brass banjo is just compressed against the plastic using the one locknut supplied in the gland pack.
Think in the absence of double nutting it then personally id opt for a metal box or an earthing Nut