Power to a multitude of sheds

[Avi46]

Hi all, I am new to the forum, just looking to get some advice on a job I am doing. I am of a electronics background so forgive me if I get confused regarding anything above 24v! I have a decent knowledge of electrics although I am not up to date with the regs in anyway hence my visit to this knowledge bank! I
I am looking to put power and comms to four sheds. I have had a local sparky to assess the situation although he was only around for 10 minutes so didn't give me the full story, as I just need to know what cables to lay as I have the next week off. I am doing the donkey work he is making the final connections testing and signing it off.
The proposal is to add a RCD switched fuse after the switched fuse I already have (meter is >3m away from CU) and for me to install 3core 6mm SWA to an RCD disboard is the main shed 25m away. From this disboard he recommends that I just install 2.5mm SWA to each of my sheds which 3 are 15m away and the 4th 30m away.
2 of the heds 15m away will only have small loads; light and socket for the odd power tool, the other one at 15m and the one at 30m I may be making it into a potential office and/or playroom in the future. All will have a small disboard for lights and sockets all rcd protected.
Does this seem reasonable to you?
I am a bit confused regarding the suggestion that 2.5mm seem correct for the radials? As I would of assumed 4mm was the norm for radials.
I am not sure I gave him the full story so I am just making sure everything knits together before purchasing the cable and burying it 500mm down with additional conduit for the comms.
Any thought are very much appreciated!

 

[Sintra]

As you are not a qualified electrician your thread has been moved to the DIY section.

 

[Avi46]

Just noticed that thanks

 

[Des 56]

Hi all, I am new to the forum, just looking to get some advice on a job I am doing. I am of a electronics background so forgive me if I get confused regarding anything above 24v! I have a decent knowledge of electrics although I am not up to date with the regs in anyway You contradict yourself with this statement hence my visit to this knowledge bank! I
I am looking to put power and comms to four sheds. I have had a local sparky to assess the situation although he was only around for 10 minutes so didn't give me the full story, as I just need to know what cables to lay as I have the next week off.10 minutes seems a very short time in which to do the vital calculations for the supply cable
There needs to be an estimate of the likely loads calculated over the distances that you have mentioned to ensure current carrying capacity is adequate and subsequently the volts drop is within limits I am doing the donkey work he is making the final connections testing and signing it off.You need the loading information in order to lay the correct sized cable,the depth of the cable and the trench it is laid into will also need attention,plus marker tape
The proposal is to add a RCD switched fuse after the switched fuse I already have (meter is >3m away from CU) and for me to install 3core 6mm SWA to an RCD disboard is the main shed 25m away.An Rcd at source may not be required unless the earth system is TT Like wise,even if it is required at source,fitting a second and third Rcd in various Dist boards is wrong From this disboard he recommends that I just install 2.5mm SWA to each of my sheds which 3 are 15m away and the 4th 30m away.
2 of the heds 15m away will only have small loads; light and socket for the odd power tool, the other one at 15m and the one at 30m I may be making it into a potential office and/or playroom in the future. All will have a small disboard for lights and sockets all rcd protected.Yet more Rcds ?
Does this seem reasonable to you? Unable to comment until design is ammended
I am a bit confused regarding the suggestion that 2.5mm seem correct for the radials? As I would of assumed 4mm was the norm for radials.Again.the size of cable depends on the available supply and the loads expected,a radial does not have a specific cable sizing
I am not sure I gave him the full story so I am just making sure everything knits together before purchasing the cable Please do not jump the gun and burying it 500mm down ( think more in the region of 600mm with prepared trench and tape? with additional conduit for the comms.
Any thought are very much appreciated!

Well there are my thoughts

If this were a school essay,the teachers prompts have been numerous, yet not harsh, the pupil would be told to obtain a "better understanding" before putting the subject into practice

You need to supply your electrician with intended loads,receive the cable size after the calculations and then return with a more suitable design for further comment

 

[Avi46]

Cheers Des, You are indeed correct, this pupil needs to get a full comprehension before all is fully understood. I understand about the loading and you have answered my question really, in the way that I may not have given him the required information, in order to makes sure everything is absolutely correct, hence your comments. That I will do to double check we are both singing from the same hymn sheet. RCD wise I may have just misunderstood him. I have a 500mm trench already dug which runs next to a path, marking tape is already purchased. Depth of cable seems to be different where you look. I have had conflicting information from a few different people hence I went for the deepest which was 500mm. My local golf club just supplied power to their new driving range and it want as deep as that! Thank for you help.

 

[Andy78]

As has been said, ten minutes is not enough time for that sparky to have worked out what you need taking everything into account.
As this is quite a largish job (depending on the scale of your input I suppose) I would get another couple of electricians in to at least quote for this job and provide their opinions. Arm yourself with all the information you can regarding load demand in the sheds and make sure it is relayed to the sparks as fully as possible.
A few prices are always best, as is meeting different tradesmen. You need someone you get on with well on a job like this where you are doing half the work.

 

[Guitarist]

Cheers Des, You are indeed correct, this pupil needs to get a full comprehension before all is fully understood. I understand about the loading and you have answered my question really, in the way that I may not have given him the required information, in order to makes sure everything is absolutely correct, hence your comments. That I will do to double check we are both singing from the same hymn sheet. RCD wise I may have just misunderstood him. I have a 500mm trench already dug which runs next to a path, marking tape is already purchased. Depth of cable seems to be different where you look. I have had conflicting information from a few different people hence I went for the deepest which was 500mm. My local golf club just supplied power to their new driving range and it want as deep as that! Thank for you help.

swa is not indestructible. It needs to be laid on sand or within some form of ducting/pipework. Sharp stones can compromise the outer sheath, leading to corrosion of the armouring.