Hi there, my brother-in-law has a 145 metre long garden (lucky him,) well not to waffle on......he wants a ring around the whole edge probably with no more than 8 double sockets, the width of the garden is approximatly 15/20 metres, will 3 core 2.5 armoured be sufficient?
Huge Garden Power
- Thread starter Netrics-PJay
- Start date
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B
breezer
extension lead plugged into an rcd protected socket would be cheaper.
gardens would come under part p
gardens would come under part p
Wonder when totallypies will turn up 
Thanks for your input breezer, do i need to buy a part p book to check on the regulations and requirements for this job?
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breezer
Netrics-PJay said:
no, try a search for part p, loads of info
but why 16 sockets in a garden?
there is also the cable route etc to be considered, i would still stick with the extension lead
Just bashed some numbers in quickly, volt drop is obviously going to be the killer, for a 330m long ring (you can have it anywhere upto 410m infact) I make it that you will need 16mm² SWA thats going to be fooking expensive . 16mm² will also do you a 20A radial of 164m length
. 16mm² will also do you a 20A radial of 164m length8 doubles i thought because perhaps 4 either side its a very long garden!and he wants to plug lots of lights and things, i didnt think an ext lead would be the correct way, i thought the correct way was armoured, i'm only qualified in auto electrics hence these posts, is an ext lead correct according to part p?
B
breezer
2 x 16 into a socket that will be fun
Cheers adam, i've just read somewhere that 2.5 armoured is good for 110 metres square, i think i read it somewhere else in this forum section i think this should be ok for my task
2.5mm gives you a max ring cable length of 65m, if you want a 330m ring in it, you are limited to 6A before the volt drop goes out of spec *
Thats of course assumeing worst case, full ring load is drawn through a bank of sockets at the mid point of the ring, if you want to design for a less 'stressful' use of the circuit, then the calculations get more complicated, and you have got to be sure that the circuit won't be pushed beyond its design
Thats of course assumeing worst case, full ring load is drawn through a bank of sockets at the mid point of the ring, if you want to design for a less 'stressful' use of the circuit, then the calculations get more complicated, and you have got to be sure that the circuit won't be pushed beyond its design
I have to say it's not a job I'd like to quote for. In my experience it is nigh-on impossible to justify the expense of providing garden circuits to regs.
Thanks adam, so im going to need 16.0mm, like you say thats huge cost,
contact want £320 for 100m
contact want £320 for 100m
ding bat, what would your solution be if it was your brother in law bearing in mind he's over six foot and built like a tank and i wouldnt want to cut corners!
Adam, if 2.5 allows upto 65m what will the voltage drop (pd) be on 330m? Please can you tell me the parametres for ohms law?
Volt drop figures (table 4D1B OSG Pg. 122)
2.5mm²... 18mv/a/m
4mm²... 11mv/a/m
6mm²... 7.3mv/a/m
10mm²... 4.4mv/a/m
16mm²... 2.8mv/a/m
Thats millivolts per metre, per amp
Radial circuits are straight forward, ring final circuits, well do the calc as if its a radial and then multiply by 4 to give the total ring cable length
FWIW. My (compromise) design would be 16mm² 2 core SWA from a B20 up one side of the garden (to a max length of 164m) the SWA would have to terminated in a large adaptable box below the socket and a very short piece of 2.5/4 of SWA making the link. Of course it'd be backed up by a 30ma RCD
I make the R1+R2 to be 0.8 for 164m of 16mm², 2 core and so as long as the Ze is in spec* then it'll comply with the 1.92 ohms allowed on a B20
* Of course assuming TN system, if its TT obviously we don't need to meet low Z's, its just got to be under 1666 for the RCD...
2.5mm²... 18mv/a/m
4mm²... 11mv/a/m
6mm²... 7.3mv/a/m
10mm²... 4.4mv/a/m
16mm²... 2.8mv/a/m
Thats millivolts per metre, per amp
Radial circuits are straight forward, ring final circuits, well do the calc as if its a radial and then multiply by 4 to give the total ring cable length
FWIW. My (compromise) design would be 16mm² 2 core SWA from a B20 up one side of the garden (to a max length of 164m) the SWA would have to terminated in a large adaptable box below the socket and a very short piece of 2.5/4 of SWA making the link. Of course it'd be backed up by a 30ma RCD
I make the R1+R2 to be 0.8 for 164m of 16mm², 2 core and so as long as the Ze is in spec* then it'll comply with the 1.92 ohms allowed on a B20
* Of course assuming TN system, if its TT obviously we don't need to meet low Z's, its just got to be under 1666 for the RCD...
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