I am nearing completion of a deck in the far corner of our garden. I
would like to add some lights and a water feature to it. The cable
run from the house is approximately 30 metres. My questions are:
1) I am planning on connecting the wiring to a fused spur with rcd in
the house. Will the length of the wire run cause a problem with the
rcd (do not want it tripping every 30 seconds)
2) Will I be able to use the one run of cable for both the lights and
the water pump or will I need to run two seperate cables.
Most installations of this type use SWA (steel wire armoured) Cable for
safety reasons. SWA gives more protection against intrusion to live
conductors from sharp tools or fencing stakes etc. and should be buried to
no less than 800 mm if not protected by any other materials. It should also
have a warning tape buried along with it, preferably 200 - 250 mm above it,
to tell people that a live cable is below.
Depending on the full load you're thinking of fitting at the end of the
cable, then you should be OK with one run of correctly gauged cable. But I
would ask you to check the full load of all lights and the water feature
when all are being switched on at the same time, as this will affect the
total current drawn through the cable. Also, an RCD is very much needed on
this type of installation, and it should be coupled along with a good earth
bonding, preferably at both ends, to provided a bit extra safety coverage if
working with digging tools and the likes.
The full load calculation will give you the gauge of cable you will need to
safely supply all the appliances and also tell you the trip value of any
automatic breakers you'll need to use. I would also ask you to take into
consideration, the fitting of an all weather outdoor socket at the decking
area. This will allow you to work with power tools or cleaning appliances
without the need to run extra extension leads and things.
13A. This gives 3120W actual, or 2990W nominal. This depends on the circuit
you are spurring from having the balls. I wouldn't spur off a kitchen ring
main, which has lots of power hungry appliances attached. Best is a new
circuit with RCBO protection.
On Wed, 27 Aug 2003 16:41:18 +0100, Christian McArdle wrote:
Thanks Christian. Looks like I'll be *well* below that - 2Kw heater not on
the highest setting so using around 1Kw. I was a bit concerned because
there is another (not high power) thingy connected to the same (double)
If it does, there is a fault in the cabling (or final load).
Yes you can. However, if you want to be able to switch them from the house,
you'll need separate supplies for both.
To calculate the cable size, add up the total load. Then go to
www.tlc-direct.co.uk and find the cable you want and bring up the
information page. Somewhere you will find a link to the cable size
calculator. Put in the required details (i.e. 2 core SWA XLPE and 1000W) and
it will tell you what minimum cable size you need. The selection will
probably be voltage drop limited. You might consider trying 3120W, as this
will enable the full benefit of your RCD fused spur should you choose to
install an IP66 socket. You may wish to check the final calculation directly
against the regs.
BTW, I tried 3120W @ 240V with SWA XLPE 2 core, with 30m and it suggested
2.5mm. It uses a large proportion of the allowed voltage drop, so any long
runs inside the house may tip it over, requiring 4mm.
"Christian McArdle" wrote
| >2) Will I be able to use the one run of cable for both the lights
| >and the water pump or will I need to run two seperate cables.
| Yes you can. However, if you want to be able to switch them from the
| house, you'll need separate supplies for both.
Unless something like X10 remote switching is used (in appropriate IP rated
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