Outside electrics

[williamglossop]

I have a 1000 watt submersible pump at the bottom of my garden. It pumps land drainage water from a sump to a drainage outlet. The pump has a 3 pin plug and is currently plugged in to a weather proof extension reel. I'm currently digging up garden and would like to replace the extension reel with something more permanent. Would it be acceptable to run a 2.5 mm 3 core SWA Cable to the bottom of garden (buried, warning tape etc) and fix a weatherproof socket on a concrete post. I have a 4mm radial circuit in the house on a 32a mcb. This circuit only has 2 double sockets on it and a light that's stepped down to 5 amps. I was considering having this 4mm radial circuit extended to the outside wall and fitting a weatherproof junction box on the outside and running the SWA to this. I'm also planning on adding a shed to the garden and I'd like to have a single double socket and light in there. Would it be feasible to run another 3 core 2.5mm swa cable from the same junction box to the shed? Sparky will be doing it, but this is what I'm gonna ask for. House was rewired 2 years ago (17th) and is TN-C-S. The cable run to pump is about 20 meters. Cable run to shed is about 10 meters.

 

[Adam_151]

Why are you wanting to drop the cable size on the circuit from 4mm to 2.5mm?

You say the shed is 10m from the house and the sump pump 20m? Are these in the same direction? i.e. would it follow that its 10m from the shed to the sump pump, as oppsed to 30m between them?

 

[ericmark]

Believe it or not we don't select cable sizes out of the air. OK some times it is very easy to see what is required, so we install and then test. However with 20 meters to a motor from an existing supply, step one is test existing supply, once the ELI and PSCC is known, then we will be able to calculate what the values will likely be at the pump.

Also must decide on earthing methods, this will take into account other building with power to them.

If we were to guess as to reading and get it wrong, we could be giving wrong advice. You can get bollards designed to supply the likes of caravans, it is likely these may be suitable for what you want, however you may need some enclosure to house control gear for the pump.

I would ask the electrician you select what he thinks is best option.

 

[ban-all-sheds]

Starting current of the pump should probably be considered.

And it doesn't sound like using a plug & socket is the most appropriate way to connect it.

As Eric said - your electrician is the person who needs to specify the cable, and what accessories go where. Also, consider a bit of future proofing when burying cables, e.g. if the shed one day morphs into a hot tub room. I know - probably unlikely, but the point is a larger cable now will add very little % to the overall cost, but could avoid digging the trenches again in the future. Or, if the runs(s) are suitable, install ducts so new cables can be pulled through. Or additional ones for phone/data.