ban-all-sheds said:
Enough headroom? How long would the cable be when extended?
If you use 6mm² when 4mm² would have done, you've wasted ~70p/m. If you use 4mm² and then later find you need 6mm² you've wasted ~£2/m.
In reality, I don't think I'll be living here for long enough to actually want to extend the circuit anyway. The cable would be around 20m if I was to extend it, so within voltage drop limits for 32A. Should it be over that limit anyway, I don't foresee a need for more than 20A anyway so could probably live with that limitation. Obviously my foresight might be wrong however my current needs could be satisfied by 1.5mm cable on a 20A breaker, so moving to 6mm seems excessive.
ban-all-sheds said:
The best way is to use bottom entries, as water rarely flows uphill. If these accessories are going to be in a location where that loop of cable needs to be armoured then they probably shouldn't be there.
Agree with the bottom entries. I'm not sure what you're getting at WRT the location - both accessories will be positioned on a retaining wall halfway down the garden so will be as exposed as they're likely to get and also susceptible to damage so I would prefer to use SWA for any accessible cabling. I imagine your point is more that they ought to be somewhere less exposed however if they're outdoors it would still be preferred to use SWA over exposed T&E, rubber cable, hi-tuf, etc?
ban-all-sheds said:
Make it a 32A one then you won't need to change it if you increase the circuit capacity.
Valid point. I'm going to connect to an already existing 20A circuit, hence the 20A isolator, however as you say no reason not to use a 32A switch now.
ban-all-sheds said:
I don't know how much space you have available, how far above ground this will be, whether you can accomplish the bend by using more than one plane, etc. If the cable emerges from the ground, would it need much of a bend anyway, given that the hole in the wall should run upwards, outside to in?
After the cable emerges from the ground it needs to run along the house, horizontally, before entering, so it would need to move from a horizontal run, clipped to the brickwork, to go through the wall. Maybe I'm overthinking but surely to get the cable into a plane to go through the outside wall, at a slight incline, it's going to need a fairly tight bend, or a loop which brings it away from the brickwork an inch or two in order to accomplish that bend?
ban-all-sheds said:
Best practice is to have as few joints as possible. But it's also to recognise the (probable?) unwieldiness of 4/6mm² SWA indoors, so terminating outside might make sense. You could do it in another socket - might come in useful. Or put your isolator outside. Again, using bottom entries rather than rear will be the best way to avoid water ingress.
I'd prefer to keep the isolator indoors. The isolator will be under the stairs so the unwieldiness of the cable isn't really a concern. It's more getting the cable from it's present path, through the wall, that's posing the concern.
Terminating in another socket is a good idea - the additional cost over an outdoor enclosure is next to nothing anyway and it probably would come in useful, so I'll probably go with that approach. I'm still interested in the best way of routing the cable should I decide to bring it inside...