MegaSack DRAW - This year's winner is user - rgwb
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I'm planning to install 4 extra 12v sockets in the van. they'll be in two pairs (two at the front, two at the rear). There is a spare fuse position in the fusebox, so I'm hoping to tap in there. What rating of wire is best for a bit of future-proofing? Is the max power available not in any case limited by the fuse and existing wiring?
If you intend to take the feed from the fuse board then a relay is required or your next post will be how to change a fuse board.
Personally I would come from the battery with sat 20amp for the short run and 40 amp for the long run. You can stick in-line fuses near the battery, but I would not go above 30amp.
If I run them from the battery, they'll be always on? I can see both the advantages and disadvantages of this 🙂
Or would you still recommend a relay from the ignition supply?
Relay would be a good idea - there's usually an easily accessible switched live in the radio harness which you can use to switch the relay.
Fuse size depends on what gauge wire you use, google cable current ratings or something like that.
If you want to switch them then switch the feed through a relay. The relay absorbs all the amps and stops the switches from burning out. You could always put a separate earth wire on, then keep a live feed and just fit a flick switch for the earth
go from the battery - fit a switch if you want as far easier and safer.
thickness of wire os the key to amp carrying capacity
google wehicl wiring products they will have all you need and a nice catalogue for you to read.
Not sure I would go to 40 amp my heater plugs were the only 40 amp fuse I had on boat and 25 amp did the entire system input for fridge,tv, pumps lights and sockets etc and never blew.
Personally one run to front from battery fused at 10 amp as close to battery as possible
One run to rear as above - rate fuses as you wish and wire thickness as per need. Perm on is no reall issue if you have wired properly and you dont leave stuff on.
E-mail if you want I wired a boat to 12 v - depends on what you plan to run tbh
EDIT Bear means negative where he is saying earth as you can earth the neg to anywhere on van - battery earths to engine for example. But I would use battery personally
Get relays, wire, heat shrink, connectors etc from Beal UK
http://www.beal.org.uk/electrical-products/cat_8.html
Amy plans for a second (leisure) battery? Split charge (or diode) relay to that an run the sockets off that. I'd go with 30 amp rated cable and put inline fuses or a small fuse box. Vehicle wiring products website ftw
If you need a hand, give me a shout.