Pre-wiring for diesel heater

Hi,

I’m part way through converting my Vivaro ‘LWB. For flexibility of use, we are using an Aferiy P210 for our 12v, and our off grid mains power. We went for the 210 as it has a 25a 12v output to feed our 12v fuse box.

I am getting my diesel heater supplied and installed by a local motorhome service company for the extra warranty that will provide. With the wait for my install date, I need to keep going with the conversion. Under our current plan, the diesel heater is going to be on the other side of the van from the 12v power and fuse box, so I need to pre-run a cable from the 12v fuse box to the other side of the van where the diesel heater will go, before the ceiling is closed. My questions are:

  1. As the cable run will probably be 3-4m long, am I best running 6mm cable from the 12v fuse box to the rough location of the diesel heater, or would I be better to run 10mm?

  2. Do I just terminate that run in a junction box, or a manual switch, or what is best? That way the install company can connect the heater’s 12v to that, and I can get my ceiling closed up while waiting for the install.

  3. Would I be best re-thinking before it’s too late and trying to get the diesel heater and 12v power nearer to each other?

I appreciate any advice, as this is my first conversion.

Thanks

Duncan