The question about an earthing point on the Fusebox was initiated (I think) by the fact that there are LEDs on the fusebox and how can the LEDs work with no earth. On that point, the earth for the LED is via the cable AND device the fuse is protecting.
In terms of Earths - or actually Chassis Grounds as they should be termed, so will use that term from now on - there are multiple ways to go and each have their own benefits and cons, and fans or otherwise.
Localised Grounds: This would typically be running a +12V power cable from fused supply (be it battery or fusebox) to devices and then running a 0V/GND cable from device to a local metal point on the chassis.
PRO: Reduced cable cost; Reduced Weight
CON: Potential issue with random poor earth connections means hassles if needing to troubleshoot
Centralised Ground: This would be running typically dual core cable from supply to device, carrying both +12V and GND cables, so providing a central +12V power AND a central Ground
PRO: Simplied Central Ground means simplied troubleshooting
CON: Increased cable cost as doubling up on length of every +12V cable while saving on the short lengths of 0V/GND cables; Subsequent increased weight; Routing cables can be harder depending on amont of cables and space
On the face of it, the centralised ground would seem to be the better option, but if care is taken when using localised grounds that localised Ground approach is just as good on a metal framed vehicle (talking road vehicles here - boats are a totally separate thing before words like "galvanic corrosion" start appearing).
Personally, I tend to use localised grounding just like the OEM vehicle electrics use. You don't see Ford, Mercedes, VAG, PSA, et al runing all their circuit grounds back to a centralised point as the vehicle monocoque IS the chassis ground. There is no reason whatsoever not to take the same approach with Leisure Electrics as was done with the Vehicle Electrics.
The last design I did interestingly enough is, however, using a central design with twin core (+12V + GND) cable to the 12V devices dotted around the vehicle as I was not sure if the installer would select the right ground points so decided to eliminate that risk (so every circuits 0V/GND is terminated in a single area).
Phil, personally I think you using 2.5mm arctic cable for eveything was not a wise idea. Not only are you using excessive cable in terms of weight (you have 3 cores when at the most only 2 was needed, so an immediate 50% extra weight incurred, plus the extra heavy outer insulation on top), and the extra cost over two-core cable, you have a cable that looks like mains cables but is carrying a ELV 12V circuit.
This is fine until someone sees a run of blue arctic cable and assumes it is more 12V DC cable (as that is the standard used) but is actually 240V AC cable. I know people do this as they have the cable spare, etc and why waste it, etc, but I feel it is very poor practice (sorry
) and should be discouraged - maybe the converter knows what cable is what when they installed it, but memories fade, and vans move on to new owners and using the albeit fairly rough standardised approach as much as possible when it comes to wiring really should be done where possible.
