Advice please

[horvath]

Hi All,

I will be starting my electrics cabling soon and would love to get some feedback about the diagram I created.
Does it seem right and more importantly are the cable sizes correct?

Thank you in advance.

 

[TheBig1]

cable sizing will be dependent on the length of cable run and maximum load. Some of the fuse ratings are OTT

 

[Ray-Vic]

I wouldn't be having 35mm cable with a 300A fuse, you should drop that to 200A.

 

[autorouter]

As already said, the cable size depends on the maximum amps and the length. Motorhome layouts can be very different, with batteries at the front under the seats, or right at the back somewhere, so some idea of lengths would be required.

At 18A, the B2B is about the minimum size, and is OK for one 100Ah battery. I don't know how easy it is to run the wires for it, but if it's at all difficult it would be a good idea to run wires that will cope with a 50A or 60A B2B, in case of future upgrades. Maybe go to 20mm² or 25mm². The 60A fuses on the B2B wires are a bit high for an 18A B2B, I'd probably go for 30A.

The wire sizes look to be in the right ballpark, but in an installation like this the wires are sized to ensure that the voltage drop is within limits. Usually the wires are sized to keep the total voltage drop over each circuit to 3% or less. If that is done, the wire sizes will be well within spec from the safety aspect. Voltage drop depends on the cable size, length, and amps carried. A voltage drop calculator is useful here, there are many available, I use this one:

Voltage Drop Calculator | 12 Volt Planet

Use our Voltage Drop Calculator to select the correct Cable for your campervan, motorhome or boat wiring application. Auto and Marine Electrical Components from 12 Volt Planet - Cable Size Calculator

www.12voltplanet.co.uk