Thread: Wiring for onboard compressor?

The fridge only draws enough to need a 10A fuse. If the wiring is standard Engel kit and has the Engel plug mounted then it will most likely have the 10A thermal fuses in line (10A) on both +ve and -ve at the plug end unless whoever fitted it removed them. There should be a 10A or 20A fuse inline near the battery if the Auto Elec has done their job well.

The compressor draws a lot more current than the fridge (probably between 20A - 30A) and I would be wiring this directly to the main battery with a much heavier wiring (at least 6mm2). There is plenty of room to terminate additional cables onto the +ve battery terminal and the -ve is easily terminated on the earth point directly under the battery box on the chassis.

Be very interested to hear how you go with this as I've considered getting an air tank and fitting my compressor on board my Puma. Where did you get the air tank from? I priced some and nearly fell over when they told me how much.

Why not a heavy feed to something like this



Whitworths Marine: Bus Bar - 2 Stud 5 Screw


Martyn

I agree with the above posts, install separate 6 sq mm minimum wiring for your compressor, or upgrade your fridge wiring to red and black 10 sq mm (that's about the thickness of a pencil ) from the battery to the point you want to splice - You'll need a heavy fuse at the battery ( maybe 40 amp ) then suitably rated fuses to each device. ( 20 or 30 amp for the compressor and 10 amp for the fridge )

Also the switching side for your compressor ( both on/off and pressure cut off switch ) should operate a 40 amp rated relay which then switches the high current supply.

Splicing and soldering thick to thin wires and then taping or heatshrink over is OK ( providing you can do a good solder joint ) but a distribution box/fuseholder is probably more practical.

Thanks DM, Bushie & Wayne

That all sounds like good advice, which will be very helpful.

I am using an expired gas BBQ cylinder, which is in good condition, and has a high pressure rating (3.3Mpa or 458 PSI), so it'll handle the 100PSI compressor cut out rating very comfortably. I have fabricated a bracket to locate it off the chassis outrigger under the RH passenger floor. I welded the bracket direct to the gas bottle bottom ring, and top valve protector/handle, & then bolted to outrigger.

Prior to welding onto the bottle, removed the valve & was surprised to find about 100mL liquid "gas" still there after being vented to empty for some time. It evaporated as soon as I blew some compressed air at it, so it was definitely liquified gas residue. I filled with water prior to welding.

This one holds 7L exactly (as measured by the water taken out after), so it should be reasonable useful.

At this stage, I won't fit a drain cock immediately, rather remove & drain at regular service intervals, as it won't get an enormous amount of use. I may do so later on, by which stage there will be no trace of any old gas residues, and will be safe (or me game enough) to weld directly onto the bottle itself.

I love these sorts of projects, and Defenders lend themselves to them so easily.

I'll post some pics when it's finished, but thanks for the advice.