4. Electrical System

I am not a qualified electrician. I describe what I have done but I cannot accept responsibility for others’ work. For this reason I will not describe the detail of my wiring. If you are in doubt, consult a qualified electrician.


Saturday 14th July

Today I have installed the 240 volt system into the van. It is a simple system that provides three 240 v plug extensions. It consists of an external mains inlet socket, a consumer unit and three circuits with standard 240 v sockets.






I have mounted the mains inlet unit on the offside of the van for two reasons. First, it avoids having an umbilical trailing across the area, on the other side, where I will be sitting and where the bar-be-que will be. Second, it will be more visible in my rear view mirror and hopefully will help me to avoid driving off with the power still connected!

I have mounted the consumer unit almost directly behind the external mains inlet unit. This is a tidy solution and also minimizes the cable run. The consumer unit is an essential piece of kit. It has the fuses and the main on/off switch. It is likely that you may not have wired a consumer unit before. The following links provide useful instruction on how to do it.



The double socket that you can see will be used for battery charging and anything else that is needed in the garage. However, I am hoping to minimize the number of appliances that need 240 volts. But it is useful to have a double socket in the garage. I have run two other rings; one into the kitchen and one to the siting area. I will put a double socket on each of those.

The next phase of the electrical system will be the 12 volt system. This will be the main electrical system for the motorhome and will run lights, water, fridge etc.


Saturday 26 July

Today has been 12v system day whilst dodging the showers. There are certain aspects of a 12v system that you, like me, may be unfamiliar with. However, I had expert advice from ND Haigh in Huddersfield who also supplied me with cable. When wiring a motorhome, it is important to make a decision on wiring, early. Are you going to install a harness before installing walls etc., or are you going to make provision and do it later. Professional builders will tell you to do it first as it is much easier. However, this does require you to have thought through the location and requirement of every electrical appliance in the project planning phase. I considered this unrealistic and am glad that I have done it this way. Early on, I put a draw cord in place to allow me later to pull cables through. Once that was in place, I could forget about the electrics and build the internal structures returning to it at this point.

The second aspect is to decide on the cables to use. It is recommended that you use different colour cables for different applications to make fault finding easier.  My plan is to use:

Lighting                    Green                   14 strands
Water taps               Green                   14 strands
SOG valve (loo)         Green                   14 strands
Sockets                    Red                      28 strands
Turbo vent                 Red                      28 Strands
Fridge                      Yellow                   28 strands
Oven igniter              Yellow                   28 strands
Water pump             Yellow                   28 Strands
Fridge fans               Brown                    28 strands
Cooker extractor       Brown                    28 strands
Water heater            Red                       44 strands
Solar panel               Red                       44 Strands
Negative                  White                     28 strands

The negative can be ‘commoned’ and so lights, for example can be connected, on the negative side, by a single cable. Positive cables are unique. It is a good idea when you have pulled through a cable, to label it straight away. That avoids any confusion later. The simplest way to label the cable is with a piece of masking tape doubled over the cable so that you can write on it.

This may look dauntingly complicated, but it is really very straightforward if each cable is done as it is put in. The right hand side of the van (driver’s side) has the sitting area and bathroom cables. The left hand side has the kitchen cables. The bedroom cables provide a third group.

Once you have installed the cables, allowing plenty of spare at both ends, they can be tidied up. I have used 25x16mm plastic conduit that is readily available in B&Q in 3m lengths. Once that is screwed in place, the cable can be put in it and the top clipped on. The result is quite pleasing as you can see in this photo. The conduit is attached to the underside of one of the bed slats and the main beams.

It makes the 240v 1.5 twin and earth look quite scruffy! Having run the conduit round to the control unit, it is time to finish the cables by making up the connectors and that is what I shall do tomorrow, all being well.



17th November 2012

The 12v system is now fully functioning.

The two 12vBanner Energy Bull110Ah batteries are installed in their box. The positives are commoned, as are the negatives. That gives me 220 amp hours of 12v power, which I calculate will be more than plenty for what I will require. The cable connecting them to the charger at the front of the vehicle are 16mm squared capable of carrying 45 amps.

At the front of the vehicle, and in due course under the single passenger seat, is the battery to battery charger. It is an excellent product made by Sterling Power Products. It is a piece of electronic wizardry that works with the vehicle battery and alternator. As soon as the alternator has charged the vehicle battery up, after starting, this charger then instructs the alternator to charge the leisure batteries. Only when they are fully charged, does it let the alternator rest. The result is that a journey of 20 miles or so will ensure full power for your 12v systems. This is clearly an ideal system if one intends to use free camping in the main. Even if a hook-up is available, it is likely that the batteries will need no charging. As one might expect, it is rather more expensive than conventional split-relay charging. It also remains to be seen what effect the additional load on the alternator has on its life’s span. However, I consider the benefits will outweigh these costs.

The heart of the 12v system is the controller. Power from the batteries is fed into this, at the bottom using standard 44 strand cable (good for 27.5 amps). The controller provides all the switching and fusing of the system. It is nowhere near as difficult as this picture might suggest. In time, hidden by its cover, it will look quite tame.

There is a neat little control panel that is installed in the living area. This provides the master switches for lights, water and heating. It also has read-outs to tell one the state of charge of the batteries and how full are the fresh and waste water tanks. I am delighted that all those read-outs are now live.


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