Campervan Cable Routing: How to Run Wires Neatly and Safely

Cable routing is the part of a campervan electrical installation that nobody finds exciting — until they get it wrong. Poorly routed cables chafe against metal edges and short out. Unlabelled cables turn a simple troubleshooting job into hours of tracing mystery wires. Cables routed near heat sources degrade and fail. And cables installed after the cladding and furniture are fitted are always a compromise.

The key insight is this: cable routing needs to happen first, before you build anything on top of it. Plan your routes, install your conduit and cable runs, and then build your furniture around them. This guide covers everything you need to route cables safely, neatly, and in a way that will not cause headaches years down the line.

For the full picture of your electrical installation sequence, see our wiring order guide. For the tools you need, see the electrical tools guide.

Design Before You Route

Our free calculator generates a complete wiring diagram for your campervan electrical system. Knowing your layout, cable sizes, and component positions before you start routing saves time and prevents mistakes.

Open Calculator

Plan Your Cable Routes Before Building

Draw It Out

Before you cut a single piece of cable, draw a plan of your van showing:

Battery and fuse box location — this is the hub of your 12V system. Most cables originate here.
Inverter location — heavy cables run between the battery, inverter, and fuse box.
Solar cable entry point — typically a cable gland on the roof.
DC-DC charger or split charge relay location — usually in the engine bay or near the bulkhead.
Shore power inlet location — usually low on the outside wall.
Consumer unit location — where your 230V circuits originate.
Every light, socket, switch, pump, fan, and appliance — each one needs a cable route.

Once you have all the endpoints marked, draw the cable routes. Look for natural channels in the van body — the factory wiring loom routes are often the best paths, as the manufacturer has already identified protected channels.

Identify Problem Areas

As you plan, note any areas where:

Cables must pass through metal panels (bulkheads, floor sections, inner walls)
Cables run near heat sources (engine bay, exhaust, heating ducts)
Cables cross water entry points (wheel arches, door seals, roof vents)
12V and 230V cables could end up in the same channel

These areas need specific protection measures, covered below.

Route Cables Before Insulation and Cladding

The single most important piece of cable routing advice: do it before you insulate and clad the van. Running cables behind cladding after it is fitted ranges from difficult to impossible, and retrofitting always looks worse. Install your conduit and cable runs on the bare metal walls, then insulate around them, then fit cladding over the top. Leave access points at key junction locations.

Using Conduit and Trunking

Split Conduit (Corrugated Loom)

Split conduit is flexible corrugated plastic tubing with a slit along its length that allows you to insert cables after the conduit is already mounted. This is the most popular cable protection in campervan builds. Available in diameters from 7mm to 28mm, it costs around £0.30-£1.00 per metre depending on diameter.

Use split conduit wherever:

Cables run along or behind metal panels
Cables pass through insulation
Cables are in areas accessible for maintenance (you can open the split to add or remove cables later)
Multiple cables run together and need bundling

Mount split conduit with adhesive-backed conduit clips every 200-300mm. P-clips (saddle clips) screwed to the van body are more secure and do not fail like adhesive clips sometimes do, but they require drilling holes.

Solid Conduit

Non-split corrugated conduit offers slightly better protection than split conduit because there is no gap for debris to enter. It is harder to work with because cables must be pulled through rather than pushed in through a slit. Use it for runs that will be permanently enclosed and where you need maximum mechanical protection.

Trunking

Rigid plastic trunking (with a snap-on cover) is excellent for visible cable runs along cabinet interiors or inside electrical cupboards. It looks professional and allows easy access for additions or modifications. Self-adhesive trunking (25mm x 16mm is a common size for campervan work) costs around £1-£2 per metre and gives a very clean finish.

Grommets for Metal Panels

Every time a cable passes through a hole in a metal panel, it needs a grommet. Without a grommet, the raw edge of the drilled hole will eventually cut through the cable insulation due to vibration, causing a short circuit.

Types of Grommets

Standard rubber grommets: Press-fit into a drilled hole. Available in sizes to suit any cable diameter. Cost pennies each. The simplest and most common solution.

Bulkhead connectors: Screw-in fittings that clamp onto the cable and seal the hole. Provide strain relief as well as chafe protection. More expensive (£1-£5 each) but more professional.

Cable glands (IP68): Waterproof fittings that create a sealed pass-through. Essential where cable passes through an external panel exposed to rain or road spray — roof penetrations for solar cables, bulkhead penetrations near wheel arches, and shore power inlet connections. See our solar cable gland guide for roof installations.

Never Run Bare Cable Through Sheet Metal

A bare cable passing through a hole in sheet metal is a fire waiting to happen. Vibration from driving causes the cable to move against the metal edge, which acts like a slow file cutting through the insulation. Eventually the copper conductor contacts the metal body, creating a short circuit. On a high-current cable, this can draw hundreds of amps from the battery and ignite surrounding materials in seconds. Always use a grommet, gland, or conduit where cable passes through metal.

Keeping 12V and 230V Cables Separate

UK wiring regulations (BS 7671) require separation between extra-low voltage (12V) and low voltage (230V) circuits. This is not just a regulation — it is a genuine safety measure. If a 230V cable develops a fault and is touching a 12V cable, dangerous voltage can appear on a circuit you believe to be safe.

Separation Rules

Physical separation: Run 12V and 230V cables on opposite sides of the van where practical, or at least 50mm apart if they must run in the same area
Barriers: If separation is not possible, use a physical barrier between 12V and 230V cables. A strip of trunking, a piece of conduit, or even a timber batten between the two sets of cables satisfies this requirement
Crossing points: Where 12V and 230V cables must cross, arrange them to cross at 90 degrees rather than running parallel. A perpendicular crossing minimises the zone of proximity
Separate conduit: Never run 12V and 230V cables in the same conduit or cable loom
Colour coding: 230V cables in the UK are grey sheathed (twin-and-earth) while 12V cables are typically red/black or other colours. Maintaining this visual distinction helps with identification

In Practice

In a typical campervan layout, the 230V system is simple — a shore power inlet, consumer unit, one or two sockets, and a mains charger. The cable runs are short and few. Route 230V cables along one side of the van (or along the floor) and keep 12V cables on the other side or along the ceiling. Most builders find this natural separation straightforward to achieve with a little planning.

Labelling Cables

Labelling every cable at both ends is one of those jobs that feels tedious during the build but saves enormous time and frustration later. When you need to trace a fault, add a new circuit, or help someone else understand your system, labelled cables make the job ten times easier.

How to Label

Cable label wraps: Pre-printed or handwritten labels that wrap around the cable and stick to themselves. Available in booklets from electrical suppliers for £5-£10.

Label maker: A Brother P-Touch or similar label maker (£20-£30) produces clear, durable labels. Use the flexible cable tape cartridges for best adhesion to round cable.

Heat-shrink labels: Print or write on white heat-shrink tubing and shrink it onto the cable. Very durable and will not fall off, but cannot be changed later.

Marker pen on masking tape: The budget option. Works, but the writing fades over time and the tape can come unstuck. Better than nothing.

What to Label

At minimum, label each cable at both ends with:

Circuit name: e.g., "Main lights", "Fridge", "USB sockets", "Inverter pos"
Destination: Where the cable goes to (at the fuse box end) or where it comes from (at the appliance end)

Some builders also label with cable size, fuse rating, and circuit number. The more information you include, the easier future maintenance becomes.

Photograph Your Wiring Before Closing Up

Before you fit cladding and panels over your cable runs, photograph everything. Take close-up photos of each junction, each cable route, and your fuse box wiring. Store these photos in a dedicated folder on your phone or in the cloud. When you need to trace a cable two years later, these photos are invaluable.

Avoiding Heat Sources and Water Ingress Points

Heat Sources

Cable insulation degrades when exposed to sustained heat. Avoid routing cables near:

Exhaust pipes and manifold — temperatures can exceed 400 degrees Celsius
Engine block — surface temperatures of 100+ degrees Celsius
Diesel heater exhaust — the exhaust pipe and outlet get extremely hot
Heating ducts — warm air ducts from diesel heaters can reach 60-80 degrees Celsius on the exterior surface
Behind the hob — if you have a gas or induction hob, cable behind or beneath it will be exposed to cooking heat

Where cables must run near a heat source (the engine bay is often unavoidable for DC-DC charger cables), use heat-resistant cable rated to at least 105 degrees Celsius. Standard PVC-insulated cable is typically rated to 70 degrees Celsius, which is insufficient for engine bay use. Tri-rated or silicone-insulated cable is a better choice for hot environments.

Water Ingress Points

Campervans leak. It is a matter of when, not if. Common water ingress points include:

Door seals — water runs down the inside of the door frame
Roof vent and solar panel penetrations — even well-sealed glands can weep over time
Wheel arches — road spray enters through factory gaps
Tailgate or rear door seals — another common leak point
Condensation — forms on cold metal surfaces, especially in winter, and drips down walls

Route cables above potential water paths wherever possible. If cables must pass through a wet zone, use waterproof conduit and IP-rated cable glands at entry and exit points. Adhesive-lined heat shrink on all connections in damp areas provides additional moisture protection.

Cable Ties vs Clamps

Cable Ties

Nylon cable ties are cheap, quick, and effective for bundling cables. Use them for:

Grouping cables within conduit
Temporary securing during construction
Low-stress bundling inside cabinets and cupboards

Downsides: Standard cable ties are single-use (cut to remove), can over-tighten and damage insulation if yanked hard, and degrade in UV light if exposed to direct sunlight. Reusable (releasable) cable ties cost slightly more but allow modification without cutting.

P-Clips and Saddle Clamps

Metal or plastic P-clips screw into the van body and hold a cable or conduit firmly. They are far more secure than adhesive-backed mounts and are the right choice for any cable run that will be subject to vibration — which is all of them in a moving vehicle.

Use rubber-lined P-clips for cable. The rubber lining prevents chafing between the metal clip and cable insulation. Space them every 200-300mm for a tidy run.

Adhesive Mounts

Self-adhesive cable tie mounts and cable clips stick to flat surfaces and are easy to install. They work well on clean, flat panels inside cabinets. They are not reliable on textured or dusty surfaces and will eventually fail under vibration if used on the van body itself. Use them for internal cabinet wiring but not for structural cable runs.

Cable Routing Best Practices Summary

Practice	Why It Matters
Route cables before insulation and cladding	Access is impossible after
Use conduit on every run along metal	Prevents chafing and short circuits
Grommet every metal penetration	Raw metal edges cut through insulation
Keep 12V and 230V separate	Prevents dangerous cross-faults
Label both ends of every cable	Essential for troubleshooting and modification
Avoid heat sources	Cable insulation degrades with heat
Use waterproof glands on exterior penetrations	Prevents water ingress to electrical areas
Photograph before closing up panels	Invaluable reference for future work
Use P-clips, not just cable ties	Secure against vibration
Leave service loops at connection points	Allows future retermination without re-routing

Leave Service Loops

At every connection point — fuse box, appliance, switch, junction — leave a 150-200mm loop of spare cable. If a terminal fails or you need to reterminate a connection, a service loop gives you enough cable to cut back and recrimp without needing to pull new cable through the entire route. This small extra cable cost saves enormous time and frustration later.

FAQ

Should I run cables before or after insulation?

Before. Install conduit and cable runs on the bare metal walls and ceiling of the van first, then insulate around them. Running cables after insulation is fitted is far harder and risks damaging the insulation. Plan your cable routes at the bare-metal stage, ideally before purchasing insulation.

How do I run cables from the engine bay to the living area?

Most vans have existing factory grommets or pass-throughs in the bulkhead (the wall between the cab and the cargo area). These are ideal for routing DC-DC charger cables and alternator sense wires. If you need a new hole, drill through the bulkhead in an area clear of existing wiring and fuel lines, deburr the hole, and fit a waterproof cable gland or a large rubber grommet. Seal both sides with silicone or butyl sealant to prevent exhaust fumes and water entering the living area.

Can I run cables under the van floor?

You can, but external cable runs need robust protection. Use UV-resistant conduit rated for outdoor use, secure it with stainless steel P-clips, and protect it from road debris and water. Under-floor routing is common for shore power inlet cables and sometimes for rear-to-front lighting runs, but keep as many cables as possible inside the van where they are protected from the elements.

How many cables can I fit in one conduit?

As a rule of thumb, cables should not fill more than 40-50% of the conduit's internal cross-section. This allows cables to be pulled through without excessive friction and prevents heat buildup from tightly packed conductors. For a 16mm conduit, three or four 1.0mm2 cables is comfortable. If you need to run more cables than your conduit can handle, use a larger conduit or run two parallel conduits.