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Grounding a Campervan Electrical System

Grounding or earthing your campervan is an essential step when setting up your electrical system. There's a lot of contradictory information on how to set up the ground in van conversion electrics. In this article, we'll explain it all in full. We'll look at the types of ground, what appliances we should ground, and how we wire up ground in our campervans.


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Shane, the founder of The Van Conversion, is a campervan professional dedicated to helping people transform ordinary vans into homes on wheels. He has authored Roaming Home, and teaches The Van Conversion Course, guiding many people through their van builds. Shane also writes The Van Conversion Newsletter, where he shares practical tips and insights. After completing two van builds and living on the road full-time since 2020, he is passionate about sharing his expertise with others.


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Note: Did you know you can get a free electrical wiring diagram by signing up for The Van Conversion Newsletter?


 

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What is Ground?

Quite often ground (or earth) means different things to different people, hence the confusion over the term (especially in the world of van conversions). For instance, ground to an electrician can mean something different than to an electronics engineer.


Proper grounding is a critical safety precaution across the world of electrics. We ground electrical equipment so that wiring failures don't raise the voltage to dangerous levels. Ground is an alternate pathway for electricity to follow if there's a fault in your system. Instead of continuing to flow at dangerous voltages through your electrical system, electricity instead flows to the ground to save your wires and appliances and hopefully stopping a fire.


As we know, a circuit must be complete for current to flow (think of a simple DC system):


complete circuit

We can use ground as an alternative circuit return path in case something goes wrong in our main circuit:


ground return path

In a vehicle, the metal chassis is the common return path for all return current to the battery:


chassis ground

In the world of van conversions, ground is simply a connection from the negative terminal of your leisure battery to the chassis of your vehicle.


BS 7671 and NEC Guidelines for Grounding in Van Conversions

Proper grounding in your campervan electrical system is essential for both safety and compliance. Below are the key regulations from BS 7671 (UK) and the NEC (US) that directly apply to grounding in van conversions.


BS 7671 - UK Wiring Regulations

Section 721.411.3.1: Protective Earthing and Bonding in Caravans and Motor Caravans

  • All exposed conductive parts, such as metal appliances or components, must be properly earthed. The chassis of the vehicle serves as the DC ground for the 12V system, providing a return path for current.

  • For the AC system (shore power), a separate AC earth must be connected to the vehicle chassis, and it must be isolated from the DC ground. This prevents any crossover between the AC and DC earthing systems, ensuring the systems remain safe and separate.


Regulation 543.2.7: Earthing Conductors and Connections

  • Ground connections in campervans must be both permanent and accessible. For instance, your main ground point should not be hidden behind cladding or insulation to allow for inspection and maintenance.

  • Use a suitable earthing conductor that is sized appropriately. The minimum cross-sectional area for a DC grounding cable must be at least as large as the main DC positive cable, and for AC grounding, the green/yellow cable must comply with the minimum sizing set out in Regulation 543.1.


Regulation 411.3.2.1: Protective Earthing of Electrical Installations

  • Any connection to shore power (AC) must have a protective earthing connection, which bonds the AC system to the van’s chassis. The earthing conductor should run directly from the consumer unit to a dedicated AC ground point on the chassis.

  • It is crucial that RCDs (Residual Current Devices) are installed in the AC system to ensure safety, as they detect faults and disconnect power if a ground fault is detected.


Regulation 411.4.2: Earthing Systems for TN-S and TN-C-S Installations

  • If your campervan is connected to a TN-S or TN-C-S earthing system via shore power, ensure the earthing conductor from the electrical installation is connected directly to the main earth terminal at the van’s consumer unit. The system must include protection against faults that may occur due to a disconnection or interruption in the supply earth.


National Electrical Code (NEC) - United States

Article 250.136(A): Chassis Grounding

  • The chassis of the vehicle must be used as the DC ground. All 12V electrical components, such as the negative bus bar, inverter, and batteries, should have a direct connection to the chassis ground.

  • For the AC system, the grounding conductor from the shore power should also be connected to the chassis via a separate ground point to ensure the system has a reliable path to ground.


Article 250.4(A): General Requirements for Grounding and Bonding

  • The grounding system must establish a low impedance path to safely conduct any fault currents. This includes both the DC negative ground and AC ground, ensuring that fault currents do not endanger users or equipment.


Article 551.56: Grounding in Recreational Vehicles (RVs)

  • For systems using shore power, the NEC mandates that the AC grounding conductor from the shore supply be connected to the chassis. The AC and DC systems should have separate grounding points to avoid interference between the two systems.

  • Install Ground Fault Circuit Interrupters (GFCIs) on all AC outlets, particularly those near wet areas or external sockets. These devices will cut power if they detect a ground fault, ensuring user safety in case of faulty wiring or exposure to moisture.


Article 250.122: Sizing of Grounding Conductors

  • The grounding conductors must be sized appropriately according to the largest conductor in the system. For example, the grounding wire should be no smaller than one size smaller than the largest conductor connected to the battery or the system.


Article 250.140: Grounding for Inverter Systems

  • Inverters and their AC outputs must be grounded separately from the DC system. The inverter chassis should have a connection to the vehicle ground, and the AC neutral-to-ground bond must only occur at one location (typically in the inverter or the shore power connection). Multiple neutral-to-ground bonds can create ground loops, leading to unsafe voltage differences.


Key Takeaways for Grounding in Campervans

DC Ground: The negative terminal of your leisure battery and all 12V components should be grounded to the chassis. Use a negative bus bar to consolidate connections, and wire the bus bar back to the van’s manufacturer-provided chassis ground point or create a new one by securely bolting into bare metal.


busbar used to tidy up ground in campervan electrical system
Using a busbar to consolidate connections for tidier grounding

AC Ground: AC systems (such as shore power) must be grounded separately to avoid cross-currents with the DC system. Use a dedicated AC ground point on the chassis for appliances like the inverter and consumer unit.


Ground Fault Protection: Install RCDs (UK) or GFCIs (US) to protect the AC system from ground faults. These devices disconnect power in the event of a fault, safeguarding the system from electrical hazards.


Accessible Ground Point: Ensure that your ground point is accessible for inspection and maintenance. Use green/yellow cables for AC ground and appropriately sized cables for DC ground, per the BS 7671 and NEC guidelines.



Types of Ground

While there are many types of ground, we are going to focus on just two: earth ground and chassis ground.


Earth Ground

Earth ground is a direct and physical connection to our beautiful planet Earth.


Earth ground in van conversions
Symbol for earth ground

In household mains systems, the third prong in a plug socket is physically connected to earth ground.


home electrical sockets showing ground

The physical ground connection looks like this: a conductive rod driven into the ground.


Earthing electrode

Chassis Ground

Chassis ground is the ground we have in our vehicles. It's a point in the vehicle chassis to which we connect the negative terminal of our batteries.

Chassis ground in a van conversion
Symbol for chassis ground

Unlike earth ground, chassis ground is not a physical connection to the earth, but to the chassis of the vehicle. This makes the van chassis the common return path for all return current to the battery.


AC Ground vs. DC Ground

The main difference between AC and DC ground is that no current should flow into AC ground during normal operation, while all current should flow into DC ground. Why?

DC appliances don't have a "ground" per se, because the negative battery terminal (which people sometimes call "ground") is itself at the same electrical potential as the chassis. The negative terminal of your leisure battery is ground for the appliances.


Which Appliances Should I Ground in my Van Conversion?

Certain elements must be grounded in a campervan:


  • Starter battery (should be grounded already)

  • Negative DC busbar - this grounds your leisure battery and the other DC components in the electrical system

  • Shore power (EHU) consumer unit (must be grounded per BS 7671:2018 – Section 721 regulations to a separate AC ground)


Others might need grounding depending on their construction. Consult the manufacturer’s guidelines:


  • MPPT

  • Battery chargers and split chargers (separate AC ground)

  • Inverter and inverter consumer unit (separate AC ground)


It is particularly important that you check the manufacturer’s guidelines as it relates to grounding your inverter (and the related consumer unit, if required), as grounding advice frequently changes with the manufacturer and how the inverter is built. As a general rule of thumb, each component in your electrical system should be grounded, unless the manufacturer’s instructions say otherwise.


It is important that all your grounds are connected together (ie. to a single ground point) to avoid ground loops. A ground loop is a closed conductive loop that will slowly but surely drain your batteries.


Note: The DC ground and AC ground should run to separate ground points - with no crossover between the two. This means that the inverter and shore power consumer unit run to a dedicated AC chassis ground.


How to Install Ground in a Van Conversion

All vehicles have ground points pre-built into the chassis. A quick Google for your van's ground points should show you where they are. Per the BS7671 regulations, you should keep the ground point somewhere accessible, i.e. not behind cladding, insulation, or furniture.


Ford Transit ground points
Ford Transit ground points

Sometimes, you may want to make your own ground point if existing points are in an awkward place:


  1. Sand down the paint on the chassis of the vehicle on an interior part of the chassis. This gives a clean connection point against the bare metal.

  2. Drill a hole into that point.

  3. Rub some dielectric grease/Vaseline on the connection point to prevent corrosion and improve the electrical connection.

  4. Screw a bolt into the hole, followed by a nut and an external tooth lock washer. This is your new ground bolt.

An external tooth locker washer
An external tooth lock washer

The correct color for a dedicated ground wire is green and yellow:


Ground wire cable van conversion

Wire Size

Guidelines state that the chassis ground cable can be no smaller than one size smaller than the largest wire in the system. In other words, you will need to use a cable about as large as your battery cable for the ground connection.


Negative Busbar as Common DC Ground

Instead of running appliances individually to the ground point, we typically use a negative busbar as a common ground for all DC components that need grounding. All DC grounds run to the negative busbar and the negative busbar runs to the ground point.


Do not run AC ground to your negative DC busbar. If you want to run AC ground to a busbar, it should go to a new dedicated busbar termed the 'earth busbar'. The negative DC busbar should be wired back to the vehicle manufacturer-assigned negative connection point on the chassis. The earth busbar should be wired to a newly created mains ground point somewhere on the chassis.


Ground Fault Protection

Ground Fault Protection safeguards your system from potentially dangerous electrical faults, where current unintentionally flows to ground through the chassis or a person.

Install Ground Fault Circuit Interrupters (GFCIs) in your AC system, particularly near outlets or wet areas. GFCIs monitor the current flow and instantly disconnect power if they detect a ground fault (a mismatch between incoming and outgoing current).


For DC systems, fuses and circuit breakers provide essential protection by preventing overcurrents in the event of a fault.


Conclusion

Grounding is an essential safety component of any electrical system, alongside fusing. If you're uncertain about your installation or how to best approach grounding, consult a professional electrician. It's best not to play around with your electrical system unless you're 100% sure of what you're doing. Check out our guides on electrical systems and electrical regulations to build on your knowledge, or consider our electrics masterclass.


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If you're looking for some guidance with your van conversion, you might be interested in our book Roaming Home, or in our online course The Van Conversion Mastery Course. You'll learn directly from our founder Shane how to convert a van into your dream home - no prior experience needed.


 

Until next time.

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