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Grounding a Campervan Electrical System

Ground is the most confusing part of van conversion electrics. Why? Because of how much conflicting information there is on the internet about it! Today we will cut through the noise and learn all about ground for your campervan! We will look at the types of ground, what appliances we should ground, and how we wire up ground in our campervans.


I'm Shane, I've been teaching people to convert campervans for years; I'm the author of Roaming Home; The Comprehensive Guide for Converting Your Van Into a Campervan, writer of The Van Conversion Newsletter, instructor of The Van Conversion Course over at Udemy. And full-time vanlifer for 4 years!


So let's jump in and have a look at ground for van conversions!


Index

 

Note: Before we hop in, you might want to grab yourself a wiring diagram which you can get for free by signing up to The Van Conversion Newsletter (suggested, but not mandatory 🙂 - wiring diagram gets sent to you straight away).


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What is ground?

Quite often ground means different things to different people, hence why there is often so much confusion over it (especially in the world of van conversions!). For instance ground to an electrician can mean something different than ground to an electronics engineer.

Proper grounding is a critical safety precaution across the world of electrics. We ground electrical equipment so that internal wiring failures don't raise the voltage to dangerous levels. Essentially ground is an alternate pathway for electricity to go; if there's a fault in your system, electricity can flow to ground to save your wires, appliances, and hopefully stop a fire.

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

complete circuit

Well, we can also use ground as the circuit return path

ground return path

The most obvious example of this is in a vehicle. The vehicle 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.

Types of Ground


While there are many types of ground (GND), 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. It is true 0V.

Earth ground in van conversions
Symbol for Earth ground

In our house, the third prong in a plug socket is physically connected to earth ground.

ground in house

And earth ground looks like this (an earthing electrode - a conductive rod driven into the ground):

Earthing electrode

Chassis ground

Chassis ground is the ground we have in our vehicles. It is a point in the chassis of the vehicle to which we connect the negative terminal of our batteries and any other relative appliances.

Chassis ground in a van conversion
Symbol for Chassis ground

Unlike earth ground, chassis ground is not a physical connection to our planet 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 say, because the negative (which people are calling "ground") is itself at the same 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?

Here is what you must ground in a campervan:

  • Starter battery (should be grounded already)

  • Negative bus bar - this grounds your leisure battery and the other components in the electrical system

  • Shore power (EHU) consumer unit [must be grounded per BS 7671:2018 – Section 721 regulations]

Here is what you might need to ground (consult the manufacturer’s guidelines):

  • MPPT

  • Battery chargers & split chargers

  • Inverter & inverter consumer unit

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), this can help 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. Ie. 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 a ground point(s) pre-built into the chassis. A quick google for your van's ground point should show you where you can find it.

Per the BS7671 regulations, you should keep the ground point somewhere accessible - ie. not behind cladding / insulation..

Ford Transit ground points
Ford Transit ground points

Sometimes the ground point might be far away or inaccessible (eg. under the hood / bonnet of the van). If this is the case, you will need to make your own ground point. Here's how:

  1. Sand down the paint on the chassis of the vehicle (on an interior / inward-facing 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 (prevents corrosion & improves connection).

  4. Pop a large bolt with an external tooth lock washer through the hole - this is our ground bolt. Everything gets grounded to this.

External tooth locker washer
External tooth locker washer

Ground point to chassis of van conversion

The correct color of for ground wire is green and yellow (not that nasty red shown in the photo above!)

Ground wire cable van conversion

Wire size

ABYC (American boat and yacht council) states 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 bus bar as common ground

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

Note: Do not run AC (Green/yellow) ground to your negative busbar. If you want to run AC to a bus bar, it should go to a new bus bar termed 'earth bus bar'. The negative bus bar should be wired back to the vehicle manufacturer assigned user negative connection point on the chassis if there is one. The earth bus bar should be wired to a newly created mains earth point somewhere suitable on the chassis.

Conclusion


I hope you found this explanation of van conversion ground electrics useful! You're now better equipped to build out a safer electrical system in your self-build campervan!


Don't forget to subscribe to The Van Conversion Newsletter for everything you need to get started with your own van conversion (I'll send you a free wiring diagram when you join).


If you're looking for some guidance with your van conversion, you might be interested in Roaming Home; The Comprehensive Guide for Converting Your Van Into a Campervan. In the 380-page book (or ebook), you'll learn directly from me how to convert a van into your dream home - no prior experience needed!

campervan conversion guide

Until next time,

Shane ✌️

2 Comments


si_woollatt
May 17, 2023

What size should your earth busbar and cabling be?

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Shane Monks O'Byrne
Shane Monks O'Byrne
May 21, 2023
Replying to

The ABYC (American boat and yacht council) states 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. The bus bar should be able to handle the same amperage as this cable - a standard 300a heavy duty bus bar should be fine in most cases.

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