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Inverters are great if you want 230V mains power while off-grid, but what many people don’t realise is that they can be dangerous if not installed correctly.

Any UK campervan using 230V AC power must have an RCD (Residual Current Device) according to BS7671 Wiring Regulations. This is to protect you from electric shock in the event of a fault.

However, for an RCD to work properly it requires a neutral to earth bond.

In a house, this bond is already present on the electrical supply, so you don’t have to think about it. The same is true when using shore power in a campervan - the neutral to earth bond exists on the supply side.

Because of this, you must not have an active neutral-earth bond inside the campervan when connected to shore power, otherwise you can create ground loop issues. This is how the majority of inverters are wired up by default.

So far, so good.

The problem appears when you go off-grid and run from an inverter. When this happens, the supply no longer provides a neutral to earth bond. Without one, your RCD may not trip during a fault, leaving you exposed to a potentially dangerous electric shock.

Some higher-end inverters, such as the Victron MultiPlus, automatically create a neutral to earth bond when operating off-grid. This allows the RCD to continue protecting you - nothing to worry about in this case.

However, many inverters on the market do not do this, and they are currently installed in many campervans.

This means the RCD may not provide the protection people expect.

There are two common solutions:

1 - Replace the inverter.

Upgrade to an inverter that automatically manages the neutral to earth bond when switching between inverter and shore power.

2 - Install a switched neutral-earth bond.

If you are always off-grid, a permanent bond can technically work.

However, if the van will ever use shore power, the bond must be disconnected before connecting to shore power. This is typically done using a contactor or relay that automatically makes or breaks the bond as required.

I’m often surprised that this topic isn’t explained more clearly by manufacturers.

One inverter I frequently see installed without this being considered is the Renogy Pure Sine Wave UPS series. It can be a good inverter for the price - as long as it’s installed correctly.

Electrical systems can be dangerous, so always consult a qualified installer if you’re unsure.

Do you know if your inverter setup provides a neutral-earth bond when off-grid?

I get asked this question a lot, and unfortunately there isn't a one size fits all answer. Let's discuss the most common reasons why leisure batteries run flat.

1. Usage vs charging imbalance.

We've all been there - you park up for a long weekend away in your camper and everything is running smoothly. Come the last day, your fridge is struggling to stay on, your lights are dim and you're left wondering why.

It's very important to assess your expected power usage and build your system around it with some contingency. Your chosen charging methods such as solar, shore power, and alternator charging all need to work together to keep your batteries charged.

2. Limited charging methods.

Relying on a single charging source can cause problems.

For example, solar may work great in summer, but when winter arrives and daylight drops significantly, your daily charging can be much lower than expected.

This is where having alternator charging via a DC-DC charger (or split charge relay) can make a big difference.

3. Incorrect charging settings/profiles.

It's easy to assume that your battery charger is configured correctly right out of the box, but this usually isn't the case.

Most modern chargers support multiple battery types and sizes, so making sure they’re set up correctly is important if you want to charge efficiently and look after your batteries properly.

4. Parasitic draw.

This is often one of the hardest problems to diagnose.

A parasitic draw is when something in the system is constantly using power, even when you don’t expect it to. In many cases this turns out to be a faulty appliance or device that needs tracking down and replacing.

5. Worn out batteries.

If you purchased your camper second-hand, it’s worth checking the health of the leisure batteries if they keep running flat.

Sometimes the issue is simply that the batteries are past their best and need replacing.

Note - If you're unsure about your electrical system, always consult a professional.

Have you experienced any of these issues with your campervan?

One of the biggest causes of electrical problems in campervans is systems that are incorrectly sized. So, the first step when designing any electrical setup is working out how much power you actually use each day.

Here’s a simple way to estimate it.

1. Make a list of everything that uses power.

Common examples include fridges, lights, ceiling fans, heaters, phone/laptop chargers, kitchen appliances.

2. Find the power consumption.

Next, find the power rating of each item. This is usually printed on the appliance itself or listed in the product specs online.

You’re looking for the power in Watts (W).

Pro tip - For 230V appliances, you can use a plug-in power meter to measure the actual power consumption directly from a household socket.

3. Estimate daily usage.

Now estimate how many hours per day each item will be used.

Multiply: Watts × quantity of items × hours of use

For example:

A spotlight that uses 2W

× 6 lights

× 5 hours per day

= 60Wh per day

Note - Not every appliance runs constantly.

For example, compressor fridges only run when cooling is needed, so over a full 24-hour period the compressor might only run for a few hours. This is important when estimating realistic usage.

4. Convert to battery usage.

To estimate how much battery power you will use per day, divide the total Watt-hours (Wh) by your system voltage.

For example:

60Wh ÷ 12V = 5Ah

Doing this for every appliance and adding them up will give you a rough estimate of your daily battery usage.

We always recommend adding a percentage buffer to your final total. Real systems are never 100% efficient. Inverters, wiring losses, and unexpected usage all adds up.

If you're planning a campervan electrical setup and want to make sure it’s properly sized and safely installed, feel free to get in touch!