Campervan consumer units – what do I need for my van electrical system?

Setting up your campervan or RV’s electrical system for some off-grid adventures means making sure it’s not just functional, but also safe, and sufficiently specced to your requirements.

When compared to major system components such as inverters and chargers, consumer units and breaker boxes are often overlooked. But, every system with AC electrics needs them, and choosing the wrong one could see your breakers tripping easily or cables overheating. Plus, trawling through electrical standards to answer questions such as, “Do I need a metal or plastic consumer unit?” isn’t simple. 

So, in this article we will demystify campervan consumer units and breaker boxes, examining their role in your electrical setup, the types you may need, and wiring examples. We’ll also dive into the British Standards and US regulations that govern these components, including details about Residual Current Devices (RCDs) and Miniature Circuit Breakers (MCBs).

By the end, you’ll have a good grasp on choosing and installing the right consumer unit or breaker box for your campervan or RV. So, buckle up and let’s get started!

Do I need a consumer unit or breaker box in my campervan electrical system?

The short answer is yes, you do need a consumer unit or breaker box in your campervan’s electrical system. But why is it so crucial? Let’s break it down.

A consumer unit, also known as a ‘breaker box or panelboard’ in the US, serves as the control centre of your campervan’s electrical system. It’s the point where the power supply enters your vehicle and is then distributed to the various circuits that run your appliances and devices. More importantly, it provides safety protection measures. A carefully selected consumer unit will protect you against electric shocks and electrical fires.

Within the consumer unit, there are devices called circuit breakers or miniature circuit breakers (MCBs). Think of these as a reusable fuse. They protect each circuit in your vehicle from overloading by ‘tripping’ and breaking the connection in case of a short circuit.

Also contained within most consumer units (but not necessarily all breaker boxes) is a Residual Current Device (RCD) or Ground Fault Circuit Interrupter (GFCI). This protects you from the risk of electric shock in the case that you touch a live part of the circuit. It rapidly disconnects the power if it detects that current is not balanced between the live and neutral wires, indicating that electricity is leaking out, potentially through a person.

What is an MCB and how does it work?

A circuit breaker or ‘MCB’ is a type of protective electrical component designed to protect a circuit from damage caused by a current overload. When it detects a current larger than a predetermined amount, the breaker ‘trips’ and disconnects the circuit.

Whilst MCBs protect your electrical appliances, their main role is to protect your circuit wiring. An overloaded cable produces lots of heat and can easily cause an electrical fire. By choosing an MCB that’s rated to trip before your cable’s current rating, you eliminate any fire risk. 

Before circuit breakers, we had fuses. These contain a thin wire, designed to melt at a specific current and break the circuit. Because they’re so simple and effective, fuses are still widely used. They offer a cheap option to protect the DC portion of your electrical system, where current surges are infrequent. But, as fuses are single use only, in AC applications, where overloads are more common, it makes sense to spend a bit more on a reusable circuit breaker. 

MCBs trip in two conditions:

Overload: If the current exceeds the MCB’s rating by a small amount and for a prolonged period, it results in an overload condition. This overload heats up the bimetallic strip inside the MCB. The strip, as its name suggests, is made of two different metals. When heated, these metals expand at different rates, causing the strip to bend. Once it bends enough, it triggers a mechanism in the MCB, causing the circuit to “trip” or open, interrupting the current flow.

Short circuit: A short circuit generates a sudden, significant increase in current which activates the electromagnet within the MCB and trips it. The high current magnetises the electromagnet, pulling a lever connected to the switch mechanism. This instant action causes the MCB to trip rapidly, disconnecting the circuit and protecting your electrical system from damage.

What is an RCD / GFCI and why do I need one?

If an electrical component becomes faulty and a part of its internal wiring touches the outer, metal casing, the component can become live. If you then touched this component, you would experience an electrical shock as the electricity passes through you, to earth. So, to prevent shocks, we earth components by connecting their casing to earth. Offering a much lower resistance than yourself, electricity from a fault will travel down this wire instead of through you, thus protecting you. 

All AC electrical installations in the UK will also contain a residual current device (RCD) to offer further protection. These components detect if any current is passing through the ground wire and immediately break the circuit. They work by measuring a difference in current between the live and neutral conductors. Current is conserved throughout a series circuit. So, all current leaving and entering a consumer unit will be the same. If there is any less current entering the RCD from the neutral wire than the live wire, it means that the remaining current is in the ground wire.

Campervan consumer units in the UK

Choosing a consumer unit for your campervan

So, now you know why you need a consumer unit, you’ll need to pick the best one (or two!) for your electrical system. There are a few things you need to consider, including different types of RCD and MCB, as well as the case material of the consumer unit itself. Picking the right consumer unit depends on the number and type of appliances you need, and what other components you have in your system.

We should also consider the regulations set out in the 18th Edition of the Wiring Regulations, also known as BS 7671. Whilst they’re not law, and no one’s forcing you to follow them, the British Standards know what they’re talking about when it comes to electrical safety. So, by choosing components that conform to these standards, you can have peace of mind when it comes to your system.

Choosing an RCD

Before shopping around for an RCD, you’ll need to consider the following properties that you need from it:

• Number of poles
• Rated residual current
• Current and voltage rating
• RCD type

These terms make choosing the right component a bit daunting. Luckily, the British Standards outline most of what we need to look for, so we can follow this guidance to help us.

What do the British Standards say about RCDs?

BS 7671 section 721 outlines standards for electrical installations in caravans and motor caravans. We’ve had a dig through it and pulled out the relevant information, so you don’t have to! You can then use this information to narrow down your search criteria for a consumer unit. 

British Standards offer the following guidance on RCDs:

The important points mentioned here for us are:

• ‘A rated residual operating current not exceeding 30mA’

• ‘Breaking all live conductors’

Residual operating current

The word residual means the remainder left after subtracting two numbers. So, we can then take this term to refer to the current difference between the live and neutral wires, i.e. the current in the ground wire, that causes the RCD to operate.

Therefore the statement, ‘a rated residual operating current not exceeding 30mA’ means that when a suitable RCD detects a difference of 30mA between the live and neutral conductors, it trips.

Maximum current and voltage rating

People often mistake the residual current rating for the overall current rating of the RCD, i.e. 25A. This rating doesn’t denote when the RCD will trip, but instead the maximum current it can handle. Likewise, the voltage rating denotes the maximum voltage that the breaker is rated for. 

Number of poles

The number of poles an RCD or MCB has refers to the number of connections it breaks when it trips. Because the British Standards require that RCDs ‘break all live conductors’ we need to choose a two pole RCD. Although we refer to the three conductors in AC cable as live, neutral and earth, both live and neutral are classed as live conductors. And so, we need an RCD that can break both conductors.

Do I need a type A or type AC RCD?

RCDs come in four different types: type AC, A, F and B. These are each designed to function under different electrical conditions of increasing complexity, and the price of the RCDs increase accordingly. We only need to worry about type AC and A RCDs for camper and RV electrical systems. However, if you want to learn about type F and B RCDs, IET has a good article on RCD types.

Type AC RCDs are traditionally the most common and are designed for use with purely AC electricity. Type A RCDs on the other hand are designed for use with AC current and a pulsating DC current component up to 6mA. 

This DC component is sometimes found when a component known as a rectifier converts a large amount of electricity from AC to DC. This only really became an issue in domestic settings with the rise in personal electric vehicle chargers. As a large amount of power is converted it is possible that a small amount of DC power is leaked into the AC power. For this reason, BS 7671 now requires that households have at least type A RCDs.

Whilst this switch from type AC to A is still optional for motorhomes, we have started to supply type A RCDs. This is because induction hobs, which can also introduce a DC power component, are starting to pop up in the camper community. 

Choosing an RCD – summary

Let’s use this information to help choose an RCD. It should meet the criteria that we deduced in the previous section. It should also have a maximum current rating larger than the trip current of the MCB you choose. 

So, our overall RCD criteria is:

• 30mA rated residual current
• Rated over 230V and 
• Double pole
• Type A

Choosing an MCB

Like with RCDs, MCBs have a few properties that you need to consider before choosing one. This includes

• Rated trip current
• Maximum voltage rating
• Curve code
• Number of poles

What do the British Standards say on MCBs?

There’s a little less guidance with MCBs than RCDs in the British Standard. All they say is:

“Each final circuit shall be protected by an overcurrent protective device which disconnects all live conductors of that circuit.” 

This means that each circuit connected to the consumer unit needs a double pole MCB.

How to size an MCB

This is easy, and you just need to make sure that you meet the following requirements. Pick an MCB that is rated 20% larger than the largest appliance that you want to power from it. And, most importantly, make sure that it’s rated less than the cable’s wire rating. 

For example, let’s say you wanted to use a 1200W kettle in a circuit with 2.5mm2 cable. Firstly, we need to find the current rating for the cable. Picking from the table below we get a maximum current of 25A.

Cable size (mm)	Current rating (A)	Max power draw @ 230V (W)
1.5	16	3680
2.5	25	5750
4	35	8050

Then, we just need to convert the kettle’s power draw in watts to a current draw in amps. Here we simply divide through by 230V.

1200W ÷ 230V = 5.2A

So, any MCB rated between 5.2A and 25A will be suitable.

Do I need a B curve or C curve MCB?

All MCBs have a curve code, either B, C, D, K or Z, which describes how long they take to trip when overloaded.  You’ll find a mix of B and C curve MCBs in most households, and the rest are generally used in commercial and industrial applications. B curve MCBs trip at 3 – 5 times the rated current, and C curve at 5 – 10 times the rated current.

You might be asking why they have these curve codes at all? Why don’t they all just trip at their rated current? Well, we expect some large appliances with inductive loads to have an inrush current. To prevent the circuit tripping every time we turn them on, we use an MCB with a larger trip curve. 

Campervans have much fewer plug sockets and usually only a couple of MCBs. So, whereas a household will have a mix of C curve and B curve MCBSs,  it’s common to only use C curve MCBs in a camper. This is perfectly safe, and suitable for a range of applications within your campervan, from protecting lighting circuits to more intensive equipment such as air conditioning units or kitchen appliances.

Choosing an MCB – summary

So, when purchasing an MCB, look for one that is:

• Double pole
• C curve
• Rated to at least 240V
• Rated higher than your appliances but lower than the circuit cable

Choosing a consumer unit

Do I need a metal or a plastic consumer unit?

There’s much debate online about whether or not your campervan’s consumer unit needs to be metal clad, or if plastic is okay. The guidance often quoted is the following from BS 7671: 

“421 .1.201 Within domestic (household) premises, consumer units and similar switchgear assemblies shall comply with BS EN 61439-3 and shall

(i) have their enclosure manufactured from non-combustible material, or

(ii) be enclosed in a cabinet or enclosure constructed of non-combustible material  and complying with Regulation 132.12.

NOTE: Ferrous metal, e.g. steel, is deemed to be an example of a non-combustible material.”

Because they direct this guidance specifically to a household, the standard doesn’t require that campervans have a metal consumer unit. There are plenty of both plastic and metal consumer units available on the market, so just go with whatever works best for your setup.

How many ‘ways’ do you need?

The final consideration to make is what size consumer unit you need. We describe a consumer unit’s size by how many ‘ways’ it has. Each component, such as an MCB or RCD, mounts on a what’s called a DIN rail, and takes up one or more ways. A single, double or triple pole component would occupy one, two or three ways.

In our Nohma systems, we supply two 6 way consumer units, each occupied with one double pole RCD and two double pole MCBs. If, instead of splitting things up as we do, you like to keep everything together in one consumer unit, you may need a 12 way one. 

Do you need more than one consumer unit?

The number of consumer units you need in your electrical system depends on whether or not you have a shore power connection and an inverter, and how you like to arrange your system. 

Any system with a shore power connection and an inverter, such as a MultiPlus, will need an RCD and MCB on both the input and output. For example, if you have a separate inverter and battery charger, the AC circuits connected to each are separate. So, they each need protection from their own MCB and RCD. 

A combined inverter/charger connects the input and output AC circuits when it detects a shore power connection. So, in normal operation the AC input would share an RCD connected to the AC output. However, this still leaves a possibility for a fault in the multiplus itself leaving the chassis live and posing a shock risk. Plus, the IET code of practice for electrical energy storage systems requires that inverter/charges have an RCD on both the input and output. So, it’s important to include both an RCD and a MCB on both the AC in and out of an inverter/charger. 

If you only need one MCB on the AC in, it may be a good option to choose an RCBO instead of a separate RCD and MCB. These breakers combine the functionality of both components into one unit. 

Whether or not you choose one or two MCBs is up to you. We like to supply two consumer units to clearly separate the input and output RCD and breakers. We find that it reduces mistakes made when wiring. But, choosing a slightly larger, single consumer unit can offer a compact solution, especially if you have an RCBO on the AC in. 

How to wire a consumer unit

Wiring a consumer unit in an off-grid system (inverter only)

This diagram shows the best way to wire your consumer unit if an inverter is your only AC power source. Here, we only need a single small consumer unit as there is only one AC circuit. This setup also works if you just use AC power on shore power. Just connect the wire labeled inverter AC output to shore power.

Wiring a consumer unit in a shore power system (inc. inverter/charger)

This diagram shows how to wire an inverter/charger such as a Multiplus. As we mentioned above, you need to protect both the input and output sides of the circuit. You can do this with two separate consumer units as we’ve shown below. Or you can combine everything into one larger consumer unit.

RV breaker boxes and panelboards – USA

Like a consumer unit in the UK, a ‘breaker box’ or panelboard in the US, serves as the control centre of your campervan’s electrical system. It both protects your system and distributes power to different branch circuits. 

If you’ve missed it, the start of this article runs through exactly what a breaker box’s purpose is, and exactly why you need one in your RV’s electrical system. Now, we can start to choose the one that’s right for you. We’ll run through everything you need to know to ensure that your panelboard allows you to utilise your systems full potential, and safely.  

Choosing an RV panelboard

In the USA, the ‘code’ (NFPA 70) is the regulatory standard for the safe installation of electrical equipment and wiring. It allows manufacturers to combine DC and AC distribution boards into one unit, which isn’t the case in the UK.  So our usual advice there is to buy a standard, domestic consumer unit.

However, thanks to different regulations in the states, there are a few RV specific panelboards available. These combine both an AC breaker box and a fused DC distribution panel, providing a neat solution that’s right for most RV owners. 

So, our advice towards buying a breaker box for your RV is to just pick up one of these combined panelboards. These examples from Furrion and WFCO each support up to 12 AC circuits and 15 DC circuits. Because these are a barebones unit, you will need to pick the right circuit breakers for your setup.

Let’s take a look at the different options you have and what the code has to say about RV panelboards. If one of these all in one units aren’t the best option for you, just go for any off the shelf panelboard and choose some breakers based on our recommendations below.

Choosing a circuit breaker

These all-in-one distribution boards from Furrion and WFCO can each house up to eight full size breakers. To make the most of your available space, we recommend using a full size, 50A or 30A breaker for the inputs, which feed into three tandem breakers, giving 6 branch circuits per leg. 

To comply with the code, it’s more than likely that you will need a ground-fault circuit interrupter (GFCI) at some point in your system. It’s possible to protect all of your receptacles in one go by choosing a 50A/30A circuit breaker with GFCI functionality. However, these go for around $150 rather than the $10 – $20 for a GFCI receptacle that can protect a whole branch. So, they won’t be the best option for many RV owners. Plus, 50A GFCI breakers tend to be double-pole and take up a couple valuable slots on the breaker board.

Any 1”, single pole, 50A or 30A breaker for your input, and any 20A tandem breaker for your branch circuits will do the trick.

Do you need a GFCI in your RV breaker box?

Ground-fault circuit interrupters (GFCIs) are now commonplace in electrical systems, with the NFPA requiring them in more and more applications. The code outlines exactly where and when they’re required in an RV or camper. Once you’ve figured out whether or not you need one, you can then decide if you want a GFCI in your breaker box or at individual receptacles. 

The code requires that you protect any receptacle in one of the following locations with a GFCI:

• Adjacent to a bathroom lavatory.

• Where the receptacles are installed to serve the countertop surfaces and are within 1.8 m (6 ft) of any lavatory or sink.

Exception No. 1: Receptacles installed for appliances in dedicated spaces, such as for dishwashers, disposals, refrigerators, freezers, and laundry equipment.

Exception No. 2: Single receptacles for interior connections of expandable room sections.

Exception No. 3: De-energized receptacles that are within 1.8 m (6 ft) of any sink or lavatory due to the retraction of the expandable room section.

• In the area occupied by a toilet, shower, tub, or any combination thereof.

• On the exterior of the vehicle.

Exception: Receptacles that are located inside of an access panel that is installed on the exterior of the vehicle to supply power for an installed appliance shall not be required to have ground-fault circuit-interrupter protection.

Put simply, any receptacle less than 6’ away from an area with water should be GFCI protected. 

As we mentioned in the previous section, you can either use a GFCI breaker or receptacle to protect your circuits. But, in an RV, GFCI receptacles make the most sense.

GFCI receptacles

• Cost $10 – $20
• Protects one branch circuit
• Can use a cheaper, smaller breaker

GFCI breaker

• Cost $100 – $150
• Protects the whole AC circuit
• Requires a wider breaker but uses standard outlets

A GFCI breaker can make sense in a house, where lots of branch circuits may need GFCI protection, and the overall price will even out. But, in an RV, with less breaker box space and fewer branch circuits, GFCI outlets make the most sense. 

50A vs 30A hookup

Whether you choose to go for a 30A or 50A shore power hookup plays a role in the breaker box you need. For a lot of people, going for 50A makes the most sense, as it allows you to pull up to 12000W of power in split phase. So, you can happily power a few AC units and a clothes dryer when on hookup. However, as components such as cables and breaker boxes come at a premium for the 50A rating, it may not be the best option for those on a budget.

Whilst doing RV research, you’ve likely heard that 50A really gives 100A of current. This statement refers to this 50A hookup being four wire, split phase. It has two hot wires, leg one and two, neutral and ground. 

L1 and L2 are 180° out of phase, meaning that when one is at 120V, the other is at -120V and the difference between them is 240V. This means that if we connect an appliance to these wires, we can deliver up to 50A at 240V. Alternatively, you can connect appliances between either L1 and neutral or L2 and neutral for a total 100A at 120V. This is really useful for RVs with any 240V appliances, or loads of 120V appliances. 

If you still need 50A at 120V, but don’t need split-phase, then you can use just one leg of the power and work in single-phase. We’ve got a handy diagram later showing exactly how to do this.

If you’re on a tighter budget and don’t need loads of appliances, then 30A could be a good option. This hookup connection is three wire, with one hot wire, neutral and ground. With 30A, you’re limited to 120V and 3600W, but this is plenty for a lot of smaller setups. 

In terms of cost savings, you’ll definitely see some if you go for 30A. But when compared to the rest of the system cost, it’s not crazy. 25’ shore power cables start at around $100 for 30A and around $180 for 50A. Shore power inlets are similarly priced and many distribution boards are rated for both 50A and 30A, so you might not save money there.

One final point to consider is that the code only permits up to five branch circuits from a 30A hookup. This means all circuits powering lights, receptacles and fixed appliances. So, if you need more than five, then you’ll need 50A.

50A service

• 100A @  120V and 50A @ 240V
• Up to 12000W of power
• More expensive
• Unlimited branch circuits
• More complicated for split-phase

30A service

• 50A @ 120V
• Up to 3600W of power
• Less expensive
• Up to 5 branch circuits
• Simple setup

Conclusion

Setting up your campervan’s electrical system can seem like a daunting task, but it doesn’t have to be. With a solid understanding of why and when you need a consumer unit or breaker box, and knowing the regulations in your specific country, you’re well on your way to creating a reliable and safe electrical system. 

For our UK readers, remember that the British Standards, whilst not law, offer a good basis for campervan electrical safety. So, by following them, you stand in good stead for a safe electrical system. And, for those in the US, you can look at NFPA 70 for equally useful advice. 

You should now be able to pick out a consumer unit or panelboard, as well as some suitable breakers to go in it. And, hopefully our wiring diagrams have helped you wire the AC side of your system.

Remember, these guidelines are a starting point. Each campervan setup is unique, and it’s important to consider your specific requirements when planning and installing your electrical system. Don’t hesitate to consult a professional if you’re unsure.

If you’re still not sure which components to buy for your electrical system, let Nohma do the hard work for you. We employ scientists and engineers, who, alongside our clever algorithm, have designed thousands of bespoke campervan electrical systems. Let us design and ship yours, for no extra cost over the parts themselves.