RCBO Compatibility Guide – Will an RCBO Fit My Consumer Unit?

If you need to replace an RCBO, one of the most important questions is whether the replacement is compatible with your existing consumer unit.

An RCBO should not be selected simply because it has the same current rating or appears to physically fit.

Different manufacturers — and even different ranges from the same manufacturer — can use different busbar arrangements, terminal positions, dimensions and connection systems.

This guide explains what you should check when identifying a compatible replacement RCBO.

Does Any RCBO Fit Any Consumer Unit?

No.

RCBOs are not universally interchangeable between consumer units.

Most RCBOs mount onto a standard DIN rail, which can make devices from different manufacturers appear physically similar.

However, DIN rail mounting does not establish compatibility.

The connection between the RCBO, busbar and consumer unit also needs to be correct, and the device must be suitable for use within that particular assembly.

Why Does the Manufacturer Matter?

The first thing to identify is the manufacturer of your existing consumer unit and RCBO.

Common UK manufacturers include:

Wylex
Hager
Crabtree
Eaton
MEM
Schneider Electric
MK
Lewden
Contactum

If you have a Wylex consumer unit, for example, this does not mean that an RCBO manufactured by another brand should be fitted simply because it appears to fit.

Manufacturer compatibility should be established before selecting the device.

Is Matching the Manufacturer Enough?

Not necessarily.

Manufacturers regularly introduce new generations and ranges of consumer units and protective devices.

As a result, two RCBOs carrying the same manufacturer's name may still belong to completely different product families.

For example, Crabtree has produced ranges including:

Loadstar

and

Starbreaker

The fact that two devices are both manufactured by Crabtree does not automatically make them interchangeable.

The specific range and manufacturer part number should also be identified.

Find the Manufacturer Part Number

The Manufacturer Part Number (MPN) is one of the most useful pieces of information when searching for a replacement.

For example:

Crabtree Loadstar 6FSR20/30C

provides much more useful identification than:

Crabtree 20A RCBO

The exact MPN can help identify:

Product generation
Electrical specification
Manufacturer range
Technical documentation
Potential compatibility information

When possible, search for the exact part number rather than only the current rating.

Why Does the Busbar Matter?

Consumer units commonly use a busbar to distribute the electrical supply to the protective devices.

The physical relationship between the RCBO and busbar can vary between product ranges.

Differences can include:

Busbar position
Terminal position
Connection depth
Device dimensions
Busbar design
Terminal configuration

A replacement RCBO may clip onto the DIN rail but still not correctly interface with the consumer unit's busbar system.

This is one reason physical fit alone should never be used to determine compatibility.

What About the Neutral Connection?

RCBOs can use different neutral connection arrangements.

Depending on the design, you may encounter:

Neutral leads
Switched neutral arrangements
Different terminal configurations
1P+N designs
Double-pole arrangements

The replacement device needs to have the appropriate configuration for the consumer unit and circuit.

A different neutral arrangement can be an immediate indication that two apparently similar RCBOs are not direct equivalents.

Does the Amp Rating Need to Match?

The current rating is an important part of the device specification.

Common RCBO ratings include:

However, matching the current rating alone is nowhere near enough to establish compatibility.

For example, there are many different 32A RCBOs from different manufacturers and product ranges.

The correct rating is determined by the circuit design and should not be changed simply because another device is available.

Does the Trip Curve Need to Match?

You should also identify the existing device's trip characteristic.

Common examples include:

B32

and

C32

Both devices are rated at 32A, but their instantaneous overcurrent characteristics are different.

A C32 should therefore not automatically be substituted for a B32 simply because both devices have the same amp rating.

For more information, see our B Curve vs C Curve RCBOs – What's the Difference? guide.

What About Type A and Type AC?

The residual-current classification also needs to be identified.

You may encounter:

Type A

Type AC

This is separate from the B or C trip curve.

For example:

B32 30mA Type A

describes several different characteristics:

B – trip curve

32A – rated current

30mA – rated residual operating current

Type A – residual-current classification

For more information, see our Type A vs Type AC RCDs & RCBOs – What's the Difference? guide.

Check the Breaking Capacity

Another specification to check is the RCBO's short-circuit breaking capacity.

Depending on the product, you may see ratings such as:

6kA

10kA

This specification is another reason why two RCBOs with the same current rating should not automatically be considered equivalent.

The replacement device must have appropriate characteristics for the installation.

What If a New RCBO Physically Fits?

Physical fit does not confirm compatibility.

This is particularly important because many modular electrical devices use similar external dimensions.

A device may:

Clip onto the DIN rail
Line up approximately with existing devices
Have the same B32 marking
Have the same 30mA rating

and still not be an appropriate replacement.

The manufacturer's information for the consumer unit and protective device should be used to establish compatibility.

Can I Mix RCBO Brands in a Consumer Unit?

You should not assume that protective devices from different manufacturers can be mixed within a consumer unit.

Consumer units are assemblies containing components selected and verified by the manufacturer.

Using a protective device from another manufacturer simply because it can physically be installed does not establish that the resulting assembly complies with the manufacturer's requirements.

When replacing a device, identify the equipment specified for the particular consumer unit.

Can Different Ranges From the Same Manufacturer Be Mixed?

Again, do not assume they can.

A manufacturer may change its protective device designs between product generations.

Changes can include:

Busbar position
Device dimensions
Terminal arrangement
Neutral configuration
Breaking capacity
Connection system
Other technical characteristics

Therefore, identifying something as simply a Wylex RCBO or Hager RCBO may not provide enough information.

The product range and MPN can be equally important.

How Do I Find Out Which Consumer Unit I Have?

Look for a manufacturer's label on or inside the consumer unit.

Useful information can include:

Manufacturer
Consumer unit range
Model number
Product code
Existing device range

If the label is unavailable, inspect the markings on the existing protective devices.

A clear photograph showing the complete row of breakers can often provide useful information about the product family.

Do not remove covers or expose live components simply to identify the consumer unit.

What Information Should I Check Before Buying an RCBO?

Before purchasing a replacement, try to identify:

Manufacturer

Product range

Manufacturer part number (MPN)

Current rating

Trip curve

Residual current rating

RCD type

Breaking capacity

Number of poles

Neutral arrangement

Consumer unit manufacturer and range

The more information you have, the easier it becomes to identify the correct product.

Example: Finding a Replacement RCBO

Suppose your existing device is:

Crabtree Loadstar

MPN: 6FSR20/30C

20A

C Curve

30mA

Type A

Searching specifically for:

Crabtree Loadstar 6FSR20/30C

is considerably more precise than searching for:

20A RCBO

The first search identifies the actual product.

The second could return many unrelated RCBOs from different manufacturers and ranges.

What If My RCBO Has Been Discontinued?

This is where replacement becomes more difficult.

Consumer units can remain in service long after a particular generation of RCBO has stopped being manufactured.

A manufacturer may introduce a newer range, but you should not automatically assume that the newest RCBO is a direct replacement for the older device.

The manufacturer's compatibility information should be checked.

Where a particular older device is still required, sourcing the original MPN may be an option.

Older & Discontinued RCBOs

ReCircuit Resale stocks a changing selection of current, older and discontinued electrical protective devices.

This regularly includes RCBOs from manufacturers such as:

Wylex
Hager
Crabtree
Eaton

Older stock can be particularly useful when someone needs a specific model for an existing consumer unit rather than a current-generation device.

Availability varies depending on the stock we acquire.

Can't Identify Which RCBO You Need?

If you're unsure which RCBO is currently installed, send ReCircuit Resale clear photographs showing:

Front of the existing RCBO
All visible markings
MPN if visible
Adjacent breakers
Consumer unit
Consumer unit manufacturer's label

We can help identify the existing product and point you towards relevant stock currently available.

Buying Replacement RCBOs From ReCircuit Resale

Our RCBO listings are designed to make identification easier.

Where possible, we provide:

Manufacturer
Manufacturer range
MPN
Current rating
Trip curve
Residual current rating
RCD type
Number of poles
Compatibility information
Condition

We stock new, new-other and used electrical equipment, including older and discontinued models that can sometimes be difficult to source.

Important: RCBOs and consumer units are electrical safety equipment. Physical fit does not establish compatibility. Replacement devices should be selected in accordance with the consumer unit manufacturer's requirements, applicable product standards and current wiring regulations. Consumer unit work should be carried out by a suitably competent person.