How to Identify Your Existing RCBO

If you need to replace an RCBO in an existing consumer unit, identifying the exact device is an important first step.

Simply knowing that you need a 32A RCBO is usually not enough.

Different manufacturers produce RCBOs with the same electrical ratings but different physical dimensions, connection arrangements and compatibility requirements. Manufacturers may also have several generations of protective devices that look similar but belong to different product ranges.

This guide explains the information to look for on your existing RCBO before searching for a replacement.

What Is an RCBO?

RCBO stands for Residual Current Breaker with Overcurrent protection.

An RCBO combines:

Overcurrent protection – protecting the circuit against overload and short-circuit conditions.

Residual current protection – detecting certain leakage currents to earth.

Because both functions are incorporated into one device, an RCBO normally carries several different electrical ratings and markings.

Understanding these markings makes identifying a replacement considerably easier.

1. Find the Manufacturer

Start by identifying the manufacturer.

Common manufacturers found in UK consumer units include:

Wylex
Hager
Crabtree
Eaton
MEM
Schneider Electric
MK
Lewden
Contactum

The manufacturer's name or logo is normally clearly visible on the front of the device.

However, knowing the manufacturer alone is not enough.

A manufacturer may have produced several different RCBO ranges over many years.

2. Identify the Product Range

Next, look for the product range or series.

Examples you may encounter include:

Crabtree Loadstar

Crabtree Starbreaker

and various generations of Wylex, Hager, Eaton and other manufacturers' protective devices.

The range can be particularly important when looking for an older or discontinued RCBO.

Two RCBOs manufactured by the same company are not automatically interchangeable simply because they carry the same current rating.

3. Find the Manufacturer Part Number

One of the most useful pieces of information is the Manufacturer Part Number, commonly abbreviated to MPN.

This is the manufacturer's specific reference for the device.

For example:

Crabtree Loadstar 6FSR20/30C

In this example:

Crabtree = manufacturer

Loadstar = product range

6FSR20/30C = manufacturer part number

Searching using the exact MPN is often the quickest way to find a like-for-like product or technical information about an older device.

4. Check the Current Rating

RCBOs have a rated current stated in amperes.

Common ratings include:

The current rating is often displayed alongside the trip characteristic.

For example:

B32

means:

B = Type B trip characteristic

32 = 32A rated current

Do not change the current rating simply because another RCBO physically fits the consumer unit.

The rating is selected according to the requirements of the circuit.

5. Identify the Trip Curve

The letter immediately before the current rating commonly identifies the circuit breaker's trip characteristic.

Two commonly encountered characteristics are:

B Curve

and

C Curve

For example:

B16 = B Curve, 16A

B32 = B Curve, 32A

C16 = C Curve, 16A

C32 = C Curve, 32A

B Curve and C Curve devices have different instantaneous magnetic operating characteristics and should not automatically be treated as interchangeable.

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

6. Check the Residual Current Rating

Another important marking is the rated residual operating current.

For many domestic RCBOs this will be:

30mA

You may also see this expressed as:

0.03A

These represent the same current:

30mA = 0.03A

Do not confuse the residual current rating with the normal rated current of the circuit breaker.

For example:

B32 30mA

means the RCBO has a 32A rated current and 30mA rated residual operating current.

7. Identify the RCD Type

Modern RCBOs may be marked with an RCD classification such as:

Type A

Type AC

This describes the residual-current characteristics the device is designed to detect.

It is separate from the B or C trip characteristic.

For example:

B32 30mA Type A

contains three different pieces of information:

B – overcurrent trip characteristic

32A – rated current

30mA Type A – residual current protection characteristics

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

8. Check the Breaking Capacity

RCBOs also have a rated short-circuit breaking capacity.

You may encounter ratings such as:

6kA

10kA

depending on the device.

This is another reason why two RCBOs displaying the same B32 or C32 marking should not automatically be considered equivalent.

Check the complete specification of the existing device and the requirements of the installation.

9. Look at the Number of Poles and Neutral Arrangement

RCBO designs can have different pole and neutral arrangements.

You may encounter descriptions such as:

1P+N

depending on the product design.

Some RCBOs also have a separate neutral lead, while others use different switching and connection arrangements.

The neutral arrangement can be particularly useful when visually identifying an older RCBO.

10. Check the Physical Design

Once you've recorded the electrical specifications, look at the physical design of the device.

Useful details include:

Overall width
Number of modules
Position of terminals
Busbar connection
Neutral lead position
Toggle position
Test button
Physical casing design

These details can help distinguish between different generations of RCBOs.

However, physical fit alone does not prove compatibility.

Two devices can look almost identical and still not be approved for use in the same consumer unit.

11. Identify the Consumer Unit

If possible, also identify the consumer unit itself.

Look for:

Manufacturer
Product range
Model number
Labels inside or on the enclosure
Existing protective device range

This is particularly useful when the RCBO markings are unclear or when trying to determine whether a newer device is suitable for an older consumer unit.

A photograph showing the complete row of existing protective devices can also provide useful identification information.

Example: Identifying an RCBO

Suppose the device is marked:

Crabtree

Loadstar

6FSR20/30C

C20

30mA

Type A

You can now describe the device much more accurately as:

Crabtree Loadstar 6FSR20/30C 20A C Curve 30mA Type A RCBO

This is significantly more useful when searching for a replacement than simply searching for:

20A RCBO

Why Isn't the Amp Rating Enough?

There can be hundreds of different RCBOs with the same current rating.

For example, a B32 30mA Type A RCBO could be manufactured by Wylex, Hager, Crabtree, Eaton or numerous other manufacturers.

Even within one manufacturer, several different product generations may exist.

Therefore:

B32 is a specification – not a model number.

The MPN and product range are usually much more useful for identifying the exact device.

What If the Model Number Has Worn Off?

Older protective devices can have faded, damaged or difficult-to-read markings.

If the MPN cannot be identified, gather as much other information as possible.

Take clear photographs showing:

Front of the RCBO
Side of the RCBO where safely visible
Manufacturer logo
All readable markings
Neutral lead
Test button
Adjacent breakers
Consumer unit
Consumer unit label

Do not remove covers or expose live parts simply to obtain a photograph.

The combination of the manufacturer, appearance and surrounding equipment may help identify the product range.

What If My RCBO Has Been Discontinued?

Electrical manufacturers regularly replace older consumer unit ranges with newer products.

This can mean that an RCBO is no longer manufactured even though many consumer units using that device remain installed.

In these situations, sourcing the exact original model can sometimes be useful when maintaining an existing installation.

ReCircuit Resale regularly stocks older and discontinued electrical protective devices alongside current products.

Can I Use a Newer RCBO Instead?

Possibly, but you should not assume that a newer RCBO from the same manufacturer is automatically compatible.

Changes between product generations can include:

Busbar design
Terminal arrangement
Device dimensions
Connection position
Technical characteristics
Manufacturer-approved combinations

Compatibility should therefore be confirmed using the manufacturer's information for the specific consumer unit and protective device.

For more information, see our RCBO Compatibility Guide – Will an RCBO Fit My Consumer Unit?

Need Help Identifying an RCBO?

If you are struggling to identify an existing device, ReCircuit Resale can help.

Send us clear photographs showing the front of the RCBO, all visible markings and the surrounding consumer unit.

Where possible, also provide a photograph of the consumer unit manufacturer's label.

We can help identify the device and point you towards relevant products we currently have available.

Buying Replacement & Discontinued RCBOs

ReCircuit Resale stocks a changing selection of new, new-other and used RCBOs, RCDs and other consumer unit components.

Our stock regularly includes products from manufacturers such as Wylex, Hager, Crabtree and Eaton, including older and discontinued ranges.

Where possible, our product listings clearly provide:

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

Using this information can make finding the correct product considerably easier than searching by current rating alone.

Important: RCBOs are electrical safety devices. Identification of an existing device does not by itself confirm that a replacement is suitable for an installation. Compatibility and electrical characteristics should be verified against the manufacturer's requirements and applicable wiring regulations. Consumer unit work should be carried out by a suitably competent person.