Can You Replace an MCB With a Different Brand or Range?
When replacing an MCB, it can be tempting to choose another breaker with the same amp rating and trip curve, particularly when the original device has been discontinued.
However, MCBs from different manufacturers or product ranges should not automatically be treated as interchangeable.
A B32 MCB from one manufacturer is not necessarily a direct replacement for a B32 MCB from another.
Can You Mix MCB Brands in a Consumer Unit?
You should not assume that an MCB from another manufacturer is suitable simply because it physically fits.
For example, a:
- Wylex B32
- Hager B32
- Crabtree B32
- Schneider Electric B32
may all be rated at 32A with a Type B characteristic, but that does not make them interchangeable.
Consumer units and their protective devices are designed and verified as assemblies using specified components.
The manufacturer's instructions and compatibility information should therefore be checked when selecting replacement devices.
Why Can Similar MCBs Be Incompatible?
Two MCBs can look almost identical from the front while having important differences elsewhere.
These can include:
- Busbar connection position
- Terminal design
- Device dimensions
- DIN rail position
- Toggle alignment
- Breaking capacity
- Terminal capacity
- Product standard
- Manufacturer's assembly requirements
Even a small difference in the connection arrangement can prevent the device from making the intended connection with the consumer unit's busbar.
If It Fits, Does That Mean It's Compatible?
No.
Physical fit alone does not establish compatibility.
An MCB may clip onto the DIN rail and appear to line up correctly while not being specified for use with that consumer unit.
This is why identifying the manufacturer and consumer unit range is important when sourcing replacement breakers.
Can Different Ranges From the Same Manufacturer Be Mixed?
Not automatically.
Manufacturers often change their protective-device ranges over time.
An older Wylex MCB, for example, may not necessarily be interchangeable with a current Wylex device.
Likewise, different generations of Hager, Crabtree, Schneider Electric, MEM/Eaton and other equipment can use different connection arrangements.
Matching the brand name alone is therefore not enough.
What If My Original MCB Is Discontinued?
Discontinued MCBs are frequently encountered in older consumer units and distribution boards.
If the original breaker is no longer manufactured, the first step is to identify:
- Manufacturer
- Consumer unit range
- Original MCB part number
- Amp rating
- Trip curve
- Breaking capacity
You can then determine whether the manufacturer specifies a suitable successor or replacement.
If there is no approved current replacement, an original unused or surplus device from the correct range may sometimes still be available.
Can I Use a Used MCB as a Replacement?
The condition, history and suitability of any protective device need to be considered before installation.
A used MCB should not be installed simply because it is the correct model.
Where used electrical protective devices are supplied, their condition and functionality should be appropriately assessed.
ReCircuit Resale clearly identifies the condition of its electrical components, with used protective devices tested where applicable before being offered for sale.
The installer remains responsible for confirming that a device is suitable for the particular installation.
How Do I Find the Correct MCB Range?
If you don't know the range of the consumer unit, start with the existing breaker.
Look for:
- Manufacturer logo
- Part number
- Range markings
- Current rating
- Trip characteristic
- Breaking capacity
Also take a clear photograph of:
- Front of the existing MCB
- Side markings where accessible
- Adjacent protective devices
- Complete consumer unit or distribution board
The surrounding devices can often provide useful information when identifying an older range.
Should I Change the Consumer Unit Instead?
A discontinued MCB does not automatically mean the complete consumer unit needs replacing.
In some cases, the correct original device or an approved replacement may still be available.
However, the condition and suitability of the overall installation should be assessed by a competent person.
Where suitable replacement components cannot be obtained, alteration or replacement of equipment may need to be considered.
Finding Older and Discontinued MCBs
Older protective devices can become difficult to obtain through standard electrical wholesalers once manufacturers change their product ranges.
ReCircuit Resale stocks a range of new, surplus and discontinued MCBs, RCBOs, RCDs and other consumer unit components from major manufacturers.
Searching by the exact part number printed on the existing MCB is usually the best starting point.
If you cannot identify the device, provide clear photographs of the MCB and consumer unit when making an enquiry.
Electrical work within consumer units and distribution boards should be carried out by a competent person with the appropriate knowledge and equipment.
Next Guide: MCB Compatibility by Consumer Unit Brand – Wylex, Hager, Crabtree & More