Can You Replace Just the SPD Cartridge?
Many Surge Protection Devices (SPDs) are designed with a replaceable protection cartridge, meaning a failed SPD does not always require the complete device and its base to be replaced.
Whether this is possible depends on the manufacturer and model of SPD installed.
What Is an SPD Cartridge?
On many modular SPDs, the device consists of two main parts:
SPD Base – the fixed section connected to the electrical installation.
SPD Cartridge – the removable section containing the surge protection components.
The cartridge is the part that can become depleted or damaged after dealing with transient overvoltages.
On compatible designs, a failed cartridge can be removed from the existing base and replaced with the correct new cartridge.
How Do I Know If My SPD Has a Replaceable Cartridge?
Look closely at the existing SPD.
A replaceable cartridge will normally be visibly separate from the base and may have:
- A removable front module
- Retaining clips or release points
- Its own model or part number
- A green/red status indicator
- Electrical ratings printed directly on the cartridge
Do not attempt to force the front section from an SPD if you are unsure whether it is designed to be removable.
Check the manufacturer's instructions for the specific model.
Do I Need to Replace the Base as Well?
Not necessarily.
If the existing base is suitable, undamaged and the manufacturer provides a compatible replacement cartridge, it may be possible to replace only the cartridge.
This can avoid replacing the complete SPD assembly.
However, the complete SPD may need replacing where:
- The base is damaged
- Terminals or connections have been damaged
- The correct cartridge is no longer available
- The manufacturer specifies complete replacement
- A suitable compatible cartridge cannot be identified
- The installation is being altered or upgraded
The condition and suitability of the complete SPD arrangement should be assessed before replacement.
How Do I Find the Correct Replacement Cartridge?
Start with the information printed on the existing cartridge.
Look for:
- Manufacturer
- Cartridge model or part number
- SPD type
- Uc rating
- Up rating
- In rating
- Imax or Iimp where applicable
- Pole or protection configuration
The exact part number is particularly useful.
If the cartridge markings are difficult to read, check the fixed SPD base as this may contain additional product information.
Are SPD Cartridges Universal?
No.
SPD cartridges should not be considered universal components.
Two cartridges may look almost identical while having different:
- Electrical ratings
- Internal protection characteristics
- Physical connections
- Keying arrangements
- Base compatibility
- Manufacturer specifications
A cartridge physically fitting into an SPD base does not by itself confirm that it is electrically compatible.
Can I Use a Different Manufacturer's Cartridge?
Unless compatibility is specifically confirmed by the manufacturer, a cartridge from another brand should not be treated as a direct replacement.
SPD cartridges and their bases are generally designed as part of a specific manufacturer's surge protection system.
For example, a cartridge designed for one manufacturer's SPD should not be assumed to work correctly with a Wylex, Hager, Crabtree, Schneider Electric, FuseBox or Lewden SPD simply because it appears similar.
What If My Replacement Cartridge Is Discontinued?
Older SPD ranges can become difficult to source after manufacturers update or discontinue products.
If the original cartridge is unavailable, do not automatically purchase the nearest-looking alternative.
Instead, identify the original:
- SPD model number
- Cartridge part number
- Manufacturer and product range
- Electrical ratings
- Configuration
You can then check whether the manufacturer specifies a direct replacement or successor product.
If no compatible cartridge is available, replacing the complete SPD assembly may be necessary.
Safety When Replacing an SPD Cartridge
An SPD may be located inside a consumer unit or distribution board containing hazardous voltages.
Replacing a cartridge should only be undertaken where it is safe and appropriate to do so, following the manufacturer's instructions.
Electrical work within consumer units and distribution boards should be carried out by a competent person with the appropriate knowledge and equipment.
Looking for a Replacement SPD Cartridge?
ReCircuit Resale stocks a range of new, surplus and discontinued SPDs and replacement SPD cartridges from major electrical manufacturers.
If you're trying to find an older cartridge, search using the exact model or part number printed on the existing unit.
If the number is unclear, photographs showing the front of the cartridge, SPD base and surrounding consumer unit can help with identification.
Next Guide: SPD Compatibility by Consumer Unit Brand