Split‑Core vs Solid‑Core Current Transformers
Split‑core and solid‑core current transformers are used in energy sub‑metering, but differ significantly in installation method and application suitability.
Start NowUnderstanding Split‑Core and Solid‑Core CTs
Both CT types measure current using magnetic induction but are designed for different installation scenarios.
Split‑Core Design
Hinged or separable core opens to fit around existing conductors without disconnection.
Solid‑Core Design
One‑piece magnetic core requires the conductor to be passed through during installation.
Split‑Core CT Installation
Split‑core CTs suit live or retrofit installations where circuit isolation is impractical or costly.
Application Flexibility
Split‑core CTs offer greater flexibility where shutdowns are impractical or costly.
Solid‑Core CT Installation
Solid‑core CTs suit new panels and factory‑built assemblies where conductors can be threaded at build stage.
Why Choose Split‑Core CTs
Split‑core CTs are the preferred choice for retrofit and live installation environments where circuit isolation is impractical.
- No need to disconnect cables — installs around live conductors
- Ideal for retrofit projects where downtime must be minimised
- Available in a wide range of ratios and window sizes
- Compatible with 333 mV and 5/1 A output types
- Simplifies installation across multiple distribution boards
- Reduces installation time and associated labour costs
Why Choose Solid‑Core CTs
Solid‑core CTs deliver the highest accuracy and stability, making them the standard choice for new‑build panels and permanent installations.
- Higher accuracy — consistent magnetic path with no air gap from hinges
- Smaller physical size for equivalent current ratings
- Long‑term measurement stability with minimal drift
- Lower cost at equivalent ratings compared to split‑core
- Ideal for factory‑built panels and new switchboard assemblies
- Well suited to new‑build projects where conductors are routed at installation
Our Sub-Meters
View all of our Sub-Metering products. All hand built in the UK with industry leading 5 year warranty.
Rail 350
High-performance, multi-function energy meter designed for monitoring a single three-phase load.
View Rail 350
Rail 310
The Rail 310 is a versatile, multi-channel energy and power sub-meter designed for space-efficient monitoring.
View Rail 310When to Use Split‑Core or Solid‑Core
The right choice depends on whether the installation is new‑build, retrofit, or a combination of both.
Retrofit Projects
Split‑core CTs are required where cables cannot be disconnected and circuits must remain live during installation.
New‑Build Panels
Solid‑core CTs are the standard choice — conductors are routed through the CT during panel build.
Commercial Buildings
Both types are used depending on the phase of work — split‑core for occupied buildings, solid‑core for new fit‑outs.
Industrial Sites
Split‑core CTs are often preferred due to the difficulty and cost of shutting down production lines.
Data Centres
High‑accuracy solid‑core CTs suit new infrastructure; split‑core supports ongoing monitoring expansion.
Mixed Environments
Projects often combine both types — solid‑core in new panels and split‑core where retrofit is required.
Key Factors When Specifying CTs
Regardless of type, correct specification ensures reliable data and long‑term system performance.
CT Ratio Matching
Both split‑core and solid‑core CTs must be correctly matched to expected load currents to avoid saturation or poor resolution.
Output Compatibility
Ensure the CT output type — 5 A, 1 A, or 333 mV — matches the input requirements of the connected sub‑meter.
Accuracy Class
Solid‑core CTs typically achieve higher accuracy classes more easily, but modern split‑core designs meet Class 1 requirements.
Physical Dimensions
Solid‑core CTs are generally more compact. Split‑core CTs require additional clearance for the hinged opening mechanism.
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