Fit a CT clamp on iHP X and Solar X (video)

This guide covers what a CT clamp is, why it matters and how to install it correctly. By the end you will be able to pick the right cable, fit the clamp the right way round, avoid common mistakes and carry out basic troubleshooting.

What is a CT clamp?

A CT (current transformer) clamp measures the electrical current flowing through a single cable. It tells the system how much energy is being used or generated, and which way it is flowing. That information is essential for accurate monitoring, smart control and safe operation.

Why it matters

When the clamp is fitted correctly, the system can optimise charging, manage loads and make accurate decisions. If it is fitted wrongly, the system may misread the energy flow, behave unpredictably or not work as intended, and even a small error can lead to incorrect charging, poor efficiency or unnecessary call-outs.

The components

• CT clamp. A split-core transformer that measures household load or PV generation. It must close fully around a single cable, and its arrow shows the direction of current flow.
• CT interface. Receives the signal from the clamp and turns it into usable data for load monitoring, PV detection and smart heating.
• Controller (J55), on iHP X. The CT interface connects to the J55 connection on the controller, so surplus solar power can go into the hot water cylinder.
• PV diverter, on Solar X. Redirects surplus solar power into the hot water cylinder, so the water heats on free solar energy.

Identifying these correctly prevents most installation issues.

Before you start

Fix the CT interface within 300 mm of the incoming mains supply, using screws or the adhesive pad supplied.

Step 1. Choose the cable and direction

Mixergy recommends fitting the clamp on the neutral cable between the main fuse and the electric meter, with the arrow pointing towards the main fuse. If that is not practical, fit it on the live cable with the arrow pointing towards the meter.

Step 2. Close the clamp fully

Position the clamp around the cable and close it fully until it clicks. Even a small gap will give inaccurate readings.

Step 3. Connect the clamp to the interface

Connect the CT clamp to the CT interface using the supplied two-core connector.

Step 4. Connect the interface

iHP X

Connect the CT interface to the J55 connection, at the lower left-hand corner of the controller PCB, either directly or through a wall plate.

Solar X

Connect the CT interface to the PV diverter using installer-supplied CAT5e or CAT6 cable wired to the T568B scheme. Use full eight-core cable and connect the RJ-45 port on the PV diverter to the RJ-45 socket on the CT interface, directly or through a wall plate.

Step 5. Test the connection

• Check the RJ-45 connections with a suitable tester. Pins 1 to 8 should light in order.
• The connection must be direct. Network switches or routers cannot be used.
• All eight conductors must be connected pin to pin.

Common mistakes

• Clamping the wrong cable, such as an earth conductor or more than one cable.
• Fitting the clamp backwards, with the arrow facing the wrong way.
• Leaving the clamp slightly open, which stops it measuring accurately.

Any of these can make the system misread the energy flow, so double-check before closing the job.

Explaining it to customers

Keep it simple. You can say: “The CT clamp measures how much electricity is flowing through your system. It helps the system make smart decisions and keeps everything running efficiently.” If the clamp is fitted wrongly, customers may notice odd behaviour or energy readings that look wrong.

Key takeaways

• Fit the clamp on the correct cable.
• Make sure the arrow points the right way.
• Close the clamp fully.
• Use a direct RJ-45 connection and test it.

Most issues come from simple installation errors, so if in doubt, recheck the installation before escalating for support.