How-to · UK domestic

How to install a Myenergi Eddi solar diverter

The Myenergi Eddi diverts surplus solar generation to your immersion heater instead of letting it export to the grid for next to nothing. Correctly installed and set up, it can heat a 150-litre cylinder on free solar electricity on any reasonable day in summer. This guide explains the installation process: CT clamp position, wiring to the immersion heater, and getting it talking to the app.

Helpful video reference. myenergi's own install montage and menu walkthrough is the video reference here. It comes from the manufacturer's official channel and covers the physical install sequence and the on-unit configuration menus in a concise format. "myenergi eddi — install montage & menu run through" is worth watching before commissioning your unit for the first time.

Before you start. The CT clamp clips around a live meter tail — the cable between your electricity meter and the main switch. These conductors are live at all times, even when the main switch is off. Do not cut, pierce or attempt to strip them. The clamp itself is non-invasive and safe when handled correctly, but you must be confident working close to live conductors. Wiring the Eddi's supply and load connections is notifiable work under Part P in England and Wales if it involves a new circuit.

1. Check system suitability

The Eddi needs two things to function: a solar PV system that generates more than the household is using at some point during the day, and an immersion heater in the hot water cylinder. It works with any single-phase inverter because it measures current on the meter tails rather than talking to the inverter directly.

If you do not have a hot water cylinder with an immersion heater — for instance, if you use a combination boiler for all your hot water — the standard Eddi installation does not apply. Some installers connect an Eddi to an infrared panel or towel rail instead, but verify the load is purely resistive and within the Eddi's rated output before doing so.

2. Isolate the immersion heater circuit

At the consumer unit, switch off the immersion heater circuit. If there is no separate MCB for the immersion, switch off the main switch. Go to the hot water cylinder, open the immersion thermostat cover and confirm dead with a voltage tester at the terminals before touching any wiring. Take a photo of the existing connections.

3. Mount the Eddi unit

The Eddi mounts on a bracket on the wall. The ideal position is near the consumer unit so the CT clamp cable reaches the meter tails comfortably and the load output cable reaches the immersion heater isolator without an excessively long run. Fix the bracket using the supplied screws and wall plugs. The unit is not particularly heavy, but the bracket must be level — the display is hard to read at an angle.

4. Fit the CT clamp on the meter tails

The CT clamp clips around the live meter tail (the single-core cable, usually red or brown, running from the electricity meter to the main switch). Open the clamp, slide it around the cable, and close it. The clamp does not break or pierce the cable — it reads the magnetic field produced by the current flowing through it.

Route the CT clamp cable back to the Eddi and plug it into the input marked CT1. The direction the clamp faces matters: if the live tail enters from the left, face the arrow on the clamp towards the meter. The display will confirm polarity during commissioning. If import shows as a negative number when you are actually importing, reverse the clamp direction.

5. Wire the incoming supply to the Eddi

The Eddi needs its own supply to power its control board. The cleanest approach is a 13A switched fused connection unit (FCU) fed from a convenient circuit — a spare way in the consumer unit or an existing socket circuit are both used in practice. Connect from the FCU's output: brown to L-in, blue to N-in, and green/yellow to the earth terminal on the Eddi. The FCU gives you a local isolator for the unit without needing to go to the consumer unit.

6. Wire the Eddi output to the immersion heater

The Eddi's load output connects to the immersion heater. If the immersion had an existing time switch or electronic programmer, the Eddi replaces it in the circuit: Eddi Load-L to the live terminal on the immersion thermostat, Eddi Load-N to the neutral, and the earth through throughout. If the immersion had no control at all and was wired direct, you wire into the same terminals. The Eddi switches the load on and off electronically as surplus power is available — there are no moving parts in the switching.

7. Power up and configure via the rotary dial

Restore power at the consumer unit. The Eddi will start up and its display will show current import or export. Use the rotary dial to navigate to the CT menu and confirm that the display shows a negative number (export) when your PV is generating more than the house is using, and a positive number (import) when the house is drawing from the grid. If the polarity is wrong, reverse the CT clamp on the meter tail and check again.

Set the divert threshold (normally 0W — divert all surplus), and confirm the load type is set to immersion (resistive). The Eddi is now diverting surplus solar to your hot water cylinder.

8. Connect the myenergi app

For monitoring and remote boost control, download the myenergi app and connect the Eddi to your home network via a myenergi hub or the Eddi's direct Wi-Fi pairing mode. The app shows live diversion power, a running total of energy diverted, and gives you a boost button to heat the cylinder from the grid when solar is not available. This step is optional — the unit divert independently whether or not the app is connected.

Stop and call an electrician if: you are not confident working close to live meter tails, the immersion heater circuit has no accessible isolator, the cylinder is wired in a way you do not recognise, or you want to connect the Eddi to a non-resistive load such as a heat pump controller (which needs a different wiring arrangement).

When to call us

Richard fits Myenergi Eddi units alongside EV chargers, battery storage and solar PV connections across east Kent. If you have an existing solar system and want to stop exporting cheap, a solar diverter is often the most cost-effective next step. Call or send a WhatsApp message for a quote.

Solar diverter in east Kent?

Richard fits Eddi units and other solar diverters alongside EV charger and battery installations across Sandwich, Deal and Dover.

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