Since upgrading our solar PV array in July we have had an excess of energy throughout the day which was being fed back into the mains grid.
With the removal of our previous solar thermal system, we no longer had heating energy going into the hot water cylinder.
To make the best use of the excess solar PV energy we decided to order a solar power diverter which monitors the incoming mains electricity and if the electric flow reverses, the excess is sent to the immersion heating element in the hot water cylinder rather than being lost to the grid.
We looked at several different models of solar power diverters and the myenergi eddi was the model which had the best reviews and had integrations available to use with the Home Assistant software we use to monitor the house.
We ordered the myenergi eddi from Cool Energy at the start of June and they were only available on a pre-order basis due to the ongoing supply chain issues with electronic components.
When we placed the order, it was for the original eddi 1.0 model which did not have Wi-Fi and ethernet connectivity and we would have to buy the internet connection module from myenergi to enable data collection and internet access.
When the order shipped in August, the newer eddi 2.1 Solar Power Diverter, model number CE-EDDI-16A1P02H was sent which now has built in Wi-Fi and ethernet ports.
In the eddi 2.1 box was the eddi unit, a metal wall bracket, CT sensor, 2 antennas, screws and instruction leaflets.
The eddi was installed in the basement shed which has our solar PV inverter and a secondary fuse box which already had a 4mm twin and earth cable running to the immersion heater element in the water tank.
The metal bracket was fitted to the side of our server rack stand with four M5 bolts and the cables were routed into the base of the unit via flexible plastic conduit.
The current transformer clamp fits to the mains incoming live cable from the electric meter to the fuse box and this is at the front of the house and the location of the eddi is under the house at the back, so we had to extend the supplied cable.
When we installed the new fuse box in the basement shed earlier this year, we ran 16mm armoured cable for the mains electricity and a Cat 6 network cable to use with the solar diverter sensor. The sensor needs to be connected using twisted-pair cables, so this was idea for the application.
The eddi was connected to the fuse box via a new RCBO (Residual Current Breaker with Over-Current) and once this was all installed, we powered on the eddi and started the WiFi setup procedure.
Setting up WiFi and myenergi account
With the eddi powered on, first you must select if it is a new device or an additional device on the myenergi network. As this is our first myenergi product we selected "1st device installed"
To access the WiFi settings, you need to navigate to: "Other Settings > Internet > WiFi > WiFi Config" using the menu and control buttons.
If WiFi is turned off, toggle the setting with the + button and then scroll down to "Access Point" which should be turned on my default.
The screen will show the WiFi network SSID and password and you need to connect to this on a mobile phone or computer.
A browser screen will open promoting you for a new password and the web page will reload with a WiFi setup screen allowing you to select from one of the available networks. Select your network and enter your WiFi password and click the Connect button to continue.
I next setup a new account on myaccount.myenergi.com and added my eddi device to the account so the data can be accessed online.
Adding the eddi to Home Assistant
Before adding the eddi to Home Assistant, I needed to generate an API key for the device in the myenergi account page myaccount.myenergi.com This page at support.myenergi.com explains how to generate the API key.
There is a custom component available at github.com/CJNE/ha-myenergi to communicate with myenergi devices and home assistant.
After downloading the archive from Github, I extracted the contents of the custom_components folder into my home assistant’s custom_components folder and restarted Home Assistant and added the new component with: Home Assistant, go to "Configuration" -> "Integrations" click "+" and then search for "myenergi".
The screen will ask for your API key and add the myenergi device to Home Assistant as eddi and Hub devices.
The new entities can now be added to your Home Assistant views.
First day immersion heater problems
For the first full day with the eddi diverting unused energy from our solar PV system we found that the water in the top 30 cm of our water tank was over 50? after a few hours, but the rest of the tank was much colder.
When we installed the dual coil hot water cylinder in 2012, we fitted a short 14” (35cm) element as we didn’t plan to use this unless an emergency. As we now wanted to heat the entire tank using the heating element we purchased a new Tesla titanium 27" (68cm) immersion heater element from Screwfix
Removing the old heating element proved very difficult as the copper threads had corroded to the elements body and unknown to us at the time, the removal had caused a small crack to appear between the mounting flange and the thin copper walls of the cylinder which resulted in a small water leak once the new immersion heater element was installed and filled again with water.
After trying a different seal, we traced the leak to the edge of the mounting flange and decided to try to fix this using solder. The copper was cleaned and using a gas flame torch the metal was heated and solder was applied to try to seal the crack. After 24 hours this appears to be holding water and isn’t leaking but I plan to check it every day in case it leaks again.
A new hot water cylinder would cost around £250, have different plumbing fitting locations and wouldn’t be available for several days so we hope the repair works.
myenergi account website reports
The myenergi account website has basic reports for energy usage of the eddi device at myaccount.myenergi.com/energy#usage
The imported numbers match our own energy logging system with the eddi reports showing varying energy consumption throughout the day being sent to the heating element.
Once the system has been running for a longer time, we will have a much better overview of the benefits of the system.
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