In this article:
Overview
The following wiring diagram shows a suggested application and are examples only; there are many more possibilities.
Please take a look at the Safety section within the installation manual and read all the installation sections before attempting to install the eddi.
A good level of electrical competence and a reasonable understanding of domestic plumbing systems is assumed for studying this application example.
Some heat pump heating systems have a buffer tank for the heating circuit as well as a hot water cylinder.
eddi can be used to make good use of any surplus generation by fully heating the water first and then heating the buffer, allowing the maximum amount of surplus energy to be stored.
Set-Up
You will need the relay board for the Eddi, and the output from the controller that normally goes to the immersion will be disconnected from the immersion. Instead, it will be connected to the eSense port of the relay board.
The heater 1 output of the eddi can then be connected to the immersion through the thermostat, which will control the temperature of the water.
The eddi will divert the excess solar to the immersion, and when the Air Sorce Heat Pump wants to do Legionella or a hot water boost, it will send 230v to the eSense port, and in the eddi menu you can tell it to boost the immersion fully when it receives this 230v signal. then it will switch back off again and the eddi can go back to diverting solar when the water cools.
Wiring Diagram
| Key for Wiring Diagram | |
| 1 - eddi device | 2 - Mains supply (230V AC from B16 circuit breaker or 13A fused spur) |
| 3 - Hot Water cylinder | 4 - Heating element 1 (max. 3.7kW) |
| 5 - Isolator (20A double pole) | 6 - Relay & Sensor Board (optional add-on for eddi) |
| 7 - Temperature probe (type PT1000) (optional) | 8 - Heat Pump (with immersion heater output) |
| 9 - Heat pump immersion heater relay | |
Functional Description
Most heat pumps require control of the immersion heater in the hot water cylinder, this is to periodically heat the water to a higher temperature in order to kill any Legionella bacteria that may have built up in the stored water. This application enables the heat pump to effectively control the immersion heater when required whilst the heater is actually connected only to the eddi.
eddi uses the Grid Sensor to monitor any surplus power that would otherwise be exported to the grid and diverts the same amount of power to the heater loads, thereby reducing the surplus power down to zero.
It is not permissible to 'back-feed' the eddi device (i.e. a voltage supply must not be connected to the heater outputs). Because of this, the heat pump immersion heater relay (9) needs to be connected to the eSense input of the Relay & Sensor Board (6) instead of the immersion heater element (4). In this application, the eddi is configured to respond to the eSense signal by fully switching on Heater 1 output regardless of available surplus.
Installation of the temperature probe (7) is optional; the heaters' mechanical thermostat can be used instead if a water temperature reading is not required.