In this article:
- Overview
- Wiring Diagram
- Functional Description
- Settings Required
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.
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 | 10 - Buffer cylinder |
| 11 - Heating element 2 (max. 3.7kW) | |
Functional Description
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.
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.
For this application two heating elements are wired to the eddi; the water immersion heater (4) is connected to Heater 1 output and the buffer tank immersion heater (11) is connected to Heater 2 output. Priority is given to the water heating and only when fully heated does the eddi switch to heating the buffer tank.
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. Remember it is not permissible to 'back-feed' the eddi device; 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 probes (7) is optional; the heaters' mechanical thermostat can be used instead if temperature readings are not required.