Owners of a PV system, a battery and/or a dynamic electricity tariff who are interested in energy-efficient control of their Bosch CS5800/6800i or Buderus WLW176/186i should take a look at evcc. evcc was originally designed for charging electric vehicles using PV surplus. Recently, however, evcc has also been testing heat pumps and now also supports Bosch/Buderus heat pumps via ems-esp.

evcc increases domestic hot water temperature to 50°C with PV surplus

The integration works via the SG Ready interface of the heat pump. The standardised SG Ready interface provides 4 functions:

  1. Utility lockout period (Ext1=1 / Ext4=0): not yet supported by evcc
  2. Normal operation (Ext1=0 / Ext4=0): normal operation
  3. Increased operation (Ext1=0 / Ext4=1): increases the room temperature setpoint and/or the domestic hot water setpoint, depending on what was configured under System settings → Photovoltaic system.
  4. Forced increased operation (Ext1=1 / Ext4=1): not yet supported by evcc

The SG Ready functions are actually implemented using corresponding control lines. To control the heat pump via evcc, you do not need control lines, but instead use a trick that is described in more detail here. The idea is to invert External input 4 with curl -d '{ "value" : "1xxxxxxxxxxx" }' https://ems-esp/api/boiler/hpin4opt in order to activate Increased operation.

Setup

To make the System settings → Photovoltaic system menu visible on the heat pump’s control panel, you must activate System settings → Heat pump → External input → External input 4 → Photovoltaic system.

You can then configure the following settings under System settings → Photovoltaic system:

  • Increase desired temperature when heating: when evcc signals PV surplus to the heat pump, the room temperature setpoint is increased by the configured value
  • Increased domestic hot water comfort: with PV surplus, the domestic hot water is heated to the stop temperature of the Comfort operating mode.
  • Reduce desired temperature when cooling: with PV surplus, the room temperature setpoint is reduced by the configured value
  • Cooling only with PV energy: cooling operation is activated only when there is PV surplus
  • Max. power for compressor: limits the compressor to the configured power when there is PV surplus

After installing evcc, you must add the following entries to evcc.yaml.

ems-esp is added similarly to a wallbox as a charger, i.e. a controllable consumer:

chargers:
  - name: wp
    type: template
    template: emsesp
    host: 192.168.178.70
    token: <token>
    tempsource: "warmwater"

For the token, it is best to create a new user in the ems-esp user management. Press the key symbol to obtain the token.

To make the heat pump appear on the evcc start screen, you must also add the heat pump under loadpoints.

loadpoints:
  - title: Heat pump
    charger: wp

Usage

In the evcc interface, you should now see a display similar to the following:

The charging setting has the following meaning:

  • Off: Normal operation – no use of PV surplus
  • PV and Min+PV: When there is PV surplus, the heat pump is signalled Increased operation
  • Fast: The heat pump is immediately signalled Increased operation