Using binary_sensor trend to detect hot water tank emptying quickly

Configuration
1

Be gentle please, I’m new!

As per the title, I’d like to automate turning my hot water on if the tank is emptying quickly. I’ve read the binary_sensor docs and configured as so:

binary_sensor:
  - platform: trend
    sensors:
      shower_on:
        entity_id: climate.hot_water
        sample_duration: 900
        min_gradient: -0.055555

The climate system is evohome, so really I wanted the entity_id to be climate.hot_water.current_temperature - but that gave me errors when validating config.

The sensor shows in hass but has sample_count is 0.

2

I’ve had a look through the source for binary_sensor, but I’m none the wiser - can anyone she any light please?

3

did you find a solution?

4

I have made a little progress, the introduction of attribute to the trend binary_sensor has enabled this:

binary_sensor:
  - platform: trend
    sensors:
      water_draining:
        entity_id: water_heater.dhw_controller
        attribute: current_temperature
        sample_duration: 1800