Heat the water heater using solar surplus
- Preface
- About SCR-485
- Add SCR-485 in Home Assistant
- Wiring diagram
- Run SCR-485 in standalone mode
- SCR-485 actual test results
- Reference
We have been committed to exploring ways to maximize profits in residential photovoltaic systems and implementing these methods in Home Assistant. These are some previous articles as below
- Monitor your solar PV system in Home Assistant
- Control the EV charging power with regard to the solar PV output and grid power reading
- Request the data of the Wi-Fi energy meter from the Modbus/TCP sensor , and control the sonoff relay in realtime
This article mainly introduces how to achieve real-time adjustment of the water heater power in Home Assistant. The power of the water heater is adjusted in real-time based on the feed-in power.
Preface
With the increasing gap between feed-in electricity prices and electricity costs, there is a desire to minimize grid electricity consumption and maximize the self-consumption rate of photovoltaic systems.
There are generally two approaches to increasing the self-consumption rate:
- Introducing a battery storage system.
- Rationally controlling the load, ideally adjusting in real-time based on grid power.
This article mainly proposes a solution for the second method and includes two parts.
- Add a controller (SCR-485) to Home Assistant that can linearly adjust the power of resistive loads (such as a water heater).
- Create an automation so that the SCR-485 adjusts the power output based on the real-time grid power.
Grid Power REV: Feed-in power
SCR_485 Power: “Set Power” of SCR_485
About SCR-485
SCR-485 is a linear power controller with a maximum power output of 4 kW (230V system).
It can linearly adjust the power output within the range of 0-4 kW, recommended for controlling resistive loads (such as boiler heaters), and provides Wi-Fi functionality.
Add SCR-485 in Home Assistant
Wiring diagram
- The SCR-485 is serially connected before the thermostat to supply power to the heater.
- Use the IAMMETER`s energy meter to measure grid power and provide the grid power data to the SCR-485 as the basis for power adjustment.
Configure “SCR_485” Wi-Fi Credentials,add Device
 |
 |
|---|
Step by step :Configure “SCR_485” Wi-Fi Credentials,add Device in the HA
Add Sensor
Add in configuration.yaml:
code link: scr-485_automation/configuration.yaml
# Example configuration.yaml entry
switch:
- platform: template
switches:
scr_ha_with_battery:
friendly_name: "With Battery"
# value_template: "{{ is_state('switch.source', 'on') }}"
turn_on:
service: switch.turn_on
target:
entity_id: switch.scr_ha_with_battery_open
turn_off:
service: switch.turn_off
target:
entity_id: switch.scr_ha_with_battery_close
sensor:
- platform: template
sensors:
tmp_grid_power:
unit_of_measurement: 'W'
value_template: >-
{% if is_state('switch.scr_ha_with_battery', 'on') %}
{{ (states('sensor.solarpv_power_b')|float - states('sensor.battery_power_a')|float)|round(1) }}
{% else %}
{{ (states('sensor.solarpv_power_b')|float)|round(1)}}
{% endif %}
dev_threshold_hysteresis:
unit_of_measurement: 'W'
value_template: "{{ (states('number.scr_485_5_threshold')|float - states('number.scr_485_5_hysteresis')|float)|round(1) }}"
add_threshold_hysteresis:
unit_of_measurement: 'W'
value_template: "{{ (states('number.scr_485_5_threshold')|float + states('number.scr_485_5_hysteresis')|float)|round(1) }}"
- Where sensor.solarpv_power_b is changed to the Grid Power of your meter
- If you don’t have a battery, just keep With Battery turned off (operate in the home assistant panel).
Add Automation
Copy the ‘Auto SCR’ code from here: scr-485_automation/auto_scr_automation
alias: Auto SCR
description: Automatically control SCR-485 via HomeAssistant
trigger:
- platform: state
entity_id:
- sensor.tmp_grid_power
condition:
- condition: time
after: "08:00:00"
before: "17:00:00"
action:
- if:
- condition: numeric_state
entity_id: sensor.tmp_grid_power
below: sensor.dev_threshold_hysteresis
then:
- service: number.set_value
data:
value: >-
{% set tmp_set_power = (states('number.scr_485_set_power')|float +
(states('sensor.tmp_grid_power')|float -
states('number.scr_485_5_threshold')|float)|abs)|round(0) %} {% if
tmp_set_power < 0 %}
{{ 0 }}
{% elif tmp_set_power > states('number.scr_485_6_max_power')|float
%}
{{ states('number.scr_485_6_max_power')|float }}
{% else %}
{{ tmp_set_power }}
{% endif %}
target:
entity_id: number.scr_485_set_power
- if:
- condition: numeric_state
entity_id: sensor.tmp_grid_power
above: sensor.add_threshold_hysteresis
then:
- service: number.set_value
data:
value: >-
{% set tmp_set_power = (states('number.scr_485_set_power')|float -
(states('sensor.tmp_grid_power')|float -
states('number.scr_485_5_threshold')|float)|abs)|round(0) %} {% if
tmp_set_power < 0 %}
{{ 0 }}
{% elif tmp_set_power > states('number.scr_485_6_max_power')|float
%}
{{ states('number.scr_485_6_max_power')|float }}
{% else %}
{{ tmp_set_power }}
{% endif %}
target:
entity_id: number.scr_485_set_power
enabled: true
mode: single
Select All and Paste
save
Add Fast Update Sensors in automation
Copy the ‘Fast Update Sensors’ code from here: Yaml in Home Assistant/scr-485_automation/fast_update_sensors.yaml
alias: Fast Update Sensors
description: Fast Update Sensors
trigger:
- platform: time_pattern
seconds: /3
condition: []
action:
- service: homeassistant.update_entity
target:
entity_id:
- sensor.tmp_grid_power
- sensor.solarpv_power_b
data: {}
mode: single
This is to be able to obtain the required sensors faster if these sensors were updated very slowly before.
Adding Home Assistant Dashboard
Copy the ‘dashboard ui’ code from here: [Solar-PV-Monitoring/Yaml%20in%20Home%20Assistant/scr-485_automation/dashboard_ui.yaml at master · lewei50/Solar-PV-Monitoring (github.com)](https://github.com/lewei50/Solar-PV-Monitoring/blob/f22af124b8e5d8ffe2e51205de2d8259e6d2b171/Yaml in Home Assistant/scr-485_automation/dashboard_ui.yaml)
type: vertical-stack
cards:
- type: entities
entities:
- entity: switch.scr_ha_with_battery
- entity: sensor.tmp_grid_power
- entity: number.scr_485_5_threshold
- entity: number.scr_485_5_hysteresis
- entity: number.scr_485_set_power
- type: history-graph
entities:
- entity: sensor.tmp_grid_power
- entity: number.scr_485_set_power
hours_to_show: 1
Run SCR-485 in standalone mode
The SCR-485 can also operate in ‘standalone mode,’ without the need for Home Assistant.
Quickstart manual for SCR-485，step by step tutorial
When the ‘auto mode switch’ option is enabled, the SCR-485 automatically adjusts the set power based on the grid power.
- When the grid power exceeds the threshold plus hysteresis, the set power will be decreased.
- When the grid power is less than the threshold minus hysteresis, the set power will be increased.
SCR-485 actual test results
This feedback is from one of the customers who tested the SCR-485 in the first batch.
21 June
Mostly cloudy day full utilisation of any generation thanks to the scr-485, previously I would have been heating the water at about 1KW and any generation over about 2KW would have been exported to the grid, now I harness all that generation into heating the water, as a result on these days also hotter water if not at full temp. couple of spikes at about 11 & 12 there was my dishwasher running
Reference
ESP32 + SCR module: Linearly adjust the power output of resistive loads, such as heaters
Quickstart manual for SCR-485，step by step tutorial
Control a boiler heater using a Wi-Fi SCR module automatically
Activities - Apply for the Linear Power Controller (SCR-485)