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Improve/fix support for Bosch Junkers boilers through EMS-ESP #154

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Improve/fix support for Bosch Junkers boilers through EMS-ESP #154

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8fce77d
Improve EMS support (tested on Bosch/Junkers Condens GC7000i).
enricoschroeder Oct 29, 2025
3dd08c6
Improve minimum setpoint logic to reflect EMS behavior.
enricoschroeder Oct 29, 2025
6f49276
Change DATA_MAX_REL_MOD_LEVEL_SETTING to burnmaxpower.
enricoschroeder Nov 18, 2025
338b615
Merge branch 'Alexwijn:develop' into improve-ems-bosch-junkers
enricoschroeder Nov 18, 2025
be3750f
Merge branch 'Alexwijn:develop' into improve-ems-bosch-junkers
enricoschroeder Jan 8, 2026
67e2d18
Merge remote-tracking branch 'upstream/develop' into improve-ems-bosc…
enricoschroeder Jan 15, 2026
1a6ed15
Disable sending 'heatingactivated' since this interferes with EMS-ESP.
enricoschroeder Feb 2, 2026
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17 changes: 13 additions & 4 deletions custom_components/sat/mqtt/ems.py
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Original file line number Diff line number Diff line change
Expand Up @@ -109,7 +109,9 @@ def get_tracked_entities(self) -> list[str]:
return [DATA_BOILER_DATA]

async def async_set_control_setpoint(self, value: float) -> None:
await self._publish_command(f'{{"cmd": "selflowtemp", "value": {0 if value == 10 else value}}}')
# Minimum valid setting for Bosch/Junkers boiler seems to be 12°.
# Lower values set the boiler to 12° except 0° which sets the boiler to 5°.
await self._publish_command(f'{{"cmd": "selflowtemp", "value": {max(value, 12)}}}')
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@Alexwijn Alexwijn Feb 28, 2026

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We never send zero here. When the heater is off, we default to 10 degrees, which translates to 12 degrees at the device according to your code. Is this expected?


await super().async_set_control_setpoint(value)
Comment on lines 111 to 116
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@coderabbitai coderabbitai bot Feb 2, 2026 •
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⚠️ Potential issue | 🟠 Major

Clamp once and pass the clamped value to super() for state consistency.

You publish a clamped value but forward the original value to the superclass, which can leave the internal state/UI out of sync with the actual boiler command. Consider clamping once and using that value for both calls.

🔧 Proposed fix 
-        await self._publish_command(f'{{"cmd": "selflowtemp", "value": {max(value, 12)}}}')
+        clamped_value = max(value, 12)
+        await self._publish_command(f'{{"cmd": "selflowtemp", "value": {clamped_value}}}')
 
-        await super().async_set_control_setpoint(value)
+        await super().async_set_control_setpoint(clamped_value)
📝 Committable suggestion

‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

Suggested change
async def async_set_control_setpoint(self, value: float) -> None:
await self._publish_command(f'{{"cmd": "selflowtemp", "value": {0 if value == 10 else value}}}')
# Minimum valid setting for Bosch/Junkers boiler seems to be 12°.
# Lower values set the boiler to 12° except 0° which sets the boiler to 5°.
await self._publish_command(f'{{"cmd": "selflowtemp", "value": {max(value, 12)}}}')
await super().async_set_control_setpoint(value)
async def async_set_control_setpoint(self, value: float) -> None:
# Minimum valid setting for Bosch/Junkers boiler seems to be 12°.
# Lower values set the boiler to 12° except 0° which sets the boiler to 5°.
clamped_value = max(value, 12)
await self._publish_command(f'{{"cmd": "selflowtemp", "value": {clamped_value}}}')
await super().async_set_control_setpoint(clamped_value)
🤖 Prompt for AI Agents 
In `@custom_components/sat/mqtt/ems.py` around lines 111 - 116, Compute a single
clamped value once (e.g. clamped = max(value, 12)) inside
async_set_control_setpoint and use that clamped variable for both the
_publish_command payload and the call to super().async_set_control_setpoint so
the internal state/UI stays in sync with the actual command sent (update
references in async_set_control_setpoint to use the clamped value for both the
publish and the super call).

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🧩 Analysis chain

🏁 Script executed:

#!/bin/bash
# Search for where the 10-degree default is set when heater is off
rg -n -C5 --type=py "10" | grep -i "off\|heater\|default" | head -30

# More targeted search for setpoint defaults or heater off logic
rg -n -C3 --type=py "async_set_control_setpoint|setpoint.*10|heater.*off"

# Search for where async_set_control_setpoint is called
ast-grep --pattern 'async_set_control_setpoint($$$)'

Length of output: 12714

@Alexwijn, you've identified an important behavioral change!

You're absolutely right - with the new code, when the heater is off and SAT sends its default 10°C setpoint, it will now be clamped to 12°C at the device instead of the previous behavior where it sent 0°C (resulting in 5°C at the device).

Old behavior:

  • Heater off → value = 10 → sent 0 → device at 5°C

New behavior:

  • Heater off → value = 10 → sent 12 → device at 12°C

This is a significant difference (7°C higher when off). If maintaining the lower temperature when the heater is off was intentional for energy efficiency or to keep the boiler truly idle, you may want to preserve that special case. Here's how you could do that:

async def async_set_control_setpoint(self, value: float) -> None:
    # Minimum valid setting for Bosch/Junkers boiler seems to be 12°. 
    # Lower values set the boiler to 12° except 0° which sets the boiler to 5°.
    # When heater is off (value == 10), send 0 to keep device at 5°C as before.
    if value == 10:
        adjusted_value = 0
    else:
        adjusted_value = max(value, 12)
    
    await self._publish_command(f'{{"cmd": "selflowtemp", "value": {adjusted_value}}}')
    await super().async_set_control_setpoint(value)

Is the new 12°C behavior when off acceptable for your use case, or would you prefer to keep the device at 5°C when the heater is off?


Expand All @@ -123,12 +125,19 @@ async def async_set_control_thermostat_setpoint(self, value: float) -> None:
await super().async_set_control_thermostat_setpoint(value)

async def async_set_heater_state(self, state: DeviceState) -> None:
await self._publish_command(f'{{"cmd": "heatingactivated", "value": "{DATA_ON if state == DeviceState.ON else DATA_OFF}"}}')

# Do not send 'heatingoff' command, as this leads to EMS toggling the boiler between
# pre-set heating and selected flow temperature. Instead, control on/off solely by setting
# a low flow temperature (SAT already does this).
# (see https://github.com/emsesp/EMS-ESP32/discussions/2641#discussioncomment-14611481)
# The alternative command 'heatingactivated` also interferes with EMS, so sending nothing
# here seems to be the correct way to handle it.
await super().async_set_heater_state(state)

async def async_set_control_max_relative_modulation(self, value: int) -> None:
await self._publish_command(f'{{"cmd": "burnmaxpower", "value": {max(value, 20)}}}')
# Do not set 'burnmaxpower' as this is an EEPROM-stored value and will wear out the EEPROM.
# Use 'selburnpow' instead.
# (see https://github.com/emsesp/EMS-ESP32/discussions/2641#discussioncomment-14611481)
await self._publish_command(f'{{"cmd": "selburnpow", "value": {max(value, 20)}}}')

await super().async_set_control_max_relative_modulation(value)
Comment on lines 136 to 142
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⚠️ Potential issue | 🟠 Major

Keep super() in sync with the clamped modulation value.

The published value is clamped, but the superclass receives the unclamped input, which can desync reported vs. applied max modulation.

🔧 Proposed fix 
-        await self._publish_command(f'{{"cmd": "selburnpow", "value": {max(value, 20)}}}')
+        clamped_value = max(value, 20)
+        await self._publish_command(f'{{"cmd": "selburnpow", "value": {clamped_value}}}')
 
-        await super().async_set_control_max_relative_modulation(value)
+        await super().async_set_control_max_relative_modulation(clamped_value)
📝 Committable suggestion

‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

Suggested change
async def async_set_control_max_relative_modulation(self, value: int) -> None:
await self._publish_command(f'{{"cmd": "burnmaxpower", "value": {max(value, 20)}}}')
# Do not set 'burnmaxpower' as this is an EEPROM-stored value and will wear out the EEPROM.
# Use 'selburnpow' instead.
# (see https://github.com/emsesp/EMS-ESP32/discussions/2641#discussioncomment-14611481)
await self._publish_command(f'{{"cmd": "selburnpow", "value": {max(value, 20)}}}')
await super().async_set_control_max_relative_modulation(value)
async def async_set_control_max_relative_modulation(self, value: int) -> None:
# Do not set 'burnmaxpower' as this is an EEPROM-stored value and will wear out the EEPROM.
# Use 'selburnpow' instead.
# (see https://github.com/emsesp/EMS-ESP32/discussions/2641#discussioncomment-14611481)
clamped_value = max(value, 20)
await self._publish_command(f'{{"cmd": "selburnpow", "value": {clamped_value}}}')
await super().async_set_control_max_relative_modulation(clamped_value)
🤖 Prompt for AI Agents 
In `@custom_components/sat/mqtt/ems.py` around lines 136 - 142, The method
async_set_control_max_relative_modulation clamps the published value but still
passes the original unclamped value to the superclass, causing a desync; change
it to compute a single clamped variable (e.g., clamped = max(value, 20)), use
that clamped value in the JSON sent to selburnpow, and call
super().async_set_control_max_relative_modulation(clamped) so both the device
and the superclass state stay consistent.


Expand Down