geoTHERM VWL 9 C (2011, no sensoCOMFORT) fully integrated in Home Assistant via ebusd + MQTT

[fgouzi]

Why I'm sharing this

My Vaillant geoTHERM VWL 9 C (air/water, built-in controller, no sensoCOMFORT) dates from 2011.
When I asked Vaillant about connecting it to a home automation system, I was told this was
not possible and that the only option was to replace the heat pump.
With ebusd and an eBUS Adapter Shield C6, it now reads and writes everything I need.
Many thanks to @john30 for this project – I hope this report helps other owners of older units.

Setup

• Heat pump: Vaillant geoTHERM VWL 9 C
  • EHP00 SW0383 HW7201 (addresses 08/23/25/50: 08.ehp, 23.ehp.cc, 25.ehp.hwc, 50.ehp.mc)
  • UIH00 SW0274 HW6901 (address 15: 15.uih)
• Combined buffer tank 560 L with instantaneous domestic hot water (DHW) coil (no DHW storage)
• eBUS Adapter Shield C6 (network, enhanced) → ebusd 26.1 (Docker on a Synology NAS)
  → Mosquitto → Home Assistant (Docker)
• PV system with grid meter, EV charger
• All writes go through MQTT: ebusd/<circuit>/<message>/set; on-demand reads via .../get

What I implemented

Domestic hot water

• One-off DHW charge: ebusd/hwc/load/set = on. It starts one charge outside the
  time windows, ignores the start threshold and ends by itself (mode goes back to night).
  If the tank is already hot, only the auxiliaries run for about 1 minute and the compressor
  does not start. (Similar approach for a VRC 470 in VRC 470: one-time DHW load — solved by writing HwcOPMode=load (see ebusd-configuration#128) #1790.)
• Solar DHW boost: between 11:00 and 14:30, if the PV surplus (including the EV charger's
  power, which can be interrupted) stays above 4 kW for 10 min and DHW is below 48 °C,
  Home Assistant triggers the one-off charge. Once per day at most, disabled during holidays.
• DHW time windows reduced to 14:30–15:00 and 23:00–24:00 (fallback when there's no sun).
• Measured: a DHW charge draws about 4.3–4.5 kW electrical, lasts 10–25 min and reaches ~52–53 °C.

Space heating (circuit mc)

• Operating mode selector in HA (OperatingMode: off / auto / eco / low / on),
  mapped to the labels on the controller display and confirmed on the display.
• Seasonal settings written once and verified by reading them back: reduced temperature
  (TempDesiredLow), summer shutdown limit (OtShutdownLimit), comfort time windows
  (Timer_*, format 00:00;00:00;09:00;16:00;-:-;-:-;selected). Heating curve left unchanged for now.
• Planned: a winter solar boost (temporary "on" mode when surplus > heat pump power).

Holiday programme (uih HolidayPeriods)

• Start/end dates set from HA, followed by an automatic read-back. A read-back sensor shows
  the programmed period and refreshes at HA start-up and twice a day.
• ⚠ The field order differs from what the names suggest: actual order is
  start1; start2; end1; end2. Details and display photo in Vaillant UIH00 SW0274 (15.uih.csv): HolidayPeriods field order does not match the device ebusd-configuration#677.

Monitoring

• Dashboard: heat pump activity, DHW temperature, flow/return/outdoor/buffer temperatures,
  24 h and 7-day history.
• Compressor statistics from the counters: ~42,000 starts, ~11,200 h, average cycle length
  (~14 min for DHW, ~15 min for heating).
• Estimated consumption (no dedicated meter): status × typical power
  (DHW 4.4 kW measured, heating still to be measured), split into DHW and heating for the
  HA Energy dashboard.

Lessons learned

• MQTT writes with ebusd are reliable; always read the value back after writing.
• Write to EEPROM-backed settings only rarely (a few times per season), never in loops.
  Home Assistant only adjusts settings: if it goes down, the heat pump keeps running on its own programme.
• Check each message on the controller display: the community definitions are excellent
  but not always exact for every firmware.
• hcflowtemp / hcreturntemp rise to ~50 °C during DHW charges (shared heat pump output).
• HwcTemp is the DHW (upper) zone; StorageTempTop/Bottom are the heating zone of the buffer.
• I first used a HACS integration based on ebusd messages, then switched to plain
  ebusd + MQTT: fewer layers and full control over writes.

Happy to share YAML snippets (MQTT select, scripts, automations) if useful.

[woody5350]

Very encouraging to read Fabrice. I too have been on the journey with my 2012 GeoTherm VWS 101/2. I am running HA on RPi4, withe C6 via wifi. I have created lots of monitoring dashboards, but have recently had a heatpump failure, which led me into a lengthy conversation with the engineer and has caused me to want to have better control over the GSHP.
My configuration is slightly different, and I am not convinced the installation of circulation pumps and indoor heat controls are the best, but no one can offer me comprehensive advice on any alternative configurations. I have a 300L Buffer tank for CH and a 300L DHW storage tank. The CH pump seems to run 24/7 whilst the circulation pump runs 6am to 10pm. (primarily for a quiet life for me and avoid the "There is no hot water" shouts....
I am in the process of trying to implement DHW instant button controls around the house. I had hoped I could used HA Virtual Buttons to do this, but i am struggling to identify if there is a write message that achieves that. AI has provided me a complicated timer programme overwrite, which has various time delays for protection involved and whilst it works, it is not the answer due to the delays.... (when people want hot water, they want it NOW!!!)
In the process of investigation, I am curious about a bunch of unknown messages that I see in my ebusd logs, which I am hoping might hide the answer to CH pump control.
I have the same csv files loaded as yourself.
Grateful for any pointers you might have.
Thank you
Paul

[woody5350]

I thought a picture would paint a thousand words.... I am sure I could make this more efficient, but it is just a hunch

[woody5350]

I should just say, this is installed in a house I built 14 years go. Not passive, but dense block construction, 380sqm, underfloor heating throughout, electricity only, 14kw of solar panels and 2 x Powerwall 2.