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Controlling values! Finally! 🎉 #604
raomin
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I would be interested to know if this would be possible for my EKHBRD016ACV1 |
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Not on the HT, sorry. The targets and the power limit are written into the memory of the hydro control board through its X10A port. The EKHBRD has no X10A: the two X41A ports sit on the outdoor unit's main board and on the hydrobox's inverter board, so we can read from them but can't reach the control board to write. I've put the list of supported units in the first post. |
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'Pump did not answer' on both idu and odu units.
…On Fri, 6 Nov 2026, 22:44 Raomin, ***@***.***> wrote:
It depends on your the software version running on your hydro board. Just
install the latest beta, check the boxed and ESPAltherma will tell you if
it's supported or not
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Yes... "Pump` did not answer" is what it shows on the HT: the boards on X41A don't answer the memory commands the control uses, which is why the HT isn't in the list. You can untick both boxes, nothing was written. |
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Issue #1, "Control over serial port" is the oldest open question of this project, December 2020. The answer has been "not directly" for five years. v2.0.0-beta.6 changes that for two values: the hot water target and the leaving water target of the main zone, set from Home Assistant or from the web page!!
It was a target from day one but was only possible with some more dedication and a very good help from Claude...
We found out how to write to memory of the hydro board. But the user interface of the heat pump owns the setpoints it shows and re-sends them to the hydro board every second, so anything written through the X10A port is overwritten within a second.
But when a setpoint mode is set to weather dependent, the hydro board computes that target itself from its own curve, and nobody re-sends the curve. ESPAltherma can now writes your target into both points of that curve: a flat curve, so the target holds whatever the weather. It applies within a second, and it is saved in the unit's memory so it survives a restart.
How to try it
On the unit's interface, set the tank setpoint mode, or the leaving water setpoint mode of the main zone, to weather dependent.
Install beta.6 from https://espaltherma.pages.dev/ and tick the box under Settings → Experimental.
Home Assistant gets a Hot water target and a Leaving water target number entity (MQTT: espaltherma/dhw_target/set, espaltherma/lwt_target/set). The home page of ESPAltherma gets a card for each, and the Home Assistant card gets a minus and a plus next to each target in its 1.0.4 release.
What you will see. Next to your target, the value the heat pump really aims for, with the reason on hover. The hot water target is capped by what the compressor reaches on its own at the current outdoor temperature, 51 °C on my unit on a mild evening; above that the booster heater would have to finish. And the tank starts heating a few degrees under that value, the hysteresis set on the unit, and stops at it: asking for one degree more moves both thresholds by one degree, nothing else. I had to learn that one the hard way.
What it cannot do: Switching the heating on and off, the setpoints in absolute mode, the room setpoint: all owned by the interface, so the relays stay the way for on/off, until we find a smarter trick.
Which units (updated 2026-11-06, v2.0.0-beta.25). The addresses are specific to the software of the hydro board, read from the unit at start. Only the versions below are accepted; on any other unit the card says "not available (hydro board software XXXX)" and nothing is ever written. The power limit (Settings → Experimental, since beta.16) uses the same list.
"Waiting for a first report" means the addresses come from the board's software and have not been tried on a unit yet: if you have one of these, your report is what confirms it. The 76F2 boards have no software command; their software is the "I/U Software ID" on the Values page.
Not possible: the Altherma HT (EKHBRD hydrobox on an ERSQ/ERRQ outdoor unit), whose control board has no X10A port to write through, and the Altherma 4. If your unit runs another software, open an issue with the version the card shows.
Experimental means experimental. It writes to your heat pump. It only does so on a recognised unit, in weather-dependent mode, within the unit's own range, and it writes the unit's memory at most every five minutes. Two things to know: the interface keeps showing its old curve until it restarts, and saving that screen on the interface puts its values back. Use at your own risk, as always, and tell me what you find :)
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