Manual legionella program with heat element

[quizilkend]

Hi there,

I stumbled upon this article (https://web.archive.org/web/20260225085904/https://www.heise.de/ratgeber/Waermepumpe-und-Legionellen-Strategien-fuer-hygienisches-Warmwasser-11177776.html?giftToken=ae89323b-3839-4c96-9e4c-685daf6795b5) which states heat pumps have a high risk of legionella and the legionella cycle doesn't help at all (the bacteria gather resilience upon the legionella cycle of 62°C).

Therefore I was thinking if I could achieve a better legionella cycle using the heat element and having the water tank heated up to about 80°C. Afterwards open all the walves to eliminate the bacteria in the pipes.

Do you think this is a good idea and would be feasible with AquaMQTT?

Thanks for your thoughts and best regards
Samuel

[tspopp]

Hey Samuel,

interesting topic, thanks for sharing. Well, AquaMQTT in a nutshell is only a helper for providing the original HMI functionalities to the MQTT backend. So with a few exceptions you only have the options available which are available in the original HMI.

From the article, they suggest to:

• Disable the Legionella Cycle
• Always ensure a minimum temperature of 55°C

In my configuration, I have the legionella cycle disabled and run the heatpump in PV Boost Mode if there is enough wattage from my solar panels available. On summer days I have permanent 60-62°C with circulation enabled (if I am home). This should be enough to get them away (at least I hope so, never went for a water test, yet).

In regards to a higher temperature:
The original HMI controller sets the requested temperature in boost mode to 62°C. With AquaMQTT it is possible to send an higher value, 70°C, 80°C or whatever (it is as setting available within Configuration.h) I never tried and never tested if the heat pump controller accepts a value greater 62°C. Moreover, I am not sure what's the highest temperature value allowed, before the controller stops with an error or the boiler is starting to melt... ;) You might want to check the specs before risking your boiler. Of course you can always control the heating element manually by shorting it from a shelly or a similar smart device independent from the original controller. But I guess this might come with some risk and will definetely void any warranty (if there is still any).

AquaMQTT/AquaMQTT/include/config/Configuration.h

Lines 143 to 147 in 814fd16

	/**
	* Maximum Water Temperature: This value is used by BOOST or PV Modes.
	* Change at your own risk, 62°C is the default value on a Windhager Aquawin Air 3 heat pump
	*/
	constexpr float MAX_WATER_TEMPERATURE = 62.0;

If you are doing experiments with the maximum temperature, I would be happy to read about your experiences...

Cheers
Thomas

[jellewie]

As a big side note warming. Our 'Atlantic Calypso 100L' has a safety fuse build into the tank (bottom in the middle) If I remember correctly it was set to around 65-70C[need to verify]. Which would pop if you experimente with setting temperatures higher than you manufacture has limited it too.

In general heat pump are not that efficient with high deltas (temperatures). And thus sometimes people recommend electric (altough it would take longer HP would still be more efficiënt for heating), But you should take care to let it run to 62C (max) regularly.

We have set the Legionella Cycle to be disabled (no need for stupid time based tings). And we heat it almost every day to 62C with PV boost when the power is cheapest. (HA records and would warn if this fails)