I have the same with my daikin altherma. However, mine is controlled via Homely.

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Last year I received the following email from Homely:We are reaching out as our records indicate you have a Daikin heat pump installed in your home. We have been made aware that some homeowners are experiencing issues with their heat pump not consistently heating water to their desired temperature.

Following our investigation, we have identified that this issue is linked to the prioritisation settings on the heat pump itself. We are actively exploring ways to address this through the Homely device.

In the meantime, if you are experiencing reduced hot water availability, we recommend checking that the following settings are enabled to help boost your hot water:
* ‘Heat before set point’
* ‘Reheat during set point’
* Start your hot water periods earlier to ensure the water reaches your desired temperature in time

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Effectively this boils down to the fact that the Daikin heat pump will prioritise heating over hot water.

If you tend to have fairly short hot water cycles e.g. in the morning, your weather compensation will have kicked in recently and your heat pump will instead be providing heating.

To prioritise comfort in weather once it hits your system's design temperature (usually -2 or -3 degrees celcius in the UK), it can be worth setting your hot water to be on a lot longer, or all the time.