Daikin Altherma hot water faults: two duties competing for one machine

What Does Error Hot water duty conditions Mean?

An Altherma serves space heating and the hot water cylinder from one heat pump, and it cannot do both at once. Priority settings decide which duty wins, so heating that pauses during a cylinder reheat, or hot water that takes longer than a boiler did, is the system working as designed rather than reporting a fault. Applies to: Daikin Altherma air-to-water heat pump systems serving space heating and a domestic hot water cylinder Altherma covers split, monobloc, and integrated cylinder configurations across several generations, with different controllers and different parameter names. The installation and operation manual for your configuration governs, and hot water behaviour in particular depends on commissioning choices as much as on the hardware. Owner-safe checks: Note whether space heating pauses coincide with hot water production, which distinguishes priority switching from a fault. | Time a full cylinder reheat and record the cylinder temperature setting alongside it. | Check whether a disinfection cycle is scheduled and at what time, since that is when the element is expected to run. Qualified technician: Cylinder temperature settings, priority parameters, and disinfection schedules affect both safety and running cost, and the installer who commissioned the system should change them. | Anything on the sealed refrigerant side of an Altherma needs a certified handler, regardless of whether the symptom appears on the hot water side.