Key information
- Typical water temperature: 30–35°C
- Series to review: AQ-Vento R290 and AQ-Casa R32
- Key comparison: Capacity and COP at A7/W35 and the design point
Air-to-water heat pumps for underfloor heating: output, water temperature and flow.
Underfloor heating is well suited to heat pumps because it can operate with low water temperatures. Good performance still depends on a proper heat-loss calculation, sufficient flow and sensible zone control.
Size from the real heat load
Use the building heat loss at the local design outdoor temperature. Floor area can provide a rough check, but it cannot replace a room-by-room or building calculation.
- Include fabric, ventilation and climate
- Keep DHW duty separate from space heating
- Check available output below zero
Hydraulics and control
The heat pump must retain minimum flow when zones close. A buffer, hydraulic separator or bypass should answer a specific water-volume or control need, not be added by habit.
- Balance the floor circuits
- Use weather compensation before high fixed setpoints
- Provide enough active water volume to limit cycling
Checks before selection
| Item | Check |
|---|---|
| Design heat load | Compare it with capacity at the minimum outdoor temperature. |
| Water temperature | Use the temperature the floor actually requires. |
| ΔT and flow | Keep both within the unit and circuit operating range. |
| Zones | Confirm what happens when several thermostats close. |
Mistakes to avoid
- Sizing from floor area alone.
- Setting 45–50°C without a design need.
- Ignoring minimum flow in heavily zoned systems.
Frequently asked questions
Is a buffer tank always required?
No. Use one when system volume, flow, defrost or zone control creates a clear need.
Which COP should I compare?
Compare values at the same air/water condition, starting with A7/W35 and then checking the winter design point.