Key information
- Main series: AQ-Impresa R32
- High-temperature option: AQ-Forza HT R417
- Control: Cascade configurations up to 8 units, subject to project design
Commercial air-to-water heat pumps in cascade for central plant.
In commercial buildings, output is only part of the design. Redundancy, modulation, hydraulic arrangement, cascade control and continuity requirements determine the right configuration.
Why use multiple units
A cascade extends the modulation range and can allow maintenance or a unit fault without stopping the whole plant. Define redundancy from the service requirement rather than adding units without a clear duty.
- Lead/lag staging
- Runtime rotation
- N+1 reserve where required
Hydraulics and control
Separation, primary and secondary flow, active water volume and staging sequence must work together. Control should avoid rapid cycling and meet setpoint with the fewest units required.
- Correctly sized buffer or separator
- Coordinated pumps and valves
- BMS integration and alarms
Cascade design inputs
| Input | Decision |
|---|---|
| Minimum and maximum load | Unit count and size for a useful modulation range. |
| Continuity requirement | Required redundancy and reserve. |
| Design water temperature | Series, COP and capacity at the real duty point. |
| Space and sound | Layout, clearances, airflow and noise control. |
Mistakes to avoid
- Splitting the load without checking minimum modulation.
- Omitting a defined staging sequence.
- Sizing buffers and pumps without all operating combinations.
Frequently asked questions
When is N+1 redundancy required?
When service must continue with one unit unavailable; agree the requirement with the client and designer.
Can AQ-Impresa also serve DHW?
It can be integrated with DHW storage; temperature, priority and recovery output must be checked for the project.