.Buildings.Templates.Plants.Controls.HeatPumps.AirToWater .Buildings.Templates.Plants.Controls.HeatPumps.AirToWaterThis block implements the sequence of operation for plants with air-to-water heat pumps. Most parts of the sequence of operation are similar to that described in ASHRAE, 2021 for chiller plants.
The supported plant configurations are enumerated in the table below.
| Configuration parameter | Options | Notes |
|---|---|---|
| Function |
Heating and cooling Heating-only Cooling-only |
|
| Heat recovery |
Without sidestream heat recovery chiller With sidestream heat recovery chiller |
This option is only available for heating and cooling plants. When selected, the plant controller incorporates logic to manage a chiller and its associated dedicated primary CHW and CW pumps. The chiller is considered connected in a sidestream configuration to both the CHW return and the HW return. |
| Type of distribution |
Variable primary-only Constant primary-variable secondary centralized |
It is assumed that the HW and the CHW loops have the
same type of distribution, as specified by this parameter. Most AWHPs on the market use a reverse cycle for defrosting. This requires maximum primary flow during defrost cycles. Consequently, variable primary plants commonly adopt a high minimum flow setpoint, typically close to the design flow rate, effectively operating akin to constant primary plants but with variable speed pumps controlling the loop differential pressure. While the flow rate directed towards the loads varies, the bypass valve control loop ensures a constant primary flow for a given number of staged units. "Centralized secondary pumps" refers to configurations with a single group of secondary pumps that is typically integrated into the plant. Distributed secondary pumps with multiple secondary loops served by dedicated secondary pumps are currently not supported. |
| Type of primary pump arrangement |
Dedicated Headered |
It is assumed that the HW and the CHW loops have the same type of primary pump arrangement, as specified by this parameter. |
| Separate dedicated primary CHW pumps |
False True |
This option is only available for heating and cooling plants with dedicated primary pumps. If this option is not selected, each AWHP uses a common dedicated primary pump for HW and CHW – this pump is then denoted as the primary HW pump. Otherwise, each AWHP relies on a separate dedicated HW pump and a separate dedicated CHW pump. |
| Type of primary HW pumps |
Variable speed Constant speed |
For constant primary-variable secondary distributions, the variable
speed primary pumps are commanded at fixed speeds, determined during the
Testing, Adjusting and Balancing phase to provide design AWHP flow in
heating and cooling modes.
The same intent is achieved with constant speed primary pumps through the
use of balancing valves. This parameter is only available for constant primary-variable secondary plants. |
| Type of primary CHW pumps |
Variable speed Constant speed |
See the note above on primary HW pumps. |
A staging matrix staEqu is required as a parameter.
See the documentation of
Buildings.Templates.Plants.Controls.StagingRotation.EquipmentEnable
for the associated definition and requirements.
Depending on the plant configuration, the term "primary HW pumps"
(and the corresponding variables containing *pumHeaWatPri*)
refers either to primary HW pumps for plants with separate primary
HW and CHW pumps (either headered or dedicated)
or to dedicated primary pumps for plants with common primary pumps
serving both the HW and CHW loops.
At its current stage of development, this controller contains no logic for handling faulted equipment. It is therefore assumed that any equipment is available at all times.