.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 |
|
| Type of distribution | Constant primary-variable secondary centralized |
"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. Options are limited to constant primary distributions because most AWHPs on the market use a reverse cycle for defrosting. This requires maximum primary flow during defrost cycles and hinders variable primary distributions. An option for constant primary-only distributions with ∆p-controlled variable speed pumps will be added in a next release. |
| 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. 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. |
| 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.