VAV room thermal power control (VavThPwrCtl11)
Overview
This AF "VAV room thermal power control 11" (VavThPwrCtl11) selects both the heating setpoint and cooling setpoint based on plant mode and room operating mode. Two PID controllers (one heating, one cooling) use the setpoints to sequence heating and cooling device components in the room segment(s).
VavThPwrCtl11 supports only a single temperature setpoint during Comfort mode, instead of separate heating/cooling setpoints.
The thermal power control function is a room temperature control algorithm that includes a PID feedback controller and heat transfer calculations. It controls the room temperature by adjusting the supply flow rate and supply flow temperature. When the supply flow changes due to pressurization or ventilation demands, this function adjusts the supply air temperature to balance the heat flow to the room.
The following devices are supported in the room segment(s):
- Radiator
- Radiant ceiling
- Heating coil
- Supply air VAV damper
- Cooling coil
Main features:
- Select active room temp setpoint for heating and cooling based on plant mode and room operating mode
- Select temperature control mode (modulate or 2-position) and active elements (air, rad)
- Feedback control for multiple heating elements: Rad, Rcg, Hcl, Primary flow
- Feedback control for multiple cooling elements: Rcg, , Ccl, Primary flow
- Feedback control for a supply air terminal as one element
- Elements enabled by collected "available" signals
Function
This AF works in collaboration with a room segment HVAC device component AF for heating and cooling. Each heating and cooling element has a PID controller and is enabled based on the HVAC devices configured for this application template.
Thermal Power Control feature Active
Thermal Power Control feature is used in Comfort mode. The supply terminal functions as a single element. The AF sets both an airflow setpoint and a supply temperature setpoint to regulate the heat transfer at the rate set by the feedback controller.
It selects flow and temperature setpoints to deliver the required heat flow at the lowest airflow rate that satisfies configured flow and temperature limits.
Heating control sequence: 1) Supply terminal, 2) Radiator, 3) Heating ceiling,4) Heating coil
Cooling control sequence: 1) Chilled ceiling, 2) Cooling coil
This default sequence can be changed by configuration.
Thermal Power Control feature Inactive
Thermal Power Control feature is not used outside of Comfort mode. The feedback controller for the terminal is disabled and the element does not participate in the heating/cooling sequence.
Heating control sequence: 1) Radiator, 2) Heating ceiling, 3) Heating coil, 4) VAV heating
Cooling control sequence: 1) Chilled ceiling, 2) Cooling coil, 3) VAV cooling
This default sequence can be changed by configuration.
Room temperature feedback
The room temperature PID output is a percentage that goes above and below zero. The value represents a heat transfer rate to the room by the supply air terminal.
Calculate supply air temperature heating and cooling setpoint
The discharge temperature setpoint comes from scaling the feedback value up or down according to the current supply airflow rate. Typically, it scales up because the actual flow is less than the maximum heating or cooling flow. If the flow rate is low, it takes a greater temperature difference to deliver the same heating or cooling power.
Calculate Supply Flow Setpoint for Cooling and Heating
When cooling is required, the value of the temperature loop is negative and is limited by the supply flow minimum and maximum. The output cooling demand, in percent, is then calculated and mapped to the cooling airflow limits.
When heating is required, the value of the temperature loop is positive and is limited by the supply flow minimum and maximum. The output heating demand, in percent, is then calculated and mapped to the heating airflow limits.
Switch output of temperature cascade control based on Plant Mode
Heating / Cooling setpoints and plant mode (VavThPwrCtl11)
| Plant operation mode | Cooling setpoint | Heating setpoint |
|---|---|---|---|
1 | Off | Protection cooling | Protection heating |
2 | Protection | Protection cooling | Protection heating |
3 | Economy | Economy cooling | Economy heating |
4 | Pre-Comfort | Pre-Comfort cooling | Pre-Comfort heating |
5 | Comfort | Comfort cooling1 | Comfort heating |
6 | Warm-up | Protection cooling | Comfort heating / Pre-Comfort heating2 |
7 | Cool down | Comfort cooling / Pre-Comfort cooling2 | Protection heating |
8 | Room low temperature protection | Protection cooling | Protection heating |
9 | Not used |
|
|
10 | Free cooling | Comfort cooling | Protection heating |
11 | Night cooling | Comfort cooling | Protection heating |
12 | Ventilation | Comfort cooling | Comfort heating |
13 | Not used |
|
|
14 | Air volume flow off | Protection cooling | Protection heating |
15 | Smoke extraction positive pressure | Protection cooling | Protection heating |
16 | Smoke extraction negative pressure | Protection cooling | Protection heating |
17 | Purge | Protection cooling | Protection heating |
1) During Comfort, the application uses only one setpoint (SpHCmf) for both heating and cooling.
2) Depends on Next room operating mode (NxROpMod) in HvacPltMod AF.
Feature configuration
Feature selections for "Room HVAC coordination" are accessed via the Application configuration task in the Configuration component.
Feature (AF) | Feature description | Ref. |
|---|---|---|
Trend for present cooling setpoint | None/Active | ☑ |
Trend for present heating setpoint | None/Active | ☑ |
Configuration
Objects
Description | Object | Type | Default value |
|---|---|---|---|
Delta cooling setpoint for pre-comfort | DSpCPcf | ACnfVal | 24.0 [°C] |
Cooling setpoint for economy | SpCEco | ACnfVal | 0.0 [°C] |
Cooling setpoint for protection | SpCPrt | ACnfVal | 0.0 [°C] |
Heating setpoint for comfort | SpHCmf | APrcVal | 21.0 [°C] |
Delta heating setpoint for pre-comfort | DSpHPcf | ACnfVal | 1.0 [K] |
Heating setpoint for economy | SpHEco | ACnfVal | 15.0 [°C] |
Heating setpoint for protection | SpHPrt | ACnfVal | 12.0 [°C] |
Parameters
Description | Parameter | Default value |
|---|---|---|
Maximum supply air temperature setpoint | SpTSuMax | 32.0 [°C] |
Minimum supply air temperature setpoint | SpTSuMin | 16.0 [°C] |
Offset for heating coil temperature setpoint | OfsSpTHcl | 2.0 [K] |
Offset for cooling VAV start | OfsClgVavStt | 0.0 [°K] |
Comfort cooling configuration 1:None | CmfClgCnf | 2:Radiant devices |
Pre-Comfort cooling configuration Enumeration see CmfClgCnf | PcfClgCnf | 4:Radiant & air treatment devices |
Economy cooling configuration Enumeration see CmfClgCnf | EcoClgCnf | 4:Radiant & air treatment devices |
Protection cooling configuration Enumeration see CmfClgCnf | PrtClgCnf | 4:Radiant & air treatment devices |
Cool down configuration Enumeration see CmfClgCnf | CoolDnCnf | 4:Radiant & air treatment devices |
Free cooling configuration Enumeration see CmfClgCnf | FreeCCnf | 4:Radiant & air treatment devices |
Cooling coil: Controller mode by comfort 0:Continuous | CclCmf | 0:Continuous |
Cooling coil: Controller mode by pre-comfort 0:Continuous | CclPcf | 0:Continuous |
Cooling coil: Controller mode by economy 0:Continuous | CclEco | 0:Continuous |
Cooling coil: Controller mode by protection 0:Continuous | CclPrt | 0:Continuous |
Cooling coil: Controller mode by cool down 0:Continuous | CclCoolDn | 0:Continuous |
Radiant cooling devices: Controller mode by comfort 0:Continuous | RdnCDevCmf | 0:Continuous |
Radiant cooling devices: Controller mode by pre-comfort 0:Continuous | RdnCDevPcf | 0:Continuous |
Radiant cooling devices: Controller mode by economy 0:Continuous | RdnCDevEco | 0:Continuous |
Radiant cooling devices: Controller mode by protection 0:Continuous | RdnCDevPrt | 0:Continuous |
Radiant cooling devices: Controller mode by cool down 0:Continuous | RdnCDevCoolDn | 0:Continuous |
Radiant ceiling cooling sequence | RcgCSeq | 1 |
Coil cooling sequence | CoilCSeq | 2 |
VAV cooling sequence | VavCSeq | 3 |
Offset for heating VAV start | OfsHtgVavStt | 0.0 [K] |
Comfort heating configuration Enumeration see CmfClgCnf | CmfHtgCnf | 2:Radiant devices |
Pre-Comfort heating configuration Enumeration see CmfClgCnf | PcfHtgCnf | 4:Radiant & air treatment devices |
Economy heating configuration Enumeration see CmfClgCnf | EcoHtgCnf | 4:Radiant & air treatment devices |
Protection heating configuration Enumeration see CmfClgCnf | PrtHtgCnf | 4:Radiant & air treatment devices |
Warm-up configuration Enumeration see CmfClgCnf | WarmUpCnf | 4:Radiant & air treatment devices |
Heating coil: Controller mode by comfort 0:Continuous | HclCmf | 0:Continuous |
Heating coil: Controller mode by pre-comfort 0:Continuous | HclPcf | 0:Continuous |
Heating coil: Controller mode by economy 0:Continuous | HclEco | 0:Continuous |
Heating coil: Controller mode by protection 0:Continuous | HclPrt | 0:Continuous |
Heating coil: Controller mode by warm-up 0:Continuous | HclWarmUp | 0:Continuous |
Radiant heating devices: Controller mode by comfort 0:Continuous | RdnHDevCmf | 0:Continuous |
Radiant heating devices: Controller mode by pre-comfort 0:Continuous | RdnHDevPcf | 0:Continuous |
Radiant heating devices: Controller mode by economy 0:Continuous | RdnHDevEco | 0:Continuous |
Radiant heating devices: Controller mode by protection 0:Continuous | RdnHDevPrt | 0:Continuous |
Radiant heating devices: Controller mode by warm-up 0:Continuous | RdnHDevWarmUp | 0:Continuous |
Radiator heating sequence | RadHSeq | 1 |
Radiant ceiling heating sequence | RcgHSeq | 2 |
Coil heating sequence | CoilHSeq | 3 |
VAV heating sequence | VavHSeq | 4 |
Temperature unit | TUnit | [°C] |
Temperature difference unit | TDiffUnit | [K] |
Interface
Interface | Description | Type | Ref. | Owned by |
|---|---|---|---|---|
PrSpC | Present cooling setpoint | APrcVal | ● | - |
TrndPrSpC | Trend for present cooling setpoint | FtrSel | ● | - |
PrSpH | Present heating setpoint | APrcVal | ● | - |
TrndPrSpH | Trend for present heating setpoint | FtrSel | ● | - |
AirFlSuAvl | Supply air volume flow available | ACalcVal | ● | - |
SpAirFlSuRC | Setpoint supply air volume flow for room cooling | ACalcVal | ● | - |
SpAirFlSuRH | Setpoint supply air volume flow for room heating | ACalcVal | ● | - |
PrSpCCmf | Present cooling setpoint for comfort | ACalcVal | ● | - |
PrSpCPcf | Present cooling setpoint for pre-comfort | ACalcVal | ● | - |
PrSpCEco | Present cooling setpoint for economy | ACalcVal | ● | - |
PrSpCPrt | Present cooling setpoint for protection | ACalcVal | ● | - |
PrSpHCmf | Present heating setpoint for comfort | ACalcVal | ● | - |
PrSpHPcf | Present heating setpoint for pre-comfort | ACalcVal | ● | - |
PrSpHEco | Present heating setpoint for economy | ACalcVal | ● | - |
PrSpHPrt | Present heating setpoint for protection | ACalcVal | ● | - |
ThPwrTRCtr | Room temperature controller for thermal power | Controller | ● | - |
VavTRCtrC | Room temperature controller cooling for VAV | Controller | ● | - |
CoilTRCtrC | Room temperature controller cooling for coil | Controller | ● | - |
RcgTRCtrC | Room temperature controller cooling for radiant ceiling | Controller | ● | - |
VavTRCtrH | Room temperature controller heating for VAV | Controller | ● | - |
CoilTRCtrH | Room temperature controller heating for coil | Controller | ● | - |
RcgTRCtrH | Room temperature controller heating for radiant ceiling | Controller | ● | - |
RadTRCtrH | Room temperature controller heating for radiator | Controller | ● | - |
RCtl | Room control | GrpMaster | ◉ | Room |
SpCCmf | Cooling setpoint for comfort | APrcVal | ● | - |
DSpCPcf | Delta cooling setpoint for pre-comfort | ACnfVal | ● | - |
SpCEco | Cooling setpoint for economy | ACnfVal | ● | - |
SpCPrt | Cooling setpoint for protection | ACnfVal | ● | - |
SpHCmf | Heating setpoint for comfort | APrcVal | ● | - |
DSpHPcf | Delta heating setpoint for pre-comfort | ACnfVal | ● | - |
SpHEco | Heating setpoint for economy | ACnfVal | ● | - |
SpHPrt | Heating setpoint for protection | ACnfVal | ● | - |
Engineering and commissioning
This temperature control feature is designed to quickly apply reheat to avoid uncomfortable drafts that might result when fume hood flow changes drive quick changes in conditioned supply air to the room. It applies adjusts reheat directly in response to flow changes, without waiting for the room temperature to drift through a deadband and out of the comfort range. Consequently, it might use more energy than a basic temperature control sequence.
If the supply air temperature loop overshoots, lab workers might notice heat being applied during the cooling season and question the operation. This might be addressed by tuning the supply air temperature control loop or by implementing basic temperature control.