blockPlantRequests
Output plant requests for fan coil unit
Information
This sequence outputs the system reset requests for fan coil unit. The implementation is according to the Section 5.22.8 of ASHRAE Guideline 36, 2021.
If there is a chilled-water coil (have_chiWatCoi=true),
chilled water reset requests yChiWatResReq
-
If the supply air temperature
TAirSupexceeds the supply air temperature set pointTSupSetby 5.56 °C (10 °F) for 5 minutes, send 3 requests. -
If the supply air temperature
TAirSupexceedsTSupSetby by 2.78 °C (5 °F) for 5 minutes, send 2 requests. -
Else if the chilled water valve position
uCooCoi_actualis greater than 0.95, send 1 request untiluCooCoi_actualis less than 0.85. -
Else if the chilled water valve position
uCooCoi_actualis less than 0.85, send 0 requests.
If there is a chilled-water coil and chilled water plant, chiller plant
request yChiPlaReq
Send the chiller plant that serves the system a chiller plant request as follows:
-
If the chilled water valve position
uCooCoi_actualis greater than 0.95, send 1 request until theuCooCoi_actualis less than 0.1. -
Else if the chilled water valve position
uCooCoi_actualis less than 0.1, send 0 request
If there is a hot-water coil (have_hotWatCoi=true),
hot-water reset requests yHotWatResReq
-
If the supply air temperature
TAirSupis 17 °C (30 °F) less than the supply air temperature set pointTSupSetfor 5 minutes, send 3 requests. -
Else if the supply air temperature
TAirSupis 8 °C (15 °F) less thanTSupSetfor 5 minutes, send 2 requests. -
Else if the hot water valve position
uHeaCoi_actualis greater than 0.95, send 1 request until theuHeaCoi_actualis less than 0.85. -
Else if the hot water valve position
uHeaCoi_actualis less than 0.85, send 0 request.
If there is a hot-water coil and heating hot-water plant, heating hot-water
plant requests yHotWatPlaReq
Send the heating hot-water plant that serves the air handling unit a heating hot-water plant request as follows:
-
If the hot water valve position
uHeaCoi_actualis greater than 0.95, send 1 request until the hot water valve position is less than 0.1. -
If the hot water valve position
uHeaCoi_actualis less than 0.1, send 0 requests.
Parameters
| Type | Name | Default | Description |
|---|---|---|---|
| Boolean | have_hotWatCoi | true | True if the unit has a hot-water heating coil |
| Boolean | have_chiWatCoi | true | True if the unit has a chilled-water cooling coil |
| Real | cooSpe_max | 1 | Maximum cooling mode fan speed |
| Real | heaSpe_max | 0.6 | Maximum heating mode fan speed |
| Request limits › Chilled water plant requests | |||
| Real | chiWatPlaReqLim0 | 0.1 | Valve position limit below which zero chilled water plant requests are sent when one request was previously being sent |
| Real | chiWatPlaReqLim1 | 0.95 | Valve position limit above which one chilled water plant request is sent |
| Request limits › Chilled water reset requests | |||
| Real | chiWatResReqLim0 | 0.85 | Valve position limit below which zero chilled water reset requests are sent when one request was previously being sent |
| Real | chiWatResReqLim1 | 0.95 | Valve position limit above which one chilled water reset request is sent |
| Real | chiWatResReqLim2 | 2.78 | Temperature difference limit between setpoint and supply air temperature above which two chilled water reset requests are sent |
| Real | chiWatResReqTimLim2 | 300 | Time period for which chiWatResReqLim2 has to be exceeded before two chilled water reset requests are sent |
| Real | chiWatResReqLim3 | 5.56 | Temperature difference limit between setpoint and supply air temperature above which three chilled water reset requests are sent |
| Real | chiWatResReqTimLim3 | 300 | Time period for which chiWatResReqLim3 has to be exceeded before three chilled water reset requests are sent |
| Request limits › Hot water plant requests | |||
| Real | hotWatPlaReqLim0 | 0.1 | Valve position limit below which zero hot water plant requests are sent when one request was previously being sent |
| Real | hotWatPlaReqLim1 | 0.95 | Valve position limit above which one hot water plant request is sent |
| Request limits › Hot water reset requests | |||
| Real | hotWatResReqLim0 | 0.85 | Valve position limit below which zero hot water reset requests are sent when one request was previously being sent |
| Real | hotWatResReqLim1 | 0.95 | Valve position limit above which one hot water reset request is sent |
| Real | hotWatResReqLim2 | 8 | Temperature difference limit between setpoint and supply air temperature above which two hot water reset requests are sent |
| Real | hotWatResReqTimLim2 | 300 | Time period for which hotWatResReqLim2 has to be exceeded before two hot water reset requests are sent |
| Real | hotWatResReqLim3 | 17 | Temperature difference limit between setpoint and supply air temperature above which three hot water reset requests are sent |
| Real | hotWatResReqTimLim3 | 300 | Time period for which hotWatResReqLim3 has to be exceeded before three hot water reset requests are sent |
| Advanced | |||
| Real | THys | 0.1 | Hysteresis for checking temperature difference |
| Real | dFanSpe | 0.05 | Fan speed hysteresis difference |
Connectors
| Type | Name | Default | Description |
|---|---|---|---|
| Buildings.Controls.OBC.CDL.Interfaces.RealInput | TAirSup | Measured supply air temperature | |
| Buildings.Controls.OBC.CDL.Interfaces.RealInput | TAirSupSet | Supply air temperature setpoint | |
| Buildings.Controls.OBC.CDL.Interfaces.RealInput | uCooCoiSet | Commanded cooling coil position | |
| Buildings.Controls.OBC.CDL.Interfaces.RealInput | uHeaCoiSet | Commanded heating coil position | |
| Buildings.Controls.OBC.CDL.Interfaces.RealInput | uFan | Fan speed signal | |
| Buildings.Controls.OBC.CDL.Interfaces.IntegerOutput | yChiWatResReq | Chilled water reset request | |
| Buildings.Controls.OBC.CDL.Interfaces.IntegerOutput | yChiPlaReq | Chiller plant request | |
| Buildings.Controls.OBC.CDL.Interfaces.IntegerOutput | yHotWatResReq | Hot water reset request | |
| Buildings.Controls.OBC.CDL.Interfaces.IntegerOutput | yHotWatPlaReq | Hot water plant request |
Components
| Type | Name | Default | Description |
|---|---|---|---|
| Buildings.Controls.OBC.CDL.Reals.Hysteresis | hysFanCoo | Check if fan is at max cooling mode speed | |
| Buildings.Controls.OBC.CDL.Conversions.BooleanToInteger | booToIntCoo | Output integer 1 when fan is at max cooling mode speed | |
| Buildings.Controls.OBC.CDL.Integers.Multiply | mulIntCoo | Output reset requests only if fan is at max cooling mode speed | |
| Buildings.Controls.OBC.CDL.Reals.Hysteresis | hysFanHea | Check if fan is at max heating mode speed | |
| Buildings.Controls.OBC.CDL.Conversions.BooleanToInteger | booToIntHea | Output integer 1 when fan is at max heating mode speed | |
| Buildings.Controls.OBC.CDL.Integers.Multiply | mulIntHea | Output reset requests only if fan is at max heating mode speed | |
| Buildings.Controls.OBC.CDL.Reals.Subtract | cooSupTemDif | Find the cooling supply temperature difference to the setpoint | |
| Buildings.Controls.OBC.CDL.Reals.GreaterThreshold | greThr | Check if the supply temperature is greater than the setpoint by a threshold value for sending three reset requests | |
| Buildings.Controls.OBC.CDL.Reals.GreaterThreshold | greThr1 | Check if the supply temperature is greater than the setpoint by a threshold value for sending two reset requests | |
| Buildings.Controls.OBC.CDL.Logical.TrueDelay | truDel | Ensure condition for sending three chilled water reset requests is true for minimum threshold time period | |
| Buildings.Controls.OBC.CDL.Logical.TrueDelay | truDel1 | Ensure condition for sending two chilled water reset requests is true for minimum threshold time period | |
| Buildings.Controls.OBC.CDL.Reals.Hysteresis | hys | Check chilled water valve position against threshold values for sending one reset request | |
| Buildings.Controls.OBC.CDL.Integers.Switch | chiWatRes3 | Send 3 chilled water reset request | |
| Buildings.Controls.OBC.CDL.Integers.Switch | chiWatRes2 | Send 2 chilled water reset request | |
| Buildings.Controls.OBC.CDL.Integers.Switch | chiWatRes1 | Send 1 chilled water reset request | |
| Buildings.Controls.OBC.CDL.Integers.Switch | intSwi3 | Send 1 chiller plant request | |
| Buildings.Controls.OBC.CDL.Reals.Subtract | heaSupTemDif | Find the heating supply temperature difference to the setpoint | |
| Buildings.Controls.OBC.CDL.Reals.GreaterThreshold | greThr3 | Check if the supply temperature is less than the setpoint by a threshold value for sending three reset requests | |
| Buildings.Controls.OBC.CDL.Reals.GreaterThreshold | greThr4 | Check if the supply temperature is less than the setpoint by a threshold value for sending two reset requests | |
| Buildings.Controls.OBC.CDL.Logical.TrueDelay | truDel2 | Ensure condition for sending three hot water reset requests is true for minimum threshold time period | |
| Buildings.Controls.OBC.CDL.Logical.TrueDelay | truDel3 | Ensure condition for sending two hot water reset requests is true for minimum threshold time period | |
| Buildings.Controls.OBC.CDL.Integers.Switch | hotWatRes3 | Send 3 hot water reset request | |
| Buildings.Controls.OBC.CDL.Integers.Switch | hotWatRes2 | Send 2 hot water reset request | |
| Buildings.Controls.OBC.CDL.Integers.Switch | hotWatRes1 | Send 1 hot water reset request | |
| Buildings.Controls.OBC.CDL.Integers.Switch | intSwi1 | Send 1 hot water plant request | |
| Buildings.Controls.OBC.CDL.Reals.Hysteresis | hys1 | Check chilled water valve position against threshold values for sending one plant request | |
| Buildings.Controls.OBC.CDL.Reals.Hysteresis | hys2 | Check hot water valve position against threshold values for sending one reset request | |
| Buildings.Controls.OBC.CDL.Reals.Hysteresis | hys3 | Check hot water valve position against threshold values for sending one plant request |
Revisions
-
May 6, 2022, by Karthik Devaprasad:
First implementation.