2.4 Heat Exchanger and 2.5 Chilled Water Plant Rules
2.4 Heat Exchangers
2.4.1.1 - Primary Chilled Water Heat Exchanger Leaving Temperature Sensor Failure
Summary
The primary chilled water heat exchanger leaving chilled water temperature sensor has failed. The temperature sensor point is invariant or is outside the expected range.
| Equipment Type |
Equipment Tag Constraints |
Tuple Constraints |
| heatExchanger |
-- |
-- |
Input Points
| Name |
Point Template |
Positional Requirements |
Optionality |
Multiplicity |
| Condenser Water Leaving Temperature |
CWLTemp |
This point must be a direct child of the equipment that the rule is attached to. |
Mandatory |
Scalar |
| Chilled Water Setpoint |
ChWSp |
This point must be a direct child of the equipment that the rule is attached to. |
Mandatory |
Scalar |
| Chilled Water Leaving Temperature |
ChWLTemp |
This point must be a direct child of the equipment that the rule is attached to. |
Mandatory |
Scalar |
| Heat Exchanger Condenser Water Isolation Valve Command |
HXCWIsoVlvCmd |
This point must be a direct child of the equipment that the rule is attached to. |
Mandatory |
Scalar |
| Heat Exchanger Chilled Water Isolation Valve Command |
HXChWIsoVlvCmd |
This point must be a direct child of the equipment that the rule is attached to. |
Mandatory |
Scalar |
Input Constants
| Name |
Data Type |
Default Value |
Description |
Delay
|
Numeric |
15 |
The delay represents a span of time in minutes during which the sensor must be in a fault state before the rule starts to actually report that it is in a fault state. The intent of the delay is to reduce the level of alert noise by ensuring that the system does not alert until the fault condition has been in effect for some minimal interval of time. |
| High Threshold |
Numeric |
70 |
MAX_VALUE |
| Low Threshold |
Numeric |
20 |
MIN_VALUE |
| Variance Threshold |
Numeric |
0.01 |
|
| Heat Exchanger Design Approach |
Numeric |
2 |
|
2.4.2.1 - Primary Chilled Water Heat Exchanger Entering Temperature Sensor Failure
Summary
The primary chilled water heat exchanger entering chilled water temperature sensor has failed. The temperature sensor point is invariant or is outside the expected range.
| Equipment Type |
Equipment Tag Constraints |
Tuple Constraints |
| heatExchanger |
-- |
-- |
Input Points
| Name |
Point Template |
Positional Requirements |
Optionality |
Multiplicity |
| Heat Exchanger Condenser Water Isolation Valve Command |
HXCWIsoVlvCmd |
This point must be a direct child of the equipment that the rule is attached to. |
Mandatory |
Scalar |
| Heat Exchanger Chilled Water Isolation Valve Command |
HXChWIsoVlvCmd |
This point must be a direct child of the equipment that the rule is attached to. |
Mandatory |
Scalar |
| Condenser Water Leaving Temperature |
CWLTemp |
This point must be a direct child of the equipment that the rule is attached to. |
Mandatory |
Scalar |
| Chilled Water Entering Temperature |
ChWETemp |
This point must be a direct child of the equipment that the rule is attached to. |
Mandatory |
Scalar |
| Chilled Water Setpoint |
ChWSp |
This point must be a direct child of the equipment that the rule is attached to. |
Mandatory |
Scalar |
Input Constants
| Name |
Data Type |
Default Value |
Description |
Delay
|
Numeric |
15 |
The delay represents a span of time in minutes during which the sensor must be in a fault state before the rule starts to actually report that it is in a fault state. The intent of the delay is to reduce the level of alert noise by ensuring that the system does not alert until the fault condition has been in effect for some minimal interval of time. |
| High Threshold |
Numeric |
70 |
MAX_VALUE |
| Low Threshold |
Numeric |
20 |
MIN_VALUE |
| Variance Threshold |
Numeric |
0.01 |
|
| Heat Exchanger Design Approach |
Numeric |
2 |
|
2.4.3.1 - Heat Exchanger Chilled Water Isolation Valve is Open When Condenser Water Location Valve is Closed
Summary
Isolation valves on both sides of the heat exchanger should either be both open or closed.
| Equipment Type |
Equipment Tag Constraints |
Tuple Constraints |
| heatExchanger |
-- |
-- |
Input Points
| Name |
Point Template |
Positional Requirements |
Optionality |
Multiplicity |
| Heat Exchanger Chilled Water Isolation Valve Command |
HXChWIsoVlvCmd |
This point must be a direct child of the equipment that the rule is attached to. |
Mandatory |
Scalar |
| Heat Exchanger Condenser Water Isolation Valve Command |
HXCWIsoVlvCmd |
This point must be a direct child of the equipment that the rule is attached to. |
Mandatory |
Scalar |
Input Constants
| Name |
Data Type |
Default Value |
Description |
Delay
|
Numeric |
0 |
The delay represents a span of time in minutes during which the sensor must be in a fault state before the rule starts to actually report that it is in a fault state. The intent of the delay is to reduce the level of alert noise by ensuring that the system does not alert until the fault condition has been in effect for some minimal interval of time. |
2.4.3.2 - Heat Exchanger Chilled Water Isolation Valve is Closed When Condenser Isolation Valve is Open
Summary
Isolation valves on both sides of the heat exchanger should either be both open or closed.
| Equipment Type |
Equipment Tag Constraints |
Tuple Constraints |
| heatExchanger |
-- |
-- |
Input Points
| Name |
Point Template |
Positional Requirements |
Optionality |
Multiplicity |
| Heat Exchanger Chilled Water Isolation Valve Command |
HXChWIsoVlvCmd |
This point must be a direct child of the equipment that the rule is attached to. |
Mandatory |
Scalar |
| Heat Exchanger Condenser Water Isolation Valve Command |
HXCWIsoVlvCmd |
This point must be a direct child of the equipment that the rule is attached to. |
Mandatory |
Scalar |
Input Constants
| Name |
Data Type |
Default Value |
Description |
Delay
|
Numeric |
0 |
The delay represents a span of time in minutes during which the sensor must be in a fault state before the rule starts to actually report that it is in a fault state. The intent of the delay is to reduce the level of alert noise by ensuring that the system does not alert until the fault condition has been in effect for some minimal interval of time. |
2.4.4.1 - Heat Exchanger Continuous Operation at High Load
Summary
When the heat exchanger is consistently operated at a load greater than its threshold.
| Equipment Type |
Equipment Tag Constraints |
Tuple Constraints |
| heatExchanger |
-- |
-- |
Input Points
| Name |
Point Template |
Positional Requirements |
Optionality |
Multiplicity |
| Heat Exchanger Chilled Water Isolation Valve Command |
HXChWIsoVlvCmd |
This point must be a direct child of the equipment that the rule is attached to. |
Mandatory |
Scalar |
| Heat Exchanger Condenser Water Isolation Valve Command |
HXCWIsoVlvCmd |
This point must be a direct child of the equipment that the rule is attached to. |
Mandatory |
Scalar |
| Chilled Water Circulation Pump Status |
ChWCPSts |
This point must be a direct child of the equipment that the rule is attached to. |
Mandatory |
Vector |
| Condenser Water Circulation Pump Status |
CWCPSts |
This point must be a direct child of the equipment that the rule is attached to. |
Mandatory |
Vector |
Input Constants
| Name |
Data Type |
Default Value |
Description |
Delay
|
Numeric |
240 |
The delay represents a span of time in minutes during which the sensor must be in a fault state before the rule starts to actually report that it is in a fault state. The intent of the delay is to reduce the level of alert noise by ensuring that the system does not alert until the fault condition has been in effect for some minimal interval of time. |
| Heat Exchanger Maximum Load Threshold |
Numeric |
95 |
|
2.5 Chilled Water Plant
2.5.3.1 - Chilled Water Supply Temperature Greater Than Setpoint
Summary
The chilled water supply temperature is greater than the supply water temperature setpoint, indicating chiller is in a low load situation and is cycling on and off. Chiller does not have modulating control capability, or poor PID tuning.
| Equipment Type |
Equipment Tag Constraints |
Tuple Constraints |
| chilled water plant |
-- |
-- |
Input Points
| Name |
Point Template |
Positional Requirements |
Optionality |
Multiplicity |
| Chilled Water Setpoint |
ChWSp |
This point must be a direct child of the equipment that the rule is attached to. |
Mandatory |
Scalar |
| Chiller Status |
ChrSts |
This point must be a direct child of a chiller. |
Optional |
Vector |
| Chilled Water Pump Status |
ChWCPSts |
This point must be a direct child of a chiller. |
Optional |
Vector |
| Chilled Water Supply Temperature |
ChWSTemp |
This point must be a direct child of the equipment that the rule is attached to. |
Mandatory |
Scalar |
Input Constants
| Name |
Data Type |
Default Value |
Description |
| Delay |
Numeric |
60 |
The delay represents a span of time in minutes during which the sensor must be in a fault state before the rule starts to actually report that it is in a fault state. The intent of the delay is to reduce the level of alert noise by ensuring that the system does not alert until the fault condition has been in effect for some minimal interval of time. |
| THRESHOLD |
Numeric |
2 |
The temperature threshold. |
2.5.4.1 - Chilled Water Supply Temperature Less Than Setpoint
Summary
The chiller water supply temperature is less than the supply water temperature setpoint, indicating poor control programming or poor PID tuning.
| Equipment Type |
Equipment Tag Constraints |
Tuple Constraints |
| chilled water plant |
-- |
-- |
Input Points
| Name |
Point Template |
Positional Requirements |
Optionality |
Multiplicity |
| Chilled Water Supply Temperature |
ChWSTemp |
This point must be a direct child of the equipment that the rule is attached to. |
Mandatory |
Scalar |
| Chiller Status |
ChrSts |
This point must be a direct child of a chiller. |
Optional |
Vector |
| Chilled Water Setpoint |
ChWSp |
This point must be a direct child of the equipment that the rule is attached to. |
Mandatory |
Scalar |
| Chilled Water Pump Status |
ChWCPSts |
This point must be a direct child of a chiller. |
Optional |
Vector |
Input Constants
| Name |
Data Type |
Default Value |
Description |
| Delay |
Numeric |
60 |
The delay represents a span of time in minutes during which the sensor must be in a fault state before the rule starts to actually report that it is in a fault state. The intent of the delay is to reduce the level of alert noise by ensuring that the system does not alert until the fault condition has been in effect for some minimal interval of time. |
| THRESHOLD |
Numeric |
2 |
The temperature threshold. |
2.5.5.1 - Chilled Water Plant Low Temperature Differential (Low Delta T)
Summary
The chilled water plant temperature differential (Delta T) is lower than design.
| Equipment Type |
Equipment Tag Constraints |
Tuple Constraints |
| chilled water plant |
-- |
-- |
Input Points
| Name |
Point Template |
Positional Requirements |
Optionality |
Multiplicity |
| Chilled Water Supply Temperature |
ChWSTemp |
This point must be a direct child of the equipment that the rule is attached to. |
Mandatory |
Scalar |
| Chiller Status |
ChrSts |
This point must be a direct child of a chiller. |
Mandatory |
Vector |
| Chilled Water Return Temperature |
ChWRTemp |
This point must be a direct child of the equipment that the rule is attached to. |
Mandatory |
Scalar |
| Chilled Water Pump Status |
ChWCPSts |
This point must be a direct child of a chiller. |
Optional |
Scalar |
Input Constants
| Name |
Data Type |
Default Value |
Description |
| Delay |
Numeric |
120 |
The delay represents a span of time in minutes during which the sensor must be in a fault state before the rule starts to actually report that it is in a fault state. The intent of the delay is to reduce the level of alert noise by ensuring that the system does not alert until the fault condition has been in effect for some minimal interval of time. |
| MIN_DELTA T |
Numeric |
5 |
The minimum temperature differential. The chilled water return temperature minus the chilled water supply temperature must be less than this constant for a period longer than delay for a fault to exist. |
2.5.6.1 - Chilled Water Supply Temperature Setpoint is Less Than Low Limit
Summary
The chilled water supply temperature setpoint is less than the low limit, wasting energy. The setpoint may be overridden or set lower than design.
| Equipment Type |
Equipment Tag Constraints |
Tuple Constraints |
| chilled water plant |
-- |
-- |
Input Points
| Name |
Point Template |
Positional Requirements |
Optionality |
Multiplicity |
| Chilled Water Setpoint |
ChWSp |
This point must be a direct child of the equipment that the rule is attached to. |
Mandatory |
Scalar |
| Chiller Status |
ChrSts |
This point must be a direct child of a chiller. |
Mandatory |
Vector |
| Chilled Water Pump Status |
ChWCPSts |
This point must be a direct child of a chiller. |
Optional |
Scalar |
Input Constants
| Name |
Data Type |
Default Value |
Description |
| Delay |
Numeric |
15 |
The delay represents a span of time in minutes during which the sensor must be in a fault state before the rule starts to actually report that it is in a fault state. The intent of the delay is to reduce the level of alert noise by ensuring that the system does not alert until the fault condition has been in effect for some minimal interval of time. |
| Low Temperature Setpoint Limit |
Numeric |
42 |
|
2.5.8.1 - Primary Loop Chilled Water Supply Temperature Sensor Failure
Summary
The primary loop chilled water supply temperature sensor has failed. The temperature sensor point is invariant or is outside the expected range.
| Equipment Type |
Equipment Tag Constraints |
Tuple Constraints |
| chilled water plant |
-- |
-- |
Input Points
| Name |
Point Template |
Positional Requirements |
Optionality |
Multiplicity |
| Chilled Water Supply Temperature |
ChWSTemp |
This point must be a direct child of the equipment that the rule is attached to. |
Mandatory |
Scalar |
| Chiller Status |
ChrSts |
This point must be a direct child of a chiller. |
Mandatory |
Vector |
| Chilled Water Pump Status |
ChWCPSts |
This point must be a direct child of the chiller. |
Mandatory |
Vector |
Input Constants
| Name |
Data Type |
Default Value |
Description |
| Delay |
Numeric |
120 |
The delay represents a span of time in minutes during which the sensor must be in a fault state before the rule starts to actually report that it is in a fault state. The intent of the delay is to reduce the level of alert noise by ensuring that the system does not alert until the fault condition has been in effect for some minimal interval of time. |
| MIN_VALUE |
Numeric |
20 |
The low threshold. |
| MAX_VALUE |
Numeric |
100 |
The high threshold. |
| VARIANCE |
Numeric |
0.01 |
The variance threshold. |
2.5.8.2 - Chilled Water Return Temperature Sensor Failure
Summary
The chilled water return temperature sensor has failed. The temperature sensor point is invariant or is outside the expected range.
| Equipment Type |
Equipment Tag Constraints |
Tuple Constraints |
| chilled water plant |
-- |
-- |
Input Points
| Name |
Point Template |
Positional Requirements |
Optionality |
Multiplicity |
| Chilled Water Return Temperature |
ChWRTemp |
This point must be a direct child of the equipment that the rule is attached to. |
Mandatory |
Scalar |
| Chiller Status |
ChrSts |
This point must be a direct child of a chiller. |
Mandatory |
Vector |
| Chilled Water Pump Status |
ChWCPSts |
This point must be a direct child of the chiller. |
Mandatory |
Vector |
Input Constants
| Name |
Data Type |
Default Value |
Description |
| Delay |
Numeric |
120 |
The delay represents a span of time in minutes during which the sensor must be in a fault state before the rule starts to actually report that it is in a fault state. The intent of the delay is to reduce the level of alert noise by ensuring that the system does not alert until the fault condition has been in effect for some minimal interval of time. |
| MIN_VALUE |
Numeric |
20 |
The low threshold. |
| MAX_VALUE |
Numeric |
70 |
The high threshold. |
| VARIANCE |
Numeric |
0.01 |
The variance threshold |
2.5.9.1 - Condenser Water Leaving Temperature Sensor Failure
Summary
The condenser water leaving temperature sensor has failed. The temperature sensor point is invariant or is outside the expected range.
| Equipment Type |
Equipment Tag Constraints |
Tuple Constraints |
| chilled water plant |
-- |
-- |
Input Points
| Name |
Point Template |
Positional Requirements |
Optionality |
Multiplicity |
| Chilled Water Leaving Temperature |
ChWLTemp |
This point must be a direct child of the equipment that the rule is attached to. |
Mandatory |
Scalar |
| Chiller Status |
ChrSts |
This point must be a direct child of a chiller. |
Mandatory |
Vector |
| Chilled Water Pump Status |
ChWCPSts |
This point must be a direct child of the chiller. |
Mandatory |
Vector |
Input Constants
| Name |
Data Type |
Default Value |
Description |
| Delay |
Numeric |
120 |
The delay represents a span of time in minutes during which the sensor must be in a fault state before the rule starts to actually report that it is in a fault state. The intent of the delay is to reduce the level of alert noise by ensuring that the system does not alert until the fault condition has been in effect for some minimal interval of time. |
| MIN_VALUE |
Numeric |
35 |
The low threshold. |
| MAX_VALUE |
Numeric |
100 |
The high threshold. |
| VARIANCE |
Numeric |
0.01 |
The variance threshold. |
2.5.9.2 - Condenser Water Entering Temperature Sensor Failure
Summary
The condenser water leaving temperature sensor has failed. The temperature sensory point is invariant or is outside the expected range.
| Equipment Type |
Equipment Tag Constraints |
Tuple Constraints |
| chilled water plant |
-- |
-- |
Input Points
| Name |
Point Template |
Positional Requirements |
Optionality |
Multiplicity |
| Chilled Water Entering Temperature |
ChWETemp |
This point must be a direct child of the equipment that the rule is attached to. |
Mandatory |
Scalar |
| Chiller Status |
ChrSts |
This point must be a direct child of a chiller. |
Mandatory |
Vector |
| Chilled Water Pump Status |
ChWCPSts |
This point must be a direct child of the chiller. |
Mandatory |
Vector |
Input Constants
| Name |
Data Type |
Default Value |
Description |
| Delay |
Numeric |
120 |
The delay represents a span of time in minutes during which the sensor must be in a fault state before the rule starts to actually report that it is in a fault state. The intent of the delay is to reduce the level of alert noise by ensuring that the system does not alert until the fault condition has been in effect for some minimal interval of time. |
| MIN_VALUE |
Numeric |
35 |
The low threshold. |
| MAX_VALUE |
Numeric |
100 |
The high threshold. |
| VARIANCE |
Numeric |
0.01 |
The variance threshold. |
2.5.10.1 - Outside Air Temperature Sensor Failure
Summary
The outside air temperature sensor has failed. The temperature sensor point is invariant or is outside the expected range.
| Equipment Type |
Equipment Tag Constraints |
Tuple Constraints |
| chilled water plant |
-- |
-- |
Input Points
| Name |
Point Template |
Positional Requirements |
Optionality |
Multiplicity |
| Outside Air Temperature |
OaTemp |
This point must be a direct child of the equipment that the rule is attached to. |
Mandatory |
Scalar |
Input Constants
| Name |
Data Type |
Default Value |
Description |
| Delay |
Numeric |
60 |
The delay represents a span of time in minutes during which the sensor must be in a fault state before the rule starts to actually report that it is in a fault state. The intent of the delay is to reduce the level of alert noise by ensuring that the system does not alert until the fault condition has been in effect for some minimal interval of time. |
| MIN_VALUE |
Numeric |
-40 |
The low threshold. |
| MAX_VALUE |
Numeric |
130 |
The high threshold. |
| VARIANCE |
Numeric |
0.01 |
The variance threshold. |
2.5.11.1 - Primary Loop Chilled Water Differential Pressure Setpoint is Excessive
Summary
All chilled water control valves are less than 100% open, not taking full advantage of the reset differential pressure setpoint.
| Equipment Type |
Equipment Tag Constraints |
Tuple Constraints |
| chilled water plant |
-- |
-- |
Input Points
| Name |
Point Template |
Positional Requirements |
Optionality |
Multiplicity |
| Cooling Command Primary Heat Exchanger |
ClgCmdPrimaryHX |
This point must be a direct child of the equipment that the rule is attached to. |
Optional |
Vector |
| Chilled Water Pressure Differential Setpoint |
ChWPressDiffSp |
This point must be a direct child of the equipment that the rule is attached to. |
Mandatory |
Scalar |
| Chilled Water Supply Temperature |
ChWSTemp |
This point must be a direct child of the equipment that the rule is attached to. |
Mandatory |
Scalar |
| Chilled Water Setpoint |
ChWSp |
This point must be a direct child of a chiller. |
Mandatory |
Scalar |
| Chilled Water Pressure Differential |
ChWPressDiff |
This point must be a direct child of the equipment that the rule is attached to. |
Mandatory |
Scalar |
| Chilled Water Pressure Differential Setpoint |
ChWCPStsChiller |
This point must be a direct child of a chiller. |
Optional |
Scalar |
| Cooling Command |
ClgCmdAhu |
This point must be a direct child of the equipment that the rule is attached to. |
Optional |
Vector |
| AHU Discharge Fan Status |
DaFanStsAHU |
This point must be a direct child of the equipment that the rule is attached to. |
Optional |
Vector |
| Fan Status |
FanSts |
This point must be a direct child of the equipment that the rule is attached to. |
Optional |
Vector |
| Cooling Command |
ClgCmdFcu |
This point must be a direct child of the equipment that the rule is attached to. |
Optional |
Vector |
| Secondary Heat Exchanger Cooling Command |
ClgCmdSecondaryHx |
This point must be a direct child of the equipment that the rule is attached to. |
Optional |
Vector |
| Secondary Loop Cooling Command |
ClgCmdSecondaryLoop |
This point must be a direct child of the rule that it is attached to. |
Optional |
Scalar |
| Primary Heat Exchanger Chilled Water Pump Status |
ChWCPStsPrimaryHx |
This point must be a direct child of the rule that it is attached to. |
Optional |
Vector |
| Discharge Fan Status |
DaFanStsUv |
This point must be a direct child of the rule that it is attached to. |
Optional |
Vector |
| Cooling Command |
ClgCmdUv |
This point must be a direct child of the rule that it is attached to. |
Optional |
Vector |
| Secondary Heat Exchanger Chilled Water Pump Status |
ChWCPStsSecondaryHx |
This point must be a direct child of the rule that it is attached to. |
Optional |
Vector |
| Secondary Loop Chilled Water Pump Status |
ChWCPStsSecondaryLoop |
This point must be a direct child of the rule that it is attached to. |
Optional |
Vector |
Input Constants
| Name |
Data Type |
Default Value |
Description |
| Delay |
Numeric |
15 |
The delay represents a span of time in minutes during which the sensor must be in a fault state before the rule starts to actually report that it is in a fault state. The intent of the delay is to reduce the level of alert noise by ensuring that the system does not alert until the fault condition has been in effect for some minimal interval of time. |
| Heat Exchanger Cooling Command Threshold |
Numeric |
0 |
|
| Chilled Water Temperature Error Threshold |
Numeric |
2 |
|
| Maximum Chilled Water Valve Threshold |
Numeric |
90 |
|
| Differential Pressure Error Threshold |
Numeric |
2 |
|
2.5.12.1 - Chilled Water Setpoint Can Be Increased (Reset)
Summary
Where DDC is used to control valves, the chilled water supply temperature set point shall be reset based on valve positions until one valve is nearly wide open or set-point limits of the system equipment or application have been reached. This would exclude control valves on a secondary loop, which has a control valve to maintain a higher chilled water supply temperature setpoint, but the secondary main control valve should be looked at, when determining the chilled water supply temperature reset value. Chilled water supply temperature reset is required by ASHRAE Standard 90.1.
| Equipment Type |
Equipment Tag Constraints |
Tuple Constraints |
| chiller |
-- |
-- |
Input Points
| Name |
Point Template |
Positional Requirements |
Optionality |
Multiplicity |
| Chiller Enable |
ChrEnab |
This point must be a direct child of a chiller. |
Mandatory |
Vector |
| VAV Cooling Command |
ClgCmd |
This point must be a direct child of an ahu/fcu. |
Mandatory |
Vector |
| Chilled Water Pump Status |
ChWCPSts |
This point must be a direct child of a chiller. |
Optional |
Vector |
| Discharge Air Fan Status |
DaFanSts |
This point must be a direct child of an ahu/fcu. |
Optional |
Vector |
| Return Air Humidity |
RaHumidity |
This point must be a direct child of an ahu/fcu. |
Optional |
Vector |
| Chilled Water Pump Status |
ChWCPSts |
This point must be a direct child of a chiller. |
Optional |
Vector |
| Chilled Water Pump Status |
ChWCPSts |
This point must be a direct child of a hx. |
Optional |
Vector |
| Cooling Command |
ClgCmd |
This point must be a direct child of a hx. |
Optional |
Vector |
Input Constants
| Name |
Data Type |
Default Value |
Description |
| Delay |
Numeric |
60 |
The delay represents a span of time in minutes during which the sensor must be in a fault state before the rule starts to actually report that it is in a fault state. The intent of the delay is to reduce the level of alert noise by ensuring that the system does not alert until the fault condition has been in effect for some minimal interval of time. |
| Valve Threshold |
Numeric |
90 |
The cooling valve threshold. |
| Cooling Equipment Percent |
Numeric |
100 |
Percent of cooling equipment valves below threshold. |
| Return Air Humidity |
Numeric |
55 |
Return air humidity high limit. The return air humidity must be less than this constant for a period greater than delay for a fault to exist. |
| Heat Exchanger Cooling Command |
Numeric |
0 |
Heat Exchanger command. The ClgCmd must be greater than this constant for a period longer than delay for a fault to exist. |
2.5.12.2 - Secondary Loop Chilled Water Supply Temperature Setpoint Could be Raised
Summary
Where DDC is used to control valves, the chilled water supply temperature set point shall be reset based on valve position until one valve is nearly wide open or set-point limits of the system equipment or application have been reached. This would exclude control valves on a secondary loop, which has a control valve to maintain a higher chilled water supply temperature setpoint, but the secondary main control valve should be looked at, when determining the chilled water supply reset value. Chilled water supply temperature reset is required by ASHRAE Standard 90.1-2016, Section 6.5.4.4.
| Equipment Type |
Equipment Tag Constraints |
Tuple Constraints |
| chilled water plant |
-- |
-- |
Input Points
| Name |
Point Template |
Positional Requirements |
Optionality |
Multiplicity |
| Chilled Water Supply Temperature |
ChWSTemp |
This point must be a direct child of the equipment that the rule is attached to. |
Mandatory |
Scalar |
| Chiller Status |
ChrSts |
This point must be a direct child of a chiller. |
Mandatory |
Vector |
| AHU Discharge Fan Status |
DaFanSts |
This point must be a direct child of the equipment that the rule is attached to. |
Optional |
Vector |
| Return Air Humidity |
RaHumidity |
This point must be a direct child of a chiller. |
Optional |
Vector |
| Chilled Water Setpoint |
ChWSp |
This point must be a direct child of the equipment that the rule is attached to. |
Mandatory |
Scalar |
| Chilled Water Supply Temperature |
ChWSTemp |
This point must be a direct child of the equipment that the rule is attached to. |
Mandatory |
Scalar |
| Chiller Chilled Water Pump Status |
ChWCPStsChiller |
This point must be a direct child of the equipment that the rule is attached to. |
Mandatory |
Vector |
| Primary Heat Exchange Chilled Water Pump Status |
ChWCPStsPrimaryHx |
This point must be a direct child of the equipment that the rule is attached to. |
Optional |
Vector |
| Primary Heat Exchange Cooling Command |
ClgCmdPrimaryHx |
This point must be a direct child of the equipment that the rule is attached to. |
Optional |
Vector |
| AHU Cooling Command |
ClgCmdAhu |
This point must be a direct child of the equipment that the rule is attached to. |
Optional |
Vector |
| Return Air High Humidity Setpoint |
RaHighHumiditySp |
This point must be a direct child of the equipment that the rule is attached to. |
Optional |
Vector |
| FCU Cooling Command |
ClgCmdFcu |
This point must be a direct child of the equipment that the rule is attached to. |
Optional |
Vector |
| Fan Status |
FanSts |
This point must be a direct child of the equipment that the rule is attached to. |
Optional |
Vector |
| Cooling Command |
ClgCmdUv |
This point must be a direct child of the equipment that the rule is attached to. |
Optional |
Vector |
| Discharge Air Fan Status |
DaFanStsUv |
This point must be a direct child of the equipment that the rule is attached to. |
Optional |
Vector |
| Tertiary Heat Exchanger Cooling Command |
ClgCmdTertiaryHx |
This point must be a direct child of the equipment that the rule is attached to. |
Optional |
Vector |
| Tertiary Heat Exchanger Chilled Water Pump Status |
ChWCPStsTertiaryHx |
This point must be a direct child of the equipment that the rule is attached to. |
Optional |
Vector |
| Tertiary Loop Cooling Command |
ClgCmdTertiaryLoop |
This point must be a direct child of the equipment that the rule is attached to. |
Optional |
Vector |
| Tertiary Loop Chilled Water Pump Status |
ChWCPStsTertiaryLoop |
This point must be a direct child of the equipment that the rule is attached to. |
Optional |
Vector |
Input Constants
| Name |
Data Type |
Default Value |
Description |
| Delay |
Numeric |
60 |
The delay represents a span of time in minutes during which the sensor must be in a fault state before the rule starts to actually report that it is in a fault state. The intent of the delay is to reduce the level of alert noise by ensuring that the system does not alert until the fault condition has been in effect for some minimal interval of time. |
| Heat Exchanger Cooling Command Threshold |
Numeric |
0 |
|
| Chilled Water Temperature High Limit Threshold |
Numeric |
50 |
|
| Chilled Water Temperature Error Threshold |
Numeric |
2 |
|
| Maximum Chilled Water Valve Threshold |
Numeric |
90 |
|
