HVAC Control System Fault Detection and Diagnostic

This article is about general and Fault Detection and Diagnostic for HVAC Control System used in Integrated Automation System or Building Automation System.

HVAC Control System Fault Detection and Diagnostic

AHU Cooling and Heating Cycling
1. Description:
  - Finds periods when the heating and cooling are cycling between each other within a threshold. This indicates that the unit is fighting back and forth between its mechanical components. Fault dependencies and associated scenarios include the following;
  - The fault rule will make sure any chilled water pump, from the chiller plant, is on if a cooling valve is utilized.
  - Will also make sure any hot water pump, from the boiler plant, is on if a heating valve is utilized.
  - If served by a steam plant, the rule will make sure steam pressure is over a threshold.
2. Requirements:
  - AHU: This rule is applied to only RTU or AHU equipment
  - Discharge Fan Status or Discharge Fan Command: Fan command will suffice, but status is used as primary
  - Cooling Valve or Cooling Stage: This can either be a numeric cooling valve position or a Boolean cooling stage
  - Heating Valve or Heating Stage: This can either be a numeric heating valve position or a Boolean heating stage
  - Chilled Water Pump (optional): Any chilled water pump command or status from the chiller plant. If Cooling stage is used, chilled water pump is not necessary.
  - Hot Water Pump (optional): Any hot water pump command or status from the hot water plant. If heating stage is used, hot water pump is not necessary.
  - Steam Pressure (optional): Steam pressure if served from a steam plant
AHU Cooling and Heating Simultaneously
1. Description:
  - Finds periods over a duration when discharge fan is on, heating is on and cooling is on. Fault dependencies and associated scenarios include the following;
  - Heating is on when the hot water valve is greater than a threshold or any heating stage is on.
  - Cooling is on when the chilled water valve is greater than a threshold or any cooling stage is on.
  - Fault rule will check to see if the unit is in dehumidification mode and will not check for cooling failure periods during this time.
  - Fault rule will ensure any chilled water pump, from the chiller plant, is on if a cooling valve is utilized.
  - Will also make sure any hot water pump, from the boiler plant, is on if a heating valve is utilized.
  - If served by a steam plant will make sure steam pressure is over a threshold.
2. Requirements:
  - AHU: This rule is applied to only RTU or AHU equipment
  - Discharge Fan Status or Discharge Fan Command: Fan command will suffice, but status is used as primary
  - Cooling Valve or Cooling Stage: This can either be a numeric cooling valve position or a Boolean cooling stage
  - Heating Valve or Heating Stage: This can either be a numeric heating valve position or a Boolean heating stage
  - Dehumidification Mode (optional): Dehumidification mode point to know when the unit is in a dehumidification sequencing mode
  - Chilled Water Pump (optional): Any chilled water pump command or status from the chiller plant. If Cooling stage is used, chilled water pump is not necessary.
  - Hot Water Pump (optional): Any hot water pump command or status from the hot water plant. If heating stage is used, hot water pump is not necessary.
  - Steam Pressure (optional): Steam pressure if served from a steam plant
AHU Cooling Failure
1. Description:
  - Finds periods over a certain duration when the discharge fan is on, cooling is on, and discharge temperature sensor is not registering below the mixed air sensor level minus a threshold. Fault dependencies and associated scenarios include the following;
  - Cooling is on when the chilled water valve is greater than a threshold or any cooling stage is on.
  - If mixed air sensor does not exist, return air temperature can be used.
  - If return air temperature does not exist zone temperature sensor can be used. Will also make sure any chilled water pump, from the chiller plant, is on during this period if a cooling valve is utilized.
  - Will also check to see if the unit is in dehumidification mode and not check for cooling failure periods during this time.
  - On a face bypass unit, when the cooling valve is in the face, the face bypass damper must be open to the face more than a threshold.
2. Requirements:
  - AHU: This rule is applied to only RTU or AHU equipment
  - Discharge Fan Status or Discharge Fan Command: Fan command will suffice, but status is used as primary
  - Cooling Valve or Cooling Stage: This can either be a numeric cooling valve position or a Boolean cooling stage
  - Discharge Temperature: Discharge air temperature
  - Mixed Air Temperature: Mixed air temperature. If not found will fall back to return air temperature. If not found and the unit is a 100% outside air unit will use outside air temperature. If not a 100% outside air unit will fall back to zone air temperature.
  - Chilled Water Pump: Any chilled water pump command or status from the chiller plant. If Cooling stage is used, chilled water pump is not necessary.
  - Dehumidification Mode (optional): Dehumidification mode point to know when the unit is in a dehumidification sequencing mode
  - Face Bypass Damper (optional): The face bypass damper position of the unit. Will be interpreted as percent open to the face. (Only if the cooling valve is in the face)
AHU Cooling

Valve Leaking
1. Description:
  - Generates a fault when discharge fan is on, cooling valve is closed, and discharge temperature sensor is under mixed air sensor by a threshold.
  - Will use multiple valves/stages if present and ensure all are closed/off.
2. Requirements:
  - AHU: This rule is applied to only RTU or AHU equipment
  - Discharge Fan Status or Discharge Fan Command: Fan command will suffice, but status is used as primary
  - Cooling Valve or Pre Cooling Valve: Numeric cooling valve position
  - Discharge Temperature: Discharge air temperature
AHU Discharge

Fan Failure
1. Description:
  - Generates a fault when discharge fan is on and duct static pressure is below a threshold.
2. Requirements:
  - AHU: This rule is applied to only RTU or AHU equipment
  - Discharge Fan Status or Discharge Fan Command: Fan command will suffice, but status is used as primary
  - Discharge Pressure: Duct static pressure
AHU Discharge Pressure Set point Unreachable
1. Description:
  - Finds periods over a duration when discharge fan is on and discharge pressure is below or above the discharge pressure set point by a threshold.
2. Requirements:
  - AHU: This rule is applied to only RTU or AHU equipment
  - Discharge Fan Status or Discharge Fan Command: Fan command will suffice, but status is used as primary
  - Discharge Pressure: Discharge pressure of the AHU
  - Discharge Pressure set point: Discharge pressure set point of the AHU
AHU Discharge Pressure Unstable
1. Description:
  - Generates a fault when the discharge fan is on and the discharge pressure bounces above and below the discharge pressure set point by a dead band. Fault dependencies and associated scenarios include the following;
  - Periods are only found when the pressure crosses (above and below) the set point by the dead band more than the given amount of crosses in any window period.
2. Requirements
  1. AHU: This rule is applied to only RTU or AHU equipment
AHU Economizing and Cooling Simultaneously
1. Description:
  - Finds periods over a duration when discharge fan is on, outdoor damper is open more than a threshold and cooling is on. Fault dependencies and associated scenarios include the following;
  - Cooling is on when the chilled water valve is greater than a threshold or any cooling stage is on.
  - This rule is not applicable in some sequences where the unit takes advantage of both free cooling and mechanical cooling at the same time.
2. Requirements:
  - AHU: This rule is applied to only RTU or AHU equipment
  - Discharge Fan Status or Discharge Fan Command: Fan command will suffice, but status is used as primary
  - Outside Damper Status or Outside Damper Command: Outside damper position
  - Discharge Fan Status or Discharge Fan Command: Fan command will suffice, but status is used as primary
  - Cooling Valve or Cooling Stage: This can either be a numeric cooling valve position or a Boolean cooling stage
AHU Economizing and Heating Simultaneously
1. Description:
  - Finds periods over a duration when discharge fan is on, outdoor damper is open more than a threshold and heating is on. Fault dependencies and associated scenarios include the following;
  - Heating is on when the hot water valve is greater than a threshold or any heating stage is on.
  - On a face bypass unit, the face bypass damper must be open to the face more than a threshold.
  - If the unit has outside airflow, the outside airflow must be above the set point by a threshold.
  - If the unit only has minimum outside airflow, the minimum outside airflow must be above the set point by a threshold.
  - If the unit has return co2 and return co2 set point, the return co2 must be below the return co2 set point by more than a threshold.
2. Requirements:
  1. AHU: This rule is applied to only RTU or AHU equipment
  2. Discharge Fan Status or Discharge Fan Command: Fan command will suffice, but status is used as primary
  3. Outside Damper Status or Outside Damper Command: Outside damper position
  4. Heating Valve or Heating Stage: This can either be a numeric heating valve position or a Boolean heating stage
  5. Hot Water Pump: Any hot water pump command or status from the hot water plant. If heating stage is used, hot water pump is not necessary.
  6. Steam Pressure (optional): Steam pressure if served from a steam plant
  7. Face Bypass Damper (optional): The face bypass damper position of the unit. Will be interpreted as percent open to the face.
  8. Outside Airflow (optional): The outside airflow of the unit
  9. Outside Airflow Set point (optional): The outside airflow set point of the unit
  10. Minimum Outside Airflow (optional): The minimum outside airflow of the unit
AHU Excessive Outside Air During Unoccupied Periods
1. Description:
  - Generates a fault when the discharge fan is on and the outside damper or minimum outside damper is open during unoccupied periods. Fault dependencies and associated scenarios include the following;
  - If the outside temperature is below a threshold, then the unit must be heating to create a fault (economizing for free cooling during un-occupancy would be acceptable).
2. Requirements:
  - AHU: This rule is applied to only RTU or AHU equipment that are not; 100% outside air, cold deck / hot deck units, or heat wheel units
  - Discharge Fan Status or Discharge Fan Command: Fan command will suffice, but status is used as primary
  - Outside Damper Status or Outside Damper Command: Outside damper position
  - Minimum Outside Damper Status or Command (optional): Minimum outside damper position
  - Occupancy: Occupancy of the piece of equipment
  - Heating Valve or Heating Stage: This can either be a numeric heating valve position or a Boolean heating stage
  - Outside Air Temperature: Outside air temperature of the AHU. If nonexistent the building outside air temperature will be used.
AHU Heating Failure
1. Description:
  - Finds periods over a duration when the discharge fan is on, heating is on, and the discharge temperature sensor value is not greater than the mixed air sensor level (plus a threshold). Fault dependencies and associated scenarios include the following;
  - Heating is on when the hot water valve is greater than a threshold or any heating stage is on.
  - If mixed air sensor does not exist, return air temperature can be used.
  - If return air temperature does not exist zone temperature sensor can be used.
  - Fault will make sure any hot water pump, from the hot water plant, is on during this period if a heating valve is utilized.
  - If served by a steam plant will make sure steam pressure is over a threshold.
  - Fault will also check to see if the unit is in dehumidification mode and not check for cooling failure periods during this time.
  - On a face bypass unit, the face bypass damper must be open to the face more than a threshold.
2. Requirements:
  - AHU: This rule is applied to only RTU or AHU equipment
  - Discharge Fan Status or Discharge Fan Command: Fan command will suffice, but status is used as primary
  - Heating Valve or Heating Stage: This can either be a numeric heating valve position or a Boolean heating stage
  - Discharge Temperature: Discharge air temperature
  - Mixed Air Temperature: Mixed air temperature. If not found will fall back to return air temperature. If not found and the unit is a 100% outside air unit will use outside air temperature. If not a 100% outside air unit will fall back to zone air temperature.
  - Hot Water Pump: Any hot water pump command or status from the hot water plant. If heating stage is used, hot water pump is not necessary.
  - Steam Pressure (optional): Steam pressure if served from a steam plant
  - Heat Exchanger Valves (optional): Valves that control heat exchanger temperatures if needed to check when it should be operational
  - Dehumidification Mode (optional): Dehumidification mode point to know when the unit is in a dehumidification sequencing mode
  - Face Bypass Damper (optional): The face bypass damper position of the unit. Will be interpreted as percent open to the face.
AHU Heating Valve Leaking
1. Description:
  - Generates a fault when discharge fan is on, heating valve is closed, and discharge temperature sensor is above mixed air sensor by a threshold. Fault dependencies and associated scenarios include the following;
  - Will use multiple valves/stages if they exist and make sure they are all closed/off.
2. Requirements:
  - AHU: This rule is applied to only RTU or AHU equipment
  - Discharge Fan Status or Discharge Fan Command: Fan command will suffice, but status is used as primary
  - Heating Valve, Pre Heating Valve, or Re Heating Valve: Numeric heating valve position
  - Discharge Temperature: Discharge air temperature
  - Mixed Air Temperature: Mixed air temperature. If not found and the unit is a 100% outside air unit will use outside air temperature. If unit is a 100% return air unit will use return air and if return air is not found will fall back to zone air temperature.
AHU Outdoor Damper Stuck Closed
1. Description:
  - Generates a fault when discharge fan is on, outside damper is greater than a threshold and the calculated outside air percentage is lower by more than a percentage. Fault dependencies and associated scenarios include the following;
  - The outside air percentage will be calculated using the return air temperature, mixed air temperature, and outside air temperature sensor.
  - If the mixed air temperature sensor is not available, then the discharge air temperature sensor will be used when cooling and heating are both off.
  - If the return air temperature sensor is not available, then the zone air temperature sensor will be used.
  - Will not find these periods when the outside air temperature sensor is within a threshold of the return air temperature sensor.
2. Requirements:
  - AHU: This rule is applied to only RTU or AHU equipment
  - Discharge Fan Status or Discharge Fan Command: Fan command will suffice, but status is used as primary
  - Outside Damper Status or Outside Damper Command: Outside damper position
  - Return Air Temperature or Zone Air Temperature: Zone temperature will only be used if return air temperature is not available.
  - Mixed Air Temperature or Discharge Air Temperature: Discharge temperature will only be used if mixed air temperature is not available.
  - Outside Air Temperature: Outside air temperature of the AHU. If nonexistent the building outside air temperature will be used.
AHU Outdoor Damper Stuck Open
1. Description:
  - Generates a fault when discharge fan is on, outside damper is lower than a threshold and the calculated outside air percentage is higher by more than a percentage. Fault dependencies and associated scenarios include the following;
  - The outside air percentage will be calculated using the return air temperature, mixed air temperature, and outside air temperature sensor.
  - If the mixed air temperature sensor is not available, then the discharge air temperature sensor will be used when cooling and heating are both off.
  - If the return air temperature sensor is not available, then the zone air temperature sensor will be used.
  - Will not find these periods when the outside air temperature sensor is within a threshold of the return air temperature sensor.
  - If a minimum outdoor damper exists, this will be added to the outside damper position, as a percentage of total outside air intake.
2. Requirements:
  - AHU: This rule is applied to only RTU or AHU equipment
  - Discharge Fan Status or Discharge Fan Command: Fan command will suffice, but status is used as primary
  - Outside Damper Status or Outside Damper Command: Outside damper position
  - Return Air Temperature or Zone Air Temperature: Zone temperature will only be used if return air temperature is not available.
  - Mixed Air Temperature or Discharge Air Temperature: Discharge temperature will only be used if mixed air temperature is not available.
AHU Low Outside Airflow
1. Description
  - Generates a fault when the discharge fan is on and the outside airflow is below the outside airflow set point during occupancy.
2. Requirements:
  - AHU: This rule is applied to only RTU or AHU equipment
  - Discharge Fan Status or Discharge Fan Command: Fan command will suffice, but status is used as primary
  - Outside Airflow: The outside airflow of the unit
  - Outside Airflow Set point: The outside airflow set point of the unit
  - Occupancy: Occupancy of the piece of equipment
AHU Unstable Outside Airflow
1. Description:
  - Generates a fault when the discharge fan is on and the outside airflow bounces above and below the outside airflow set point by a dead band. Fault dependencies and associated scenarios include the following;
  - Periods are only found when the airflow crosses (above and below) the set point by the dead band more than the given amount of crosses in any window period.
2. Requirements:
  - AHU: This rule is applied to only RTU or AHU equipment
  - Discharge Fan Status or Discharge Fan Command: Fan command will suffice, but status is used as primary
  - Outside Airflow: The outside airflow of the unit
  - Outside Airflow Set point: The outside airflow set point of the unit
AHU Unit on Discharge Fan is Off
1. Description:
  - Generates a fault when discharge fan is off and anything is on; hot water valve is more than a threshold, any heating stage is on, chilled water valve is more than a threshold, or any cooling stage is on. Fault dependencies and associated scenarios include the following;
  - Both cooling and heating are not required, but one or the other is required for this rule to run successfully.
2. Requirements:
  - AHU: This rule is applied to only RTU or AHU equipment
  - Discharge Fan Status or Discharge Fan Command: Fan command will suffice, but status is used as primary
  - Cooling Valve or Cooling Stage (optional): This can either be a numeric cooling valve position or a Boolean cooling stage
  - Heating Valve or Heating Stage (optional): This can either be a numeric heating valve position or a Boolean heating stage
Bad Energy Data
1. Description:
  - Find periods for at least a duration when data contains values outside of low and high limits or the data is NaN. Fault dependencies and associated scenarios include the following;
  - All data will be imported into the SCMS ‘as is’ from its existing system.
2. Requirements
  - Consumption or Demand Point: Any point that has consumption or demand type units
Building Floor Running Too Late
1. Description:
  - Finds periods over a duration after occupancy is over, when the demand of a particular floor does not drop off by at least a percentage or threshold. Fault dependencies and associated scenarios include the following;
  - A shutdown window can be specified for an allotted time to wait until after occupancy to check for the decrease in demand. This makes sure that a particular floor is shutting down when occupancy is over and equipment is not manually operating or overridden.
2. Requirements:
  1. Floor Lighting Submeter: Any floor lighting submeter meter of the site
  2. Floor Power Submeter: Any floor power submeter meter of the site
  3. Floor Lighting Demand: The demand of the floor lighting submeter
  4. Floor Power Demand: The demand of the floor power submeter
  5. Occupancy: Occupancy or schedule for the building
Building Floor Starting Too Early
1. Description:
  - Finds periods over a duration before building occupancy when the demand of a particular floor increases by a percentage or threshold. Fault dependencies and associated scenarios include the following;
  - A startup window can be specified for an allotted time before occupancy that demand is allowed to increase. This indicates that a particular floor is starting ahead of occupancy or too many pieces of equipment are coming on outside of normal occupancy on the associated floor.
2. Requirements:
  - Floor Lighting Submeter: Any floor lighting submeter meter of the site
  - Floor Power Submeter: Any floor power submeter meter of the site
  - Floor Lighting Demand: The demand of the floor lighting submeter
  - Floor Power Demand: The demand of the floor power submeter
  - Occupancy: Occupancy or schedule for the building
Boiler Cycling
1. Description:
  - Generates a fault when the boiler stays on or off for less than a duration.
2. Requirements:
  - Boiler: This rule is applied to only boiler equipment
  - Boiler Status or Boiler Command: Boiler on/off status
Boilers Running During Warm Weather
1. Description:
  - Finds periods when boilers are running and the outside air temperature is above a threshold.
2. Requirements:
  - Boiler Plant: This rule is applied to only boiler plant equipment
  - Boiler(s) Status or Boiler(s) Command: Boiler(s) on/off status
  - Outside Air Temperature: Outside air temperature of the Boiler Plant. If nonexistent the building outside air temperature will be used.
Cabinet/Door Heater Zone Temperature Out of Range
1. Description:
  - Finds periods for longer than a duration when the space temperature is less than or greater than, the heating temperature setpoint by a threshold. Fault dependencies and associated scenarios include the following;
  - If occupancy exists temperature will only be checked when occupancy is true.
2. Requirements:
  - Space Temperature: Space temperature adjacent to the cabinet/door heater
  - Heating Setpoint: Setpoint associated with the zone air temperature.
  - Occupancy (optional): Occupancy of the piece of equipment
  - Fan Status (is applicable): Fan status of the piece of equipment.
Chiller Cycling
1. Description:
  - Generates a fault when the chiller stays on or off for less than a pre-specified duration.
2. Requirements:
  - Chiller: This rule is applied to only chiller equipment
  - Chiller Status or Chiller Command: Chiller on/off status
Chilled Water Plant Demand Peak
1. Description:
  - Finds chilled water demand peaks throughout the day, as measured against a facility benchmark. Fault dependencies and associated scenarios include the following;
  - Looks for an increase in demand by a percentage or threshold and then an immediate decrease by a percentage or threshold. This increase and decrease in demand is looked at in consecutive historic data intervals to identify a short demand peak.
2. Requirements:
  - Chilled Water BTU Meter: Any meter, including main plant, data centers, E-rooms.
  - Electrical Submeter: Any meter
  - Demand: The demand of the meter (electrical only)
  - Chilled Water Plant Benchmark: BTUs and Electrical
Chilled Water Plant Pressure Setpoint Unreachable
1. Description:
  - Finds periods over a duration when the differential pressure is unable to maintain within a threshold of differential pressure set point, while any chilled water pump is on. Fault dependencies and associated scenarios include the following;
  - This will account for the pressure being too high or too low from set point.
  - If a freeze protection sequence is in place then will only Spark when any pump is over a speed threshold, but will still Spark anytime the outside air temperature is above a threshold.
  - If chilled water flows and flow min/max set points exist, then the flows must be above/below set points.
2. Requirements:
  - Chiller Plant: This rule is applied to only chiller plant systems
  - Pump Status or Pump Command: Pump on/off status. At least one pump is required to be able to check when water is flowing and trying to maintain set point.
  - Chilled Water Differential Pressure: The differential pressure of the chiller plant system
  - Chilled Water Differential Pressure Set point: The differential pressure set point of the chiller plant system
  - Outside Air Temperature (optional): Outside air temperature of the Chiller Plant. If nonexistent the building outside air temperature will be used.
  - Chilled Water Leaving Flow (optional): The secondary water leaving flow
  - Chilled Water Leaving Flow Min Set point (optional): The secondary water leaving flow minimum set point.
  - Chilled Water Leaving Flow Max Set point (optional): The secondary water leaving flow maximum set point.
  - Chiller Evaporator Leaving Flow (optional): The chiller(s) evaporator leaving flow
  - Chiller Evaporator Leaving Flow Min Set point (optional): The chiller(s) evaporator leaving flow minimum set point
  - Chiller Status (optional): The chiller(s) status or command. This is necessary if both chiller flow and chiller flow min set point is to be taken into consideration.
Chilled Water Plant Pressure Unstable
1. Description:
  - Finds periods when the secondary differential pressure bounces above and below the secondary differential pressure set point by a dead band. Fault dependencies and associated scenarios include the following;
  - Periods are only found when the differential pressure crosses (above and below) the set point by the dead band more than the given amount of crosses in any window period.
  - Must occur while any pump is on.
2. Requirements:
  - Chiller Plant: This rule is applied to only chiller plant systems
  - Pump Status or Pump Command: Pump on/off status. At least one pump is required to be able to check when water is flowing and trying to maintain set point.
  - Chilled Water Differential Pressure: The differential pressure of the chiller plant system
  - Chilled Water Differential Pressure Set point: The differential pressure set point of the chiller plant system
Chilled Water Plant Temperature Setpoint Unreachable
1. Description:
  - Finds periods when any chiller is on and the leaving CHW temperature is unable to reach a pre-specified threshold of the CHW supply setpoint for over a duration.
2. Requirements:
  - Chiller Plant: This rule is applied to only chiller plant systems
  - Chiller Status or Chiller Command: Chiller on/off status. At least one chiller is required to be able to check when chilled water is being chilled.
  - Chilled Water Plant Leaving Temperature: This is the chiller plant leaving water temperature that is being supplied to the building
Chilled Water Plant Leaving Temperature Unstable
1. Description:
  - Finds periods when the leaving CHW temperature bounces above and below the CHW supply temperature setpoint by a dead band. Fault dependencies and associated scenarios include the following;
  - Periods are only found when the leaving CHW temperature crosses (above and below) the set point by the dead band more than the given amount of crosses in any window period.
  - Must occur while any chiller is on.
2. Requirements:
  - Chiller Plant: This rule is applied to only chiller plant systems
  - Chiller Status or Chiller Command: Chiller on/off status.
  - Pump Status or Pump Command: Pump on/off status. At least one pump is required to be able to check when water is flowing and trying to maintain set point.
  - Leaving (Supply) Chilled Water Temperature
  - Chilled Water Temperature Set point: The chilled water setpoint of the chilled water plant
Chiller Running During Unoccupied Periods
1. Description:
  - Finds periods when any chiller is operating outside the normal occupancy schedule. Fault dependencies and associated scenarios include the following;
  - Will only violate if no AHU’s are running or if all AHU’s running has Return Air Temperatures under a certain threshold (cool temperatures) or if only X AHU’s are running with Return Air Temperatures above a threshold (warm temperatures).
  - The synopsis will also include any available records to indicate authorized overtime usage.
2. Requirements:
  - Chiller Plant: This rule is applied to only chiller plant systems
  - Chiller Status or Chiller Command: Chiller on/off status. At least one chiller is required to be able see if it is running.
  - Occupancy or Schedule: The chiller plant or site must have a schedule point record or an occupancy point record.
  - AHU’s: Air Handling Units attached to the chiller plant
  - AHU Return Air Temperature: Return Air Temperature for each of the attached AHU’s. If return air temperature is not available will fall back to zone temperature. This rule will not fail if not every AHU has a return air temperature.
CRAC Unit Cooling Setpoint Out of Range
1. Description:
  - Finds periods over a duration when the computer room temperature is unable to maintain a threshold above or below the cooling setpoint. Fault dependencies and associated scenarios include the following;
  - This is used to determine if the cooling set point can be maintained or whether it has been set too low and high.
2. Requirements:
  - Cooling Set point: A set point specifically for cooling associated with a CRAC unit.
  - Computer Room Temperature
CRAC Unit Relative Humidity Setpoint Out of Range
1. Description:
  - Finds periods over a duration when the computer room relative humidity is unable to maintain a threshold above or below the relative humidity setpoint. Fault dependencies and associated scenarios include the following;
  - This is used to determine if the relative humidity set point can be maintained.
2. Requirements:
  - Relative Humidity Set point: A set point specifically for cooling associated with a CRAC unit.
  - Computer Room Relative Humidity
Double Dipping Data
1. Description
  - Finds periods for at least a duration when a point’s history contains two or more data points within a leeway of an interval. Fault dependencies and associated scenarios include the following;
  - All data will be imported into the SCMS ‘as is’ from its existing system.
2. Requirements
  - Consumption or Demand Point: Any point that has consumption or demand type units
EF Not Running When Emergency Generator is Engaged
1. Description:
  - Generates a fault when any exhaust fan serving an emergency generator is not operating when the generator has been engaged. Fault dependencies and associated scenarios include the following;
  - Periods are only found when an emergency generator is operation.
2. Requirements:
  - Exhaust Fans serving Emergency Generators: This rule is applied to only EFs serving an emergency generator.
  - EF Status or EF Command: EF on/off status.
  - Emergency Generator Status or Command: On/off status
EF Not Running Under Thermostatic Control
1. Description:
  1. Finds periods when any exhaust fan controlled via thermostat is not operating when space temperature. Fault dependencies and associated scenarios include the following;
  2. Periods are only found when the EF operates per thermostatic command.
2. Requirements:
  1. Exhaust Fans w/ Space Thermostats: This rule is applied to only EFs are thermostatically controlled.
  2. EF Status or EF Command: EF on/off status.
  3. Space Temperature.
EF Running During Unoccupied Periods
1. Description:
  - Finds periods when any exhaust fan is operating outside the normal schedule. Fault dependencies and associated scenarios include the following;
  - Periods are only found when the EF is not scheduled to operate or during unoccupied hours.
2. Requirements:
  - Scheduled Exhaust Fan: This rule is applied to only EFs which operate per schedule command and excludes EFs that are thermostatically controlled.
  - EF Status or EF Command: EF on/off status.
  - Occupancy or Schedule: The EF must have a schedule point record or an occupancy point record.
Floor VAV Unstable Airflow
1. Description:
  - Generates a fault when the floor VAV is active and the supply airflow bounces above and below the airflow set point by a dead band. Fault dependencies and associated scenarios include the following;
  - Periods are only found when the airflow crosses (above and below) the set point by the dead band more than the given amount of crosses in any window period.
2. Requirements:
  - Floor VAV Distribution Terminals: This rule is applied to only floor VAV distribution terminals
  - Floor VAV Status or Command: Command will suffice, but status is used as primary
  - Supply Airflow: The supply airflow of the unit
  - Supply Airflow Setpoint: The supply airflow setpoint of the unit
Heat Exchanger Temp Setpoint Unreachable
1. Description:
  - Finds periods over a duration when the secondary leaving water temperature cannot get within a threshold of secondary leaving water temperature set point, while either a heat exchanger pump is on or a water system pump is on. Fault dependencies and associated scenarios include the following;
  - This will account for temperature being too high or too low from set point.
2. Requirements:
  - Heat Exchanger: This rule is only applied to heat exchanger equipment
  - Pump Status: Must have at least one heat exchanger pump or hot water system pump Boolean status point in order to determine when set point should be maintained
  - Water Temperature: Secondary leaving water temperature
  - Water Temperature Set point: Secondary leaving water temperature set point
  - Summer Winter Mode (optional): Point to determine when the HX is active based on season
  - Heat Exchanger Valves (optional): Valves that control heat exchanger temperatures if needed to check when it should be operational.
3. Heat Exchanger Temp Unstable
4. Description:
  - Generates a fault when the secondary leaving water temperature bounces above and below the secondary leaving water temperature set point by a dead band. Fault dependencies and associated scenarios include the following;
  - Periods are only found when the water temperature crosses (above and below) the set point by the dead band more than the given amount of crosses in any window period.
  - Must occur while either a heat exchanger pump is on or a water system pump is on.
5. Requirements:
  - Heat Exchanger: This rule is only applied to heat exchanger equipment
  - Pump Status: Must have at least one heat exchanger pump or hot water system pump Boolean status point in order to determine when set point should be maintained
  - Water Temperature: Secondary leaving water temperature
  - Water Temperature Set point: Secondary leaving water temperature set point
Hot Water Circ Pump Running
1. Description:
  - Generates a fault when hot water heating coil pumps are running and no secondary hot water pumps are running in the system.
2. Requirements:
  - Hot Water Circ Pump: This rule is applied to only heating coil circulation pumps
  - Hot Water Circ Pump Status or Command: Pump on/off status
  - Secondary Pump Status or Pump Command: Pump on/off status. At least one pump is required to be able to check when water is flowing.
Hot Water Plant Demand Peak
1. Description:
  - Finds hot water demand peaks throughout the day, as measured against a facility benchmark. Fault dependencies and associated scenarios include the following;
  - Looks for an increase in demand by a percentage or threshold and then an immediate decrease by a percentage or threshold. This increase and decrease in demand is looked at in consecutive historic data intervals to identify a short demand peak.
2. Requirements:
  - Meter: Any natural gas submeter
  - Hot Water Plant Benchmark: Natural gas
Hot Water Pressure Set Point Unreachable
1. Description:
  - Finds periods over a duration where the secondary differential pressure cannot get within a threshold of secondary differential pressure set point, while any hot water pump is on. Fault dependencies and associated scenarios include the following;
  - This will account for pressures being too high or too low from set point.
2. Requirements:
  - Boiler Plant: This rule is applied to only boiler plant systems
  - Pump Status or Pump Command: Pump on/off status. At least one pump is required to be able to check when water is flowing and trying to maintain set point.
  - Hot Water Differential Pressure: The differential pressure of the boiler plant system
  - Hot Water Differential Pressure Set point: The differential pressure set point of the boiler plant system
Hot Water Pressure Unstable
1. Description:
  - Finds periods when the secondary differential pressure bounces above and below the secondary differential pressure set point by a dead band. Fault dependencies and associated scenarios include the following;
  - Periods are only found when the differential pressure crosses (above and below) the set point by the dead band more than the given amount of crosses in any window period.
  - Must occur while any pump is on.
2. Requirements:
  - Boiler Plant: This rule is applied to only boiler plant systems
  - Pump Status or Pump Command: Pump on/off status. At least one pump is required to be able to check when water is flowing and trying to maintain set point.
  - Hot Water Differential Pressure: The differential pressure of the boiler plant system
  - Hot Water Differential Pressure Set point: The differential pressure set point of the boiler plant system
Hot Water Plant Temperature Setpoint Unreachable
1. Description:
  - Finds periods when any boiler is on and the leaving HW temperature is unable to reach a pre-specified threshold of the HW supply setpoint for over a duration.
2. Requirements:
  - Boiler Plant: This rule is applied to only boiler plant systems
  - Boiler Status or Boiler Command: Boiler on/off status. At least one boiler is required to be able to check when hot water is being conditioned.
  - Hot Water Plant Leaving Temperature: This is the boiler plant leaving water temperature that is being supplied to the building
Hot Water Plant Leaving Temperature Unstable
1. Description:
  - Finds periods when the leaving HW temperature bounces above and below the HW supply temperature setpoint by a dead band. Fault dependencies and associated scenarios include the following;
  - Periods are only found when the leaving HW temperature crosses (above and below) the set point by the dead band more than the given amount of crosses in any window period.
  - Must occur while any boiler is on.
2. Requirements:
  - Boiler Plant: This rule is applied to only boiler plant systems
  - Boiler Status or Boiler Command: Boiler on/off status.
  - Pump Status or Pump Command: Pump on/off status. At least one pump is required to be able to check when water is flowing and trying to maintain set point.
  - Leaving (Supply) Hot Water Temperature
  - Hot Water Temperature Set point: The hot water setpoint of the boiler plant
Missing Data
1. Description
  - Finds periods for at least a duration when a record’s history contains zero data points within a leeway of an interval. Fault dependencies and associated scenarios include the following;
  - All data will be imported into the SCMS ‘as is’ from its existing system.
2. Requirements
  - Consumption or Demand Point: Any point that has consumption or demand type units
Occupied Cooling Setpoint Out of Range
1. Description:
  - Finds periods over a duration when the occupied cooling set point is below a threshold. Fault dependencies and associated scenarios include the following;
  - This is used to determine if the zone occupied cooling set point has been set too low.
2. Requirements:
  - Zone Occupied Cooling Set point: A set point specifically for occupied cooling associated with a zone air temperature
Occupied Heating Setpoint Out of Range
1. Description:
  - Finds periods over a duration when the occupied heating set point is above a threshold. Fault dependencies and associated scenarios include the following;
  - This is used to determine if the zone occupied heating set point has been set too high.
2. Requirements:
  - Zone Occupied Heating Set point: A set point specifically for occupied heating associated with a zone air temperature
Pump Cycling
1. Description:
  - Finds periods when the pump stays on or off for less than a specified duration.
2. Requirements:
  - Pump: This rule is applied to only pump equipment
  - Pump Status or Pump Command: Pump on/off status
Sensor Failure
1. Description:
  - Finds periods over a duration when a sensor does not change by a threshold for a 24-hour period and equipment is running.
2. Requirements:
  1. Sensor: Any numerical data point
Short Demand Peak
1. Description:
  - Finds short demand peaks throughout the day, including natural gas and electricity. Fault dependencies and associated scenarios include the following;
  - Looks for an increase in demand by a percentage or threshold and then an immediate decrease by a percentage or threshold. This increase and decrease in demand is looked at in consecutive historic data intervals to identify a short demand peak.
2. Requirements:
  - Meter: Any meter
  - Demand: The demand of the meter (electrical only)
  - Utility Benchmark: Electrical and natural gas
Split System A/C Unit Cooling Setpoint Out of Range
1. Description:
  - Finds periods over a duration when the room or zone temperature is unable to maintain a threshold above or below the cooling setpoint. Fault dependencies and associated scenarios include the following;
  - This is used to determine if the cooling set point can be maintained or whether it has been set too low and high.
2. Requirements:
  - Cooling Setpoint: A set point specifically for cooling associated with a split system A/C unit.
  - Space Temperature
Terminal Unit Airflow Setpoint Unreachable
1. Description:
  - Finds periods over a duration when the discharge airflow cannot get within a threshold of discharge airflow set point (while the FCU fan is on).
2. Requirements:
  - Terminal Unit: This rule is applied to only VAV or DDT equipment
  - AHU Discharge Fan Status or Discharge Fan Command: AHU fan command will suffice, but status is used as primary
  - Discharge Airflow: Terminal unit discharge airflow
  - Discharge Airflow Set point: Terminal unit discharge airflow set point
  - Discharge Airflow Maximum Set point (optional): Terminal unit discharge airflow maximum set point. If available will be used to calculate an appropriate threshold.
Terminal Unit Airflow Unstable
1. Description:
  - Generates a fault when the discharge airflow bounces above and below the discharge airflow set point by a dead band. Fault dependencies and associated scenarios include the following;
  - Periods are only found when the discharge airflow crosses (above and below) the set point by the dead band more than the given amount of crosses in any window period.
  - Must occur while the AHUs discharge fan is on.
2. Requirements:
  - Terminal Unit: This rule is applied to only VAV or DDT equipment
  - AHU Discharge Fan Status or Discharge Fan Command: AHU fan command will suffice, but status is used as primary
  - Discharge Airflow: Terminal unit discharge airflow
  - Discharge Airflow Set point: Terminal unit discharge airflow set point
  - Discharge Airflow Maximum Set point (optional): Terminal unit discharge airflow maximum set point. If available will be used to calculate an appropriate dead band.
Terminal Unit Heating Failure
1. Description:
  - Generates a fault when the FCU fan is on (if applicable), heating is on, and discharge temperature sensor is not greater than the discharge air sensor plus a threshold. Fault dependencies and associated scenarios include the following;
  - Heating is on when the hot water valve is greater than a threshold or any heating stage is on.
  - Will also make sure any hot water pump, from the hot water plant, is on during this period if a heating valve is utilized.
  - If no pumps are available, the rule will not fail.
2. Requirements:
  - Terminal Unit: This rule is applied to only VAV, DDT, or PIU equipment
  - AHU Discharge Fan Status or Discharge Fan Command: AHU fan command will suffice, but status is used as primary
  - AHU Discharge Temperature: AHU discharge air temperature
  - Heating Valve or Heating Stage: This can either be a numeric heating valve position or a Boolean heating stage
  - Discharge Temperature: Discharge air temperature
  - Hot Water Pump (optional): Any hot water pump command or status from the hot water plant. If none are found it will not be incorporated into the rule
  - Steam Pressure (optional): Steam pressure if served from a steam plant
Terminal Unit Heating Valve Leaking
1. Description:
  - Generates a fault when FCU fan is on (if applicable), heating valve is closed, airflow is above a threshold, and the discharge temperature sensor is above discharge temperature by a threshold. Fault dependencies and associated scenarios include the following;
  - Will use multiple valves if they exist and make sure they are all closed.
2. Requirements:
  - Terminal Unit: This rule is applied to only VAV, DDT, or PIU equipment
  - AHU Discharge Fan Status or Discharge Fan Command: AHU fan command will suffice, but status is used as primary
  - AHU Discharge Temperature: AHU discharge air temperature
  - Heating Valve or Heating Stage: This can either be a numeric heating valve position or a Boolean heating stage
3. Terminal Unit Zone Temperature Out of Range
4. Description:
  - Finds periods for longer than a duration when the zone air temperature is less than or greater than, the zone set point(s) by a threshold. Fault dependencies and associated scenarios include the following;
  - If occupancy exists temperature will only be checked when occupancy is true.
5. Requirements:
  - Zone Air Temperature: Zone temperature of a piece of equipment
  - Zone Effective Set point or Zone Cooling Set point or Zone Heating Set point: Set point associated with the zone air temperature. This can either be one set point or a heating or cooling set point.
  - Occupancy (optional): Occupancy of the piece of equipment
  - Fan Status (optional): Fan status of the piece of equipment or the fan status of the AHU supply air to the piece of equipment.
Underfloor Heating Space Temperature Out of Range
1. Description:
  - Finds periods when the underfloor heating space temperature is less than or greater than the setpoint(s) by a threshold for longer than a duration. Fault dependencies and associated scenarios include the following;
  - If occupancy exists temperature will only be checked when occupancy is true.
2. Requirements:
  - Underfloor Space Temperature: Space temperature sensor serving underfloor heating system.
  - Underfloor Heating Space Temperature Setpoint: Setpoint associated with the underfloor heating system space temperatures.
  - Manifold Status or Command: Underfloor heating manifold is engaged.
  - Occupancy (optional): Occupancy of the piece of equipment
Unoccupied Cooling Set Point Out of Range
1. Description:
  - Finds periods over a duration when the unoccupied cooling set point is below a threshold. Fault dependencies and associated scenarios include the following;
  - This is used to determine if the zone unoccupied cooling set point has been set too low.
2. Requirements:
  - Zone Unoccupied Cooling Set point: A set point specifically for unoccupied cooling associated with a zone air temperature
Unoccupied Heating Set Point Out of Range
1. Description:
  - Finds periods over a duration when the unoccupied heating set point is above a threshold. Fault dependencies and associated scenarios include the following;
  - This is used to determine if the zone unoccupied heating set point has been set too high.
2. Requirements:
  - Zone Unoccupied Heating Set point: A set point specifically for unoccupied heating associated with a zone air temperature
3. Zone Cooling Damper Malfunction
4. Description:
  - Finds periods over a duration when the cooling damper is open above a threshold and the zone damper discharge air temperature is not within a threshold of the cold deck discharge air temperature. Fault dependencies and associated scenarios include the following;
  - The AHU discharge fan must be on during this period too.
5. Requirements:
  - Zone Damper: This rule is applied to only zone damper equipment
  - Zone Damper Discharge Temperature: Discharge temperature of the zone damper
  - Zone Damper Position: Position of the damper in the cold deck
  - AHU Cold Deck Discharge Temperature: Cold deck discharge temperature of the AHU serving the zone damper
  - AHU Discharge Fan Status or Discharge Fan Command: Fan command will suffice, but status is used as primary
Zone Heating Damper Malfunction
1. Description:
  - Finds periods over a duration when the heating damper is open above a threshold and the zone damper discharge air temperature is not within a threshold of the hot deck discharge air temperature. Fault dependencies and associated scenarios include the following;
  - The AHU discharge fan must be on during this period too.
2. Requirements:
  - Zone Damper: This rule is applied to only zone damper equipment.
  - Zone Damper Discharge Temperature: Discharge temperature of the zone damper.
  - Zone Damper Position: Position of the damper in the hot deck.
  - AHU Hot Deck Discharge Temperature: Hot deck discharge temperature of the AHU serving the zone damper.
  - AHU Discharge Fan Status or Discharge Fan Command: Fan command will suffice, but status is used as primary.
Zone Temperature Out of Range (Cooling)
1. Description:
  - Finds periods when the zone air temperature is less than the zone heating set point by a threshold, and discharge air temperature is less than the zone heating set point by a threshold for more than a duration.
2. Requirements:
  - AHU or Terminal Unit: This rule is applied to only AHU, VAV, ATU, DDT, or FPB equipment
  - Zone Air Temperature: Zone temperature of a piece of equipment
  - Discharge Air Temperature: Discharge temperature of a piece of equipment
  - Zone Effective Set point or Zone Heating Set point: Set point associated with the zone air temperature. This can either be the effective set point or the heating set point.
  - Occupancy (optional): Occupancy of the piece of equipment
  - Fan Status (optional): Fan status of the piece of equipment or the fan status of the AHU supply air to the piece of equipment.
Zone Temperature Out of Range (Heating)
1. Description:
  - Finds periods when the zone air temperature is more than the zone cooling set point by a threshold, and discharge air temperature is more than the zone cooling set point by a threshold for more than a duration.
2. Requirements:
  - AHU or Terminal Unit: This rule is applied to only AHU, VAV, ATU, DDT, or FPB equipment
  - Zone Air Temperature: Zone temperature of a piece of equipment
  - Discharge Air Temperature: Discharge temperature of a piece of equipment
  - Zone Effective Set point or Zone Cooling Set point: Set point associated with the zone air temperature. This can either be the effective set point or the cooling set point.
  - Occupancy (optional): Occupancy of the piece of equipment
  - Fan Status (optional): Fan status of the piece of equipment or the fan status of the AHU supply air to the piece of equipment.

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HVAC Control System Fault Detection and Diagnostic

AHU Cooling and Heating Cycling

AHU Cooling and Heating Simultaneously

AHU Cooling Failure

AHU Cooling

AHU Discharge

AHU Discharge Pressure Set point Unreachable

AHU Discharge Pressure Unstable

AHU Economizing and Cooling Simultaneously

AHU Economizing and Heating Simultaneously

AHU Excessive Outside Air During Unoccupied Periods

AHU Heating Failure

AHU Heating Valve Leaking

AHU Outdoor Damper Stuck Closed

AHU Outdoor Damper Stuck Open

AHU Low Outside Airflow

AHU Unstable Outside Airflow

AHU Unit on Discharge Fan is Off

Bad Energy Data

Building Floor Running Too Late

Building Floor Starting Too Early

Boiler Cycling

Boilers Running During Warm Weather

Cabinet/Door Heater Zone Temperature Out of Range

Chiller Cycling

Chilled Water Plant Demand Peak

Chilled Water Plant Pressure Setpoint Unreachable

Chilled Water Plant Pressure Unstable

Chilled Water Plant Temperature Setpoint Unreachable

Chilled Water Plant Leaving Temperature Unstable

Chiller Running During Unoccupied Periods

CRAC Unit Cooling Setpoint Out of Range

CRAC Unit Relative Humidity Setpoint Out of Range

Double Dipping Data

EF Not Running When Emergency Generator is Engaged

EF Not Running Under Thermostatic Control

EF Running During Unoccupied Periods

Floor VAV Unstable Airflow

Heat Exchanger Temp Setpoint Unreachable

Heat Exchanger Temp Unstable

Hot Water Circ Pump Running

Hot Water Plant Demand Peak

Hot Water Pressure Set Point Unreachable

Hot Water Pressure Unstable

Hot Water Plant Temperature Setpoint Unreachable

Hot Water Plant Leaving Temperature Unstable

Missing Data

Occupied Cooling Setpoint Out of Range

Occupied Heating Setpoint Out of Range

Pump Cycling

Sensor Failure

Short Demand Peak

Split System A/C Unit Cooling Setpoint Out of Range

Terminal Unit Airflow Setpoint Unreachable

Terminal Unit Airflow Unstable

Terminal Unit Heating Failure

Terminal Unit Heating Valve Leaking

Terminal Unit Zone Temperature Out of Range

Underfloor Heating Space Temperature Out of Range

Unoccupied Cooling Set Point Out of Range

Unoccupied Heating Set Point Out of Range

Zone Cooling Damper Malfunction

Zone Heating Damper Malfunction

Zone Temperature Out of Range (Cooling)

Zone Temperature Out of Range (Heating)

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