Insight

Description

AHU Command Off While Occupied

The AHU is occupied but is commanded off. Check to see if there is a local override, alarm or safety that may be preventing the unit from running.

AHU No Cooling Command When Required

The cooling command on this unit did not enable when space temperature was above setpoint by 1.0Δ°F for a period of 1hr.

AHU No Heat Command When Required

The heating command on this unit did not enable when space temperature was below setpoint by 1.0Δ°F for a period of 1hr.

CO2 above setpoint

The CO2 concentration in the space is above the setpoint by 200 ppm for at least 2hr. Check the supply fan status and the outside air damper minimum position.

Discharge Air Temp greater than setpoint

The Discharge Air Temp is greater than the setpoint. Check the compressor or cooling valve function.

Duct Static Pressure unable to reach setpoint

The Duct Static Pressure is less than the setpoint. This may cause uncomfortable conditions in the zones served by this AHU. The fan may be undersized, the setpoint may be too high or there may be an obstruction in the airflow.

Heating not functional

The discharge air temperature is within 4Δ°C of the AHU supply temperature while the VAV is heating. Check the function of the heating valve or actuator.

High space temperature

The space temperature was at least 3°F higher than the setpoint for 4 hours.

Low Discharge Air Temperature

Check fan speed, fan belt tension, and/or filter

Low space temperature

The space temperature was at least 3°F lower than the setpoint for 4 hours.

Unable to provide cooling to space

The cooling command is on, but the temperature split across the coil is less than 4°F. Check to see if the air handler cooling has been disabled.

Unable to provide heating to space

The Discharge Air Temperature is less than Zone or Return Air Temperature while the fan and heat are On.

Zone Equipment Operating in the Wrong Mode

The HVAC mode of the equipment indicates that the equipment is cooling when it should be heating or vice versa.

Insight

Description

AHU Heat and Cool Cycling

The AHU is short cycling between heating and cooling for at least 2 hr. The minimum OFF time between heating and cooling is less than 1 hour. This may be caused by an inadequate deadband between the heating and cooling setpoint. It is also possible that the AHU is oversized for the space in which it serves or the zone temperature sensor is installed too close to the supply diffuser.

AHU Heat Recovery Heat Transfer Happening in Bypass Mode

The AHU is bypassing the heat recovery but heat transfer across the core (more than 6Δ°F delta T) is still occurring.

AHU Heat Recovery Lower than Optimal

Based on the calculated effectiveness, the heat recovery appears to be under performing.

AHU Low Load

The AHU is running while under very little load. If ventilation is not needed consider turning off AHU and running when demand requires.

AHU Occupied When Site Closed

Rule for detecting AHUs which are in occupied mode while a site is closed

Chilled Water DP higher than setpoint

The chilled water differential pressure is greater than the setpoint. Check the pump speed and control.

Chilled water supply temperature is lower than setpoint

The chilled water supply temperature is greater than the setpoint. Check the local CHWS setpoint and confirm the chiller is in auto mode.

Chiller running while all cooling valves closed

The chiller is running while all down stream chilled water valves are closed. Consider implementing an optimized chiller operation strategy for maximum efficiency.

Chiller supply temp setpoint does not match plant setpoint

The plant chilled water supply temperature setpoint doesn't equal the chiller setpoint for at least 2hr. Check the logic to ensure the plant setpoint is being sent to the chiller controller.

CHW Plant Equipment On while Plant is Off

Equipment within the chilled water plant is operating even though the plant is off. Check that the equipment needs to operate.

Condenser water supply temperature is higher than setpoint

The condenser water supply temperature is greater than the setpoint.

Condenser water supply temperature is lower than setpoint

The condenser water supply temperature is lower than the setpoint.

Discharge Air Temp lower than setpoint

The Discharge Air Temp is less than the setpoint for at least 4 hours. Confirm the compressor or cooling valve control is not in override.

Duct Static Pressure greater than setpoint

The Duct Static Pressure is greater than the setpoint. Check the fan speed control or minimum fan speed.

Equipment in Hand

The equipment start/stop command is OFF, but the status is ON for a minimum duration of 2 hours. Confirm that the equipment is on and check to see if the control is in hand.

Fan Commanded On 24/7

The supply fan commanded on for 24 continuous hours. Confirm that this AHU needs to run 24/7. If not, apply a schedule.

Fan in hand

The fan start/stop command is OFF, but the status is On or the discharge air pressure is greater than 0.15 IWC for 15 minutes. Confirm that the fan is on and check to see if the VFD or motor starter is in hand.

Fan on while AHU Unoccupied

The fan is commanded on while the AHU is unoccupied for at least 2 hours. Confirm the fan command is in override. Check the AHU occupied schedule.

Hot Water DP higher than setpoint

The hot water differential pressure is greater than the setpoint. Check the pump speed and control.

Hot water supply temperature is higher than setpoint

The hot water supply temperature is greater than the setpoint. Check the boiler's local setpoint and/or the temperature control valve if one exists.

Reverse Flow in Chiller Bypass

The Chilled Water Plant Supply Temperature is at least 2°F greater than the active chiller leaving temperature for at least 2hr. If a primary/secondary system: The secondary chilled water flow could be greater than the primary flow causing water to recirculate through the bypass, otherwise the isolation valves on the other chillers could have failed.

Unnecessary Cooling

The cooling command is on, but the space temperature is below the occupied cooling setpoint.

Unnecessary Heating

The heating command is on, but the space temperature is above the heating setpoint.

Valve leakby

The difference between the entering air temperature and the discharge air temperature is greater than 4°F for at least 1hr while the valve is closed. Check if the valve actuator is functioning properly and causing the valve to close completely.

VAV airflow greater than setpoint

The VAV airflow is greater than the setpoint for at least 2h. The damper may be overridden or non-functional.

VAV High Damper Position

The VAV cooling command is on, but the zone temperature is less than the effective temperature setpoint.

VAV not providing full cooling to space

The cooling command is on at the VAV, but the discharge air temperature at the VAV is more than 6 degrees higher than the discharge air temperature at the upstream air handler.

VAV Unnecessary Cooling

The VAV cooling command is on, but the zone temperature is less than the effective temperature setpoint.

VAV Unnecessary Heating

The VAV heating command is on, but the space temperature is above the effective zone temperature setpoint.

Unit Occupied Out of Sync with Schedule

The equipment has been in Occupied mode for more than 2hrs when it is expected to be Unoccupied. This algorithm evaluates schedules and was expected to be Unoccupied based on several possible factors: a Rule Tuning-specific schedule; a schedule with equipRef to the equipment; a schedule with siteRef to the equipment's site; or a generic building schedule with the same time zone as the equipment's site. Review your equipment schedules with particular focus on one of these parameters and make adjustments accordingly.

Insight

Description

AHU Under Ventilating

Based on the OAT, DAT and RAT, the AHU appears to be under ventilating.

Air quality sensor greater than standard limit

The air quality sensor is reading higher than the standard limit for this quantity.

Air quality sensor less than standard limit

The air quality sensor is reading lower than the standard limit for this quantity.

Insight

Description

AHU Fan Speed Higher than Predicted

The fan speed is higher than predicted indicating that the fan has to move faster to move the same amount of air at a given pressure. Possible causes of high fan speed include: a slipping fan belt, obstruction in the AHU or ductwork such as a dirty filter or coil, and motor wear. Recommend checking that AHU has clean filter and no obstructions and servicing fan.

Cooling Tower Makeup Water Consumption Higher than Predicted

The cooling tower makeup water consumption is higher than predicted indicating that cooling tower is using more water than normal. Possible causes of high makeup water consumption include: leaks or excessive blowdown cycles. Recommend checking that cooling tower does not need cleaning/servicing and checking for leaks in the condenser water piping.

Cooling Tower Makeup Water Consumption Lower than Predicted

The cooling tower makeup water consumption is lower than predicted indicating that cooling tower is using less water than normal. Possible causes of low makeup water consumption include: meter issues or abnormal blowdown cycles. Recommend checking that the system is blowing down often enough and that the meter reading is accurate.

Discharge Air Temp higher than predicted

The discharge air temperature is higher than predicted. This may be a sign of a capacity problem with the equipment. Possible causes of capacity loss include: refrigerant leaks and low airflow on condenser coil. Clean condenser if it is dirty, check condenser fan motor and verify refrigerant charge.

Discharge Air Temp lower than predicted

The discharge air temperature is lower than predicted. One possible cause is low airflow. Verify that the discharge fan is providing adequate airflow by checking motor and fan operation and belt tension. It is also recommended to check the filters and other sources of airflow obstruction.

Pump Speed Higher than Predicted

The pump speed is higher than predicted indicating that the pump has to move faster to move the same amount of water flow at a given pressure. Possible causes of high pump speed include: obstruction in the pump or pipes such as a dirty strainer or coil and motor wear. Recommend servicing pump.

VAV Damper Position Greater than Predicted

The VAV damper position is greater than predicted indicating that the VAV has to open more than normal to provide the same amount of air. Possible causes include: an airflow obstruction in the ductwork, the damper is not able to open freely or the sensor calibration is off. Recommend servicing the VAV and checking the sensor, damper and ductwork.

VAV Damper Position Less than Predicted

The VAV damper position is less than predicted indicating that the VAV has to close more than normal to provide the same amount of air. Possible causes include: loose coupling between the actuator and damper or the sensor calibration is off. Recommend servicing the VAV and checking the sensor, damper and ductwork.

Insight

Description

AHU Over Ventilating

Comparing the discharge air temperature with the return (or zone) air temperature and outside air temperature and computing the outside air percentage. If that percentage is greater than 40% it creates a spark. If the AHU has an economizer, check the minimum damper position and adjust accordingly. For greater control add digital economizer controls and connect to the BMS.

Convert AHU to Variable Speed

The AHU's Bypass Damper is less than 50% for at least 4hrs. Consider removing damper and installing a VFD for improved control, reduced energy consumption and lower utility bills.

Duct Static Pressure Reset Opportunity

The majority of the discharge air dampers served by this AHU are partially closed for at least 2hrs. Decreasing the duct static pressure will reduce fan power without impacting zone comfort. Consider implementing a duct static pressure optimization strategy for maximum efficiency.

Chilled water supply temperature optimization opportunity

The majority of the AHUs served by the CHW Plant have valves that are less than 75% open. Consider implementing a CHWS temperature optimization strategy for maximum efficiency.

Low DeltaT in Chilled Water Plant

The Chilled Water Plant is on and the difference between return temperature and supply temperature is less than 4°F for at least 2hr. The chilled water flow is likely greater than it needs to be. There is an opportunity to increase the efficiency of the plant by optimizing the flow.

Cooling Tower Relief Optimization Opportunity

All cooling tower fan speeds are running at greater than 95% (threshold) for 2 hr (minDur) while the approach temperature (difference between condenser water supply temperature and ambient wetbulb from weather station) is less than 5 (maxDelta).

Cooling On While OAT Lower Than SAT Sp

The cooling command is on when the outside air temperature is lower than the effective discharge air temperature setpoint. The economizer command may be overridden or the economizer is broken.

Economizer at 100% While Heating is On

When the outside air damper is commanded to open to 100%, the heat command is on. Check if the outside air damper is open to 100%, the outside air damper command may be overridden.

Economizer not optimized for free cooling

The cooling command is on and the outside air temperature is lower than the return air temperature, yet outside air damper position is below 100%. The economizer command may be overridden, the economizer lockout setpoint may be too high or the economizer is broken.

Economizer unable to provide 100% outside air

When the outside air damper is open to 100%, the difference between discharge air temperature and outside air temperature is larger than 4Δ°F. The return air damper may not be closed. Check the control for return air damper and outside air damper.

Outside air damper not closing to minimum

The weather station outside air temperature (OAT) is greater than the return or space temperature, but the economizer is not at the minimum position. The economizer should be locked out at this OAT. Check the economizer lockout (changeover) temperature setpoint and damper overrides.

Hot water differential pressure optimization opportunity

The majority of the hot water valves served by the HW Plant have valves that are less than 75% open. Consider implementing a HW differential pressure optimization strategy for maximum efficiency.

Condenser Water Setpoint Optimization Opportunity

The condenser water supply temperature setpoint is greater than 75F (maxTemp) while the cooling tower fan speed is less than 50% (threshold) for 2hr (minDur).

High Fan Speed when Zone in Deadband

The fan speed was higher than 90% while the zone temperature was between the occupied heating and cooling setpoints. For optimum efficiency the fan speed should drop to minimum while no cooling or heating is required. Check the fan speed control.

Optimum start opportunity

The equipment was on and the zone setpoint was between the occupied heating and cooling setpoints for more than 1 hr while the site was unoccupied. Consider implementing an optimum start/stop routine to minimize unneeded runtime.

Precooling Opportunity

The OAT was lower than 65°F for at least 1hr prior to a call for cooling. There is an opportunity to pre-cool the space with outside air and reduce mechanical cooling.

Spike in electrical power

There was a sudden and temporary spike in electrical power on the meter for a duration of less than 1 hour. Check the equipment served by this meter and confirm the staging strategy of that equipment.

Discharge Air Temperature Reset Opportunity

The majority of the zone temperatures served by this AHU are less than 74F 2hrs. Decreasing the discharge air temperature setpoint will reduce reheat energy without impacting zone comfort. Consider implementing a discharge air temperature optimization strategy for maximum efficiency.

VAV discharge air temperature too high

The VAV supply air temperature is over 105°F for at least 1 hr. This may cause stratification and increased energy consumption. Consider implementing dual max airflow logic or increase the maximum heating airflow setpoint.

Insight

Description

OAT Sensor Inaccurate

The outside air temperature sensor is more than 6°F from the temperature recorded at the local weather station for at least 2 hours. The inaccurate outside air temperature reading may be caused by poor sensor location or calibration issues.

Power Sensor Out of Range

The sensor reading appears to be an outlier and is removed from aggregation and other rules.

Low water flow through chiller

The chilled water temperature difference across the chiller is greater than 8°C for at least 2hr. This may indicate there is lower than expected chilled water flow. Check the CHWP and/or water balancing.

Chiller CWR Higher than Predicted

The condenser water temperature leaving the chiller (CWR) is higher than predicted indicating that the chiller is not able to reject as much heat through the condenser as normal. Possible causes of high CWR include: fouling in the tubes. Recommend servicing CW tubes in chiller.

Chiller Power Higher than Predicted

The chiller is using more power than predicted indicating that the chiller has to work harder for a given amount of cooling. This chiller may be starting to show signs of fouling or other forms of degradation and failure. Recommend servicing chiller and specifically checking tubes for fouling.

Chiller uneven loading

The reported load on two running chillers is significantly different. This indicates a potential situation where one chiller may require maintenance and is wasting energy.

Cooling Tower Leaving Water Temperature Higher than Predicted

The cooling tower leaving water temperature is higher than predicted indicating that cooling tower is not working at optimal effectiveness. Possible causes of high leaving water temperature include: capacity degradation due to cooling tower fouling. Recommend checking that the Cooling Tower(s) are clean and servicing fan(s).

Connection Down

The connection was down for at least 4hr. Check the connection error message.

Controller points may be stale

Multiple sensors have been constant for more than 3h. All points for this controller may be stale.

Cycling Damper, VFD Speed or Valve

The damper, VFD speed, or valve is fluctuating rapidly. Check that the control loop is properly tuned.

Cycling Damper, VFD Speed or Valve High Amplitude

The damper, VFD speed, or valve is fluctuating continuously for a long period. Check that the control loop is properly tuned.

Equipment Failed to Start

The equipment has been commanded to start, but the status is OFF for a minimum duration of 15min. Confirm that the equipment is off. Check the power, relays, and contactors.

Equipment Short Cycling

The equipment is cycling on and off with a minimum ON/OFF time less than 5 min. Confirm that the equipment is actually cycling. If cycling is found, check the control logic, if not check the status sensor for a proper connection and/or calibration.

Fan failed

The fan has been commanded to start, but the status is OFF or the discharge air pressure is lower than 0.15 IWC for 15 minutes. Confirm that the fan is off and check the fan motor, motor starter/contactor, and fan belt.

Incorrect Effective Space Temp Setpoint

The effective temperature setpoint for the space doesn't equal to any occupied/unoccupied cooling/heating setpoints for at least 4 hours. Check if the effective temperature setpoint is overridden.

MAT sensor out of range

The MAT is either above the OAT (weather station) or below the RAT for at least 4h. Check the location or accuracy of the sensor.

Missing History

The percentage of points with up to the date histories was less than 75% for at least 10 hours. Check the connection status and/or the local history collection.

Rapid Cycling of Temp Sensor

The temperature sensor is cycling rapidly. Check sensor for faulty connection.

Rapid Cycling of Temp Setpoint

The temperature setpoint is cycling rapidly. Check the control logic.

Sensor out of range

The sensor is reporting a value outside the expected range. Check that the appropriate range and scale have been set up and check the physical connection to the sensor. If necessary recalibrate or replace the sensor.

Status does not equal Command

A command point is indicating that something is true, while the status reports false (or off or closed) or vice versa. This rule looks for status mismatch for fans, pumps, valves, occupancy sensors, and dampers.

Near zero airflow sensor value

This rule will generate spark when a airflow sensor is reading a near-zero value, likely due to a wiring or sensor failure. Also possibly caused by duct obstruction.

No change in sensor value

The sensor reading is constant for more then 12 hr. The communication may be down, the sensor may be disconnected or damaged. Check the sensor reading and sensor connection at the local controller.

Rapid Cycling of VAV Airflow Sensor

The airflow sensor is fluctuating. Check the connection to the sensor or for electrical interference.

No change in airflow sensor value

The airflow sensor reading is constant for more than 4 hours and all other indications (fan, damper, etc) show that it should have a non-zero reading. The communication may be down or the sensor may be disconnected of damaged. Check the sensor reading and the sensor connection at the local controller.

VAV airflow less than setpoint

The VAV airflow is less than setpoint.

VAV Flow Out Of Range

The VAV airflow sensor is reporting a non-zero value, while the AHU that serves that VAV is off. The the air flow sensor may be out of calibration or faulty.

VAV min:max airflow setpoint ratio is too high

The ratio of the minimum to maximum airflow setpoints has exceeded 45% for at least 2 hours.

Insight

Description

Low power factor

The power factor was lower than 85% for more than 2hrs. Low power factor may be caused by voltage and current that is out of phase or by distortion.

Energy low load factor

The load factor for this building is below the recommended threshold. There may be an opportunity for demand reduction in this building.

Elec meter energy readings negative

The meter reported negative values.

Meter divergent energy readings

The difference between the calculated energy based on the power readings and the reported energy is greater than the set limit.

Elec meter erratic energy readings

Significant and momentary spikes or dips in energy readings were detected.

Elec meter no change in readings

The meter is reporting power and energy readings which have not changed all day.

Power sensor out of range

The sensor reading appears to be an outlier and is removed from aggregation and other rules.

Elec meter energy readings reset

The kWh reading has rolled over today.