Overview

The Re-tuning Dashboard allows you to apply Re-tuning measure(s) in order to compare the performance of the building with the applied measure(s) to your completed baseline building model. In addition to re-tuning measures, several other common energy upgrade measures are included as options. Measures can be applied individually or in packages.

The measures are organized into different categories in terms of the Re-tuning principle (turn it off, turn it down, mitigate simultaneous heating and cooling, and reduce outdoor air/infiltration) for control measures, or as a capital project or operations and maintenance (O&M) measure. To apply a measure, simply click in the box for that measure that says “Enable Measure”. This will reveal the simulated details about the baseline building for reference on the left side as well as revealing prompts (usually as updates to those baseline details) for simulating the measure on the right side.

When you have applied as many measures as you would like, you can name the new run at the bottom of the page and hit the run button. This will create a new comparison simulation and a new column of results in the table in the Emissions and Savings Impacts module. You can come back to the Re-tuning Dashboard module as often as you need to in order to create new runs and add them to the table in Emissions and Savings Impacts. Below are a list of measures and any unique instructions associated with each:

In-Depth

The 28 potential re-tuning measures are listed below, along with details on each measure. The measures are broken down into 4 savings categories/principles: “Turn-it-off”, “Turn-it-down”, “Mitigate Simultaneous Heating and Cooling”, and “Reduce Infiltration and Excess Outdoor Air.”

“Turn-it-off” Measures

• Adjust HVAC Schedules: This updates the schedule applied to the AHUs. You will see on the left side the name of the schedule that was used and the start and stop hours. Note that unfortunately, the simulation cannot capture the impact of sub-hourly schedule changes…for example changing a schedule from a 5:00 start time to a 5:30 start time. Schedule values must remain on-the-hour to simulate accurately. For this measure, you will need to go back and create a new schedule in the Define Building Schedules module , then find it and select it in the drop-down here.


• Adjust Lighting Schedules: This updates the schedule applied to the lighting for each zone You will see on the left side the name of the schedule that was used for lighting for each zone. Note that unfortunately, the simulation cannot capture the impact of sub-hourly schedule changes…for example changing a schedule from a 5:00 start time to a 5:30 start time. Schedule values must remain on-the-hour to simulate accurately. For this measure, you will need to go back and create a new schedule or schedules for lighting in the Define Building Schedules module, then find it and select it for the applicable zones in the drop-down here. Reduced lighting schedules can be created by starting from an existing lighting schedule in the Define Building Schedules module and making only the necessary changes to the hourly values.


• Cooling System Outdoor Air Enable: This allows you to add an outdoor air temperature-based lockout to the chiller, cooling plant, and/or cooling coils. You can also improve or update an existing lockout.


• Heating System Outdoor Air Enable: This allows you to add an outdoor air temperature-based lockout to the boiler, heating plant, and/or heating coils. You can also improve or update an existing lockout.


• Holiday Scheduling: This allows the user to simulate adding programmed holidays into a building automation system, when they are not otherwise applied. Eleven federal holidays are provided as options. Enabling a holiday makes the building HVAC systems run as if it were a Sunday on those days. In the event of buildings that operate normally on Sundays, this measure may not have the desired impact.



• Optimal Start: This measure allows the user to simulate a common feature in building automation systems for scheduling air-handling units. Optimal Start is a machine learning algorithm where the BAS learns how long it takes for zones to warm up based on morning zone temperatures and outdoor air temperatures and then decides each morning when to start up the air-handling units.

  An important note is that Optimal Start references the AHU schedules. Before Optimal Start is implemented, the AHU schedules are typically set to represent the fixed time that AHUs must start up to accommodate morning warm-up and cool-down operations, and these morning schedules are often set early enough to accommodate the worst case weather conditions and associated start up requirements.

  After optimal start is implemented, the AHU schedules should now represent the latest start-up time (usually more or less in line with the beginning of occupancy). So in most cases, this Optimal Start measure should be paired with a change in AHU schedules.

  • Maximum Early Start: The maximum number of hours prior to the latest start time that the AHU is allowed to turn on.
  • Recovery Rate: The rate of temperature rise or drop during morning warm up or cool down operations. Recommend 2°F for heavy thermal mass construction, 3°F for typical construction and 4°F for light thermal mass construction.
  • Weekday latest start time: The rate of temperature rise or drop during morning warm up or cool down operations. Recommend 2°F for heavy thermal mass construction, 3°F for typical construction and 4°F for light thermal mass construction.
  • Saturday latest start time: Latest start time on Saturdays for the Optimal Start program. Typically the same as the new AHU schedule and in line with the start of occupancy. If Saturdays are unoccupied, any hour value can be input.
  • Sunday latest start time: Latest start time on Sundays for the Optimal Start program. Typically the same as the new AHU schedule and in line with the start of occupancy. If Sundays are unoccupied, any hour value can be input.
  Note that correct implementation of Optimal start usually requires a paired change in the HVAC operation schedule. The HVAC schedule needs to be changed to reflect the latest start times defined in the algorithm (they should be equal to or later than the latest start time parameters in the measure).


• Pump Shutdown When there is No Load: This measure allows the user to change the change the operation scheme of the chilled water and/or hot water building loop pumps according to whether the pumps run all the time. Options include:
  • TRUE (Pumps run all the time)
  • FALSE (Pumps run only when there is a load that requires them to operate)
  • OA Lockout (Pumps run when there is no load, but only when the outdoor air temperature is below a threshold for hot water pumps or above a threshold for chilled water pumps
    • OA Lockout setpoint


• Turn Fans off During Night Heating Cycles:This measure can be applied to buildings that have a means of maintaining zone heating after hours with zone heating only while keeping the air-handling unit off. This is possible with zone heating options that include parallel fan-powered VAV boxes, perimeter fan coil/baseboard heating, or radiant panel heating. Enable the measure for perimeter and/or interior zones by selecting “yes” from the drop-down.

“Turn-it-down” Measures

• Static Pressure Reset: This measure allows the user to apply a static pressure reset to the duct static pressure setpoint control of the supply fan. This allows the fan to slow down to meet reduced duct static pressure setpoints during times of low demand for airflow.

  Duct static pressure can be controlled to a fixed setpoint, can be scheduled to reset based on time of day, or can be reset using either a linear reset between user-defined minimum and maximum setpoints based on a user-defined range for a selected feedback variable (sensor), or a trim-and-respond logic can be used, in which a desired value for a feedback variable (sensor) is defined, and the duct static pressure setpoint is updated at each timestep to attempt to target that desired value. Other options for static pressure reset include the ASHRAE Standard 36 method, which uses a three step process for translating feedback indicators of zone airflow demands to duct static pressure setpoints, and TRANE’s sequential method of resetting both the supply air temperature and the duct static pressure in a sequential manner.

  Parameters for linear resets include:

  • Feedback variable e.g. outdoor air temperature, zone heating or cooling demand (0-100 value based on deviation from setpoint), fan speed, average zone damper, maximum zone damper, etc.
  • Minimum value for feedback variable
  • Setpoint at minimum value of feedback variable (if the feedback variable goes lower than the minimum, the setpoint will remain at this limit)
  • Maximum value for feedback variable
  • Setpoint at maximum value of feedback variable (if the feedback variable goes higher than the maximum, the setpoint will remain at this limit)

  Parameters for trim-and-respond resets include:

  • Feedback variable maintenance setpoint
  • Change rate: this is the maximum rate of change per hour in the setpoint based on deviation of the feedback variable from its maintenance setpoint.
  • Minimum SAT: This is the minimum limit for the supply air temperature setpoint
  • Maximum SAT: This is the maximum limit for the supply air temperature setpoint
• Night Setback: This measure allows the user to adjust the unoccupied heating and cooling setpoints that determine when the AHUs will turn back on overnight. This measure allows the user to update the zone-by zone unoccupied thermostat setpoints that govern night setback.


• Chilled Water Differential Pressure Reset: The setpoint for the chilled water loop differential pressure (DP) can be set to a constant value, or can use a linear reset based on the AHU chilled water valve command that allows the differential pressure setpoint to be reset lower, slowing down the chilled water building loop pumps when there is less demand for chilled water. At this time, there is only one option for feedback variable for chilled water DP reset: average chilled water coil valve command. Note that because of the simplified simulation of a single air-handler, there is not enough information to differentiate average from maximum chilled water coil valve commands.


• Condenser Water Temperature Reset: This measure allows for the reset of the condenser water temperature setpoint. Setting the setpoint lower improves the efficiency of the chiller by lowering the compressor lift, however lower setpoints increase the cooling tower fan consumption. Best practice for this measure is to set the condenser water temperature setpoint as a constant offset from the outdoor air wet bulb temperature. For variable speed cooling towers, a good practice is to set this value somewhat higher than the design approach temperature of the cooling towers to the wet bulb temperature, to keep the fans from going to 100%. Minimum and maximum limits should be applied. 65F is usually safe as a lower limit for most chillers, however when the chiller manufacturer specifies it is safe to go lower (55-60F), this can save additional energy.


• Chilled Water Temperature Reset: The chilled water temperature setpoint can be reset based on the average chilled water valve command. Higher values for chilled water temperature setpoints reduce chiller power consumption by lowering the compressor lift, however they can increase the volume of water pumped to the building and resulting pump power. At this time, there is only one option for feedback variable for chilled water temperature reset: average chilled water coil valve command. Note that because of the simplified simulation of a single air-handler, there is not enough information to differentiate average from maximum chilled water coil valve commands.


• Hot Water Differential Pressure Reset: Coming Soon


• Hot Water Temperature Reset: Hot water temperature reset is most applicable for buildings using condensing boilers, as these boilers have more efficient operating points at lower hot water temperatures. For these boilers, the reset should feature low-end setpoints below 120°F and ideally, closer to 100°F to take full advantage of these efficiency gains.
  Other boilers and hot water loops interfacing with district heating can also utilize hot water temperature reset to save energy through reduced convective heat losses from pipes, fittings, and other hot water loop components, especially as they transverse mechanical rooms, chases, plenums, and other unconditioned spaces. The reset can also potentially save energy through reduced plant-side simultaneous heating and cooling (transfer of heat between hot water and chilled water loops- in some buildings) There are two control options for hot water temperature; a constant temperature setpoint and a linear reset.
  Linear Reset: A linear reset makes a linear adjustment to the control variable (in this case duct static pressure reset) between a minimum and maximum value based on the span of a feedback variable between its specified minimum and maximum values (or vice versa; an inverse linear relationship). Outside of the two specified values for the feedback variable, the setpoint will remain at a minimum or maximum value. There are four parameters for the reset
  • Feedback variable: Choices for feedback variables include outdoor air temperature and average hot water valve command.
  • Minimum for feedback variable
  • Maximum for feedback variable
  • Hot water temperature setpoint at minimum feedback variable: A minimum (or maximum) value of the hot water temperature setpoint associated with the minimum value for the feedback variable. Note that a minimum value for hot water temperature setpoint should be around 150°F for non-condensing boilers (unless there is a separate building loop that can go lower), and as low as 100° for condensing boilers.
  • Hot water temperature setpoint at maximum feedback variable: A minimum (or maximum) value of the hot water temperature setpoint associated with the maximum value for the feedback variable)


• Pump Staging: This measure allows you to adjust the staging of the chilled water secondary pumps according to their part load ratios (PLRs) to optimize pump power consumption. Typical staging would allow each pump to be fully loaded (100% PLR) before staging on the next pump. Pump power is typically proportional to the cube of pump speed, so staging the next pump on earlier (e.g. at 60-80% PLR) may save pump energy. New stage-up and stage-down PLR’s should be specified for each pump. Note that the stage-down PLR’s should be less than half of the stage-up PLR, to avoid rapid switching between 1 pump and 2.


• Chiller Staging: This measure allows you to adjust the staging of the chillers according to their part load ratios (PLRs) to optimize chiller power consumption. Typical staging would allow each chiller to be fully loaded (100% PLR) before staging on the next chiller. Chiller part load efficiency for most chiller types is optimal in the range of 30-80% loading, so it can be beneficial to stage on a new chiller when the other chillers get close to 80% loaded, unless each new chiller entails bringing on additional pumps (e.g. condenser pumps). New stage-up and stage-down PLR’s should be specified for each pump. Note that the stage-down PLR’s should be less than half of the stage-up PLR, to avoid rapid switching between 1 pump and 2.


• Secondary Pump Staging: Building loop (typically “secondary loop”) pumps are often staged in parallel (or lead-lag). Pump power often increases exponentially with increasing part load ratio, such that is can reduce overall system pump power to have multiple pumps running at part load, rather than a single pump running at or near full load.
  For each stage, the user should specify the part load ratio for stage-up and for stage down. For example, in stage 2, this would apply when the first two pumps are running. The stage-up value would indicate which speed the two running pumps would have to rise to in order to stage-up to stage 3 (3 pumps). The stage-down value would indicate which speed the two running pumps would have to fall to, in order to stage down to a single pump. The user should leave a buffer between stage-up and stage-down commands. For example, if the stage-down threshold in Stage 2 were set at 50% and the stage-up threshold in stage 1 were set at 80%, two running pumps at 50% would stage down to a single running pump at 100%, which would then force an immediate stage-up back to 2 pumps. A smarter staging scheme would be a stage-down from Stage 2 at 30%, then a stage-up from Stage 1 to 2 at 75%.

Mitigate Simultaneous Heating and Cooling

• Supply Air Temperature Control: This measure allows you to change the control of the temperature setpoint for the main AHU (or cold deck) supply/discharge air temperature setpoint by applying or improving an automatic reset.
  
  

  Supply air temperature can be controlled to a fixed setpoint, or it can be reset using either a reset between user-defined minimum and maximum setpoints based on a user-defined range for a selected feedback variable (sensor), a trim-and-respond logic can be used, in which a desired value for a feedback variable (sensor) is defined, and the supply air temperature is updated at each timestep to attempt to target that desired value. Other options for supply air temperature reset include the ASHRAE Standard 36 method, which uses a three step process for translating feedback indicators of zone thermal demands to supply air temperature setpoints, and TRANE’s sequential method of resetting both the supply air temperature and the duct static pressure in a sequential manner.

  Parameters for linear resets include:

  • Feedback variable, e.g. outdoor air temperature, zone heating or cooling demand (0-100 value based on deviation from setpoint), fan speed, average zone damper, maximum zone damper, etc.
  • Minimum value for feedback variable
  • Setpoint at minimum value of feedback variable (if the feedback variable goes lower than the minimum, the setpoint will remain at this limit)
  • Maximum value for feedback variable
  • Setpoint at maximum value of feedback variable (if the feedback variable goes higher than the maximum, the setpoint will remain at this limit)

  Parameters for trim-and-respond resets include:

  • Feedback variable maintenance setpoint
  • Change rate: this is the maximum rate of change per hour in the setpoint based on deviation of the feedback variable from its maintenance setpoint.
  • Minimum SAT: This is the minimum limit for the supply air temperature setpoint
  • Maximum SAT: This is the maximum limit for the supply air temperature setpoint
  • Variable SAT limits: This option can be used to dynamically adjust the minimum and maximum SAT setpoints based on outdoor air temperature. Both setpoints can be reset linearly. For example, the minimum AHU SAT setpoint could be set to 60°F at 30°F outdoor air temperature and reset down to 55°F at 60°F outdoor air temperature. This could prevent excessively cool SAT setpoints during cold weather. A similar strategy can be used for the maximum AHU SAT setpoint to prevent excessively warm SAT setpoints during hot weather.
• VAV Box Minimum Airflow Setpoints: This measure allows the user to modify the global values for the VAV heating maximum, cooling minimum and heating minimum airflow setpoints.
• Economizer Control: This measure allows the user to apply airside economizer control to the AHU or to make adjustments to existing economizer controls.
  
  

  Economizer control options include “No Economizer”, in which case, the minimum outdoor air setpoint is utilized at all times, “Differential Dry Bulb”, which activates the economizer for free cooling when the outdoor air temperature is cooler than the return air temperature”, “Differential Enthalpy” which activates the economizer when the outdoor air enthalpy is below the return air enthalpy, “Fixed dry bulb”, which activates the economizer when the outdoor air temperature is below a fixed economizer lockout threshold, and “Fixed Enthalpy”, which activates the economizer when the outdoor air enthalpy is below a fixed lockout threshold.

  Economizer high and low dry bulb temperature lockouts: Whether or not the economizer uses a fixed dry bulb strategy, an additional layer of lockouts on the economizer based on outdoor dry bulb can be added. A high dry bulb lockout prevents the use of the economizer when outdoor air temperatures are above the lockout setpoint and a low dry bulb lockout prevents the use of an economizer when the outdoor air temperatures are below the lockout setpoint.

• Thermostat Setpoints and Deadbands: This measure allows the user to modify the global values for the zone occupied heating and cooling setpoints.
• DOAS SAT Reset: This measure allows the user to apply an automatic reset to the discharge air temperature setpoint for the dedicated outdoor air system. The available reset option is a linear reset based on outdoor air temperature. Effective resets often use this setpoint to keep heat recovery and mechanical heating and cooling off during cool to mild weather. For example, resetting the supply air temperature from 50 degrees at 50 degrees outdoor air temperature to 65 degrees at 65 degrees outdoor air temperature.
• Eliminate Fighting Thermostats: One source of simultaneous heating and cooling can occur between zones with different thermostat setpoints - particularly when some adjacent zones have heating setpoints that are warmer than other adjacent cooling setpoints. Heat can be transferred and lost directly between the zones, or the applied heating and cooling can be cancelled out as return air is mixed and drawn back to the air-handlers. This measure allows upper and lower limits to be put on the heating and cooling setpoints. It is recommended that maximum heating setpoints not be greater than minimum cooling setpoints among the zones.

Reduce Outdoor Air and Infiltration

• Reduced Minimum Outdoor Air: This measure allows the user to reduce the minimum outdoor air brought in to the AHU via minimum outdoor air damper control. Regardless of the baseline state, this measure will change the minimum outdoor air control type to minimum outdoor air fraction, and the user can enter a minimum faction of outdoor air.
• Demand Control Ventilation: This measure allows the user to implement or modify a demand control ventilation strategy. This strategy changes the minimum outdoor air control to a linear reset of the minimum outdoor air fraction based on the return air CO2 concentration. Minimum and maximum parameters for the CO2 concentrations and associated minimum and maximum values for the minimum outdoor air fraction are required.
• Building Pressurization Control: This measure allows the user to apply a linear reset on the return fan speed (via the offset from the supply fan speed) in order to prevent the building pressure from going too positive or too negative. A recommended reset would be to reset from 60% return fan offset at 0 building pressure to 10% return fan offset at 0.05 in. w.c. building pressure.
• Exhaust Fan Control/Scheduling: This updates the schedule applied to the miscellaneous building exhaust fans. You will see on the left side the schedule that was used and the start and stop hours. Note that unfortunately, the simulation cannot capture the impact of sub-hourly schedule changes…for example changing a schedule from a 5:00 start time to a 5:30 start time. Schedule values must remain on-the-hour to simulate accurately.
• Close OA Dampers at Night/Morning Warm-up: AHU outdoor air dampers are often controlled to open to the same minimum position whenever the AHUs run, including for night cycle operation and during morning warm-up. Ventilation is generally not needed during these times, and an alternative schedule can be applied to minimum OA damper control that is in line with occupied hours. This updates the schedule applied to the minimum outdoor air damper. You will see on the left side the schedule that was used and the start and stop hours. Note that unfortunately, the simulation cannot capture the impact of sub-hourly schedule changes…for example changing a schedule from a 5:00 start time to a 5:30 start time. Schedule values must remain on-the-hour to simulate accurately. For this measure, you will need to go back and create a new schedule in the Define Building Schedules module , then find it and select it in the drop-down here.

O&M Measures

• Fix Leaking Cooling Coil/Heating Coil: This measure should be applied to buildings that were noted and programmed in the baseline model to have leaking heating or cooling coils. On the right side for this measure, the leaking coil fault can be corrected by entering 0.
• De-lamping: This measure allows the user to make zone-by-zone reductions to the lighting power density to mimic de-lamping. The user should enter the percent reductions in lighting power density for each zone individually. /li>

Capital Project Measures

• More Efficient Chillers: This measure allows the user to update the chiller efficiency to mimic the replacement of chillers with more efficient models
• More Efficient Boilers: The user can evaluate the impact of a boiler replacement by adjusting the design boiler efficiency
• More Efficient Boilers: This measure allows the user to update the boiler efficiency to mimic the replacement of boilers with more efficient models
• More Efficient AHU Fans: This measure allows the user to update the AHU fans with more efficient models.
• More Efficient Windows: This measure allows the user to update the window U-factor and solar heat gain coefficient
• Added Insulation: This measure allows the user to update the wall u-factor to represent added wall insulation
• Building Sealing/Reduced Infiltration: This measure allows the user to lower the infiltration rate to represent building sealing or other measures that reduce infiltration rates.
• Cooling Tower Variable Speed Upgrade: This measure allows the user to switch from a single-speed or two-speed cooling tower to a variable speed cooling tower.