Rees-Stealy Otay Ranch
Total Annual Savings:
Connected commissioning optimizes building performance, reduces operating and maintenance costs and extends equipment lifetimes. As a result of the energy audit, high priority lighting, automation/controls and heating, ventilation and air conditioning (HVAC)-related ECMs are recommended for implementation through a packaged connected commissioning project delivery. In most cases, the building automation system will be used to collect and analyze on-going performance data, identify new trends and ensure persistent savings from previously-implemented ECMs.
Perform connected commissioning with a focus on optimizing automated control sequences through programming and control device upgrades to achieve the following energy conservation measure outcomes. The connected commissioning process includes follow up investigation, controls upgrade specifications and sequences, coordination with installing contractor(s), and optimized control sequences validations. Control specifications and optimized sequences of operation will also be provided for all budgeted HVAC unit replacements.
The following measures were identified as specific opportunities to be completed as part of a connected commissioning process. These opportunities may be implemented independently or as part of a coordinated effort:
• Equipment Schedules for Air Handler Units (AHUs) and Boiler - Reduce equipment scheduled run times. Standardize schedule by space type for portfolio where possible, e.g. 5am-7am for medical offices. May also vary based on equipment, e.g. chiller and boilers vs AHUs. Implement optimal start where possible to enable schedules to be fully optimized to actual occupancy hours. Create after-hours capability that can be used as needed to temporarily override normal schedules.
• Program Air Handler/Rooftop Unit (AHU/RTU) Economizer Lockouts - AHU economizers currently lock out at 65°F; optimize control sequence where the economizer shall be enabled when outside air temperature is 1) lower than 50°F and 2) when outside air temperature is lower than the return/zone air temperature by 2°F. Economizer control should be disabled when outside air temperature is 1) higher than 70°F or 2) when the outside air temperature is greater than return/zone air temperature.
• Program Air Handler/Rooftop Unit (AHU/RTU) Supply Air Temperature Reset - Program air handler unit supply air temperature resets to modulate the supply air temperature setpoint (e.g. if supply air temperature setpoint is fixed at 55°F, reset between 55-63°F) in order to maintain total zone temperature cooling error at an adjustable setpoint. Use zone feedback to reset supply air temperature for both VAV zone and single zone units.
• Program Air Handler/Rooftop Unit (AHU/RTU) Static Pressure Reset - Static pressure setpoint resets are not configured for variable volume AHU systems. Program AHU supply air static pressure reset to modulate the supply air static pressure setpoint in order to maintain the maximum (critical) zone supply air damper position at an adjustable setpoint. For example, if static pressure setpoint is fixed at 1.5" water column (W.C.), reset between 0.2 - 1.75” W.C. based on VAV zone voting as referenced in ASHRAE Guideline 36.
• Boiler Lockout - Determine if the building has a temperature above which the boiler load is low enough that it may safely be locked-out (e.g. outside air temperature above 80°F). Program the boiler to be disabled at this temperature with wide hysteresis (10°F typ.) to prevent constant on/off cycling.
• Program Boiler System Heating Hot Water (HHW) Reset - Program outside air temperature reset of boiler supply temperature setpoint. For conventional boilers or boilers with 3-way valves, use 180-140°F when outside air temperature varies from 20-70°F. For condensing boilers, use 180-80°F when outside air temperature varies from 20-70°F. Alternatively, use voting or hot water value (HWV) rollup based trim and respond based resets.
• Heating Hot Water (HHW) Variable Speed Pumps & Loop Differential Pressure (DP) Reset - Install variable frequency drives (VFDs) & differential pressure sensors; program HHW loop differential pressure reset by modulating pump speed based on outside air temperature or difference in temperature between supply and return loop water (delta T) to reduce pumping demand.
• Building Exhaust Fan Schedules or Interlocks - Schedule or interlock exhaust fans that do not need to operate 24/7 with the AHU/RTU which serves as makeup air for the exhaust fans, ensuring the building does not achieve negative pressure when the AHU/RTUs are off.
• Domestic Hot Water (DHW) Recirculation Pump Control Optimization - Ensure aquastat controls for recirculation pump are operating to proper setpoint (typically 110°F). Add timeclock control to disable DHW system when building is unoccupied.
• Program Dual Maximum Variable Air Volume (VAV) Control - Program dual maximum VAV control for VAV boxes with a single minimum CFM setpoint. Where minimum air flow setpoint requirements for heating are greater than the requirement for ventilation, minimum air flow setpoints can be reduced.
• Replace Broken Air Handler Unit (AHU) Economizers - AHU-1 has a frozen outside air damper that is completely closed; replace damper and actuator for unit. Verify damper actuation on other units. Broken economizers should be confirmed by physically testing the automatic damper operation. Test and balance the unit to ensure minimum ventilation airflow levels and configure economizer programming so that economizer control is the first stage of cooling.
• Demand Response Sequence - Program sequences to allow non-critical loads such as common area lighting, fountains, displays, etc. to remain OFF during peak hours. Use any available load-shifting technology to delay energy use until after the peak period.