Mesa Vista Hospital
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:
• BAS Retrofit - Existing Desigo system does not have control of either central plant and multiple issues with air handler operation were observed. A full BAS retrofit should include optimized sequences of operation, required controls device upgrades, and validation through analytics-connected commissioning & functional testing from the equipment level up. Centralized digital insight and control of these terminal units will allow for:
‐ Better management of space conditions affecting patients and staff
‐ Proactive maintenance of terminal units by removing aging infrastructure and allowing computer-based troubleshooting
‐ Ability to shut off or setback non-critical spaces during unoccupied hours
‐ Ability for primary equipment to stage and react to the building load throughout the day and seasons, allowing for resets on static pressure, chilled water (CHW) temperature, and heating hot water (HHW) temperature.
Note: Costs reported for this measure are based on pursuing this upgrade as a single project, but BAS and terminal equipment can be upgraded as spaces are renovated. This sequential approach will require much tighter standardization across projects & may potentially expose Sharp to maintenance and operational risks as well as utility waste.
Additionally, costs are based on transitioning the project from a sole source provider (Siemens) to a multi-vendor platform (Niagara), which will require new controllers for central equipment. If Sharp desires to stay with Siemens for this project, some central equipment controllers may be re-used, but total lifecycle costs will likely rise due to a non-competitive bid and service environment.
• Equipment Schedules for Terminal Units - The first floor of the CAP building is served by pneumatic VAV zones which can be retrofitted to DDC boxes to allow for supply temperature reset at the air handler, supply air static pressure reset, and zone scheduling. Determine the actual occupancy requirements by space/area and reduce terminal equipment run times with automatic schedules configured to occupancy requirements. Standardize schedule by space type where possible, e.g. 6am-6pm for offices. Create after-hours capability that can be used as needed to temporarily override normal schedules.
• Chilled Water (CHW) Variable Speed Pumps & Loop Differential Pressure (DP) Reset - Program the system differential pressure setpoint to modulate pump speed and reset the CHW setpoint based on valve position of the air handlers. CHW pumps operate at a constant speed but all fan coil units have 3-way valves. Complete by installing 2-way valves at the fan coils, variable frequency drives (VFDs) on the chilled water pump, and loop pressure sensors.
• Prevent Simultaneous Heating/Cooling Control - Chilled and hot water valves are not functioning on several air handler units (AHU) and four-pipe fan coils resulting in simultaneous heating & cooling. Repair or replace all faulty valves and commission all air handlers and fan coils.
• Program Air Handler/Rooftop Unit (AHU/RTU) Economizer Lockouts - Optimize control sequence for AHUS with economizers 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) Economizer Staging - Economizers use mixed air temperature setpoints and mixed temperature sensors were observed to be failed. Re-sequence air handlers to use economizer dampers as the first stage of cooling rather than controlling to a mixed air temperature setpoint.
• Program Air Handler/Rooftop Unit (AHU/RTU) Supply Air Temperature Reset - Supply temperature setpoints are constant instead of modulating. Program air handler unit supply air temperature resets to modulate the supply air temperature setpoint in order to maintain total (critical) 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 Boiler System Heating Hot Water (HHW) Reset - Boiler plant retrofit is in process; when complete, 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.
• Program Condenser Water (CDW) Reset - Condenser water temperature from main central plant is controlled by a stand-alone Honeywell controller and fans were observed to cycle. As a part of the central plant retrofit, integrate cooling tower controls and reset condenser water temperature as chiller operating conditions permit. Program fans to modulate fan speed in order to maintain cooling tower leaving chilled water (CW) temperature setpoint and reset CDW temperature setpoint between 60 - 75°F. For example, if cooling tower fan speed is above 90%, increase CDW setpoint. If cooling tower fan speed is below 60%, reduce CDW setpoint.
• Program Chilled Water (CHW) Setpoint Reset - Chilled water temperature setpoint is constant and set at the local chiller controls. As part of the central plant retrofit, program control of chiller supply water temperature (e.g. from 42 - 48°F), reset when outside air temperature varies from 70 - 90°F, consider lockout controls.
• 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.
• Repair Slipped Air Handler (AHU) Damper/Valve Actuators - Outside air and mixed air dampers are variously failed in air handlers. Dampers observed in good condition but do not move when commanded by controls. Repair known failed dampers as part of ongoing maintenance and use analytics-based connected commissioning to identify other faulty equipment.
• Replace Broken Air Handler Unit (AHU) Sensors - Mixed and return sensors are variously failed in air handlers. Repair known failed sensors as part of ongoing maintenance and use analytics-based connected commissioning to identify other faulty equipment.