Grossmont Hospital



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Connected Commissioning of Chilled Water (CHW) Plant

Not Started

FY 2020




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 of chilled water (CHW) central plant 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:

• Program Condenser Water (CDW) Reset - Cooling towers currently control to a constant setpoint of 78°F. 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 - Program reset of chiller supply temperature setpoint, (e.g. from 42 - 48°F) when outside air temperature varies from 70 - 90°F.

• Automate and Optimize Chiller Staging Programming - Some chiller staging logic is programmed, but it is overridden by operator & staging parameters are not optimized for energy efficiency. Update programming and commission to ensure that operations team can rely on fully automated chiller staging.

• Chilled Water (CHW) Variable Speed Pumps & Loop Differential Pressure (DP) Reset with Linear Accelerator Heat Exchanger (HX) Controls Update - Program the system differential pressure setpoint to modulate pump speed and reset the CHW setpoint based on valve position of the air handlers. Install additional sensors where needed along the critical junctures of the campus loop. The Linear Accelerator Process CHW Heat Exchanger was identified as driving the required supply pressure of 68 pounds per square inch (PSI), with heat exchanger (HX) alarms that were based on a flow switch. The process HX serves a closed process CHW loop with a constant speed pump. The HX should be controlled to a leaving CHW supply temperature on the process water side. Increase in campus CHW loop pressure should only be performed if temperature is not being met. Implementing this measure will allow the CHW pumps to be turned down to lower operating loop pressures significantly more often.