PGE Wireless Pneumatic Thermostat ET Final Report.pdf

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PG&E’s Emerging Technologies Program ET11PGE3171 Figure 5: Pilot Site 1 - Thermostat Deadband Setpoints The figure above shows the space temperature, cooling setpoint and heating setpoint for the various thermostat zones. When the trending data for an individual thermostat is viewed, the deadband control range is apparent, as seen in the following figure. Branch Pressure (psi) 16 14 12 10 8 6 4 2 0 65 70 75 80 Zone Temperature (°F) Figure 6: Pilot Site 1- Branch Pressure versus Zone Temperature, single zone In this figure, between zone temperatures of 70°F to 74°F, the WPT is controlled to a neutral branch pressure, not requesting heating or cooling. However, when all the zones for the entire building over the post-installation monitoring period are viewed, the deadband is not obvious; see the figure below. Pilot Site 1 Pilot Site 1- Single Thermostat 24
PG&E’s Emerging Technologies Program ET11PGE3171 Branch Pressure (psi) 20 18 16 14 12 10 Figure 7: Pilot Site 1- Branch Pressure versus Zone Temperature, all zones In this figure, which shows all the buildings thermostats in aggregate, the impact of setpoint deadband is not discernible. This is due to the variability in heating and cooling setpoints across the different zones in the building. Energy Savings Calculations 8 6 4 2 Pilot Site 1- All Thermostats 0 65 70 75 80 Zone Temperature (°F) We expect that the energy savings from the deadband measure will be small because the impact cannot be seen directly. When a thermostat is in the deadband range, the dampers for the heating and cooling duct will be in a more closed position with lower airflow. If enough dampers are at minimum, the fan will turn down to maintain the desired static pressure setpoint. With lower flow, there should also be a small, corresponding reduction of load across the heating and cooling coils due to decreased overlap of heating/cooling between zones. Actual savings, however, is complicated by many factors, including changing zone loads, different setpoints across the building, setpoint overrides, return and mixed air temperatures, and by the single supply fan serving both duct systems. We can first look for savings in reduction to the fan speed. The figure below shows the average fan power at different outdoor air temperatures. 25
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