1. A Calculator for Reliably Measuring the Savings from Advanced RTU Control Retrofits August 27, 2015 Presentation to: RTF Commercial Rooftop Unit Working Group Presented by: SBW Consulting, Inc. Bill Koran, Santiago Martin Rodriguez-Anderson, Gina Hicks, Michael Baker

2. Background and Review  A best practice method was used to estimate savings for 61 RTUs.  The best practice method used total RTU power.  A simplified method was developed and used to estimate savings for 54 RTUs.  The simplified method used fan power from the VFD. 2 August 27, 2015

3. Previous Conclusions Fan savings are very well estimated by the simplified method. Cooling savings are well estimated, on average, by a multiplier on the fan savings. Cooling savings vary unit-to-unit, and estimation is uncertain even with a best practice method. The simplified method, using supply fan VFD power, is the simplest reliable method of verifying ARC Retrofit electrical savings. 3 August 27, 2015

4. Demonstration The calculator is based on the simplified method presented in February. 4 August 27, 2015

5. Approach Compare calculator output to previous calculations Demonstrate calculator Discussion 5 August 27, 2015

6. Approach – Simplified Method Simplified savings estimates  Savings estimate based on regressions  Baseline and post power from VFD on fan 6 August 27, 2015

7. Steps in the Simplified Method 1. Collect hourly average fan speed, fan power (VFD output) and OAT from the RTU that has advanced controls. 2. Fit a power regression to fan power vs. speed, for all speeds occurring in the efficient mode of operation. 3. Calculate the 100% speed fan power using the fit curve. 4. For each hour compute savings as the difference between the 100% speed fan power and the VFD input power. Input power is derived by dividing the output VFD power by.96. 5. Fit a model to fan savings vs. OAT (Outside Air Temperature) and use TMY (Typical Meteorological Year) OAT to extrapolate to annual fan savings. This is only applicable for cases where time and outside air temperature are the primary independent variables. 7 August 27, 2015

8. Comparison of Fan Savings Previously Reported with Calculator Output 8 August 27, 2015

9. Comparison of Fan Savings Previously Reported with Calculator Output 9 August 27, 2015

10. Comparison of Fan Savings Previously Reported with Calculator Output 10 August 27, 2015

11. Normalized Savings using TMY3 11 August 27, 2015

12. Future Chart to Evaluate Suitability of the Range of Temperatures Available 12 August 27, 2015