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Evaluation of the RTF Standard Protocol Fan and Cooling Savings from Commercial-Sector Heat Pump Units. Rooftop Unit Working Group (RTUG) August 20, 2012. BEGINNINGS. RTUG recommendation to RTF in 2010 to add heat pumps to the RTU Protocol and Annual Energy Use and Savings Calculator

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Evaluation of the RTF Standard Protocol Fan and Cooling Savings from Commercial-Sector Heat Pump Units

Rooftop Unit Working Group (RTUG)

August 20, 2012

  • RTUG recommendation to RTF in 2010 to add heat pumps to the RTU Protocol and Annual Energy Use and Savings Calculator
  • 3 heat pumps were selected (Vancouver, WA) for metering for winter-summer 2011, continuing to winter 2011-2012, and currently into summer 2012
  • Change of data service provider from Powermand to Makad Energy disrupted data acquisition
    • 1 site survived with all required data
    • 1 site had most of the data
    • 1 site dropped out due to gateway failure during provider transition


  • Heat pump heating is different because it includes resistance backup heat + defrost cycles. Principal research questions included:
  • Do these heating differences fit in an energy signature model?
  • How widespread is poorly controlled/contradictory heating and cooling?
  • If the heating signature is accurately derived, how should heat pump monitoring be staged for summer/winter measurement?


  • Per RTF/RTU protocol:
  • One-minute data intervals
  • Total power
  • Outside air temperature
  • Supply air temperature
research tasks
  • Assure measurement & data acquisition equipment installed & operating effectively properly
  • Collect initial 12 months data + tracking of maintenance work done by the HVAC service techs
  • Test the data with the standard RTF/RTU protocol including:
    • Identifying the applicable monitoring period
    • Making recommendations as necessary for changes in the standard protocol to accommodate heat pumps in cooling and heating modes
    • Present results to the RTUG for review and recommendations to the RTF on next steps
metered predicted energy use

Long-term metered energy use was constructed from the

winter and summer energy signatures

heat pump analysis requires annual perspective
  • Summer signature from July or August
  • Winter Signature from December or January
  • September, October, November have minimal useful signature data
  • Measure installation needs to be coordinated with metering
recommended next steps

1. Update Regional RTU Research Database to included metered data from the heat pump project.

2. Notify the Vancouver facility operator of observed deficiencies in RTU operation.

3. Continuing metering/data collection for another 12 months, assuming there is continued access to the Dreamwatts system data, which is unknown at this time.

4. Adapt the RTF/RTU Standard Protocol and Calculator to produce winter signatures. In the near term, this adaptation could take the form of an adapted spreadsheet tool. The adaptation includes annualizing a normalized year estimate by dividing the year into portions associated with the winter and summer signatures.

recommended next steps 2

5. Further test and substantiate the two-season signature approach on additional heat pump units = 10 units, 5 east side, 5 west side, with at least 6 months data, to provide for normalized annual energy use and savings estimates in the Calculator.

6. Expand the tested application of the heat pump signature by revisiting earlier heat pump metering data from the BPA RTU research program and coordinate with future BPA-sponsored heat pump metering and Pacific Northwest National Laboratory heat pump metering that is just underway.

7. Consider proposing a heat pump addition to the RTU standard protocol by the RTF in 2014 or sooner if additional data is available. In this project as well as others, the existence of an approved protocol has been shown to be a substantial analytical time saver.

expanding the rtf rtu protocol
  • NBI is developing a detailed physical RTU model for cooling/ventilation through the Variable Rate RTU Test (VRTUT) project with NEEA/BPA
  • The physical model can provide measure savings estimates, benchmarking and zone characterization (net energy transfer out of the zone/space, effect of outside air temperature)
  • The RTF/RTU Protocol measurement approach and the aggregate results from the Calculator are not changed.
  • Linking the characteristics of the RTU signature to the physical circumstances of the RTU including schedules/controls, results in an enhanced predictive modeling capability supported by the energy signature under a range of variable zone and RTU operating conditions

Mark Cherniack

Howdy Reichmuth