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Residential Variable Capacity Heat Pump Field and Lab Testing: Final Results

Residential Variable Capacity Heat Pump Field and Lab Testing: Final Results. 20 November 2013 Ecotope. History.

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Residential Variable Capacity Heat Pump Field and Lab Testing: Final Results

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  1. Residential Variable Capacity Heat Pump Field and Lab Testing: Final Results 20 November 2013 Ecotope

  2. History • Inverter-driven compressor tech making increasing inroads (ductless systems now at 20,000 plus installs in NW); BPA has incented central ducted systems via PTCS on provisional basis • Advisory committee formed to guide research plan • Range of experience on committee • Interest in zoned systems, delivery temperatures • Timeline/budget limited research scope • Study summary • Heating season only • ‘Detailed’ (full capacity/COP) vs non-detailed sites • Combination of field/lab info (EPRI) • ASHRAE 152 duct model exercised plus SEEM for full season estimates

  3. Major Findings – Expectations/Reality • VCHP performs 25-30% better than a single speed 7.9 HSPF heat pump on an annual basis (note nominal average HSPF for this product ~12). • Duct losses increased ~5% over a single speed heat pump • Overall system offers improved performance over single speed base cases • Heat pump sizing still matters • Auxiliary heat lockout control still matters

  4. Field Deployment • Planning/refinement occurred through late 2012 • Field deployment set for late February, 2013 (six sites); central OR chosen for likelihood of remaining cold weather (about 24 potential sites) • Critical points measured • 5 minute metering for electricity usage (including air handler circuit power- CFM mapping) • One-time measurements of house heat loss (including blower door test (system sizing, heating season simulation)), duct area/R-values, duct leakage, system CFM (at least 3 points so CFM could be correlated with power), heat pump control settings

  5. Site Pictures

  6. Site Summaries

  7. Duct Leakage/Air Handler Data

  8. Airflow & Fan Power • Site 91009

  9. Air Handler Curves - All Sites

  10. Balance Points (for 2 sites)

  11. Heat Pump Balance Points

  12. Detailed Field Results(834 monitored hours)

  13. Capacity and COP Calculations • Capacity determined by multiplying fitted airflow by coil temperature split • True RMS power is measured at the panel for both indoor and outdoor units and converted to Btu/hr • COP is ratio of capacity to input power at a given outdoor temperature • Following 2 graphics do not include duct losses

  14. Performance vs Outdoor Temp (1)(no duct effects included)

  15. Performance vs Outdoor Temp (2)(no duct effects included)

  16. Measured Field Performance (common five week period)

  17. Compressor Response to Changing Heating Load • Low compressor speed: input power < 1.25 x observed minimum input • Medium compressor speed: anything in between low and high • High compressor speed: input power > 0.87 x observed maximum input

  18. Air Handler Response to Changing Heating Load • Low fan speed: airflow < 1.25 x listed minimum airflow (comfort mode) • Medium fan speed: anything in between low and high • High fan speed: airflow > 0.87 x listed maximum airflow (comfort mode)

  19. Operating Mode Summary • Fan and compressor speeds track one another • Given a compressor speed, there is a preferred fan speed • High compressor outputs almost never pair with low and medium fan • Low compressor speeds pair with both low and medium fan • Runtime Fractions:

  20. Rolling in the Ducts…

  21. Duct System Inputs • Duct leakage, normalized to fraction of air handler flow (which changes at different flows) • Duct R-value • Duct area • Buffer space temperature (measured only for supply buffer space) • ASHRAE 152 used to calculate distribution efficiency

  22. Average Duct Performance and Calculated Duct Distribution Efficiency (DE) (common five week period)

  23. Modeling VHCPs – Annual Performance • Annual performance estimated with SEEM • Simulation largely unchanged from September 2012 RTF presentation • Performance curve from catalogue data found to work well enough for systems modeled • Field study found that the operating modes pair fan and compressor speed (previous default assumption in simulation – remains unchanged)

  24. Modeled VCHP and Duct System Efficiency (using SEEM for entire heating season)

  25. Lab (EPRI) vs Field Results • Agreement on capacity and COP measurements generally good; more divergence for some cases • Lab tests done in EFFICIENCY mode • All sites in Oregon set up in COMFORT mode • Lab showed higher COPs as expected because of EFFICIENCY vs COMFORT mode • Possibility of variability for individual pieces of equipment, as well

  26. Lab vs Field Comparison(2 ton system) Lab results Field results

  27. Overall Findings • VCHP performs 25-30% better than a single speed 7.9 HSPF heat pump on an annual basis • Duct losses increased ~5% over a single speed heat pump • Overall system offers improved performance over single speed base cases • Heat pump sizing still matters • Auxiliary heat lockout control still matters

  28. Next Possible Steps • Cost analysis. Collect data on installed costs and compare to annual estimates of savings. • More complete set of SEEM runs- additional comparisons to base cases (HP and/or EFAF) • Possible UES process (depends on cost analysis) • Further discussion of how system could be commissioned (PTCS)

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