Heat Pump Water Heaters: Interior, Ducted Installations Presentation to the Regional Technical Forum December 13, 2011 Ben Larson, Ecotope 1

Background In October 2011, Provisional UES approved for heat pump water heater (HPWH) for: – Northern Climate Specification Tier 1 Buffer space installs Interior (non-ducted installs) – Northern Climate Spec Tier 2 Buffer space installs Northern Climate Spec Tier 2 Interior Installations require exhaust ducting – Left as “TBD” in October. – Today’s presentation covers ongoing analysis 2

Overview Equipment airflows and installation Analysis method Analysis output and findings Continued research 3

Equipment Exhaust Airflows Flow range of interest: 350cfm to 150cfm Flow measurements in lab: – Static pressure variation created with damper at duct outlet – Different models have different fans and flow characteristics Field airflows will depend on specifics of each installation 4

Analysis Inputs Used the same assumptions as with earlier HPWH analysis – 45 gallons per day of hot water water temperature rise: 72.5F results in a little less than 4 hrs per day of runtime for indoor temperatures ranging from ~64F – 78F – house characteristics the same tightness: 7ach50 ducts: sealed 4 HVAC system types – baseline tank EF: 0.92 (50 gallon size) 5

Analysis Updates Using updated version of SEEM which allows direct infiltration modeling in combination with exhaust airflows HPWH exhaust air ducted outside Water heater runs based on draw schedule Water heater COP varies as indoor temperature changes – Ex: higher inside T in summertime for houses without cooling gives better performance than wintertime situations 6

7 Interior installation temperature range.

DHW Energy Use and Savings Baseline DHW Energy Use: ~3100kWh/yr Measure DHW Energy Use: kWh/yr – varies because indoor temperature varies with season and climate HPWH Interior Install Annual COP:

Overall Savings Estimates Impact on house heating + cooling system depends on climate, exhaust airflow, and HVAC system type Combining DHW energy savings with heating + cooling impact produces the overall energy savings estimate 5 scenarios in 5 climates considered on next slide: – Interior non-ducted (0 cfm flow to outside) – 4 levels of exhaust ducting to outside 150, 200, 250, and 300 cfm 9

Analysis Outputs: Savings Estimates DHW Savings Combined with Heat+Cool Interaction 10

Analysis Caveats Caution: as yet, analysis does not include performance variation of HPWH with airflow – Performance at lower airflows could be expected to decrease but what is the critical airflow where performance drops significantly? 11

Measured Airflow Variation Effects NEEA lab testing of ATI66 at 40F ambient found a decrease in COP of 10% for an airflow decrease from 338 to 177cfm BPA HPWH lab evaulation observed Voltex compressor performance for 3 flow scenarios at 67F ambient temperature – Full flow: 475 cfm – ⅓ filter area blocked: 372 cfm – ⅔ filter area blocked: 284 cfm  Small changes in performance 12

Analysis Discussion Space heating impact (and therefore overall savings) is highly dependent on amount of exhaust airflow – Also, climate dependence due to increased infiltration rate: more outside air at lower temperatures increases heating load Is there a optimized airflow which might reduce HPWH performance but at the same time provide a minimal space heating impact? 13

Continued Research – Next Steps Field Measurements: – NEEA project with ducted, indoor installations will measure airflow as installed – Project will also provide incremental install cost estimates Lab Measurements: – Plans to measure AirGenerate compressor performance at 200cfm and 150cfm at 67F ambient air. Installation Specification: – Is it desirable to write a spec to limit airflow upon installation? 14