Maximizing the Use of Ductless Mini-Splits in Existing Homes Cheryn Metzger, Erica Johnson, Yan Chen

Project Goal: Identify controls approaches for a ductless mini-split heat pump to limit the use of electric resistance heating or other backup heating systems. Phase 1 - identify all use cases and current product available Phase 2 - multi-zone building simulation to estimate performance Phase 3 - lab homes testing at PNNL Phase 4 - extrapolation to other climates

Funding NEEA $30k Phase 1, $45k Phase 3 ~$10k for Ecotope and Clearesult for tech support BPA $50k Phase 2 Silicon Valley Power $50k Phase 3&4 American Public Power Association $125k? Phase 3 & 4

Project Advisory Team Primary Investigators Advisory Team Cheryn Metzger, Erica Johnson, Yan Chen - PNNL Advisory Team Christopher Dymond – NEEA Robert Weber – BPA Janice Peterson – BPA Ben Larson – Ecotope Mary Medeiros McEnroe - SVP Bruce Manclark - Clearesult David Lis - NEEP

Phase 1 – Systems for Zonal Heated Homes

Phase 1 – Systems for Central Forced Air

Phase 1 – Systems for PTHPs and Central Hydronic

Background https://www.colwood.ca/city-services/solar-colwood/ductless-split-heat-pumps

Background (cont.) http://www.mississippipower.com/my-home/programs-and-services/heat-pumps/ductless-heat-pumps

Floor Plan of the Lab Home

System Type 1: Zonal + DHP Key HVAC system parameters DHP: Mitsubishi model MUZ-FH15NA Fan Total Efficiency: 0.7 Fan Delta pressure: 300 Pa Maximum air flow rate: 425 cfm/ton Maximum supply air temperature: 50°C Supply air volumetric flow rate when no cooling or heating is needed: 0.2 Number of speeds for heating: 3 Number of speeds for Cooling: 3 Rated HSPF: 12.0 Rated SEER: 22.0 Window AC sizing: 5000 Btu (smallest available) Window AC cooling DX type: two speed Window AC maximum air flow rate: 130 cfm Window AC motor efficiency: 0.9 Window AC design pressure rise: 75 Pa Window AC: Rated SEER: 13 Baseboard Baseboard design capacity: auto size Baseboard efficiency: 0.97 Window AC Baseboard DHP Cooling only Heating only Heating and cooling Door Grille DHP is sized to meet 65% of the whole house load   Building assumptions Heat conduct through 0.5 inch drywall on both sides of interior wall Occupants enter all bedrooms at 9pm and leave bedrooms at 7am Occupants enter living room at 7am and leave living room at 9pm No occupants in bedrooms during the day Duct Leakage: 250-550 cfm @ 25Pa

DHP in Living Room + Zonal Electric + Window AC (Heating) Baseline Baseboards set to 71 degrees F in bedrooms. Baseboards in main living area decommissioned. How it Will Be Modeled How it Will Be Experimented On A Set bedrooms at ~5 degrees cooler than DHP in living room. Multi-zone model. 71 heating set point on DHP. Doors shut with conduction only between walls. Baseboards will be set to 66 in bedrooms. Same as model. Exact airflow TBD to each room and under doors. B Power transfer grills between living room and bedrooms with all zonal turned off at breaker. Model will include a small fan between the living room and each bedroom zone with ~200 cfm constant air flow. Power transfer grills actually installed in Lab Homes. Power transfer fans always on. Zonal always turned off, unless there is need to turn on. C CLVTs and connected DHP. Limit zonal heat. Vary set points and time of day. Model will start the same as option A. In addition, to favor the DHP, living room will be set at 72 and baseboards will be set at 71,69 and 67 to determine various energy savings and comfort implications. Temperatures in the bedrooms will control wall heaters like a thermostat through the Campbell data loggers. Set temperatures will be determined by models.

DHP in Living Room + Zonal Electric + Window AC (Cooling) Baseline Window AC set to 76 degrees F in bedrooms. No window AC in living room How it Will Be Modeled How it Will Be Experimented On A Set bedrooms at ~5 degrees warmer than DHP in living room. Multi-zone model. 76 cooling set point for DHP and window AC. Window AC will only be on in bedrooms during night hours (off during the day when no occupancy). Same as model. Exact airflow TBD to each room and under doors. B Power transfer grills between living room and bedrooms with all zonal turned off at breaker. Model will include a small fan between the living room and each bedroom zone with ~200 cfm constant air flow. Power transfer grills actually installed in Lab Homes. Power transfer fans always on. Zonal AC always turned off, unless there is need to turn on. Exact airflow TBD to each room and under doors. C Connect DHP and window unit to external control and use external user interface to limit window unit cooling. Model will start the same as option A. In addition, to favor the DHP, living room will be set at 75 and window AC will be set at 76,78 and 80 in bedrooms to determine various energy savings and comfort implications. Temperatures in the bedrooms can control window AC like a thermostat through the Campbell data loggers. Set temperatures will be determined by models. Exact airflow measured to each room (max 150 cfm). Airflow will be modeled to return to central living room under each bedroom door.

System Type 2: Central FAF and Air Conditioning System +DHP Key HVAC system parameters DHP parameter stay the same Air Handler 4 speed, 4 ton 1/3 HP 2.9 full load amp rating Central AC/HP sizing: 2.5 ton cooling DX type: single speed maximum air flow rate: Air flow checked at each register. Fan motor efficiency: 0.9 Fan control: ON/OFF design pressure rise: 75 Pa Cooling SEER: 13 Forced Air Furnace electrical heating sizing: 2-element, will check sizing electric heating efficiency: 0.99 DHP Cooling only Heating only Heating and cooling Electric Furnace DX coil Fan T1 T2 DHP is sized to meet 65% of the whole house load

DHP in Living Room + Central FAF Baseline 1 Baseline 2 Central furnace set to 71 and DHP set to 71 everywhere. Set FAF to 68 degrees and DHP at 71. How it Will Be Modeled How it Will Be Experimented On A Run central system as a circulator continuously. Assume tight ducts. Multi-zone model. DHP 71 heating set point, 76 cooling set point. Doors shut with air flowing back under doors. Same as model. Airflow will be measured at each grill and used for model (can use the same return airflow for zonal system). Conducted duct leakage testing in lab homes. 250-550 cfm @ 25Pa. B First stage – circulator fan, second stage – heat kicks on. Ecobee remote sensor in back bedroom. Set back bedroom temp to 71,69 and 67. Actual set temperatures will be determined by models. C What the manufacturers are providing? Connected central thermostat and connected DHP (occupancy based control from a single location). DHP preference (full load all the time). Doors closed. Grills closed. What happens to the back bedrooms? Need to determine how to model two systems in one model and how to divide the load into two parts? If DHP has been on for some amount of time, and temperature at central thermostat is still not met, kick on the Central AC.

Relevant Modeling References DHP https://unmethours.com/question/4053/how-can-i-model-a-ductless-split-hvac-system/ Window AC https://bigladdersoftware.com/epx/docs/8-7/engineering-reference/zone-equipment- and-zone-forced-air-units.html#window-air-conditioner Baseboard https://bigladdersoftware.com/epx/docs/8-7/input-output-reference/group-radiative- convective-units.html#zonehvacbaseboardconvectiveelectric PTHP https://bigladdersoftware.com/epx/docs/8-4/input-output-reference/group-zone- forced-air-units.html#zonehvacpackagedterminalheatpump