Heat Pump Water Heaters for Single and Multifamily Residential

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Heat Pump Water Heaters for Single and Multifamily Residential Buildings

October 10, 2014

Learning Objectives 

Understand important concepts governing heat pump performance



Present range of available heat pump water heater technologies currently available



Learn about critical code and design issues to ensure good heat pump water heater performance in residential applications



Review case studies and lessons learned from actual installations

Regional Residential Baseline

Superinsulation and DHP

Low Flow Fixtures

Energy Star Appliances

LED

Occupant Conservation

Refrigeration Cycle

Coefficient of Performance

1 Unit of Electricity + 3 Units of transferred heat = COP of 4

Source vs. Load Source  Indoors or Outdoors?  Air or Water? Load  Domestic Hot Water  Hydronic Space Heating?

Source vs. Load Temperatures

Refrigerant 410a Minimum Source Temperature -20F Maximum Load Temperature 115F

134a 744 (CO2) 40F

-10F

150F

150F

Storage vs. Heating Capacity

Back-up or Finishing Fuel

Double Walled Heat Exchanger

http://encyclopedia.che.engin.umich.edu/Pages/HeatTransfer/HeatExchangers/HeatExchangers.html (Copyright of Alfa Laval, Richmond, VA)

Legionella

Hot Water Recirculation

Hot Water Recirculation

Packaged Residential Equipment

 

Rated COP ~2 Actual COP ~1.8

Manufacturer Comparison

Refrigerant Operating Range Features # Showers 1st hour rating Cost Problems

Voltex

Voltex

Rheem

GeoSpring

AirGen

(60, 80)

(50)

(50)

(50)

(66, 80)

R134a

R134a

R410a

R134a

R410a

45°F min

42°F min

42°F min

45°F to 120°F

32°F min Duct-able

Ducting Kit 3,4

2.5

2.5

2.5

3,4

67.8, 87

63.5

55.8

66

67.9, 79

$1495

~$1300

~$1200

$1109

$2268

Cannot efficiently handle large or frequent draws

R410a can have trouble heating to setpoints above 135

Cannot efficiently handle large or frequent draws

See discussion

None noted

AirGenerate ATI66 

Recently de-listed from Northern Climate Qualified products list due to reliability problems. 

Units exhibited signs of leaking refrigerant 



No refrigerant = no heat pump cycle

AirGenerate is addressing the problems

Biggest HPWH Energy Problem 

“Hybrid” design 





Packaged HPWHs have a resistance element and heat pump When resistance element runs, there is no energy savings over a standard tank

Solution  

Change control strategy to heat pump only Get a unit with a big tank, 60 gallons or greater

Northern Climate Specification Designates equipment which will perform in colder climates:







Climates with 4,000 heating degree days + and average ambient temperatures below 60 degrees Fahrenheit. Roughly locations in North America with latitudes above 40 degrees. In these climates, use the Northern Spec Equipment. Found at the link: http://neea.org/northernclimatespec

HPWHs: Ducting?

Where installation location impacts performance of heat pump

Small Closet Installation

Where installation location impacts comfort in a conditioned space

Conditioned Basement Installation

HPWHs: Space Heat Interactions 

Integrated HPWHs will scavenge heat from the house 

You save energy on water heating but lose some (not all) to added space heating

HPWHs: Exhaust Venting is not a Panacea 

Added infiltration load can cool house in winter requiring more space heat

HPWHs: Solutions/Design Options 

Garage  

No space heating interaction Air temperatures are cooler so pick the best HPWH performers 



Unconditioned Basement  



Rheem, AO Smith (large tanks), AirGenerate

Temperatures mild compared to garage Small space heating interaction

Inside  

If using a heat pump for space heating, this is a great option Tiny closet 

Consider ducting to exterior to guarantee a supply of warm air to the HPWH

Multifamily - Preheat • Cheap method to shave off load • Integrates well if there is waste heat available • Requires Back-up

Sanden CO2 Heat Pump Sanden (40) COP

3.0

Refrigerant

R744 (CO2)

Water Temps

149° F

Operating Range

Down to 5° F

Features

GWP of 1

# Showers

4

1st hour rating

58 gallons

Cost

+$3000

Problems

UL

NEEA NextStep Homes

R410a –Altherma    

Operate down to sub-zero ambient temp. Produce up to about 115F water Annual COP ~2-3 Retrofit with existing central electric

Small Multifamily

VRF – Refrigerant to Water  



 

Mitsubishi and LG Operate down to subzero ambient temp. Produce up to about 115F water Annual COP ~2? Can integrate with VRF space heat systems

Puyallup Phase 2 VRF Heat Plant

Reverse Cycle Chiller (RCC) R134a  Operate down to ~40F airsource  Produce water up to 130-160F  Single Pass Design  Annual COP ~2.6 for garage 

RCC Schematic

Sunset Electric, Stackhouse, Stream

Geothermal: Water-to-Water



COP ~3

Geothermal: Phase 1 Puyallup

Sewage Heat Pump • Potential for very high COP (5-6) • Sewage Handling Issues • Well-matched Source and Load

Questions? [email protected]

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Heat Pump Water Heaters for Single and Multifamily Residential

Heat Pump Water Heaters for Single and Multifamily Residential Buildings October 10, 2014 Learning Objectives  Understand important concepts gove...

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