Central Heat Pump Water Heating
Transcript of Central Heat Pump Water Heating
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Central Heat Pump Water HeatingKey Design Considerations
Andy BrooksDirector, West Coast Operations
Association for Energy Affordability
ASHRAE + CBE + PG&E Building Decarbonization Workshop
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Heat Pump Water Heating Configurations
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HPWH Configurations
• Individual – One HPWH per unit
• Central – HPWH plant serving whole building; w/ recirculation
• Semi-Decentralized – 1-3 residential HPWHs serving multiple units; no recirculation
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HPWH Configuration – How to choose?
• Individual• More spread-out developments with larger units• Individually-metered buildings, or condos (owner-occupied)• Large equipment selection, eliminates T24 solar hot water (PV or thermal) requirements• Can save cost on recirculation piping, but more pieces of equipment in each unit
• Central• Very dense developments with smaller units and tight sites• Master-metered buildings (supportive housing)• More limited equipment selection, subject to T24 solar hot water requirements• Less hot water equipment overall, and easier to access/maintain
• Semi-Decentralized• Saves on recirculation piping costs & energy waste – most efficient?• Need to locate equipment
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CentralHeat Pump Water Heating
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HPWH Equipment – Central/CommercialSplit / Built-Up
Combined
ColmacR-134a
NyleR-134a
SandenR-744 (CO2)
MayekawaR-744 (CO2)
MitsubishiR-744 (CO2)
AO SmithR-134a
RheemR-134a
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Image: AEA
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Image: AEA
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Image: AEA
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Image: AEA
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Images: AEA
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Central HPWH – Key Considerations
• Sizing of heat pumps vs. storage tanks• Equipment location• Single-pass vs multi-pass and piping options• Recirculation• Renewables – solar thermal vs solar PV• Mixing valve• T24 compliance• Commissioning
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Central HPWH Sizing
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Central HPWH – Sizing
Large Storage Tanks + Small Heat Pumps
• Advantages• Reduces overall hot water system cost, since tanks are cheaper than heat pumps• Reduces building electrical service requirements including wiring, panels, and service• Reduces owner exposure to high peak demand (kW) charges• Reduces heat pump equipment short cycling• Improves resiliency in event of power outage – thermal battery
• Disadvantages• Large tanks need space
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Central HPWH – Sizing• Example Building Loads (ASPE): • 1 hr: 440 gal• 2 hr: 710 gal• 3 hr: 960 gal
• In a nutshell: Size storage to meet 3-hr peak demand, and heat pumps to recharge tanks between peaks
Storage (gal)
Recovery (Btu/hr)
Recharge Time Total System
GasTankless 0 3 x 199,000 - 0 gal
597,000 BTU/hr
GasTank-Type 2 x 200 2 x 199,000 0.5 hrs 400 gal
398,000 BTU/hr
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Central HPWH – Sizing• Example Building Loads (ASPE): • 1 hr: 440 gal• 2 hr: 710 gal• 3 hr: 960 gal
• In a nutshell: Size storage to meet 3-hr peak demand; heat pumps to recharge tanks between peaks
Storage (gal)
Recovery (Btu/hr)
Recharge Time Total System
GasTankless 0 3 x 199,000 - 0 gal
597,000 BTU/hr
GasTank-Type 2 x 200 2 x 199,000 0.5 hrs 400 gal
398,000 BTU/hr
Electric Heat Pump 1,200 140,000 7 hrs 1,200 gal
140,000 BTU/hr
47 kW
31 kW
11 kW
Peak Power Draw
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Central HPWH Piping
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HOT UP HERE
Stratified Storage
Tank
LESS HOT DOWN HERECold Water
Makeup
Hot WaterTo Building
Multi-Pass HPWH
Multi-Pass HPWH
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HOT UP HERE
Highly-Stratified Storage
Tank
LESS HOT DOWN HERECold Water
Makeup
Hot WaterTo Building
HPHP
Single-Pass HPWH
Single-Pass HPWH
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Stratified StorageTank(s)
Cold WaterMakeup
Hot WaterTo Building
Single-Pass HPWH
What about Recirculation Return?
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Stratified StorageTank(s)
Cold WaterMakeup
Hot WaterTo Building
Single-Pass HPWH
What about Recirculation Return?
Recirc Pump
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Stratified StorageTank(s)
Cold WaterMakeup
Hot WaterTo Building
Single-Pass HPWH
What about Recirculation Return?
Recirc Pump
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Stratified StorageTank(s)
Cold WaterMakeup
Hot WaterTo Building
Single-Pass HPWH
What about Recirculation Return?
Recirc Tank
HP or Elec Res
Recirc Pump
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Stratified StorageTank(s)
Cold WaterMakeup
Hot WaterTo Building
Single-Pass HPWH
What about Recirculation Return?
Recirc Tank
HP or Elec Res
Recirc Pump
Mixing Valve
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Stratified StorageTank(s)
Cold WaterMakeup
Hot WaterTo Building
Single-Pass HPWH
Single-Pass w/ Recirc Tank
Recirc Tank
HP or Elec Res
Recirc Pump
Mixing Valve
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Stratified StorageTank(s)
Cold WaterMakeup
Hot WaterTo Building
Single-Pass HPWH
Recirc – Single Pass w/ Swing Tank
Swing Tank
HP or Elec Res
Recirc Pump
Mixing Valve
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Stratified StorageTank(s)
Cold WaterMakeup
Hot WaterTo Building
Multi-Pass HPWH
Multi-Pass w/ Recirc Tank
Recirc Tank
HP or Elec Res
Recirc Pump
Mixing Valve
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Stratified StorageTank(s)
Cold WaterMakeup
Hot WaterTo Building
Multi-Pass HPWH
Recirc – Multi-Pass Direct Return
VSRecirc
Pump w/ Thermal
Balancing
Mixing Valve
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Cold WaterMakeup
Hot WaterTo Building
Recirc – Single-Pass Direct Return??
Mixing Valve
Stratified StorageTank(s)
Single-Pass HPWH
VSRecirc
Pump w/ Thermal
Balancing
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Central HPWH – Piping
• There are many options and tradeoffs
• Weigh simplicity vs performance for your project
• Most efficient CHPWH system may be more complex, higher first cost
• Talk to heat pump manufacturer
• Onsite QA/Commissioning to verify it was done correctly
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Thank You!