Central Hot Water Temperature Maintenance Pilot Study | Central Heat Pump Performance

1. Understand typical hot water loads for multifamily projects 2. The relative merits of three different hot water temperature maintenance systems for small apartment buildings 3. Central heat pump water heating system efficiencies and performance impacts 4. Design considerations for high efficiency central hot water heat pump systems for multifamily buildings

Learning Objectives

Background on Multi-Family DHW Energy

Multifamily Building Energy End Use

Based on billing analysis of 10 Multi-family Buildings in Seattle Median Energy Use Index (EUI): 39 kBTU/sf/yr

EUI ~ 10 (22 Gal Hot Water/pp/pd Central Gas)

Annual Hot Water Heating Load

Heating Water + Losses

= Total MF Hot Water Heating Load

~(16 gal/pppd) 30-50%

Parts of a Central Hot Water System • Central Plant • Primary Supply • Risers • Balancing • Re-circulation

Central Hot Water Heating System

Temperature maintenance

1. Keep loop hot, it is constantly losing heat

2. We need to add heat to keep water hot.

3. Losses

Losses

Poor or low insulation Exposed Pumps, Valves

Thermal Bridging Poorly Insulated Pipe Clamps

• We first came up with the RCC concept after studying these buildings and the energy end uses

• WE got funding from BPA to monitor these pilots • The RCC was a design for larger buildings with buffered parking spaces. • This led to research on R410a inverter driven RCC’s for smaller buildings. • Through the research and monitoring we have been able to optimize the

design of central HPWH systems delivering RCC 2.0

RCC Study

• Through the research and monitoring we have evolved to RCC 2.0.

RCC-1.0 - 2.30 Seasonal

RCC-2.0 - 2.75 Seasonal

• Decouple the heating water load from the temperature maintenance loads allows optimization of both

RCC Finding

9500

16000

8500

7500

0

5000

10000

15000

20000

25000

Sunset Electric (47%) Stream Uptown (32%)

Losses (watts)

Water Heating Load (watts)

• We started designing RCC’s for smaller buildings and also decided to test out the temp maintenance systems and combine to research and M&V project

• This led to research on R410a inverter driven

RCC’s for smaller buildings and out of that we also arrived at a temperature maintenance study

RCC for smaller buildings

DHW System Losses

Watts/Apt

Smaller MF Buildings 75-125

Larger MF Buildings 65-90

Electric Tank in Unit 60

Ecotope figured out how big the losses were and we came up with test for the Grow Communities MF project. We got BPA involved and designed a double study: Temperature Maintenance Options 1. Traditional Circulation Loop with increased insulation 2. Heat Trace 3. Pipe in a Pipe Daikin Altherma for Central DHW 1. With Recirculation Water Mixed In 2. With only Cold Water Entering Tank

Temperature Maintenance and Heat Pumps Research

• Improved Insulation on a traditional recirculation

• 2” Pipe Insulation, no TB in garage

• Risers dense-packed in stud bays, up to R-13

Traditional Circulation Loop

Heat Trace Electric controller set to maintain temp Results in reduced piping length and elimination of pumping energy *(24/7 typ) Disadvantage is no COP on reheating Advantage is it is simpler.

Electric Heat Trace

Pipe in a Pipe Circulation Loop

Reduced Exposed Piping with Concentric piping Advantage is you still get COP on the reirc and you have reduced Pipe Losses by 30-40%, Reduced Insulation Costs trades off with copper risers

Building A Traditional Recirculation Loop 12 Units ~ 1450 SF each, 2 Bedroom Vacant Units: 1 Part-time residency: 3 units = 6 adults Full time residency: 8 units = 13 adults 2 children

Building B Electric Heat Trace 12 Units ~ 1450 SF each, 2 Bedroom No Vacant units Part-time residency: 1 unit – 2 adults Full time residency: 22 adults 7 children

Building D Pipe in a Pipe Recirculation Loop 13 Units ~ 1450 SF each, 2 Bedroom Vacant Units: 7 Part-Time residency: 1 unit – 2 adults Full Time residency: 5 units - 8 adults

# Occupants

Building A 18

Building B 30

Multi-Family Hot Water Usage

Hot Water Usage Grow Building A

12 Units

Building #

Occupants

Mean DHW/

Day Hot Water /pp/day

A 18 250 13.9

Hot Water Usage Grow Building B

12 Units

Building #

Occupants

Mean DHW/

Day Hot Water /pp/day

B 30 490 16.3

Hot Water Usage Stream Uptown

118 Units

Building #

Occupants

Mean DHW/

Day Hot Water /pp/day

SU 144 2640 18.3

Hot Water Usage Sunset Electric

92 Units

Building #

Occupants

Mean DHW/

Day Hot Water /pp/day

SE 106 1530 14.5

Seasonal Impact of City Water

Findings – Actual Losses

Grow Building Research Theoretical

3000

1000 857 1000

500 900 400

0

500

1000

1500

2000

2500

3000

3500

Base Load Grow A Grow B Grow D

Theoretical Prediction – With Heat Pumps

Temp Maintenance

Water Heating Load

Base – Straight Water Load (COP 1) Grow A – COP on Water and Temp Maintenance Grow B - Better COP on Water Only, Temp Main-COP 1 Grow D – COP on both, Pipe in Pipe has Less Losses

Theoretical Calculated Losses-Grow A HOT WATER HEAT LOSS CALCULATOR

SYSTEM INPUTS BUILDING INPUTS INSULATION INPUTS

SYSTEM NAME

SYSTEM ABBREVIATION

FLUID TEMPERATURE

INDOOR TEMP 70

TAG TYPE K VALUE (BTU-FT/HR-FT2-F)

WALL THICKNESS

(INCH)

PERCENTAGE OF PIPE

INSULATED R VALUE

DOMESTIC COLD WATER

DCW 70 GARAGE TEMP 50

A FIBERGLASS 0.0231 1.5 100% Garage Value

DOMESTIC HOT WATER

DHW 122 B FIBERGLASS 0.0231 2 100% Riser Value

DOMESTIC HOT WATER CIRCULATION

DHWC 118 C

HEATING WATER RETURN

HWR 80 D

HEATING WATER SUPPLY

HWS 90 E

PIPE INFORMATION PIPE SIZE INSULATION HEAT LOSS

TAG SYSTEM MATERIAL LOCATION FLOOR DIAMETER

(INCH) LENGTH

(FT) QUANTITY

90 DEG BENDS

TAG K VALUE (BTU-FT/HR-FT2-F)

PERCENT INSULATED

LINEAR (BTU/HR-FT)

TOTAL (BTU/HR)

Primary Supply DHW CPVC Garage Garage 1 1/2 35.5 1 0 A 0.0231 100% 9.51 337.51 Header in Garage DHW CPVC Garage Garage 1 1/2 23.5 1 0 A 0.0231 100% 9.51 223.42 Header in Garage DHW CPVC Garage Garage 1 1/4 94.0 1 0 A 0.0231 100% 8.53 802.29 Riser Supply DHW CPVC Unit Unit 1 1/4 6.0 4 0 B 0.0231 100% 5.26 126.16 Riser Supply DHW CPVC Unit Unit 1 10.0 4 0 B 0.0231 100% 4.69 187.48 Riser Supply DHW CPVC Unit Unit 3/4 10.0 4 0 B 0.0231 100% 4.09 163.47 Riser Return DHW CPVC Unit Unit 3/4 27.0 4 0 B 0.0231 100% 4.09 441.38 Return in Garage DHW CPVC Unit Unit 3/4 165.0 1 0 B 0.0231 100% 4.09 674.32

N/A N/A N/A N/A N/A 1 3/32 371.0 20.0 0.0 N/A 0.023 100% 49.75 2956

Supply Loop – 2000 BTU/hr Return Loop – 1000 BTU/hr Other Losses - 2500 Btu/hr

Total ~ 5500 Btu/hr All Losses are Surface Area * U Value

Building A Actual Losses

~5500 Btu/hr

Building B Actual Losses

~2600 Btu/hr

Preliminary Findings

1500 3000

9500

16000

1500 900

8500

7500

0

5000

10000

15000

20000

25000

Grow A (50%) Grow B (23%) Grow D Sunset Electric(47%)

Stream Uptown(32%)

Tota

l wat

t/D

ay

Losses (watts)

Water Heating Load (watts)

Building # Units Temperature Maintenance

Water Heating Load (watts)

Losses (watts)

% Losses

Watts/Unit

Grow A (50%) 12 Traditional Recirc 1500 1500 50% 125

Grow B (23%) 12 Heat Trace 3000 900 23% 75

Grow D 13 Pipe in Pipe Recirc

Sunset Electric (47%) 92 Traditional Recirc 9500 8500 47% 92

Stream Uptown (32%) 118 Traditional Recirc 16000 7500 32% 64

Preliminary Findings

125

75

0

92

64 60

0

20

40

60

80

100

120

140

Grow A(50%)

Grow B(23%)

Grow D SunsetElectric(47%)

StreamUptown

(32%)

ElectricWaterHeater

Losses Watts/Unit

Daikin Altherma-Grow Communities- DHW

Daikin Altherma for DHW Monoblock

Daikin Altherma

Daikin Altherma

Building A: COP 3.2 (Based on 5 Months) Building B: Lower COP (Controls, Cx) Building D: Not Completed Yet

Daikin Altherma

Design Considerations

• Back to back bathrooms sharing a single stack reduces UA by factor of 2

• Locate hot water storage and primary distribution in heated space to capture losses ½ the year

• Plan for super-insulated hot water piping runs, Risers- 2x8

studbays, Adequate room for insulated pipe clamps • Consider Distributed Plants versus Single Central Plant.

(closer to use, smaller piping)

• Use heat pumps when heating with utility provided power, lowest carbon

Design Considerations Programming and Design

Design Considerations Continuous Insulation – 2-3” thick wall, w/vb

Design Considerations Full Piping Insulation Mounts

Design Considerations Insulation Jackets on Tanks and Valves

Piping Insulation Requirements – Too Low

Delta T of 50-70 degrees year round We insulate houses to R-20 and 30 for 1 week of 47F delta T Pipe Insulation is Cost Effective, Need More

Super-Insulated Hot Water Storage and Distribution System that reduces losses from 75 Watts to 15 watts per unit. Increase U value by factor of 5

PassivLoop • R-25 Insulation on central hot water piping • R-25 jackets around storage tanks • Eliminate Thermal Bridging on Pipe Mounts and Penetrations • Hot Water Storage Tanks located inside heated space • Insulated Valves and Pumps. • 1 hot water stack per 2 back to back apartment stacks (1/2 UA) • Consider small plant on each riser • Targeted losses are less than 15 Watts/apartment

PassivLoop

Central CO2 sanden Heat Pumps applied to smaller multi-family projects, (30 units or less) • Distributed micro plants • Elimination of recirculation loops • Larger Sanden CO2 heat pumps for larger buildings

Future Research

Wastewater Heat Pumps (2019) • Heat Plant COP ~ 4.5 Using Wastewater as Source

Future Research

Questions/Comments:

Shawn Oram, PE 206.596.4703

shawn@ecotope.com

Ecotope.com