3C Charlotte Bonneville
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Transcript of 3C Charlotte Bonneville
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ACEEE 2010 Hot Water Forum
Central Domestic Hot Water
Systems in Multi-FamilyBuildings
May 13, 2010Charlotte Bonneville
Heschong Mahone Group, Inc.
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Water Heater
Losses
Distribution Losses
End-Use
Energy
40%30%
30%
Branch
LossesRecirculation
Loop Losses
Hot water supply
Hot water return
Cold water
supply
Mechanical Room
Branch
DHW System Energy Flow
??
??
??
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Study Goals
Conduct field monitoring of DHW systems
in more than 30 multi-family buildings in
California
Assess and analyze the detail energyperformance of each DHW System
components Assess the energy saving potential of
control strategies
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System Definition
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System Energy Flow Analysis
ERecirc_RERecirc_Loss
ERecirc_S
EGas
EHeater_Loss
EBranch_Loss
Water Heater
Control Volume
EDraw
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Monitoring Plan
AmbientTemperature
Cold Water
Temperature
Hot Water Supply
Temperature
Hot Water ReturnTemperature
Recirculation
Flow
Draw Flow
Gas consumption
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DHW Distribution Configuration
Level 3
Level 1
Level 2
Site #1
Sacramento, CA
CWS
HWS
HWR
Site #2
San Francisco, CA
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Water Heater
Losses
Distribution Losses
End-Use
Energy
40%30%
30%
Branch
LossesRecirculation
Loop Losses
Hot water supply
Hot water return
Cold water
supply
Mechanical Room
Branch
DHW System Energy Flow
45%
29%
1%
25%Distribution Losses
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0
0.1
0.2
0.3
0.4
0.5
0.6
Percentag
10%
20%
30%
40%
50%
DHW System Performance
Variation
EBranch_Los
sBranchLosses
EDrawOverall
SystemEfficiency
EHeater_LossWater
Heater
Losses
30%
20%
49%
23%
2%
Site #1
Site #2
Site #3
Site #4
ERecirc_Loss
Recirculation Loop
Losses
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Energy Consumption per Gallon
of Hot Water Draw
0
500
1000
1500
2000
2500
Site #1 Site #2 Site #3 Site #4
Btu/gal
Overall System Efficiency
Branch LossesRecirculation Loop Losses
Water Heater Losses
End-Use Energy
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DHW system controls
0
20
40
60
80
100
120
140
160
0:00 4:00 8:00 12:00 16:00 20:00 0:00
Temperature(F)
-3
0
3
6
9
12
15
18
21
Flow(
gpm)
0
20
40
60
80
100
120
140
160
0:00 4:00 8:00 12:00 16:00 20:00 0:00
emperaure
-3
0
3
6
9
12
15
18
21
Flow(
gpm)
Demand Control
Timer
Temperature Modulation
Pump Control Temperature Supply
Control
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DHW system performance under
Controls
Site #2 SF, CA
59%
Gas Consumption Reduction
normalized by gallon of water
0%
2%
4%
6%
8%
10%
12%
14%
16%
0%
10%
20%
30%
40%
50%
60%
Demand Control
Timer
TemperatureModulation
Recirculation Loop Losses Reduction
normalized by gallon of water
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Control Analysis
The key to energy savings Reduce recirculation loop temperatures as much as
possible
The return portion of the recirculation loop doesntneed to be warm
Pump off Cold Recirculation loop Pipe insulation can keep recirculation loop warm for
extended period (~1hr) hot water draws will also help sustain recirc. loop
temperatures
pump can be kept off periodically even duringpeak usage
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A Better Control Strategy?
Turn on recirculation
pump periodically(every 1-2 hr)
Modulate water heater
temperature during off peaktime
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Hot Water Draw Study
Wide range of water usage per occupant
Strong influence of weather on waterusage
No observation of obvious water usageincrease under controls
Analysis of hot water usage pattern to
provide peak demand statistics to guidesystem and pipe sizing
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Guideline for DHW System Design
Water heater/boiler efficiency is still the most
important component to system efficiencyProper system sizing will help to reduce standby
and short-cycling losses
Distribution system designPlace recirc. loop through the middle of the building(this is the same concept as placing water heaternear fixture
Control and monitoringEven a simple temperature indicator on HW return
can be very useful
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Charlotte Bonneville
Associate Project Manager
HMG Main Office - Sacramento
11211 Gold Country Blvd., #103
Gold River, CA 95670
Thank you!
