electric tankless water heaters · 2016. 4. 16. · designed and installed electric tankless water...
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ELECTRIC TANKLESS WATER HEATERS ise15a Credit: 1 AIA HSW CE Hour
Developed & Sponsored By David Seitz, CEO,
Seisco International 888-296-9293
Authored By: David Seitz – CEO, Seisco International Limited, Inc. Dr. Tom Harman, Ph.D. – Electrical Engineering, Rice University Dr. Louis J. Everett, Ph.D. – Mechanical Engineering, Texas A&M University Eddie Wilcut, MAG – Texas State University
© InfoSpec, Inc. 2013
An American Institute of Architects (AIA) Continuing Education Program Approved Promotional Statement: • InfoSpec, Inc. is a Registered Provider with The American Institute of
Architects Continuing Education Systems (AIA/CES). Credit(s) earned on completion of this program will be reported to AIA/CES for AIA members. Certificates of Completion for both AIA members and non-AIA members are available upon request.
• This program is registered with AIA/CES for continuing professional education. As such, it does not include content that may be deemed or construed to be an approval or endorsement by the AIA or InfoSpec, Inc. of any material of construction or any method or manner of handling, using, distributing, or dealing in any material or product.
• Questions related to specific materials, methods, and services will be addressed at the conclusion of this presentation.
An American Institute of Architects (AIA) Continuing Education Program • Course Format: This is a structured, live, instructor-led course. • Course Credit: 1 AIA Health Safety & Welfare (HSW) CE Hours • Completion Certificate: A copy is sent to you by email upon request.
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Design professionals: Certificates of Completion are sent to your email address
Did You Know?
• Did you know about electrical service requirements needed to accommodate a whole house tankless electric water heater?
• Did you know about “interlocks”?
• This course will teach you this and much more.
Course Description
This learning unit will address the benefits of a properly designed and installed electric tankless water heater and explore how installing electric tankless water heaters in new construction, in a retrofit situation, or as a companion to other water heating technologies already in place can offer a reliable, endless supply of hot water while maximizing both water savings and energy efficiency.
Course Objectives
By completing this course, the design professional will be able to:
1. Explain the Water/Energy Nexus as it relates to water heating.
2. Discuss consumption patterns associated with typical residential
hot water usage.
3. Identify the different classifications of water heater designs currently on the market.
4. Discuss the benefits and shortcomings associated with each classification of water heating design.
Course Objectives
By completing this course, the design professional will be able to:
5. Explain the role and effectiveness of electric tankless water
heaters.
6. Discuss the difference between flow control and temperature control as separate demand water heating activation technologies.
7. Explain the issues of light flicker “power quality” related issues in evaluating different electric tankless models and manufacturers.
8. Discuss the impact of hot water systems on electrical load and
peak demand.
Course Objectives
By completing this course, the design professional will be able to:
9. Describe how properly designed electric tankless water heaters
integrate into a sustainable, low-flow, energy efficient plumbing design.
10. Identify the benefits associated with the use of new low-flow electric tankless system technology.
11. Identify the fuel source for each technology and how each is related to renewable energy.
OBJECTIVE 1 Understanding the nexus between energy & water.
Image source: http://alexansouthwoodblog.com/files/2012/02/energy-lights.jpg/
The Water/Energy Nexus
• 3.9 trillion gallons of water are consumed in the U.S. monthly.
• 93.6 billion kilowatt hours of energy are needed to produce and treat that water every year.
• Our current water consumption results in approximately 122 billion pounds of CO2 emissions yearly.
The Water/Energy Nexus
• It takes 2 gallons of water to produce 1 kilowatt hour of electricity.
• U.S. consumes 3.9 trillion kilowatt hours (kWh) annually.
• 17% of all the water consumed in the U.S. is used for power production.
The Water/Energy Nexus
• We consume 93.6 billion kilowatt hours to produce and treat water; that’s 187 billion gallons of water to produce that energy.
• 1% of the water we consume each day is consumed during the production and treatment process.
The Water/Energy Nexus
• Every time you save energy you save water and every time you save water you save energy!
• Replacing an older 60 watt light bulb with a new 15 watt CFL will save approximately 98 gallons of water per year.
• Replacing an older high flow toilet with a new High Efficiency Toilet (HET) will save 32 kWh per year.
The Water/Energy Nexus
You can save water and energy with an electric tankless water heater. 1. Locate unit close to fixtures 2. Flow/no flow 3. Eliminate standby losses 4. Increased efficiency
Remember, it takes water to generate electricity! It takes electricity to deliver water!
OBJECTIVE 2
Understand the true consumption patterns associated with typical residential hot water usage.
Tankless Sizing: Whole Household
• 2.5 gallons of hot water per minute will satisfy nearly every U.S. household.
• The Energy Star program establishes a minimum 2.5 gallons per minute (GPM) at a 77⁰F rise. • A residential tank water heater provides 50-90 gallons
in the first hour and less during the second hour. • Tankless water heaters provide more than double the
output of a typical tank water heater. • A little planning can help to avoid common oversizing
of tankless water heaters.
Case Study:
• In March of 2003, the National Association of Home Builders (NAHB) Research Center conducted a study.
• A copy of this study can be found using the following internet link: http://www.nrel.gov/docs/fy03osti/32922.pdf
• In both a high-flow and low-flow home, a tankless water heater meets nearly 99% of the demand.
Hot Water Consumption by Flow Rate – Annual Minutes of Use at Given Flow Rates for High & Low Volume Homes
Source: National Renewable Energy Laboratory, “Performance Comparison of Residential Hot Water Systems” March 2003
Percent of Total Minutes over 3 GPM Low Volume Homes – 0% High Volume Homes – 3%
Gallons per Minute (GPM) Flow Rates 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 6 + Minutes per Year at Flow Rate - Low Volume Home 34,000 3,500 2,100 305 380 100 5 3 1 0 0 0 0 Minutes per Year at Flow Rate - High Volume Home 31,800 6,000 3,000 2,500 2,200 1,000 250 210 80 20 5 6 25
*ALL STUDIES SHOW THAT 96 to 98 PERCENT OF ALL RESIDENTIAL HOT WATER U.S.AGE OCCURS AT FLOWS OF 1 GPM OR LESS*
OBJECTIVE 3
Understand the different classifications of water heater designs currently on the market.
Water Heating Classification • Non-Condensing Gas – Storage Type
Water Heater
• Condensing Gas – Storage Type Water Heater
• Non-Condensing Gas – Tankless Water Heater
• Condensing Gas – Tankless Water Heater
• Non-Condensing Gas – Hybrid
• Condensing Gas – Hybrid
• Heat Pump
• Desuperheater
• Geothermal
• Solar
• Electric – Storage Type Water Heater
• Electric Tankless • Whole House • Point of Use • Hydronic Space Heaters
Traditional Tank Water Heaters
• Heated water must be maintained
• High flue temperature
• Heat loss
• Insulation issues
Source: http://eternalwaterheater.com/technology.html
Source: http://www.diyanswerguy.com
Condensing Gas Storage Water Heaters
• Draft-inducing fan pushes air and fuel into a combustion chamber. Combustion gas is exhausted through a secondary heat exchanger consisting of coiled tubing.
• Heat transfer is efficient.
• Some manufacturers claim efficiencies up to 96% percent.
Picture taken from U.S. EPA Energy Star Website
Gas Tankless Water Heaters
• Modern units invented with the intent of eliminating standby losses.
• Efficiency dependent upon consumption patterns.
• 97% of all hot water events in a home with high flow fixtures are less than three gallons per minute, while 100% of all hot water in a home with high flow fixtures are less than three GPM.
Source: http://www.hvacdesmoines.com/tankless_water_heater.html
Gas Tankless Water Heaters
• Require a minimum flow.
• Start up and shutdown processes can trigger a delay in heating the water.
• At every shut down, the unit is cooled. The unit must then be reignited to heat the water.
Source: http://www.energystar.gov/index.cfm?fuseaction=find_a_product.showProductGroup&pgw_code=WH
Condensing Gas Tankless Water Heaters
• Second heat exchanger cools exhaust gases and condenses water vapor. The exhaust gases are generally much cooler.
• Heat exchanger needs to be of higher quality materials to withstand corrosion from condensation.
• Gas condensing tankless water heaters are more efficient than their non-condensing storage tank counterparts.
Source: http://www.navienamerica.com/rearning/ condensing.aspx?skin=condensing
Gas Condensing & Non-Condensing Hybrids • Addresses low flow rate and cold
water sandwich effect with incorporation of small storage tank.
• Hot water is consistently maintained within the storage tank to compensate for delay in heating.
Source: http://www.hotwater.com/water-heaters/residential/hybrid/next-hybrid-gas/
Heat Pump Water Heaters
Source: http://www.heatpump-waterheater.com/
Solar Water Heaters
• Harnesses sun’s energy to heat the water and then store it.
• Direct system: water is pumped directly through solar collector and into a storage tank.
• Indirect system: freeze resistant heat-transfer fluid is pumped through the solar collector and passed through a heat exchanger where the heat is transferred to the potable water.
Source: http://www.dudadiesel.com
Electric Storage Type Water Heaters
• Consist of an upper and lower heating element, each interlocked so that only one element at a time can be turned on.
• Incur standby losses related to the insulation.
• No heat losing flue.
• Very efficient and can have a thermal efficiency above 95%. Source: http://omurtlak9.bloguez.com
Electric Tankless Water Heaters
• Advanced tankless water heaters help reduce scald potential and work well in many water heating technology applications.
• Electric tankless water heater categories: • Whole house • Point of use • Booster • Extender
Electric Tankless Water Heaters
Whole house units
Point of use heaters
Extenders & boosters
OBJECTIVE 4
Understand the benefits and shortcomings associated with each classification of water heating design.
Benefits
Technology Benefits Inexpensive X X X Easy to Install X X X X Compatible with Low Flow Fixtures X X X X X X X X X Available Hot Water During Loss of Power X X X Claim to be Up to 96% Efficient X X X X X Availability of Rebates & Incentives X X X X X X X X X
Gas
Sto
rage
Elec
tric
Sto
rage
Cond
ensi
ng G
as
Stor
age
Gas
Tan
kles
s
Cond
ensi
ng G
as
Tank
less
Gas
Tan
kles
s Hy
brid
Elec
tric
Tan
kles
s
Hea
t Pum
p
Sola
r
Desu
perh
eate
r
Geo
ther
mal
Poin
t of
Use/
Exte
nder
s &
Boos
ters
Benefits
Technology Benefits Reduced Consumption of Non Renewable Resources x X X X X X X X X X X
Increased Efficiency as Compared to Non-Condensing Gas Storage X X X X X X X X X X
Some Models of Gas Condensing Storage units have high Btu ratings and will provide endless hot water X
Unlimited Supply of Hot Water X X X X X
Gas
Sto
rage
Elec
tric
Sto
rage
C
onde
nsin
g G
as
Stor
age
Gas
Tan
kles
s C
onde
nsin
g G
as
Tank
less
Gas
Tan
kles
s Hy
brid
Elec
tric
Tan
kles
s
Heat
Pum
p
Sola
r De
supe
rhea
ter
Geo
ther
mal
Poin
t of
Use/
Exte
nder
s &
Boos
ters
Benefits
Technology Benefits
Claim to be Up to 99% Efficient X X X X Some Models Provide Excellent Back Up for Other Technologies X X X
Can Be Centrally Located X X
Gas
Sto
rage
Elec
tric
Sto
rage
Co
nden
sing
Gas
St
orag
e
Gas
Tan
kles
s
Cond
ensi
ng G
as
Tank
less
G
as T
ankl
ess
Hybr
id
Elec
tric
Tan
kles
s
Heat
Pum
p
Sola
r De
supe
rhea
ter
Geo
ther
mal
Poin
t of
Use/
Exte
nder
s &
Boos
ters
Shortcomings
Technology
Shortcomings Standby Losses X X X X X X X Reduced Efficiency X X Limited Hot Water Availability X X X X X X X Difficult to Centrally Locate X X X X X X X
Space Requirement X X X X X X X
Sediment Accumulation within Tank X X X X X X
Gas
Sto
rage
Elec
tric
Sto
rage
Cond
ensi
ng G
as
Stor
age
Gas
Tan
kles
s
Cond
ensi
ng G
as
Tank
less
Gas
Tan
kles
s Hy
brid
Elec
tric
Tan
kles
s
Hea
t Pum
p
Sola
r
Des
uper
heat
er
Geo
ther
mal
Poin
t of
Use/
Exte
nder
s &
Boos
ters
Shortcomings
Technology Shortcomings Uses a 100% Non-Renewable Fuel Source X X X X X Higher Upfront Costs X X X X X X X X X
Potential for Scaling X X X X X X X X X Most Installations Require Backups X X X Slower Recovery Rates X X X X X Performance Deviations dependent upon Climate X X
Gas
Sto
rage
Elec
tric
Sto
rage
Cond
ensi
ng G
as
Stor
age
Gas
Tan
kles
s
Con
dens
ing
Gas
Ta
nkle
ss
Gas
Tan
kles
s Hy
brid
Elec
tric
Tan
kles
s He
at P
ump
Sola
r
Desu
perh
eate
r
Geo
ther
mal
Poin
t of
Use
/Ext
ende
rs &
B
oost
ers
Shortcomings
Technology Shortcomings Incompatibility with Low Flow Fixtures X X
Reduced Efficiency Associated with Smaller Draws X X
Cold Water Sandwich Effect X X
Some Models Experience Power Flicker Issues X
High Upfront Costs with Whole House Units X X X X X
Most Models Not Suitable for Use with Pre Heated Water X X X X X
Gas
Sto
rage
El
ectr
ic S
tora
ge
Cond
ensi
ng G
as
Stor
age
Gas
Tan
kles
s
Cond
ensi
ng G
as
Tank
less
Gas
Tan
kles
s Hy
brid
Elec
tric
Tan
kles
s
Heat
Pum
p
Sola
r
Desu
perh
eate
r
Geo
ther
mal
Poin
t of
Use/
Exte
nder
s &
Boos
ters
OBJECTIVE 5
Understand the applications and effectiveness of electric tankless water heating.
U.S. Coal Reserves and Clean Coal Electric Generation The U.S. currently has the largest proven recoverable coal reserves in the world.
• Clean coal electric generation and the efficient use of electricity produced through clean coal production increase jobs, support local economies and is environmentally responsible.
• The U.S. Power Industry has pledged a new commitment to even more use of advanced clean coal technologies.
Applications and Effectiveness
• The move to renewable energy is a move to electricity as the energy source of choice.
• Electric Tankless enjoy efficiencies greater than 95%.
• Electric Tankless can be installed closer to the point of use.
• Radiant heat loss through the plumbing distribution can be reduced.
• Opportunities for off peak applications, including space heating.
THE DEVIL IS NOT IN THE kW DEMAND, BUT IN THE CURRENT AND VERY INEFFICIENT
DISTRIBUTION (GRID) SYSTEMS.
Energy Sources & Hot Water: Electric
Electric tankless can make other technologies more efficient while improving their performance. • Ideal companion technology • Add to gas tankless to serve low flow draws, use
smaller more efficient gas burner sizing. Save energy and water.
• Add to gas tankless units to eliminate the “cold water sandwich effect.”
• Significant opportunity for off peak electrical use in hybrid situations, especially in dual space heating applications.
Energy Sources & Hot Water: Electric
Why are electric tankless not more prevalent? What improvements have been made? • Historically used in point of use applications, considered “throw aways,” very inexpensive, highly susceptible to scald potential and failure.
• Power quality issues weren’t uncommon with these systems.
Energy Sources & Hot Water: Electric
• Gross misstatements from competing “off shore” manufacturers of gas tankless
• Lack of education for both the consumer and installer
• Disparity in features and quality between different manufacturers of electric tankless products
• Misinformation on sizing that would provide for the use of the appropriate model
• Electric tankless provide savings in energy, water and operating cost. Renewable electricity is the principle energy source of the future.
Install Cost Comparisons Whole House Solutions (New Construction)
Heater Type Cost Install T&P Electric Gas Line Vent Total
Electric Tankless $900 $450 $500 $1,850 Electric (60 Gallon) $350 $450 $125 $250 $1,175
Gas Tankless (199 KBTU) $1,100 $450 $125 $250 $500 * $450 $2,875
Natural Gas HE (50 Gallon) $675 $450 $125 $250 $250 $250 $2,000
Natural Gas (80 Gallon) $525 $400 $125 $250 $275 $1,575
Natural Gas HE (80 Gallon) $725 $450 $125 $250 $250 $275 $2,075
Desuperheater $500 $450
Heat Pump $1300 $450 $250 $2000
* Eliminate vent for all outside gas tankless installs
Operating Cost Comparisons Forecast Whole House Solutions
Energy Cost 2012 2017 2022
Assumed Price Increase per Year
2012-2022 Electricity (kWh) $0.12 $0.14 $0.15 2.5% per year Gas (CCF) $1.53 $2.25 $3.30 8.0% per year Propane $2.87 $4.22 $6.20 8.0% per year Gallons per Day 65 60 55 N/A Water & Sewer (kGal) $6.60 $8.03 $9.77 4.0% per year
Annual Operating Costs Assumed Efficiency
Rating Natural Gas Tank $423.38 $538.03 $683.05 50% Natural Gas Tankless* $439.19 $526.79 $636.86 90% Propane Tank $713.87 $932.25 $1,214.82 50% Propane Tankless $639.57 $831.40 $1,078.99 70% Electric Tank $739.16 $803.24 $812.31 80% Electric Tankless $651.77 $709.13 $719.89 98%
*Includes $100 for annual maintenance expense recommended by DOE and Manufacturer
Cost Comparison
• Cheaper to install in new construction.
• Lower cost alternative for retrofit buyers.
• Preferred solution where butane and propane are used.
• Can be centrally located, reducing the length of the piping runs, resulting in energy/water savings.
OBJECTIVE 6
Discuss the difference between flow control and temperature control as separate demand water heating activation technologies.
Demand Water Heating Activation Technologies Flow Activated • Most typical design. Use a turbine or
magnet to mechanically detect flow/no flow.
• Requires a minimum flow rate of 0.75 GPM to activate.
• Delays delivery of hot water.
Demand Water Heating Activation Technologies Temperature controlled • Advanced microprocessor design uses
multiple temperature sensors and computer algorithms to detect flow.
• Works with low flow fixtures and high efficiency appliances with virtually no minimum flow.
Solutions for High Flow Applications
Temperature controlled electric tankless are the ideal technology.
• Multiple units may be used.
• A unit can be added to increase the deliverable hot water.
• Use a high efficiency heat-pump, geothermal or solar tank to maximize energy savings.
• A supercharger paired with a storage tank water heater produces an endless supply of hot water. A supercharger can work with water that is already preheated.
OBJECTIVE 7
Understand the light flicker/power quality related issues in evaluating different electric tankless models and manufacturers.
Light Flicker and Power Fluctuation
• Methods to manage power to maintain flicker and power quality related issues: • Multiple and varied kW elements • Power-sharing
• Methods currently used for modulating power
in demand electric water heaters can create disruption in power quality.
Power Sharing
Utilizes computer algorithms and electronic TRIACs to pulse power on and off to all of the heating elements equally. The algorithms provide for high kW load switching at frequencies that avoid light flicker, while providing uniform temperature modulation.
Staged Activation
This table represents four independent heating elements operating continuously at 25% of the heater’s rated output.
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
OFF
ON
ON
ON
OFF
ON
OFF
ON
OFF
ON
OFF
ON
OFF
ON
OFF
ON
OFF
ON
OFF
ON
OFF
ON
OFF
ON
OFF
ON
OFF
ON
OFF
ON
OFF
OFF
Element # 1
Element # 2
Element # 3
Element # 4
OFF
Benefits of Power Sharing
Sequentially activated systems represent typical control scheme
Sequences elements to full power one element at a time
At the end of the hot water event, at least one fully powered element on
Greatly increases potential for mineral deposits
Shutdown temperature of smaller sheath different than larger sheath creating electric power quality issues
Benefits of Power Sharing
By equally and incrementally distributing the power requirements to each element, no single element is on at 100% of its power.
Typically only one application is on at the time the water heater is turned off.
Latent heat in any element is much lower, and scaling is virtually eliminated.
Benefits of Power Sharing
The TVA noted blinking of lights due to poor control of high wattage heating element control.
New “power sharing” feature developed reduced light flicker to “unnoticeable levels” (according to TVA).
No additional power quality issues were noted after this modification.
Benefits of Power Sharing
• Minimizing potential for boiling along the element’s sheath and mineral deposition.
• Minimizes element operating temperature along the heating element sheath.
• The higher the shutdown temperature, the greater the opportunity for boiling and precipitation of minerals.
Programmed Combination of Multiple Sized kW Elements
• Uses multiple heating elements of differing wattages within the heating chambers.
• Temperature is modulated by varying the combination of elements that best match the current demand.
• Drawbacks: • Non-standard elements • All elements operate at 100% or 0% resulting in
boiling and scale buildup • Reduced element life and higher cost of repair
Sizing Made Simple
System match
• For whole house use, use the largest kW system possible.
• Electric tankless units with temperature controlled flow/no flow activation are the only electric tankless units optimized for use with low flow fixtures and high efficiency appliances.
• Temperature controlled ETWH are the ideal choice.
Flow Restriction
• Check the manufacturer’s published pressure drop curves.
• Match rated flow rate with the application.
• Many models reduce internal pipe sizing below acceptable levels for whole house applications.
OBJECTIVE 8
Understanding the truth of the real impact, if any, of high wattage electric tankless water heaters on power quality and fully diversified peak electric demand.
Tankless Water Heaters: Determining The Proper Electric Load Requirements A simplified view of Electric Tankless load
• 50-80 gallons of hot water per day (NREL/ASHRAE)
• At 1.5 GPM = 40 to 60 minutes a day.
• “Non-continuous" = loads that do not continue for more
than 3 hours. Electric tankless water heaters are non-continuous.
Tankless Water Heaters: Electrical Load Requirements Typical Residential Load Calculations
Square Feet 5,000 3,500 3,000 2,500 2,000 1,500
Lights 15,000 10,500 9,000 7,500 6,000 4,500
Appliances 22,700 22,700 22,700 22,700 22,700 22,700
ETWH * 32,000 32,000 28,000 28,000 28,000 28,000
Subtotal Load 69,700 65,200 59,700 58,200 56,700 55,200
10 kW@100% 10,000 10,000 10,000 10,000 10,000 10,000
Remainder@40% 23,880 22,080 19,880 19,280 18,680 18,080
A/C 13,568 10,176 10,176 8,480 5,088 5,088
Total Load (kW) 47,448 42,256 40,056 37,760 33,768 33,168 Total Load (A) 198 176 167 157 141 138
Panel Size (A) 200 200 200 200 150 150
* 32,000 Denotes a 32 kW Heater and 28,000 Denotes a 28kW Heater
Maximum Flow Rates KW Design Rating
TEMPERATURE RISE IN °F & RELATED FLOW RATES IN GPM kW 25° 30° 35° 40° 45° 50° 60° 65° 70° 77°
2.5 0.7 0.6 0.5 0.4 0.4 0.3 0.3 0.3 0.2 0.2 3.5 1.0 0.8 0.7 0.6 0.5 0.5 0.4 0.4 0.3 0.3 5.0 1.4 1.1 1.0 0.8 0.8 0.7 0.6 0.5 0.5 0.4 7.0 1.9 1.6 1.4 1.2 1.1 1.0 0.8 0.7 0.7 0.6 9.0 2.4 2.0 1.7 1.5 1.4 1.2 1.0 0.9 0.9 0.8
11.0 3.0 2.5 2.1 1.9 1.7 1.5 1.2 1.1 1.1 1.0 14.0 3.8 3.2 2.7 2.4 2.1 1.9 1.6 1.5 1.4 1.2 16.0 4.3 3.6 3.1 2.7 2.4 2.2 1.8 1.7 1.6 1.4 18.0 4.9 4.1 3.5 3.1 2.7 2.4 2.0 1.9 1.7 1.6 22.0 6.0 5.0 4.3 3.7 3.3 3.0 2.5 2.3 2.1 1.9 28.0 7.6 6.3 5.4 4.8 4.2 3.8 3.2 2.9 2.7 2.5 32.0 9.5 8.0 6.8 6.0 5.3 4.8 4.0 3.7 3.4 3.1 44.0 11.9 10.0 8.5 7.5 6.6 6.0 5.0 4.6 4.3 3.9
kW
Tankless Water Heaters: Electrical Load & Importance of Interlock Relays An interlock’s control automatically activates to disengage resistance loads at the commencement of hot water use and enables these loads after the end of the hot water period. Does not impact the comfort of the user. The use of the interlock eliminates competing resistive loads.
Tankless Water Heaters: Electrical Load & Importance of Interlock Relays • Interlock devices associated with water
heating should never be used to control air-conditioning condensers or heat pumps directly for periods of shutdown of less than 15 minutes.
• Check with your manufacturer to be sure the products have been listed by a recognized listing agency for both water and space heating.
Electrical Load: Interlock Relay
Current Wattage Requirements
Current AMP Requirements
New Wattage Requirements
New AMP Requirements
Lighting & Outlets 9600 40 9600 40 Water Heater 7200 30 31920 133 Total all Non HVAC 52800 220 77520 323 First 10,000 Watts at 100% 10000 42 10000 42 Remainder at 40% 17040 71 24240 101 Resistance Space Heating 7200 30 7200 30 Total Load Requirement 34240 143 41440 173 Recommended Safe Capacity at 80% (Based on 200 AMP Panel) 38400 160 38400 160 Interlock Relay Load Interruption 0 -7200 -30 Total Load Requirement 34320 143 34320 143
CASE STUDY
127 Unit Apartment Complex – Melbourne, Florida Conclusion: Based on independent measured demand and energy consumption. “Electric tankless water heaters reduce fully diversified peak system electric demand as well as kW consumption.”
Case Study
Florida Power billing history for the Senior Apartment project shows:
• Total of 138,000 sq. ft., with 127 apartments each equipped with an electric tankless water heater, single metered to include the 127 apartments, as well as all common areas and outside lighting.
• Experienced an average maximum peak demand of less than 1 kW per apartment including the load for the common area and restaurants in the total.
Case Study
FPL Account Number: 0228609152 CRANE CREEK APARTMENTS, MELBOURNE, FLA. Date Service Days kWH Use Max Demand Amount Description
1/23/2007 35 41,280 85 $4,403.88 Electric Bill 12/19/2006 34 38,760 84 $4,412.42 Electric Bill 11/16/2006 28 36,240 102 $4,333.44 Electric Bill 10/18/2006 29 41,280 102 $4,806.34 Electric Bill 9/19/2006 32 51,480 114 $5,868.40 Electric Bill 8/18/2006 29 50,400 122 $5,837.03 Electric Bill 7/20/2006 30 48,720 113 $5,600.68 Electric Bill
Billing / Charges History
Case Study Conclusion
• Electric tankless water heaters actually reduce the peak load. • Remember our charts and assumptions.
• 60-80 gallons of hot water per day, 20-30 minutes a day for the tankless, but nearly 2-4 hours for the tank.
• What does this mean? • In the late morning, most electric tank
water heaters are running at the same time.
• Multiple electric tankless, even on the
same transformer will be turning on and off as each draw occurs with less opportunity for overlap.
OBJECTIVE 9
Describe how a properly sized electric tankless water heater integrates into a sustainable, low-flow, energy efficient plumbing design.
Dedicated Use/Larger Dwellings
“On Demand" Recirculation
New Installation
Demand Recirculation
Retrofit installation
Single Unit Configurations
Compatibility: Dual Unit Configuration
• With temperature activated units, two or more units can be placed in line as back up. Water leaving one unit at the optimal temperature will not trigger activation in the next unit. • Units should be plumbed in parallel • Temperature settings should be the same • Both units should be the same model
DO NOT USE THIS DESIGN WITH ANY TANKLESS ELECTRIC WATER HEATER NOT “CERTIFIED OR LISTED FOR SAFE USE WITH PREHEATED WATER”
High Volume Endless Hot Water
Install in series with conventional or heat pump tank water heater. Size smaller tank for peak demand.
DO NOT USE THIS DESIGN WITH ANY TANKLESS ELECTRIC WATER HEATER NOT “CERTIFIED OR LISTED FOR SAFE USE WITH PREHEATED WATER”
Compatibility: With Gas, Electric, Geothermal, Solar, Desuperheater & Heat Pump Storage Water Heaters
• There are times where little or no hot water is capable of being produced. A temperature activated electric tankless water heater is capable of boosting the water leaving the tank to the desired temperature.
• An electric tankless water heater at the hot water outlet of the existing tank extends its capacity.
DO NOT USE THIS DESIGN WITH ANY TANKLESS ELECTRIC WATER HEATER NOT “CERTIFIED OR LISTED FOR SAFE USE WITH PREHEATED WATER”
Gas Tankless Companion
Smaller more efficient electric tankless allows smaller GPM draws. Hybrid configuration reduces equipment costs and additional gas service requirements. Can eliminate “cold water sandwich effect”
DO NOT USE THIS DESIGN WITH ANY TANKLESS ELECTRIC WATER HEATER NOT “CERTIFIED OR LISTED FOR SAFE USE WITH PREHEATED WATER”
OBJECTIVE 10
Understand the benefits associated with the use of this new low flow “Electric Tankless” system.
The Benefits • By locating the unit closer to the fixture, you
reduce the amount of water that must be displaced in order to get hot water.
• Allows for the installation of lower flow fixtures not compatible with flow activated systems.
The Benefits • Eliminate standby losses and increase the efficiency
of the resource that is being used.
• Can increase the efficiency of other systems when added as a booster. They accommodate smaller hot water draws and boosts temperature only to the level that is needed.
OBJECTIVE 11
Understand the fuel source for each technology and how each is related to renewable energy.
Gas Storage & Tankless Water Heaters
• Fuel Source – Natural Gas • Renewable? NO • Sustainable? NO
• Alternatives – Bio Gas • Renewable? YES • Sustainable? YES
http://www.grainger.com/Grainger/RINNAI-Water-Heater-10D428
http://greenarchitecturenotes.com/2012/02/water-heater-basics-gas-or-electric/
Electric Storage, Heat Pump Storage, Geothermal, Desuperheater & Electric Tankless Water Heaters • Fuel Source – Coal Generated
Electricity • Renewable? NO • Sustainable? NO
• Fuel Source – Natural Gas Generated
Electricity • Renewable? NO • Sustainable? NO
• Fuel Source – Nuclear Generated
Electricity • Renewable? NO • Sustainable? YES
• Fuel Source – Heat Recovery • Renewable? YES • Sustainable? YES
• Alternatives – Solar, Wind, Hydro, Bio
Gas, Geothermal & Wave Energy • Renewable? YES • Sustainable? YES
Source: http://www.reliable-mechanical.com/green/geothermal.html
Solar Water Heaters
• Fuel Source – Solar Energy • Renewable? YES • Sustainable? YES
http://www.made-in-china.com/showroom/prcsolar/product-detailyMOmiGuVAPhK/China-Separated-Solar-Water-Heater-FTSL-03-.html
BASIC WATER HEATING CALCULATIONS NATIONAL WATER HEATING STATISTICS U.S. AVERAGE GROUND WATER TEMPERATURES U.S. NATURAL GAS PRICES AVAILABILITY OF STATE REBATES AND INCENTIVES
APPENDIX
Basic Water Heating Calculations
• One British Thermal Unit (Btu) is the amount of energy needed to raise one pound of water by one degree Fahrenheit.
• One gallon of water weighs 8.33 pounds.
Basic Water Heating Calculations – Natural Gas • Approx. 1,020 Btu in 1 cbft. natural gas.
• 1 cbft. of natural gas increases the temperature of 10 gallons of
water by approx. 12.24° F
• The amount of natural gas needed to raise a 50 gallon tank starting at 70° F to 130° F = (50 x 8.33 x 60) /1020 = 24.5 cbft.
• If the current heating system is only 80% efficient, the amount of
natural gas consumed would increase by 20% to 29.4 cbft.
Basic Water Heating Calculations – Electric • There are approximately 3412 Btu in one kilowatt hour (kWh) of
electricity.
• One kWh of electricity has the potential to raise the temperature of 10 gallons of water by approx. 40.96° F
• The amount of electricity needed to raise a 50 gallon tank starting at 70° F to 130° F = (50 x 8.33 x 60) / 3412 = 7.3 kWh
• If the current heating system is only 90% efficient, the amount of
electricity consumed would be increased by 10% to 8.03 kWh.
National Averages
According to the Department of Energy, water heating represents 20% of total annual household energy consumption in the U.S.
U.S. Average Groundwater Temperatures
The required temperature rise for a given water heating system is directly related to the incoming water temperature and is an important factor in choosing and designing the most efficient water heating system.
Source: http://www.best-money-saving-tips.com/instant-flow-water-heater.html
COOL NORTHERN CLIMATE Cold temperature increases required heater size by 35% to 50%.
Availability & Pricing
The availability of the fuel source can be just as important as any other factor in choosing and designing a water heating system.
These states budgeted over 2% of electric revenues for electric energy efficiency programs in 2010
These states budgeted between 1% and 2% of electric revenues for electric energy efficiency programs in 2010
These states budgeted between 0.5% and 1% of electric revenues for electric energy efficiency programs in 2010
These states budgeted less than 0.5% of electric revenues for electric energy efficiency programs in 2010 or did not provide data
These states have distributed generation (including renewables) programs available
These states have gas programs
Source: U.S. Department of Energy – Federal Energy Management
Program
Rebates & Incentives • Rebates and incentives at the federal, state and local levels can significantly
reduce the payback. Check with your local utility provider.
Course Summary
Now, the design professional will be able to:
1. Explain the water/energy nexus as it relates to water heating.
2. Discuss consumption patterns associated with typical residential hot water usage.
3. Identify the different classifications of water heater designs currently on the market.
4. Discuss the benefits and shortcomings associated with each classification of water heating design.
Course Summary
Now, the design professional will be able to:
5. Explain the role and effectiveness of electric tankless water heaters.
6. Discuss the difference between flow control and temperature control as separate demand water heating activation technologies.
7. Explain the issues of light flicker “power quality” related issues in evaluating different electric tankless models and manufacturers.
8. Discuss the impact of hot water systems on electrical
load and peak demand.
Course Summary
Now, the design professional will be able to:
9. Describe how properly designed electric tankless water heaters integrate into a sustainable, low-flow, energy efficient plumbing design.
10. Identify the benefits associated with the use of new low-flow electric tankless system technology.
11. Identify the fuel source for each technology and how each is related to renewable energy.
The next 10 minutes will focus on discussing the course material.
QUESTIONS?
ELECTRIC TANKLESS WATER HEATERS ise15a Credit: 1 AIA HSW CE Hour
© InfoSpec, Inc. 2013
Authored By: David Seitz – CEO, Seisco International Limited, Inc. Dr. Tom Harman, Ph.D. – Electrical Engineering, Rice University Dr. Louis J. Everett, Ph.D. – Mechanical Engineering, Texas A&M University Eddie Wilcut, MAG – Texas State University
Developed & Sponsored By David Seitz, CEO,
Seisco International 888-296-9293