Let s Go Back to the Future!

Transcription

1 Let s Go Back to the Future! Welcome to the 2 nd Hot Water Forum Larry Weingarten and Gary Klein

2 The Water-Energy-Greenhouse Gas Connection

3 A Birdseye View Near Raleigh and Durham, North Carolina December 13, 2007, 1 PM

4 Falls Lake, North Carolina Water level down approximately 20 feet

5 Jordan Lake, North Carolina Water level down approximately 10 feet

6 Wastewater Treatment These are source of water running in the rivers shown entering Falls Lake and Jordan Lake

7 Sharon Harris Nuclear Power Plant Evaporates approximately ½ gallon of potentially potable water per kwh to produce electricity

8 Why Hot Water? Because it s too cold to bathe in cold water, particularly in the winter! It s a measure of civilization.

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15 Let s See Who s Here Manufacturer Water Heater Distribution System Component Fixtures, Fittings, Appliances Government Codes Consultant Utility Architect, Engineer, Builder, Plumber Anyone else? Those who use hot water

16 Annual Household Energy Use for Heating Water Natural Gas Gallons Per Day 60 Electricity Gallons Per Year 21,900 Energy into Water 16.4 Million Btu Efficiency Cost per Unit $1.00/therm $0.10/kWh Cost per Year $275 $535 Assumes hot water is 90 degrees F above incoming cold water. Cost per year has been rounded off. Add about $110 per year for water and sewer (at $0.005 per gallon combined)

17 How Big is Hot Water? Water heating is the 1 st or 2 nd largest residential energy end-use: 15 30% of a house s total energy pie. What is number 1? Number 3? Percentage grows as houses and appliances get more efficient How does this compare to your: Cell phone bill? Internet bill? Cable or Satellite bill? Starbucks bill?

18 Do You Know: Anyone who waits a long time to get hot water somewhere in their house? At their job? In their favorite restaurant? If your community has building or appliance energy standards or incentive programs? Green building programs? Someone who has ever run out of hot water? Any health inspectors who are enforcing compliance with hot water requirements in kitchens and restrooms? Someone who is thinking about charging their kids for each shower they take? Anyone who is tired of adjusting their lifestyle to the performance of their water heating system? Any communities that have a you-can t-build-unless-you-can-guaranteea-long-term-supply-of-water ordinance? Anyone who wants instantaneous hot water? Someone who thinks that most tankless water heaters are instantaneous? Anyone who would like to learn how to get hot water to every fixture wasting no more than 1 cup waiting for the hot water to arrive?

19 Typical Hot Water Event Temperature Water Heater Temperature Useful Hot Water Temperature Delivery Use Cool Down Time

20 What Do You Want from your Hot Water System? Clean clothes Clean hands Relaxation Clean dishes Clean body Enjoyment The service of hot water

21 What Do You Expect from your Hot Water System? Safety Not too hot Not too cold No harmful bacteria or particulates Sanitation Reliability Little or no maintenance Last forever Low cost Convenience Adjustable temperature and flow Never run out Quiet Hot water now

22 Guiding Principle Provide people what they want... The Service of Hot Water with what they expect Safety, Reliability and Convenience as efficiently as possible

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26 Typical Simple Hot Water System for Single Family or Single Unit Applications Water Heater Hot Water Energy Cold Water Mixed Temperature Water Fixture or Appliance Drain Indoor Boundary Fuel Source Water Source Sewer

27 Typical Central Boiler Hot Water System Indoor Boundary Hot Water Storage Tank Standard Hot Water Circulation Loop Boiler Boiler Loop Energy Cold Water Mixed Temperature Water Apartment, Fixture or Appliance Drain Fuel Source Water Source Sewer

28 The Hot Water System Use in the Building Water Heater Piping Fixtures, Fittings and Appliances Behavior Water Down the Drain How do the interactions among these components affect system performance?

29 Making Hot Water

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42 Getting Hot Water

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51 Central Plumbing Core Copper-to-PEX Manifold Manifold can be located very close to the water heater. The trunk line is very short. Separate ball valves for each individual line. One manifold for the hot fixtures, another for the cold fixtures. Individual twig lines are 3/8 inch nominal pipe diameter.

52 Distance from Water Heater to Manifold: Actual Distance: 14 ft Most Direct: 11 ft Shortest: 5 ft (Move manifold closer by starting the box from the corner behind the water heater)

53 Nothing New.. "The efficiency of storage hot-water systems may be increased if pipe-runs are kept as short as possible. Eight feet of ¾ inch copper pipe holds one pint of water. Therefore, in a pipe 32 ft long, half a gallon may cool off between operations of the tap it feeds. This not only wastes electricity, but lengthens the time before really hot water reaches the tap. Source: Your House and How to Build It: A Complete Illustrated Guide for the Home Builder and House Owner. With plans and working drawings. Written and designed by Ken Sherrott. A color gravure publication. Australia 1954

54 Using Hot Water

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63 Single Head

64 Multiple Head

65 Cascade or Downpour

66 Shower Panel or Shower Tower

67 Rain System

68 Water Tile

69 Body spray Body Spa

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74 Body Spa with Recirculation

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82 The Future is Now

83 Potentially Conflicting Trends On one hand: Larger houses More plumbing fixtures Increased desire for hot water Higher expectations of performance Desire to be Green On the other: Lower city water pressures Lower fixture flow rates Greater pressure drop in piping Tightening of codes and standards New policies to reduce GHG emissions Result: Longer wait, less pressure, lower performance, less satisfied customers, increased complaints

84 Water Heating Technologies Electric Gas

85 Still More Ways to Heat Water

86 The Essential Differences Big Tank Small Tank Small Burner Small Element Big Burner Big Elemen t

87 Small Water Heaters NAECA Tank (Storage) <4000 Btu/hr/gal Tankless (On demand) < 2 gallons Natural Gas 75,000 Btu 200,000 Btu Oil 105,000 Btu 210,000 Btu Electric Resistance Heat Pump Measure of Efficiency 12 kw 12 kw 24 amps NA Energy Factor (EF)

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89 Large Water Heaters EPAct Tank (Storage) Tankless (On demand) < 2 gallons Natural Gas > 75,000 Btu > 200,000 Btu Oil > 105,000 Btu > 210,000 Btu Electric > 12 kw > 12 kw Measure of Thermal Efficiency (TE) Efficiency and standby loss

90 What People Want Hot Water Now = Instantaneousness Need hot water available before the start of each draw Need the source of hot water close to each fixture or appliance Point of Use is not about water heater size, its about location Never Run Out in My Shower = Continousness Need a large enough tank or a large enough burner or element Or, a modest amount of both

91 Effective Capacity of Storage Water Heaters 50 gallon tank with 70% available volume (35 gal) 1 gpm = 35 minute shower 2 gpm = 17.5 minute shower 2.5 gpm = 14 minute shower 5 gpm = 7 minute shower 10 gpm = 3.5 minute shower 20 gpm = 1.5 minute shower Typical burner or element: Natural gas 40,000 Btu, 75% thermal efficiency Electric 4,500 watts in each of 2 elements, 98% thermal efficiency

92 Effective Capacity of Tankless Water Heaters Incoming cold water 50F. Hot output 120F. Natural Gas Electric 20,000 Btu = 0.5 gpm = 5 kw 40,000 Btu = 1 gpm = 10 kw 100,000 Btu = 2.5 gpm = 25 kw 200,000 Btu = 5 gpm = 50 kw 400,000 Btu = 10 gpm = 100 kw 800,000 Btu = 20 gpm = 200 kw Natural Gas nominal 75% thermal efficiency Electric nominal 98% thermal efficiency

93 A Good Water Heater Residential Does not have to be large enough for extreme peak periods, but it must have a large enough burner or element to keep up with the hot water needed for one standard shower. Must be able to serve an infinite number of hot water use patterns Commercial Serves the intended loads Meets the requirements of the applicable codes: Health and Safety, Plumbing, Energy, Building, Green

94 Neither Tank or Tankless is Necessarily the Answer A combination of the two might be better: Burner or element Sized for some amount of continuous use Residential Approximately 2-3 GPM ,000 Btu Natural Gas, kw Electric Commercial Modest tank Some volume for peak conditions Hot water available at the beginning of every draw Enables a simpler burner control strategy Possible in both gas and electric Pick the right combination of burner or element and storage

95 Relative Efficiency of Water Heaters 100% 80% 60% Electric Boost Electric Storage Electric Tankless Condensing Gas Gas Storage Gas Tankless 40% 20% 0 Daily Hot Water Consumption Standby losses less of a factor as consumption increases typical of commercial applications DOE Test Volume-64 Gallons Per Day

96 How Much Energy is Used and Water Runs Down the Drain While Waiting for the Hot Water to Arrive?

97 Historical Overview: Or how we got where we are now 1940 s Development of the Plumbing Code Based on fixture 7.5 gpm Greater distance and more fixtures, fittings and appliances = bigger diameter pipe 1960 s Beginning of large-scale development in the South and West What is different about houses in the South and the West from those in the North and the East? 1990 s Energy Codes for water heaters and fixtures Fixture flow rates reduced to less than 2.5 gpm

98 Inadvertent Conflict Between the Plumbing and Energy Codes Today Median US home increased from 1600 to 2400 square feet Distance to the furthest fixture increased from 30 to 80 feet Number of hot water fixtures increased from 6 to 12 Result - 18 times as long to get hot water Pipe area increased by 3, velocity reduced by 3 Fixture flow rate reduced by 3, velocity reduced by 3 Distance increased by at least 2, time increased by 2 Water, energy and time are wasted while waiting

99 Waste versus Use Use + Waste Water Heater Efficiency = Purchased Energy 1. You cannot waste more than you purchase. 2. But you can waste more than you use. 3. Structural waste 4. Behavioral waste Reduce the waste. Improve the use. Increase the efficiency.

100 The Ideal Hot Water Distribution System Has the smallest volume (length and smallest possible diameter) of water in the pipe from the source of hot water to the fixture. Sometimes the source of hot water is the water heater, sometimes a trunk line. For a given layout (floor plan) of hot water locations the system will have: The shortest buildable trunk line Few or no branches The shortest buildable twigs The fewest plumbing restrictions Insulation on all hot water pipes, minimum R-4

101 The Challenge Deliver hot water to every fixture or appliance wasting no more energy than we currently waste and wasting no more than 1 cup waiting for the hot water to arrive.

102 Question: If you want to waste no more than 1 cup while waiting for hot water to arrive, what is the maximum amount of water that can be in the pipe that is not usefully hot? Answer: 1 cup = 8 ounces = 1/16 th gallon = gallon

103 Gallons Wasted as a Function of Time and Fixture Flow Rate (Green < 2 cups), Red >1/2 Gallon) Flow Rate (GPM) Time Until Hot Water Arrives (Seconds) cup = 8 ounces = 1/16 th gallon = gallon

104 Back to Possible Solutions A. Central plumbing core Only if all fixtures are within 1 cup of one water heater. Unlikely without shift in perceptions of floor plans. B. 1 water heater for every hot water fixture More expensive to bring energy to the water heaters than it is to bring plumbing. Then you have the additional cost for the heaters, flues, and space. Not to mention the future maintenance. C. 2-3 water heaters per home Same as above. Might make sense in buildings with distant hot water locations and very intermittent uses. D. Heat trace on the pipes Long, skinny, under insulated water heater. Expensive to install. Great on water conservation. Competitive in certain applications, otherwise can be very be expensive on energy. E. Circulation loop 1 cup from every hot water fixture Most buildable option. All circulation systems can save water, only one can save energy.

105 Recirculating Hot Water Systems There are six types of recirculation systems: Thermosyphon (gravity convection with no pump), Continuously pumped systems, Timer controlled, Temperature controlled, Time and temperature controlled, and Demand controlled. Given the same plumbing layout, all of these systems will waste the same amount of water at the beginning of a hot water event. The difference in these systems is in the energy it takes to keep the trunk line primed with hot water.

106 Annual Energy Use for a Circulation System Attached to a Gas Water Heater (Therms) Continuous Pumping at 1 Gallon Per Minute Temperature Drop in o F Days ,168 Pump Flow Rate in Gallons Per Minute , ,460 2,920 5, ,920 5,840 11,680 Steady state heat transfer efficiency is assumed to be 75%. Electrical energy to operate the pump is additional

107 Annual Energy Use for a Circulation System Attached to an Electric Water Heater (kwh) Continuous Pumping at 1 Gallon Per Minute Temperature Drop in o F Days ,050 2, ,278 6,388 12,775 25,550 Pump Flow Rate in Gallons Per Minute 1 1,278 6,388 12,775 25, ,388 31,938 63, , ,775 63, , ,500 Steady state heat transfer efficiency is assumed to be 98%. Electrical energy to operate the pump is additional

108 Structured Plumbing Circulation loop located close to the fixtures and appliances Fully-heated or half-heated loop, with dedicated or cold-water return line, depending on floor plan Small volume twig lines No larger than ½ inch diameter May need larger diameter for high flow rate fixtures and appliances No more than 10 plumbing feet long - 2 cups volume Some exceptions: garden tubs, washing machines, island & peninsula sinks Demand-controlled pumping system Wired or wireless buttons or motion sensors Activate the pump to prime (or preheat) the insulated line Pump shuts off automatically, usually in much less than a minute Minimum R-4 insulation on all hot water pipes Water in pipes stays hot minutes after last hot water event Benefits: Minimizes the waste of water, energy and time The most flexible and cost effective solution for today s floor plans high customer satisfaction

109 Structured Plumbing Layout Using a Dedicated Return Line Return (¾ inch minimum) Pump, Controls and Thermo-sensor (in one of these two locations) Twig Hot Water Piping Water ¾ inch ½ Hot Wide Radius Elbows Locate activation mechanisms in hot water locations

110 Structured Plumbing Layout Using the Cold Water Trunk Line as the Return Pump, Controls and Thermo-sensor under sink in hot water location furthest from the water heater. Twig Hot Water Piping Water ¾ inch ½ Hot Wide Radius Elbows Locate activation mechanisms in hot water locations

111 Drain Heat Recovery (DHR)

112 DHR Applications

113 How Much? How Hot? Residential Commercial Food Service How Fast? Governed by Building & Health and Safety Codes

114 What are Your Hot Water Usage Patterns? Volume Flow Rate Duration Frequency of Use Number of Occupants Hot Water Fittings and Appliances Number Location Have you measured the hot water demand in the facilities you are designing for lately? How many hours a day do you use hot water?

115 Time and Temperature at the Master Bath Sink Hot water arrived right away Hot water arrived in seconds Hot water never arrived Average draw is 30 ± 29 seconds Source: National Renewable Energy Laboratory

116 Fixture Flow Rates Maximum allowable flow rates allowed by Federal and California regulation: Shower heads: psi Lavatory and kitchen faucets: psi Replacement aerators: psi Commercial Pre-rinse Spray Valves psi Capable of cleaning 60 plates at not more than 30 seconds per plate Concerns: Single lever versus dual lever fixtures Temperature regulation Cross-over

117 Improved Hot Water Event Temperature Water Heater Temperature Useful Hot Water Temperature Delivery Use Cool Down Time

118 To Improve the Delivery Phase: Get hotter water sooner by minimizing the waste of water, energy & time Reduce the volume of water in the pipe (smaller diameter, shorter length) Reduce the number of restrictions to flow (decrease effective length ) Increase the flow rate (use a demand controlled pump) Insulate the pipe (becomes critical for very low flow rates and adverse environmental conditions)

119 To improve the use phase: Minimize the thermal losses the water heater needs to overcome in the piping during a hot water event. Insulate the pipes Increases pipe temperature and reduces heat loss during a hot water event. This is particularly important for low flow fixtures and appliances. Take advantage of the energy savings: Keep the water heater temperature the same and change the mix point Reduce the water heater temperature setting. Combine both strategies.

120 To improve the cool-down phase: Increase the availability of hot water and minimize the waste of water, energy and time Insulate the pipes Increases the time pipes stay hot between events. R-4 insulation doubles cool down time with ½ inch pipe, triples it with ¾ inch pipe. Four Questions: 1. Where is the location of the hot water event in relation to the source of hot water? 2. How long is the time until the next hot water event? 3. What is the temperature of the hot water needed for that subsequent event? 4. What is the volume of water in the pipe that eventually cools down?

121 Improved Simple Hot Water System Insulated, On Demand Hot Water Circulation Loop Energy Cold Water Fixture or Appliance Drain Heat Recovery Indoor Boundary High Energy Factor Water Heater Mixed Temperature Water Drain Fuel Source Water Source Sewer

122 Improved Simple Hot Water System Insulated, On Demand Hot Water Circulation Loop Energy Cold Water Fixture or Appliance Drain Heat Recovery Indoor Boundary High Energy Factor Water Heater Mixed Temperature Water Drain Reclaim Grey Water (for Garden, Toilet, Laundry Wash) Fuel Source Water Source Sewer

123 Improved Central Boiler Hot Water System Insulated, On-Demand Hot Water Circulation Loop Energy Controls Cold Water Apartment, Fixture or Appliance Drain Heat Recovery Indoor Boundary Hot Water Storage Tank Boiler Boiler Loop Mixed Temperature Water Drain Fuel Source Water Source Sewer

124 Comparing Water Heaters 1. Efficiency Energy Factor or Thermal Efficiency As compared to use pattern 2. Performance Characteristics How does the water heater interact with the fixtures? 3. Ability to meet loads Minimum, normal and maximum Volume and flow rate 4. Installation Size Location Bringing gas or electricity Venting Cost 5. Life Expectancy 6. Warranties

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127 How to Take Advantage of this Conference Think system not silo Attend sessions outside your comfort zone

128 Guiding Principle Provide people what they want... The Service of Hot Water with what they expect Safety, Reliability and Convenience as efficiently as possible