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Codes and High‐Performance Hot Water Systems Gary Klein Affiliated International Management, LLC 916‐549‐7080 [email protected]
Codes and High‐Performance Hot Water Systems
Gary Klein Affiliated International Management, LLC
916‐549‐7080 [email protected]
Annual Energy Use for Heating Water
Natural Gas Electricity Gallons Per Day 60
Gallons Per Year 21,900
Energy into Water 16.4 Million Btu
Efficiency 0.6 0.9 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 $130 per year for water and sewer (at $0.006 per gallon combined)
How Big is Hot Water?
Water heating is the 1st or 2nd 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?
– Designer coffee bill?
The Hot Water System
• Treatment and Delivery to the Building
• Use in the Building – Water Heater – Piping
– Fixtures, Fittings and Appliances – Behavior – Water Down the Drain
• Waste Water Removal and Treatment
Which is the biggest variable in determining water and energy use?
How do the interactions among these components affect system performance?
Typical “Simple” Hot Water System
Fuel Source
Water Source
Indoor Boundary
Hot Water Cold
Water Mixed
Temperature Water
Energy
Water Heater
Hot Water Outlet
Drain
Sewer
Typical Central Boiler Hot Water System
Energy
Cold Water
Mixed Temperature
Water
Indoor Boiler Boundary Loop
Water Source
Boiler Hot
Water Storage
Tank
Standard Hot Water
Circulation Loop
Apartment, or Hot Water Outlet
Drain
SewerFuel Source
Do You Know: • Anyone who waits a long time to get hot water somewhere in their house? At
their job? In their favorite restaurant?
• Someone who has ever run out of hot water?
• Any Communities that have a “you can’t build unless you can guarantee a longterm supply of water” ordinance?
• Someone who has a “routine”’ that they do while waiting for hot water toarrive at their shower? At the kitchen sink? For the dishwasher?
• Anyone who wants instantaneous hot water?
• Someone who thinks that a tankless water heater is instantaneous?
• Anyone who thinks that a whole‐house manifold plumbing system will save water?
• Someone who is confused about how to implement the LEED, NAHB, WaterSense, Build‐it‐Green or other hot water distribution system credits?
• Anyone who would like to learn how to get hot water to every fixture wastingno more than 1 cup waiting for the hot water to arrive?
• Someone who wants to know “the answer”?
Tempe
rature
Typical Hot Water Event
Water Heater Temperature
Useful Hot Water Temperature
UseDelivery Cool Down
Time
How do we use hot water?
• Frequent short, low flow‐rate draws • Occasional long draws at low flow‐rates
• High flow‐rate and high volume draws are rare
How Do We Conserve Hot Water? Use less hot water (volume) per event • Begins with the water heater • Passes through the hot water distribution system • Discharges through the fixture fittings and appliances • Mixed temperature water runs down the drain • Total is due to a combination of structural and behavioral
considerations.
The supply of hot water ends at the fixtures and appliances, not at the customer’s meter,
• The future of water conservation programs depends on getting the structural considerations correct today.
Begin with the end in mind… How much do you want to waste?
Remember What People Want Hot Water Now = “Instantaneousness”
– Need hot water available before the start of each draw. • A tank with hot water • Heated pipes
– 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 orelement
– Or, a modest amount of both
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 waterevent?
3. What is the temperature of the hot waterneeded for that subsequent event?
4. What is the volume of water in the pipe thateventually cools down?
Water Waste as a Function of Flow Rate (Really Velocity)
Flow Rate ¾ inch Nominal Diameter Pipe Relative Water Waste
Percent Approximate Velocity
Feet per Second Greater than 4 gpm Just over 100% Greater than 3
4 gpm 110% 2.65 3 gpm 120% 1.99 2 gpm 130% 1.33 1 gpm 150% 0.66
0.5 gpm Roughly 200% 0.33 0.25 gpm ???? 0.17
The velocity of 0.5 gpm in ¾ inch nominal pipe is roughly equivalent to the velocity of
2 gpm in 1.5 inch nominal pipe
The Ideal Hot Water Distribution System
• Has the smallest volume (length and smallest “possible” diameter) of pipe from the source of hot water to the hot water outlet.
• 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, wall thickness = pipe diameter
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 face‐velocity (smaller diameter pipe or a demand controlled pump)
• Insulate the pipe (becomes critical for very low flow rates and adverse environmental conditions)
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 lossduring a hot water event. This is particularlyimportant for low flow fixtures and appliances.
•Take advantage of the energy savings: – Keep the water heater temperature the same andchange the mix point
– Reduce the water heater temperature setting. – Combine both strategies.
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. • Equal heat loss per foot, regardless of pipe diameter
Is there a priority to insulating the pipes? • Trunks, branches, twigs?
• Duration of hot water events?
• Time between hot water events?
Improved Hot Water Event
Water Heater Temperature
Tempe
rature
Useful Hot Water Temperature
UseDelivery Cool Down
Time
The Key to Efficient Hot Water Distribution
• Reduce the volume of water between the source of hot water and the hot water outlet.
• Delivery time: consistent and short • How much do you want to waste?
– 1 gallon or more? – 0.5 gallons? – 0.25 gallons (4 cups)? – 0.125 gallons (2 cups)? – 0.0625 gallons (1 cup)?
Allowable Volume from Source to Use System without a Circulation Loop or Heat Traced Line (ounces)
System with a Circulation Loop or Heat Traced Line (ounces)
Comments
IPC No limit No limit 2012 maximum of 50 feet. (currently 100 feet)
IECC‐Res No Limit No Limit
IECC Non‐Res
No Limit No Limit
GPMCS 32 16
IgCC 80 24 Proposed: 2 oz. for Lavatory Faucets 64 oz. for other fixtures
Original IgCC Table702.8
Revised IgCC Table 702.8.2
Pipe Insulation – IECC
• Requires insulation for large diameter and long pipe. Kitchen runs.
• Not necessary to insulate if the volume from the source to the fixture is less than roughly 1 quart (table shows feet)
• Must individually insulate all hot water piping in home‐run systems.
• Residential: Minimum R‐3, non circulating, circulating for pipes less than or equal to 1”; R‐4 for larger circulating pipes
• Non‐Residential: Minimum R‐4
Pipe Insulation – GPMCS and IgCC
• GPMCS and IgCC: both implement the idea of equalheat loss per foot, regardless of diameter. – Wall thickness of insulation is equal to the nominaldiameter of the pipe.
• GPMCS and IgCC: both address protection, installationand removal of buried pipe
• GPMCS separates hot water from chilled water and steam. – Table for chilled water and steam comes from ASHRAE 90.1. 7 rows by 8 columns. Down from 14 by 8 in draft!
– Same table in IECC non‐residential • IgCC covers hot water, chilled water and steam in asimple table – Wall thickness is double for steam
Original 90.1 Pipe Insulation Table
Revised 90.1 Pipe Insulation Table
The Answer – Part 1
• Wring out the waste. – Decrease the volume between source of hot water and the use – Insulate the hot water piping – Utilize the waste heat running down the drain
• Improve the efficiency of using hot water. – Reduce hot water outlet flow rates – Reduce the volume of hot water needed for each task
• Increase the efficiency of making hot water. – Preheat – solar, heat pump, off‐peak electric – Select a very efficient booster that works with preheated water
to reach the desired temperature and for continuousness – Combine water and space heating
Combi Systems – One Thermal Engine
• How many days a year do we use hot water?
• In a BA home, how many days a year do we need heating?
• Size of heating peak?
• Size of water heating peak?
• Why are we still so focused on condensing furnaces and not on condensing water heaters that can also heat the house?
Can We Solve a Problem?
• Space within assemblies. The space within building assemblies shall be large enough to accommodate the mechanical, electrical, plumbing and insulation systems installed within them, including those that must cross.
• Rough‐Ins for Renewables – Applicability
– Access for future installation
What Makes for “Good” Code?
• How we get compliance that results in intended performance?
• Precision in tables? • Calculations before construction?
– Costs of calculations? – Moving mass markets? – Compliance based on calculation?
• Signature of contractor? • Verification before certificate of occupancy? • Is it memorable? • Is it easy to inspect?
Has Someone Moved Our Cheese?
Energy Pie 1990
Heating and Cooling Water Heating Refrigeration Lighting Clothes Drying Television Computers Vampires Miscellaneous
100 Units of Energy
Energy Pie 2010
Heating and Cooling Water Heating Refrigeration Lighting Clothes Drying Television Computers Vampires Miscellaneous
89 Units of Energy
Energy Pie 2020
Heating and Cooling Water Heating Refrigeration Lighting Clothes Drying Television Computers Vampires Miscellaneous
45 Units of Energy
0
2
4
6
8
10
12
14
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan
1990 Annual Energy Use Pattern
Peak
Base
2010 Annual Energy Use Pattern 14
12
10
8 Peak
6 Base
4
2
0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan
2020 Annual Energy Use Pattern 14
12
10
8 Peak
6 Base
4
2
0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan
Looking Into the Future • High Performance Programs
– Consistent Analysis; Targeted Improvements – Set Maximum Operational Costs – Pay for Long‐term Persistence
• Simplify Code Compliance – Pipe Insulation – Measure Installed Quality of Systems
• Before Certificate of Occupancy
– Sizing Peak Heating and Cooling Capacity • BTU/Hour/Square Foot
• Systems Trump Components • Feedback
Sizing Example to Consider:
Given human nature, it is our job
to provide the infrastructure
that supports efficient behaviors.
The Answer – Part 2 R r i i g g h t
SHORT, “STRAIGHT”, SMOOTH, t -
h
pipe s i z e d
