# Presentation: 442981

## Improving the Efficiency and Effectiveness of Delivering theService of Hot Water

- Gary Klein
- California Energy Commission
- Jim Lutz
- Lawrence Berkeley National Laboratory
- with thanks to Alan Shedd of Jackson EMC

## Why Hot Water?

- Water heating is the 2nd or 3rd largest residential energy end-use: 15 – 30% of a house’s total energy pie.
- 107 million households consumed 1.68 quadrillion BTUs worth $21.6 Billion in 2001.

## What Do You Think Of When Someone Says Water Heating?

- Most think of water heater itself, some may also think of piping, and fixtures.
- This is traditional approach – deal with hardware, address efforts here.
- Step back and take a different approach.

## What Do You Need from your Hot Water System?

- The service of hot water

|  Clean clothes |  Clean dishes |
| --- | --- |
|  Clean hands |  Clean body |
|  Relaxation |  Enjoyment |

## What Do You Expect fromyour Hot Water System?

**Safety**
- Not too hot
- Not too cold
- No harmful bacteria or particulates

**Reliability**
- Little or no maintenance
- Last forever

**Convenience**
- Adjustable temperature and flow
- Never run out*
- Hot water now
- Quiet

- *except for parents of teenagers

## Traditional Approach-Part 1

- Making hot water
- Put a pot of water over a fire

## Slide 7

## Slide 8

## Slide 9

## Slide 10

## Traditional Approach-Part 1

- Making hot water
- Put a pot of water over a fire
- Put something hot into pot of water

## Slide 12

## Slide 13

## Tank and Tankless

**Notes:**
Could also be electric, not just gas.

## Traditional Approach-Part 1

- Making hot water
- Put a pot of water over a fire
- Put something hot into pot of water
- Fairly easy to show how both approaches morph into common water heater designs.
- Add an engineer, an architect, a manufacturer, a marketing agent, and a regulator and what do you get?

## Typical Modern-Day Water Heaters

- Design
- Efficiency
- Capacity
- Where are losses and inefficiencies?

## Federal WH Efficiency Std.

- April 1991
- Gas:      EF = 0.62 – (0.0019 x Volume)
- Electric: EF = 0.93 – (0.00132 x Volume)
- January 2004
- Gas:      EF = 0.67 – (0.0019 x Volume)
- Electric: EF = 0.97 – (0.00132 x Volume)

## Federal WH Efficiency Std.

- Gas
- Cost increase: $58
- Energy savings: 22 therm/yr
- SPP: 3.6 yrs
- Electric
- Cost increase: $101
- Energy savings: 188 kWh/yr
- SPP: 7.4 yrs
- National savings:  4.6 Quads over 26 yrs

## State-of-the-Art Water Heaters

- Improvements
- Incremental gains
- How much real improvement?
- Relatively small
- Ignores some significant sources of waste
- Worse we have strayed from our original objectives – what do we want?

## Traditional Approach-Part 2

- Use hot water
- Carry pot to point-of-use
- Dip it out or dunk it in
- Fixtures and Appliances
- Trend toward water conservation

## Traditional Approach-Part 3

- Means of Delivery
- Distribution piping
- Length
- Volume
- Insulation
- Recirculation
- How did we get from a simple bowl of hot water to central mechanical room with pumps and pipes, controls and insulation, cost and inefficiency?

## Traditional Approach-Part 4

- Behavior
- How much do we need?
- How much do we want?
- When do we want it?

## The Hot Water System

- Treatment and Delivery to the Building
- Use in the Building
- Water Heater – the source(s) of heat
- Piping – the means of delivery
- Fixtures and Appliances
- Behaviors
- Water Down the Drain
- Waste Water Removal and Treatment

## Current DHW System

## Do You Know Anyone Who Waits a Long Time to Get Hot Water Somewherein their House?

## What is Your “routine”?

- Where is the wait the longest?
- How long is the wait?
- How much water runs down the drain?
- Where is the wait the shortest?
- How far is the water heater from the furthest fixture?

## Historical Overview

- 1940’s  Development of the Plumbing Code
- Based on “fixture units” @ 7.5 gpm
- Greater distance and more fixtures = bigger diameter pipe
- 1960’s  Beginning of large-scale development 	     in the South and West
- 1990’s  Energy Codes for water heaters and fixtures
- Fixture flow rates reduced to less than 2.5 gpm

**Notes:**
What’s different in the South & West? No basements or central core.

## Inadvertent ConflictBetween Codes

- 1970 - 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 and energy are wasted while waiting

**Notes:**
Pipe cross-sectional area increases by 2.25 when going from 1⁄2” to 3⁄4”

## How Much

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

## Annual Water and Energy Use

|  | 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 | $0.13/kWh |
| Cost per Year | $275 | $700 |

- Assumes hot water is 90 degrees F above incoming cold water. Cost per year has been rounded off.

**Notes:**
These are ballpark parameters with rounded numbers.

## Annual Water and Energy Waste

| Annual Water Waste and Cost 
(Combined water and sewer $0.005/gallon, rounded off, California prices) |  |  |
| --- | --- | --- |
|  |  |  |
|  | Water Waste | Cost (Water and Sewer) |
|   5 Gallons Per Day (  8%) | 1825 gallons | $9 |
| 10 Gallons Per Day (17%) | 3650 gallons | $18 |
| 20 Gallons Per Day (33%) | 7300 gallons | $36 |
|  |  |  |
| Annual Energy Cost (rounded off, California prices) |  |  |
|  |  |  |
|    | Natural Gas | Electricity |
|   5 Gallons Per Day | $23 | $58 |
| 10 Gallons Per Day | $46 | $116 |
| 20 Gallons Per Day | $92  | $232 |

## How Big is this Opportunity?

|  | Existing Homes | New Construction |
| --- | --- | --- |
| California | 3 Million | 100,000 per year |
| Potential Savings | $200 Million per year | $14 Million per year |
| United States | 20 Million | 1 Million per year |
| Potential Savings | $2 Billion per year | $100 million per year |
| Estimates are for single family homes and include costs for water, waste water treatment and energy. |  |  |

**Notes:**
For existing homes, assume could save 10 gallons/day in 20%
For new construction, assume could save 20 gallons/day

## Does Your CommunityNeed More Water?

- Existing Homes
- Approximately 100 homes = 1 acre foot of water/year
- New Construction
- Approximately 50 homes = 1 acre foot of water/year
- Still more potential in multi-family and commercial buildings

**Notes:**
Existing homes ~10 gallons/day. New construction save 20 gallon/day

## WhichDistribution Systemis inYour House?

## Radial, Manifold, Parallel Pipe-Central Core

**Notes:**
Usually older homes

## Radial, Manifold, Parallel Pipe-Distributed

**Notes:**
Pipes not insulated.  Common to run in bundles with hot next to cold or cooled off.
In production houses can have up to 900’ in hot water pipe alone. 
Watch out for the manifold, have to fill it for every draw.

## Single Trunk and Branch

**Notes:**
Pipes not insulated.  Often run the main trunk under slabs.  No connections allowed under slab, so longer than expect.

## Multiple Trunk and Branch

## Full Loop Recirculation

**Notes:**
Can use on-demand controls.  Loop is full of hot water.  Branches off the loop are problem area.

## Half Loop RecirculationPump Separated from Thermo-sensor

**Notes:**
Short branches.  Thermo-sensor at farthest fixture.

## Half Loop RecirculationPump Located with Thermo-sensor

## How Does Hot Water Behave in a Pipe?

**Notes:**
This is tentative results of early research.  Still not definite. 

## Ideal Pipe

**Notes:**
This is how people think hot water pushes cold water out of a pipe.  Like a can of hot water pushing out a can of cold water.

## Real Pipe

**Notes:**
Unfortunately it doesn’t work that way at all.  This is a schematic of what happens. About 11⁄2 times the volume of water in the pipe has to come out before you get usably hot water.

## Fast Flow

**Notes:**
We’ve seen nearly plug flow in PEX pipes at high flow rates.  We think this is due to the slipperiness of the plastic tubing.  We’re not sure how fittings would impact this.  It may happen in copper tubing as well.

## Slow Flow

**Notes:**
This is the most unexpected of all.  At slow flow rate, the hot water slides across the top of the cold water.  This may be due to the different viscosities of hot and cold water.  More noticeable in copper , may be due to heat transmission along the copper pipe.

## Guiding Principle

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

## The Challenge

**Deliver ****hot water**
**to every fixture in the house**
**wasting no more energy**
**than we currently waste and**
**wasting no more than 1 cup**
**waiting for the hot water to arrive. **

**Notes:**
Looking for solutions.  How would you do it?

## Possible Solutions

- Central plumbing core
- 1 water heater for every hot water fixture
- 2-3 water heaters per home
- Heat trace on the pipes
- Distribution system located within 1 cup of every hot water fixture

**Notes:**
Central core in modern construction?
Multiple heaters? Copper pipe is cheaper than 220V wiring & upgrading main box or putting in gas & vent lines. And additional standby loss.
2-3 water heaters? Where going to put them? Never want to maintain or replace, why have more than 1?
Heat trace? Saves water at the cost of energy.

## Five Important Questions

- How many feet of pipe in 1 cup of water?
- What capacity water heater is needed to supply 1 gpm?
- What is the heat loss (gain) in the pipe under different conditions?
- How does effective pipe length impact the delivery?
- What is the actual flow rate from fixtures at different pressures?

**Notes:**
Talk about pipe samples here.

## Length of Pipe that Holds8 oz of Water

|  | 3/8" |  |  | 1/2" |  |  | 3/4" |  |  | 1" |  |  |
| --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- |
|  | ID, in | gal/ft | ft/cup | ID, in | gal/ft | ft/cup | ID, in | gal/ft | ft/cup | ID, in | gal/ft | ft/cup |
| "K" copper | 0.402 | 0.0066 | 9.48 | 0.527 | 0.0113 | 5.52 | 0.745 | 0.0226 | 2.76 | 0.995 | 0.0404 | 1.55 |
| "L" copper | 0.440 | 0.0079 | 7.92 | 0.545 | 0.0121 | 5.16 | 0.785 | 0.0251 | 2.49 | 1.025 | 0.0429 | 1.46 |
| "M" copper | 0.450 | 0.0083 | 7.57 | 0.569 | 0.0132 | 4.73 | 0.811 | 0.0268 | 2.33 | 1.055 | 0.0454 | 1.38 |
| CPVC | N/A | N/A | N/A | 0.489 | 0.0098 | 6.41 | 0.715 | 0.0209 | 3.00 | 0.921 | 0.0346 | 1.81 |
| PEX | 0.356 | 0.0052 | 12.09 | 0.481 | 0.0094 | 6.62 | 0.677 | 0.0187 | 3.34 | 0.871 | 0.0309 | 2.02 |

| Ave | 8 feet | 5 feet | 2.5 feet | 1.5 feet |
| --- | --- | --- | --- | --- |

## Relative Costs of Operation

**Notes:**
Assuming 60 gallons/day, 20 gallons/day wasted.

## Design Principles

- Insulation improves performance during all 3 phases
- Delivery, Use, Between Uses
- To waste no more than 1 cup while waiting
- There must be less than 1⁄2 cup of water between the hot water source and the fixture
- “Prime the insulated line”, then shut off the pump
- To optimize economics, water conservation and comfort
- Structured plumbing
- Insulated circulation loop with small volume branch lines and on-demand circulation system.
- Practical, cost-effective way to optimize the distribution system and provide what customers want

## Recommended Design Procedures

- Determine how much water to waste at each fixture. Minimize the waste and wait at sinks and showers.
- Plan to install pipe that contains less than 1⁄2 that volume between the fixture and the hot water loop.
- Plan to insulate the loop and the branches.
- Select one of the Structured Plumbing designs.
- Design and build to code.
- Verify that “as-built” performs “as designed”.

## The Rest of the System

- Water Heater
- Tank or Tankless
- Energy Factor
- Fixtures
- Low Flow
- Single Lever Fixtures
- Drain Heat Recovery
- Upstream and Downstream

## Improved DHW System

## What Next?

- Hardware
- System
- Policy
- Regulation
- Design and Field Practices
- Programs
- Research

## The Big Picture

- Occupants
- Owners, Renters and Property Managers
- System Component Manufacturers
- Heater, Insulation, Piping, Fixtures Appliances
- Building Professionals
- Builders, Plumbers, Remodelers
- Water Utilities
- Water supply, Wastewater treatment
- Energy Utilities
- Electric Utilities
- Natural Gas Utilities
- Oil/Propane Suppliers
- Regulators
- Energy and Environmental
- Building, Plumbing, Public Health

## Contact Information

- Gary Klein
- California Energy Commission
- 1516 Ninth Street
- Sacramento, CA 95814
- Tel: 916-653-8555
- Fax: 916-653-6010
- Email: gklein@energy.state.ca.us

- Jim Lutz
- Lawrence Berkeley National Laboratory
- 1 Cyclotron Rd MS90R4000
- Berkeley, CA 94720
- Tel: 510-486-7302
- Fax:510-486-6996
- Email: jdlutz@lbl.gov