Energy Efficiency Manual Wulfinghoff Pdf File

1. Energy Efficiency Manual Wulfinghoff Pdf Files

Wulfinghoffenergyefficiencymanual. 1. ENERGY EFFICIENCY MANUAL Donald R.

Wulfinghoff for everyone who uses energy, pays for utilities, controls energy usage, designs and builds, is interested in energy and environmental preservation ENERGY INSTITUTE PRESS Wheaton, Maryland U.S.A. Energy Efficiency Manual by Donald R.

Wulfinghoff published by: Energy Institute Press 3936 Lantern Drive Wheaton, Maryland 20902 U.S.A. 301-946-1196 888-280-2665 (orders only) Copyright © 1999 Donald R. Wulfinghoff All rights reserved. No part of this book may be reproduced, or put into or stored in a retrieval system, or transmitted in any form or by any means, including but not limited to electronic, mechanical, photocopying, or recording, without prior written permission from the copyright holder, except for brief quotations that are included in legitimate reviews. Custom excerpts and course packs from the Energy Efficiency Manual are available for purchase.

Please contact the publisher for selections and prices. Library of Congress Catalog Card Number 99-22242 ISBN 0-9657926-7-6 Library of Congress Cataloging-in-Publication Data Wulfinghoff, Donald R. Energy efficiency manual: for everyone who uses energy, pays for utilities. ISBN 0-9657926-7-6 (alk. Energy conservation Handbooks, manuals, etc. Energy consumption-Handbooks, manuals, etc.

Title TJ163.3.W85 1999 697-dc21 Printed in the United States of America 99-22242 CIP. Measure The is the unit of information in the Energy Efficiency Manual. Each Measure is a self-contained, hands-on guide to one specific method of saving energy and reducing utility costs. The Measure number locates this Measure within the 400 Measures of the Manual. The Section tells you the major subject area, such as boilers, water systems, or lighting.

The Subsection tells you the specific type of energy system, such as boiler fuel systems. Or, it tells you a specific area of efficiency, such as reducing solar cooling load.

The Ratings suggest the priority that this Measure deserves in your overall energy conservation program, in typical situations. For New Facilities: for Retrofit: for Operation & Maintenance: A Do it wherever it applies. It costs little, and it has no significant disadvantages. A A Simple, quick, and foolproof. Or, it must be done to prevent damage or major efficiency loss. B Do it in most cases.

Pays back quickly. Does not need special skill or increased staffing. Do it wherever it applies.

Simple and quick. Costs little in comparison with its benefits. The risks can be managed easily by the present staff. B B Do it in most facilities where it applies. Pays back quickly.

Easy to accomplish. Requires a modest amount of money, effort, and/or training. May have pitfalls that require special attention. C Expensive or difficult. Or, the saving is small in relation to the money, effort, skill, or management attention required. The risks are clear and manageable.

Will be done in a well-managed facility. Pays back quickly. Fairly easy to accomplish.

Not too risky. Requires a modest amount of money, effort, and/or training. Or, it is a less critical maintenance activity. C Requires substantial money, effort, special skill, and/or management attention. Or, the benefit is small.

D The benefit is small in relation to cost. Or, it is exceptionally difficult to accomplish.

Or, it has potential for serious adverse side effects. The sequence number within the Subsection. The Measures are grouped logically. The subsidiary sequence number.

Only 'subsidiary' Measures have this. NOTE: In the text, 'ff' after a Measure number means 'the Measure and every Measure that is subsidiary to it.' C D the Measure title says what to do. The Summary highlights aspects of the Measure that place it in perspective within your overall efficiency program. The text of the Measure explains who, what, where, when, how, and why.

It focuses on issues that are directly related to accomplishing the Measure. (Important background information for the Measures is in the Reference Notes, Section 11.) Economics rates the Measure in terms of three primary financial criteria. You must make detailed estimates for your individual applications. Savings Potential states the amount of savings you can expect, usually expressed as a fraction of the system's operating cost. Cost indicates the amount of money required. Gives you specific equipment and labor costs where possible.

Payback Period estimates the length of time needed to pay off the investment. Traps & Tricks alert you to factors that threaten success. Gives you hints for getting it right the first time and for keeping the Measure effective in the long term.

It is very expensive. Or, the payback period is relatively long. Or, operation may require substantial effort, special skill, or continuing management attention. It provides only a small benefit in relation to its cost. Or, it may have high risk because it is novel, unreliable, difficult to install, or difficult to maintain.

D Expensive, and provides only little benefit. Or, exceptionally risky because it is difficult to accomplish correctly, or difficult to maintain, or unproven, or unpredictable. The Selection Scorecard rates the financial and human factors that are most important for deciding whether to exploit the Measure in your application.

The scores are for typical commercial applications. Shaded symbols indicate a range of scores. Savings Potential is expressed as a percentage of the facility's total utility cost. Rate of Return estimates the percent of the initial cost that is saved each year. Over 5% 0.5% to 5% 0.1% to 0.5% less than 0.1% over 100% 30% to 100% 10% to 30% less than 10% Reliability indicates the likelihood that the Measure will Ease of Retrofit or Ease of Initiation indicates remain effective throughout its promised service life.

How easy it is for the people involved to accomplish the Measure properly. Equipment or materials will last as long as the facility. Maintenance requirements will not cause the Measure to be abandoned. If a procedure, it is easy to administer. Or, it is a simple, one-time effort. Equipment has long service life, is not very vulnerable to damage, negligence, or poor operating practice.

May fail visibly at long intervals. If a procedure, it is fairly easy to maintain and requires only modest skill.

FAILURE PRONE. Equipment needs skilled maintenance, or it is vulnerable to damage or poor operating practice. Fails invisibly. If a procedure, it is easily forgotten or requires continuing supervision. Equipment has poor or unknown reliability. Or, it needs frequent maintenance.

If a procedure, it is difficult to learn or it may easily cause damage. Only minimal effort and no extra skill are required. No tricky factors. Not much effort or skill required. May need to learn a new procedure. Needs major staff effort. Or, hard to find reliable contractors.

May be tricky. VERY CHALLENGING. Can be unpleasant, likely to be resisted. Or, installation is difficult and expensive. Or, requires major experimentation.

How to Use the Energy Efficiency Manual The Energy Efficiency Manual is your primary tool for improving energy efficiency and reducing your utility costs. It is a comprehensive, step-by-step guide that is designed to help you manage your activities effectively and with confidence.

The core of the Energy Efficiency Manual is 400 energy efficiency “Measures.” The Measures have a standard format that makes it easy to organize them into an optimum efficiency program for your facility. Refer to the inside of the front cover to learn how to exploit the Measures.

The Measures are grouped into Sections and Subsections. These correspond to types of energy systems (for example, boilers, chillers, or lighting) or to energy waste in specific components (for example, air leakage through doors, or solar heat gain through windows). This arrangement lets you quickly identify whole groups of Measures that may or may not apply to your facility. For example, if your boilers are fueled by natural gas, you can bypass the Subsection that deals with fuel oil systems.

Use the Table of Contents to find the Sections and Subsections that apply to your situation. The Reference Notes, the last Section of the book, serve you in two important ways.

They support the Measures with additional explanation, which may be more basic or more advanced than the “working” information in the Measures. Also, you can read each Reference Note by itself for a concise overview of an important energy conservation topic. Use the Index to find specific topics that interest you, or to find definitions of terms. U If you are involved in new construction — if you are an architect, an engineer, a construction manager, a contractor, or a code official — use the Energy Efficiency Manual as a design review guide. As you develop your design, continually check the Manual for efficiency features that you can exploit. Use it to find where the design wastes energy, and to find better ways of saving energy. U If you own, manage, or operate facilities — anything from a private house to an office complex or hospital or paper mill — use the Energy Efficiency Manual to find all your opportunities for savings.

Then, use it to prioritize your activities. Finally, let it guide you in accomplishing and preserving your improvements. U If you are a specialist in energy efficiency, use the Energy Efficiency Manual as a designer or facility manager would, depending on whether you deal with new or existing facilities. It will improve the quality of your work and reduce the time you need to provide the best service to your clients. U If you are a student or teacher, start with the Reference Notes to learn fundamental principles.

With each Reference Note, use the related Measures as examples of practical applications. U If you are an advocate for efficiency or the environment, use the Energy Efficiency Manual to learn the real-world aspects of the conservation activities that interest you. The Manual will help you to promote resource conservation that produces credible results.

Now, please read “A Personal Note: the Right Way to Do Energy Conservation.”. 7 A PERSONAL NOTE: THE RIGHT WAY TO DO ENERGY CONSERVATION Improving energy efficiency may be the most profitable thing that you can do in the short term. How much you will actually benefit from this opportunity depends on how you approach it. Please take a few minutes to read the following suggestions about using the Energy Efficiency Manual and about your role in energy conservation. Invest a little time in learning how to use the Manual, and it will reward you with years of savings and achievement. If you are involved in new construction — if you are an architect, an engineer, a construction manager, a contractor, or a code official — use the Energy Efficiency Manual as a design review guide.

As you develop your design, continually check the Manual for efficiency features that you can exploit. Use it to find where the design wastes energy, and to find new ways of saving energy.

If you own, manage, or operate facilities — anything from a private house to an office complex or hospital or steel mill — use the Energy Efficiency Manual first to find all your opportunities for savings. Then, use it to prioritize your activities. Finally, let it guide you in accomplishing and preserving your improvements. If you are a specialist in energy efficiency — if you are an energy consultant, a utility energy specialist, or an energy services provider — use the Energy Efficiency Manual in the same way, depending on whether you deal with new or existing facilities.

You will find that it greatly improves the quality of your work and reduces the time you need to provide service of top quality to your clients. If you are a student preparing to enter any of these important fields, or if you are a teacher, you will use the Energy Efficiency Manual in a different way. Start with the Reference Notes to learn fundamental principles. With each Reference Note, use the related Measures as examples of practical applications. If your job or your vocation is to advocate efficiency — for example, if you are a government energy official or an environmental advocate — use the Energy Efficiency Manual to learn the real-world aspects of the conservation activities that interest you. Both governments and advocacy groups have played an invaluable role in promoting efficiency. At the same time, naive enthusiasm sets the stage for failures, which undermine public confidence in energy conservation and actually waste energy.

The Energy Efficiency Manual will help you to promote resource conservation that produces credible results. How to Use the Energy Efficiency Manual The Energy Efficiency Manual is designed to be your primary tool for improving energy efficiency and reducing your utility costs. It is a comprehensive, step-by-step technical guide, and it also helps you manage your activities efficiently.

Learning to use this tool proficiently will take only a few moments. The core of the Energy Efficiency Manual consists of four hundred energy efficiency “Measures.” Each Measure is a specific energy efficiency improvement or cost saving activity. Each Measure gives you the information you need to plan the activity efficiently and accomplish it successfully.

All the Measures have a standard format. This includes special features, Ratings and a Selection Scorecard, that help you to quickly judge the value of each Measure for your applications. Other features, the Summary, Economics, and Traps & Tricks, give you the main features of each Measure. To become familiar with these features, refer to the key to the Measures, inside the front cover, as you browse through the Measures. The Measures are grouped into Sections and Subsections. These correspond to types of energy systems (e.g., boilers, chillers, lighting) or to energy waste in specific components (e.g., air leakage through doors, solar heat gain through windows). This lets you quickly identify whole groups of Measures that may or may not apply to your facility.

For example, if your boilers are fueled by natural gas, you can bypass the Subsection that deals with fuel oil systems. Use the Table of Contents to select the Sections and Subsections that apply to your facility. First, find all your opportunities. Resist the temptation to rush into energy conservation projects without considering all your opportunities first. You may be eager to get started after attending a seminar, or reading an article, or getting a sales pitch. Those are good ways to get an introduction to new concepts, but they are no substitute for knowing all your opportunities.

Wulfinghoff 1999. All Rights Reserved. 8 If you grab at opportunities randomly, you will miss many good ones and waste money.

In a facility of any size, there will be many things that you can do to reduce your utility costs. Every building and plant wastes energy in hundreds or thousands of places. Find them all. There is no way to find the best opportunities first. It is like an Easter egg hunt. You can’t tell how big the prizes are until you have searched everywhere and found all the eggs. By the same token, don’t expect to find a “short list” of improvements that are best for your facility.

Each building and plant wastes energy in different ways. Your search for efficiency improvements will be time-consuming.

(In existing facilities, this search is often called an “energy audit.”) Typically, it requires weeks or months. In a large, diverse facility, it may require more than a year. Demand the time to do it right. A false concept that came out of the popular energy conservation movement of the 1970’s is the “walk-through” or “one-day” energy audit. According to this notion, whizzing through a facility reveals energy conservation opportunities by a mystical kind of inspiration.

Reject this ouija board approach, even as a starting point. Quickie surveys fool you into believing that you know your options when you really don’t.

Energy efficiency is a profit maker. So, you could borrow money to fund any project that you know will pay off. The skills and effort of the people involved are the real limiting factors. Traps & Tricks, located right after Economics, alert you to aspects of the Measure that will challenge the people involved.

Give priority to the Measures, or groups of Measures, that will produce the largest savings, even though they may not pay off most quickly. Don’t divert your time to minor activities while there are more important things to be done. On the other hand, if you see that you can accomplish a Measure quickly and reliably, go ahead and do it. Don’t waste time analyzing small improvements in detail.

Try to accomplish groups of related Measures together. For example, make all the control improvements to your air handling systems as a single activity. This avoids duplication of effort, saves money in contracting, and produces a better overall system. The Energy Efficiency Manual is organized to make this easy for you. Most important, don’t get in over your head at the beginning with a large project that demands all your attention. If a Measure seems overwhelming, defer it until you have more time to study it. Don’t start any Measure until you are ready to complete it successfully.

Budget your time as wisely as your money. Don’t expect instant gratification. When you complete your list of potential efficiency improvements, your next job is to decide the most effective sequence for accomplishing them. You want to produce the greatest payoff in the shortest time.

Be shrewd about managing your program’s two most important resources, money and personal capabilities. The desire for quick and effortless results has ruined more energy conservation projects than any other cause. Rushing into a project blindly is unprofessional. You would not want your surgeon to rush through your operation just to prove how quickly he can do it. The Energy Efficiency Manual helps you make the best use of both these resources. The Ratings in each Measure suggest its overall priority, taking into account the economics of the Measure, the difficulty of accomplishing it, and the degree of risk.

To refine your ranking, the Selection Scorecard, just below the title, rates these factors individually. At the end of each Measure, the Economics gives you general estimates of the potential savings, the cost, and the rate of return. Recognize that your time is a more precious resource than the money needed to make the You have heard expressions like “no-cost energy conservation measure,” “pick the low fruit,” and so forth, to describe retrofit projects that are supposed to be “easy” or “simple.” These notions are illusions that lure you into being too hasty. Every opportunity for saving energy requires significant effort, if it is going to work and to endure. Your willingness to invest the needed effort and time is what guarantees the success of your projects. The Energy Efficiency Manual will show you how to make your improvements as quickly and easily as possible.

ENERGY EFFICIENCY MANUAL. 9 Rely on proven equipment and methods. Energy conservation is not a license to use the owner as a guinea pig. In most cases, rely on conventional equipment and methods.

Contrary to popular opinion, energy efficiency does not require exotic technology. That’s good news. The bad news is that fads in energy conservation have strong appeal, distracting people from proven profit makers. The only good reason to do energy conservation is to produce predictable, certain savings. Everyone is fascinated by innovation. Innovation drives progress. But, the price of innovation is a big chance of failure.

Most owners can’t afford that risk. Leave unproven equipment and methods to those who develop new products and have a laboratory budget.

On the other hand, if you are in a position to work at the frontiers of energy efficiency, the Energy Efficiency Manual will help you survive as a pioneer. You will find many Measures at the leading edge of energy efficiency (and a few that are just on the outer fringe). These too can be profitable if you give them the attention they need. Riskier Measures have a Rating of “C” or “D”, and their Traps & Tricks warn you of the dangers of unexplored territory. Why is there so much stress on reliability? The Energy Efficiency Manual devotes a lot of attention to the details that make the difference between a reliable system and one that is riddled with problems. This emphasis on avoiding pitfalls and dealing with tricky factors is intended to alert you, not to frighten you.

Energy conservation is still a new subject. The blunt truth is that many energy conservation projects have failed, almost always because people ignored vital issues at the outset.

These issues are often simple. For example, a common cause of energy waste is failing to mark controls so that people know how to use them. Only successful projects pay off. We want you to contribute to the successes, not to the failures.

The Measures spell out the issues that you need to consider. It’s like driving around potholes. Keep your eyes open and don’t rush. Why all the explanations? A large part of the Energy Efficiency Manual is devoted to explaining how things work.

There are several important reasons for this. If you understand the principles, you are much less likely to make mistakes.

Knowing the principles also enables you to keep up with changes in technology. And, knowing what you are doing at a basic level turns the work into fun. The “theory” is located in two places. Each Measure offers the basic information that you need, and if necessary, it suggests where to get more information.

Often, a Measure will refer you to one or more Reference Notes. Each Reference Note is a self-contained explanation of a specific topic. Don’t let mere words get in your way. Each area of design, construction, and facility operation has a separate vocabulary. Architects have one set of jargon, mechanical engineers have another, electrical contractors still another, and so forth. Don’t let this deter you from making efficiency improvements in each of these areas. The principles are important, not knowing particular words.

The Energy Efficiency Manual keeps the language as simple as possible. For example, we say “lamp” or “light fixture” instead of “luminaire.” We say “window” or “skylight” instead of “fenestration.” To help you communicate with specialists who may be fussy about language, the Manual explains specialized terms in the places where you need to know them. Fortunately, each area has only a few specialized terms that are important.

If you find a word that is unfamiliar, the Index will steer you to a concise, practical explanation. You don’t need much math, but be comfortable with numbers. You will probably be happy to see that the Energy Efficiency Manual uses little mathematics.

There are only a few simple formulas, and you need only arithmetic to use them. Even so, energy efficiency is all about numbers. In most cases, you are not doing something that is fundamentally new. Instead, you are doing something better. To judge whether the improvement is worth the cost, you have to be able estimate the benefit in terms of numbers.

If you are not comfortable doing the math, of if you need a calculation that requires specialized knowledge, get a specialist to make the calculations for you. Recognize that energy savings are uncertain to some extent.

They are subject to conditions that you cannot predict, including future energy costs, © D. Wulfinghoff 1999.

All Rights Reserved. 10 operating schedules, weather, and human behavior. Make your estimates of savings for a reasonable range of conditions. Keep your facility efficient for its entire life. When energy conservation became a public issue during the 1970’s, it was promoted by many wellintentioned people who lacked experience in keeping things working. Energy conservation was treated as a magic pill that would cure the disease of energy waste once and for all.

In reality, energy waste is a degenerative condition that keeps trying to return. Maintaining efficiency is like maintaining your physical fitness.

You have to keep it up. Design your efficiency improvements to survive as long as the facility. Each Measure that requires maintenance tells you how to keep it profitable. Let all your information sources work for you. Capable professionals depend primarily on a few well-worn references. But, they also know how to get information from other sources quickly. Whether you are a professional or not, the Energy Efficiency Manual is your primary reference for energy efficiency.

However, no single book can tell you everything you need to know. To do battle with energy waste, assemble an armory of information that is appropriate for the level of improvements that you plan to make. You will see that the Energy Efficiency Manual is not cluttered with formulas and tables. When you need detailed engineering data, get it from the appropriate reference books. Fortunately, you need only a few of these.

If you are involved at a professional level with heating, air conditioning, refrigeration, or designing a building’s skin, you should have the four-volume ASHRAE Handbook on your shelf. For electric lighting, the prime reference source is the IESNA Handbook. Many books are available on specialized aspects of energy conservation, such as solar energy, cogeneration, and residential insulation. Don’t hesitate to get another book to expand your knowledge about a subject.

There is no better bargain. A good book costs almost nothing in comparison with your utility expenses, and it protects your most valuable assets, which are your time and your professional reputation.

Once you decide to use a particular type of equipment, study the catalogs and equipment manuals of different manufacturers. These are a treasure of important details, and they are your most current source of information. The big weakness of manufacturers’ literature is a selective rendition of the truth. Knowing potential problems beforehand is critical to success, but manufacturers tend to omit or minimize this vital information. Talk to others. Two heads are better than one.

Seek other people’s opinions before you get involved with unfamiliar equipment or procedures. You can get practical advice from books, trade magazines, professional organizations, consultants, colleagues, and vendors. Talk to facility operators for their opinions about how well something really works. As you do this, take everything with a grain of salt.

People’s perceptions are distorted by wishful thinking, embarrassment about disappointing outcomes, and inability to measure actual performance. I have listened to experienced plant operators brag about big efficiency improvements that they were convinced they had achieved with gadgets that were purely bogus. Don’t try to do everything yourself.

If you have a big facility, you will not live long enough to make it efficient by yourself. If you try, energy and money will bleed away while valuable efficiency improvements wait to be made. Spread the work effectively. In a big facility, your main job is to decide which Measures to accomplish, and to make sure that they get done correctly. Use engineers, architects, contractors, specialized consultants, along with the facility staff. As your program gains momentum, you will have your hands full making sure that others do their work correctly.

Many Measures straddle the boundaries of the established design and construction disciplines. For example, successful daylighting requires close coordination between the architect, the lighting designer, the electrical engineer, and the mechanical engineer. You have to bring all these people together and require them to address all the issues that are critical for success. This is not always easy. Select your people for their willingness to listen and learn. ENERGY EFFICIENCY MANUAL. 11 Seize the opportunity!

Enjoy yourself. The most important point is to get started. At every moment, motors and fans are running, lights are turned on, boilers are burning fuel, and other equipment is consuming energy.

Some of this energy is being wasted, and it is probably more expensive than you realize. Remember that cost savings are pure profit. You would have to sell a lot more of your product or service to make as much profit as you can from energy efficiency. Start tapping this resource. At this point, you may feel that you got into more than you bargained for. Energy conservation is a bigger challenge than most people expect, but the Energy Efficiency Manual breaks it down into easy steps. Set a comfortable pace, and stick with it.

Your energy savings will soon show up on your utility bills, and those saving will continue to grow and accumulate. On an industry-wide basis, the efficiency of your facilities will increasingly determine whether your organization can continue to survive and compete.

On a global scale, improving efficiency is the most satisfactory way for civilization to adapt to declining energy resources and to minimize harm to the environment. Your energy efficiency program can be the most interesting and rewarding part of your career. It will give you an opportunity to become involved in every aspect of your industry. There is probably no other way that you can have as much fun while doing something of fundamental importance. Wulfinghoff 1999. All Rights Reserved.

Donald Wulfinghoff Wheaton, Maryland, USA. 13 Expression of Gratitude This book aspires to bring order and understanding to the vast field of energy efficiency. It organizes what I have learned about the subject during a career that has spanned the most exciting years of energy conservation in the United States and the world.

Almost everything that I know was learned from others in one way or another. I would like to begin the book by recognizing those who contributed generously and specifically to the book, and also to recognize several persons and organizations who contributed more generally to my education in energy efficiency. This book is largely their achievement. The following brief acknowledgments cannot adequately recognize the individuals who made important contributions. However, I hope that these mentions will be accepted as a token of my deep gratitude. Phillips, a figure revered in the air conditioning industry for his limitless contributions, erudition, and charm, meticulously reviewed two separate drafts of the material that deals with cooling systems. In addition to checking the text, he made important comments on both the theory of refrigeration and the lore of practical applications.

Henry Borger, a leader in construction research as well as a talented writer on diverse subjects, reviewed the entire book, suggesting improvements in structure and content. Charles Wood reviewed the text that deals with boiler systems, providing valuable comments on this technical area and on the editorial approach. Jim Crawford of the Trane Company contributed extensive and detailed information about the fast-changing world of refrigerants. Dave Molin of the Trane Company reviewed the Reference Note on energy analysis computer programs.

Richard Ertinger and Edward Huenniger of Carrier Corporation provided valuable information about the most recent advances in cooling technology. Ken Fonstad, of the Graham Division of Danfoss, Inc., wrote lucid explanations of the electrical subtleties of variable-frequency motor drives, accompanied by extensive oscilloscope traces that he made.

He also contributed a number of illustrations. Sean Gallagher shared his experience with the practical aspects of lighting retrofits and with utility purchasing in this era of rapid change in the utility industry.

Don Warfield of Solarex provided information about the current state of photovoltaic technology, and made several illustrations available. Many others contributed information during the twenty years of the book’s preparation. It is impossible now to recall all the valuable discussions and presentations.

I hope that the individuals will approve of the way that the book reflects their expertise. Many organizations contributed illustrations that help to achieve the book’s goal of bringing to life many unfamiliar and subtle concepts. These organizations are listed in the back of the book.

1: Municipal water feed 2: Fluid from water storage tank to external (passive) heat source; passive heat source can be the ground (soil or groundwater), sun or air via heat pump, or 3: Fluid from heat pump, or thermodynamic solar panel to water storage tank 4: Pump, actuator, controller and other parts 5: Water heater 6: Water storage tank 7: Hot water to domestic appliances Water heating is a heat transfer process that uses an energy source to heat water above its initial temperature. Typical domestic uses of hot water include cooking, cleaning, bathing, and space heating. In industry, hot water and water heated to have many uses.

Domestically, water is traditionally heated in vessels known as water heaters, kettles, cauldrons, pots, or coppers. These metal vessels that heat a batch of water do not produce a continual supply of heated water at a preset temperature. Rarely, hot water occurs naturally, usually from natural. The temperature varies with the consumption rate, becoming cooler as flow increases. Appliances that provide a supply of hot water are called water heaters, hot water heaters, geysers, or calorifiers.

These names depend on region, and whether they heat or non-potable water, are in domestic or industrial use, and their energy source. In installations, potable water heated for uses other than space heating is also called domestic hot water ( DHW). Fossil fuels (, ), or are commonly used for heating water. These may be consumed directly or may produce that, in turn, heats water. Electricity to heat water may also come from any other electrical source, such as.

Such as, and can also heat water, often in combination with backup systems powered by fossil fuels or electricity. Densely populated urban areas of some countries provide of hot water.

This is especially the case in, and. District heating systems supply energy for water heating and from, from industries, geothermal heating, and. Actual heating of tap water is performed in heat exchangers at the consumers' premises. Generally the consumer has no in-building backup system, due to the expected high availability of district heating systems. Gas furnace (top) and storage water heater (bottom) (Germany) In household and commercial usage, most North American and Southern Asian water heaters are the tank type, also called storage water heaters, these consist of a cylindrical vessel or container that keeps water continuously hot and ready to use.

Typical sizes for household use range from 75 to 400 liters (20 to 100 US gallons). These may use, or other energy sources. Natural gas heaters are most popular in the US and most European countries, since the gas is often conveniently piped throughout cities and towns and currently is the cheapest to use. In the United States, typical natural gas water heaters for households without unusual needs are 40 or 50 US gallons with a burner rated at 34,000 to 40,000 BTU/hour. Some models offer 'High Efficiency and Ultra Low NOx' emissions. This is a popular arrangement where higher flow rates are required for limited periods, water is heated in a pressure vessel that can withstand a close to that of the incoming mains supply. In North America, these vessels are called hot water tanks, and may incorporate an electrical resistance heater, a, or a gas or oil burner that heats water directly.

Where hot-water space heating boilers are installed, are usually heated indirectly by primary water from the boiler, or by an electric (often as backup to the boiler). In the UK these vessels are called indirect cylinders, or direct cylinders, respectively.

Additionally, if these cylinders form part of a sealed system, providing mains-pressure hot water, they are known as unvented cylinders. In the US, when connected to a boiler they are called indirect-fired water heaters. Compared to tankless heaters, storage water heaters have the advantage of using energy (gas or electricity) at a relatively slow rate, storing the heat for later use. The disadvantage is that over time, heat escapes through the tank wall and the water cools down, activating the heating system to heat the water back up, so investing in a tank with better insulation improves this standby efficiency. Additionally, when heavy use exhausts the hot water, there is a significant delay before hot water is available again. Larger tanks tend to provide hot water with less temperature fluctuation at moderate flow rates.

Heaters in the United States and New Zealand are typically vertical, cylindrical tanks, usually standing on the floor or on a platform raised a short distance above the floor. Volume storage water heaters in Spain are typically horizontal. In India, they are mainly vertical. In apartments they can be mounted in the ceiling space over laundry-utility rooms.

In Australia, gas and electric outdoor tank heaters have mainly been used (with high temperatures to increase effective capacity), but solar roof tanks are becoming fashionable. Tiny point-of-use (POU) electric storage water heaters with capacities ranging from 8 to 32 liters (2 to 6 gallons) are made for installation in kitchen and bath cabinets or on the wall above a sink. They typically use low power heating elements, about 1 kW to 1.5 kW, and can provide hot water long enough for hand washing, or, if plumbed into an existing hot water line, until hot water arrives from a remote high capacity water heater. They may be used when retrofitting a building with hot water plumbing is too costly or impractical. Since they maintain water temperature thermostatically, they can only supply a continuous flow of hot water at extremely low flow rates, unlike high-capacity tankless heaters.

In tropical countries, like Singapore and India, a storage water heater may vary from 10 L to 35 L. Smaller water heaters are sufficient, as ambient weather temperatures and incoming water temperature are moderate. Point-of-use (POU) vs. Centralized hot water A locational design decision may be made between point-of-use and centralized water heaters. Centralized water heaters are more traditional, and are still a good choice for small buildings. For larger buildings with intermittent or occasional hot water use, multiple POU water heaters may be a better choice, since they can reduce long waits for hot water to arrive from a remote heater. The decision where to locate the water heater(s) is only partially independent of the decision of a tanked vs.

Tankless water heater, or the choice of energy source for the heat. Tankless heaters. The inside of a operated two-stage tankless heater, heated by 3-phase electric power. The copper tank contains heating elements with 18 maximum power. Tankless water heaters—also called instantaneous, continuous flow, inline, flash, on-demand, or instant-on water heaters—are gaining in popularity.

These high-power water heaters instantly heat water as it flows through the device, and do not retain any water internally except for what is in the heat exchanger coil. Are preferred in these units because of their high thermal conductivity and ease of fabrication. Tankless heaters may be installed throughout a household at more than one point-of-use (POU), far from a central water heater, or larger centralized models may still be used to provide all the hot water requirements for an entire house. The main advantages of tankless water heaters are a plentiful continuous flow of hot water (as compared to a limited flow of continuously heated hot water from conventional tank water heaters), and potential energy savings under some conditions.

The main disadvantage is their much higher initial costs, a US study in Minnesota study reported a 20- to 40-year payback for the tankless water heaters. In a comparison to a less efficient natural gas fired hot water tank, on-demand natural gas will cost 30% more over its useful life. Stand-alone appliances for quickly heating water for domestic usage are known in North America as tankless or on demand water heaters. In some places, they are called multipoint heaters, geysers or ascots. In Australia and New Zealand they are called instantaneous hot water units. In Argentina they are called calefones. In that country calefones use gas instead of electricity.

A similar wood-fired appliance was known as the. A common arrangement where hot-water space heating is employed, is for a boiler to also heat, providing a continuous supply of hot water without extra equipment. Appliances that can supply both space-heating and domestic hot water are called combination (or combi) boilers. Though on-demand heaters provide a continuous supply of domestic hot water, the rate at which they can produce it is limited by the thermodynamics of heating water from the available fuel supplies. Electric shower heads. A poorly installed electric shower head can pose an hazard As the name implies, an element is incorporated into such shower heads to instantly heat the water as it flows through. These self-heating shower heads are specialized point-of-use (POU) tankless water heaters, and are widely used in some countries.

Invented in Brazil in the 1930s and used frequently since the 1940s, the electric shower is a home appliance often seen in South American countries due to the higher costs of gas distribution. Earlier models were made of chromed copper or brass, which were expensive, but since 1970, units made of injected plastics are popular due to low prices similar to that of a hair dryer. Electric showers have a simple electric system, working like a coffee maker, but with a larger water flow.

A flow switch turns on the device when water flows through it. Once the water is stopped, the device turns off automatically. An ordinary electric shower often has three heat settings: low (2.5 kW), high (5.5 kW) or cold (0 W) to use when a central heater system is available or in hot seasons. Energy usage The power consumption of electric showers in the maximum heating setting is about 5.5 kW for 120 V and 7.5 kW for 220 V. The lower costs with electric showers compared to the higher costs with boilers is due to the time of use: an electric shower uses energy only while the water flows, while a boiler works many times a day to keep a quantity of standing water hot for use throughout the day and night. Moreover, the transfer of electric energy to the water in an electric shower head is very efficient, approaching 100%.

Electric showers may save energy compared to electric tank heaters, which lose some standby heat. Safety There is a wide range of electric showers, with various types of heating controls. The heating element of an electric shower is immersed in the water stream, using a resistance element which is sheathed and electrically isolated, like the ones used in oil heaters, radiators or clothes irons, providing safety. Due to electrical safety standards, modern electric showers are made of plastic instead of using metallic casings like in the past. As an electrical appliance that uses more electric current than a washer or a dryer, an electric shower installation requires careful planning, and generally is intended to be wired directly from the electrical distribution box with a dedicated and ground system. A poorly installed system with old aluminum wires or bad connections may be dangerous, as the wires can overheat or electric current may leak via the water stream through the body of the user to earth.

Solar water heaters. Main article: Increasingly, water heaters are being used. Their solar collectors are installed outside dwellings, typically on the roof or walls or nearby, and the potable is typically a pre-existing or new conventional water heater, or a water heater specifically designed for solar thermal. The most basic solar thermal models are the direct-gain type, in which the potable water is directly sent into the collector. Many such systems are said to use integrated collector storage (ICS), as direct-gain systems typically have storage integrated within the collector.

Heating water directly is inherently more efficient than heating it indirectly via heat exchangers, but such systems offer very limited freeze protection (if any), can easily heat water to temperatures unsafe for domestic use, and ICS systems suffer from severe heat loss on cold nights and cold, cloudy days. By contrast, indirect or closed-loop systems do not allow potable water through the panels, but rather pump a heat transfer fluid (either water or a water/antifreeze mix) through the panels. After collecting heat in the panels, the heat transfer fluid flows through a, transferring its heat to the potable hot water. When the panels are cooler than the storage tank or when the storage tank has already reached its maximum temperature, the controller in closed-loop systems stops the circulation pumps. In a drainback system, the water drains into a storage tank contained in conditioned or semi-conditioned space, protected from freezing temperatures. With antifreeze systems, however, the pump must be run if the panel temperature gets too hot (to prevent degradation of the antifreeze) or too cold (to prevent the water/antifreeze mixture from freezing.) Flat panel collectors are typically used in closed-loop systems.

Flat panels, which often resemble, are the most durable type of collector, and they also have the best performance for systems designed for temperatures within 56 °C (100 °F) of. Flat panels are regularly used in both pure water and antifreeze systems.

Another type of solar collector is the evacuated tube collector, which are intended for cold climates that do not experience severe hail and/or applications where high temperatures are needed (i.e., over 94 °C 201 °F). Placed in a rack, evacuated tube collectors form a row of glass tubes, each containing absorption fins attached to a central heat-conducting rod (copper or condensation-driven).

The evacuated description refers to the vacuum created in the glass tubes during the manufacturing process, which results in very low heat loss and lets evacuated tube systems achieve extreme temperatures, far in excess of water's boiling point. Geothermal heating In countries like and, and other volcanic regions, water heating may be done using, rather than combustion.

Gravity-fed system Where a space-heating water boiler is employed, the traditional arrangement in the UK is to use boiler-heated ( primary) water to heat potable ( secondary) water contained in a cylindrical vessel (usually made of copper)—which is supplied from a cold water storage vessel or container, usually in the roof space of the building. This produces a fairly steady supply of DHW (Domestic Hot Water) at low but usually with a good. In most other parts of the world, water heating appliances do not use a cold water storage vessel or container, but heat water at pressures close to that of the incoming supply. Other improvements Other improvements to water heaters include check valve devices at their inlet and outlet, cycle timers, electronic in the case of fuel-using models, sealed air intake systems in the case of fuel-using models, and pipe insulation. The sealed air-intake system types are sometimes called 'band-' intake units. 'High-efficiency' condensing units can convert up to 98% of the energy in the fuel to heating the water.

The exhaust gases of combustion are cooled and are mechanically either through the roof or through an exterior wall. At high efficiencies a drain must be supplied to handle the water condensed out of the combustion products, which are primarily carbon dioxide and water vapor. In traditional plumbing in the UK, the space-heating boiler is set up to heat a separate hot water cylinder or water heater for potable hot water. Such water heaters are often fitted with an auxiliary electrical immersion heater for use if the boiler is out of action for a time. Heat from the space-heating boiler is transferred to the water heater vessel/container by means of a heat exchanger, and the boiler operates at a higher temperature than the potable hot water supply. Most potable water heaters in North America are completely separate from the space heating units, due to the popularity of / systems in North America. Residential combustion water heaters manufactured since 2003 in the United States have been redesigned to resist ignition of flammable vapors and incorporate a thermal cutoff switch, per Z21.10.1.

The first feature attempts to prevent vapors from flammable liquids and gases in the vicinity of the heater from being ignited and thus causing a house fire or explosion. The second feature prevents tank overheating due to unusual combustion conditions. These safety requirements were made in response to homeowners storing, or spilling, or other flammable liquids near their water heaters and causing fires. Since most of the new designs incorporate some type of screen, they require monitoring to make sure they do not become clogged with lint or dust, reducing the availability of air for combustion. If the flame arrestor becomes clogged, the thermal cutoff may act to shut down the heater. A wetback stove , wetback heater (NZ), or back boiler (UK), is a simple household secondary water heater using incidental heat.

It typically consists of a hot water pipe running behind a or (rather than ), and has no facility to limit the heating. Modern wetbacks may run the pipe in a more sophisticated design to assist. These designs are being forced out by government efficiency regulations that do not count the energy used to heat water as 'efficiently' used. Kerosene water heater, 1917 Though not very popular in North America, another type of water heater developed in Europe predated the storage model. In London, England, in 1868, a painter named Benjamin Waddy Maughan invented the first instantaneous domestic water heater that did not use. Named the after an Icelandic gushing hot spring, Maughan's invention made cold water at the top flow through pipes that were heated by hot gases from a burner at the bottom.

Hot water then flowed into a sink or tub. The invention was somewhat dangerous because there was no flue to remove heated gases from the bathroom. A water heater is still sometimes called a geyser in the UK.

Maughn's invention influenced the work of a Norwegian mechanical engineer named. The first automatic, storage tank-type gas water was invented around 1889 by Ruud after he immigrated to (US). The Ruud Manufacturing Company, still in existence today, made many advancements in tank-type and tankless water heater design and operation. Thermodynamics and economics. Gas-fired tankless condensing boiler with hot water storage tank (US) Water typically enters residences in the US at about 10 °C (50 °F), depending on latitude and season. Hot water temperatures of 50 °C (122 °F) are usual for dish-washing, laundry and showering, which requires that the heater raise the water temperature about 40 °C (72 °F) if the hot water is mixed with cold water at the point of use.

The reference shower flow rate is 2.5 US gallons (9.5 L) per minute. Sink and dishwasher usages range from 1–3 US gallons (3.8–11.4 L) per minute. Natural gas in the US is measured in CCF (100 cubic feet), which is converted to a standardized energy unit called the, which is equal to 100,000 (BTU). A BTU is the energy required to raise one pound of water by one degree Fahrenheit. A US gallon of water weighs 8.3 pounds (3.8 kg).

To raise 60 gallons of water from 10 °C (50 °F) to 50 °C (122 °F) requires 60 × 8.3 × (122 − 50) = 35856 BTU, or approximately 0.359 (35856/100,000), at 88% efficiency. A 157,000 BTU/h heater (as might exist in a tankless heater) would take 15.6 minutes to do this, at 88% efficiency. At $1 per, the cost of the gas would be about 41 cents. In comparison, a typical 60 gallon tank electric water heater has a 4500 watt (15,355 BTU) heating element, which at 100% efficient results in a heating time of about 2.34 hours. At 16 cents/kWh the electricity would cost $1.68. Energy efficiencies of water heaters in residential use can vary greatly, particularly depending on manufacturer and model. However, electric heaters tend to be slightly more efficient (not counting power station losses) with recovery efficiency (how efficiently energy transfers to the water) reaching about 98%.

Gas fired heaters have maximum recovery efficiencies of only about 82-94% (the remaining heat is lost with the flue gasses). Overall can be as low as 80% for electric and 50% for gas systems. Natural gas and propane tank water heaters with energy factors of 62% or greater, as well as electric tank water heaters with energy factors of 93% or greater, are considered high-efficiency units.qualified natural gas and propane tank water heaters (as of September 2010) have energy factors of 67% or higher, which is usually achieved using an intermittent pilot together with an automatic flue damper, baffle blowers, or power venting. Direct electric resistance tank water heaters are not included in the Energy Star program, however, the Energy Star program does include electric units with energy factors of 200% or higher. Tankless gas water heaters (as of 2015) must have an energy factor of 90% or higher for Energy Star qualification. Since electricity production in thermal plants has efficiency levels ranging from only 15% to slightly over 55% ( gas turbine), with around 40% typical for thermal power stations, direct resistance electric water heating may be the least energy efficient option.

However, use of a heat pump can make electric water heaters much more energy efficient and lead to a decrease in carbon dioxide emissions, even more so if a source of electricity is used. Unfortunately, it takes a great deal of energy to heat water, as one may experience when waiting to boil a gallon of water on a stove.

For this reason, tankless on-demand water heaters require a powerful energy source. A standard 120 V / 15-ampere rated wall electric outlet, by comparison, only sources enough power to warm a disappointingly small amount of water: about 0.17 US gallons (0.64 L) per minute at 40 °C (72 °F) temperature elevation. US minimum requirements On April 16, 2015, as part of the (NAECA), new minimum standards for efficiency of residential water heaters set by the went into effect. All new gas storage tank water heaters with capacities smaller than 55 US gallons (210 l; 46 imp gal) sold in the United States in 2015 or later shall have an energy factor of at least 60% (for 50-US-gallon units, higher for smaller units), increased from the pre-2015 minimum standard of 58% energy factor for 50-US-gallon gas units. Electric storage tank water heaters with capacities less than 55 US gallons sold in the United States shall have an energy factor of at least 95%, increased from the pre-2015 minimum standard of 90% for 50-US-gallon electric units. Under the 2015 standard, for the first time, storage water heaters with capacities of 55 US gallons or larger now face stricter efficiency requirements than those of 50 US gallons or less. Under the pre-2015 standard, a 75-US-gallon (280 l; 62 imp gal) gas storage water heater with a nominal input of 75,000 British thermal units (79,000 kJ) or less was able to have an energy factor as low as 53%, while under the 2015 standard, the minimum energy factor for a 75-US-gallon gas storage tank water heater is now 74%, which can only be achieved by using condensing technology.

Storage water heaters with a nominal input of 75,000 btu or greater are not currently affected by these requirements, since energy factor is not defined for such units. An 80-US-gallon (300 l; 67 imp gal) electric storage tank water heater was able to have a minimum energy factor of 86% under the pre-2015 standard, while under the 2015 standard, the minimum energy factor for an 80-gallon electric storage tank water heater is now 197%, which is only possible with technology. This rating measures efficiency at the point of use. Depending on how electricity is generated, overall efficiency may be much lower. For example, in a traditional coal plant, only about 30-35% of the energy in the coal ends up as electricity on the other end of the generator.

Losses on the electrical grid (including line losses and voltage transformation losses) reduce electrical efficiency further. According to data from the Energy Information Administration, transmission and distribution losses in 2005 consumed 6.1% of net generation. In contrast, 90% of natural gas’ energy value is delivered to the consumer. (In neither case is the energy expended exploring, developing and extracting coal or natural gas resources included in the quoted efficiency numbers.) Gas tankless water heaters shall have an energy factor of 82% or greater under the 2015 standards, which corresponds to the pre-2015 Energy Star standard. Water heater safety Explosion hazard. Temperature/pressure safety valve installed atop a tank-type water heater (US) Water heaters potentially can explode and cause significant damage, injury, or death if certain safety devices are not installed. A safety device called a (T&P or TPR) valve, is normally fitted on the top of the water heater to dump water if the temperature or pressure becomes too high.

Most plumbing codes require that a discharge pipe be connected to the valve to direct the flow of discharged hot water to a drain, typically a nearby, or outside the living space. Some building codes allow the discharge pipe to terminate in the garage. If a gas or propane fired water heater is installed in a or basement, many plumbing codes require that it be elevated at least 18 in (46 cm) above the floor to reduce the potential for fire or explosion due to spillage or leakage of combustible liquids in the garage. Furthermore, certain local codes mandate that tank-type heaters in new and retrofit installations must be secured to an adjacent wall by a strap or anchor to prevent tipping over and breaking the water and gas pipes in the event of an. For older houses where the water heater is part of the space heating boiler, and plumbing codes allow, some plumbers install an automatic gas shutoff (such as the 'Watts 210') in addition to a TPR valve. When the device senses that the temperature reaches 99 °C (210 °F), it shuts off the gas supply and prevents further heating.

In addition, an or exterior pressure relief valve must be installed to prevent pressure buildup in the plumbing from rupturing pipes, valves, or the water heater. Thermal burns (scalding). Scalding injury to right hand is a serious concern with any water heater. Quickly at high temperature, in less than 5 seconds at 60 °C (140 °F), but much slower at 53 °C (127 °F) — it takes a full minute for a. Older people and children often receive serious scalds due to disabilities or slow. In the United States and elsewhere it is common practice to put a on the outlet of the water heater. The result of mixing hot and cold water via a tempering valve is referred to as 'tempered water'.

A tempering valve mixes enough cold water with the hot water from the heater to keep the outgoing water temperature fixed at a more moderate temperature, often set to 50 °C (122 °F). Without a tempering valve, reduction of the water heater's setpoint temperature is the most direct way to reduce scalding. However, for sanitation, hot water is needed at a temperature that can cause scalding.

This may be accomplished by using a supplemental heater in an appliance that requires hotter water. Most residential, for example, include an internal electric heating element for increasing the water temperature above that provided by a domestic water heater. Bacterial contamination. Bacterial colonies of Legionella pneumophila (indicated by arrows) Two conflicting safety issues affect water heater temperature—the risk of scalding from excessively hot water greater than 55 °C (131 °F), and the risk of incubating bacteria colonies, particularly, in water that is not hot enough to kill them. Both risks are potentially life-threatening and are balanced by setting the water heater's thermostat to 55 °C (131 °F).

The European Guidelines for Control and Prevention of Travel Associated Legionnaires’ Disease recommend that hot water should be stored at 60 °C (140 °F) and distributed so that a temperature of at least 50 °C (122 °F) and preferably 55 °C (131 °F) is achieved within one minute at points of use. If there is a dishwasher without a booster heater, it may require a water temperature within a range of 57–60 °C (135–140 °F) for optimum cleaning, but tempering valves set to no more than 55 °C (131 °F) can be applied to faucets to avoid scalding. Tank temperatures above 60 °C (140 °F) may produce deposits, which could later harbor bacteria, in the water tank.

Higher temperatures may also increase in the dishwasher. Tank thermostats are not a reliable guide to the internal temperature of the tank.

Gas-fired water tanks may have no temperature calibration shown. An electric thermostat shows the temperature at the elevation of the thermostat, but water lower in the tank can be considerably cooler. An outlet thermometer is a better indication of water temperature. In the renewable energy industry (solar and heat pumps, in particular) the conflict between daily thermal Legionella control and high temperatures, which may drop system performance, is subject to heated debate. In a paper seeking a green exemption from normal Legionellosis safety standards, Europe's top CEN solar thermal technical committee TC 312 asserts that a 50% fall in performance would occur if solar water heating systems were heated to the base daily.

However some analysis work using Polysun 5 suggests that an 11% energy penalty is a more likely figure. Whatever the context, both energy efficiency and scalding safety requirements push in the direction of considerably lower water temperatures than the legionella temperature of around 60 °C (140 °F). However, legionella can be safely and easily controlled with good design and engineering protocols. For instance raising the temperature of water heaters once a day or even once every few days to 55 °C (131 °F) at the coldest part of the water heater for 30 minutes effectively controls legionella. In all cases and in particular energy efficient applications, Legionnaires' disease is more often than not the result of engineering design issues that do not take into consideration the impact of stratification or low flow. It is also possible to control Legionella risks by chemical treatment of the water.

This technique allows lower water temperatures to be maintained in the pipework without the associated Legionella risk. The benefit of lower pipe temperatures is that the heat loss rate is reduced and thus the energy consumption is reduced. See also. Archived from on 2012-09-09. Retrieved 2012-02-29. pg28. Chai, Hung Yin.

The New Paper. Archived from on 2 October 2014. Retrieved 2 October 2014. The New Zealand Herald. 24 August 2005.

April 16, 2010. Retrieved September 7, 2012. National Electrical Manufacturers Association. Retrieved 1 October 2015.

Energy Efficiency Manual Wulfinghoff Pdf Files

Enbridge Gas New Brunswick (Canada). Archived from (PDF) on October 2, 2015. Retrieved 1 October 2015.

1951 article with illustrations on basics of water heater safety pressure relief valve. (PDF).

International Association of Plumbing and Mechanical Officials. Retrieved 23 Feb 2010. Domestic Water Heating Design Manual (2nd Edition), American Society of Plumbing Engineers (ASPE), 2003, pages 13-14.

Smith, Timothy A. Plumbing Systems & Design, May/June 2003. European Working Group for Legionella Infections. Archived from (PDF) on 2007-09-22.

Retrieved 2008-02-12. Department of Energy. Retrieved 2007-10-14. Wulfinghoff Energy Efficiency ManualEnergy Institute Press, 1999 pages 458-460 External links.

from.