Domestic Water Heating Design Manual

530 Pages·2003·16.274 MB·English

Domestic
Water
Heating
Design
Manual
Published by
American
Society of
Plumbing
Engineers Second Edition
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The Domestic Water Heating Design Manual, Second Edition, is designed to provide accurate
and authoritative information for the design and specification of domestic water heating
systems. The publisher makes no guarantees or warranties, expressed or implied, regarding
the data and information contained in this publication. All data and information are provided
with the understanding that the publisher is not engaged in rendering legal, consulting,
engineering, or other professional services. If legal, consulting, or engineering advice or other
expert assistance is required, the services of a competent professional should be engaged.
American Society of Plumbing Engineers
2980 S. River Rd
Des Plaines, IL 600018
[phone]
E-mail: [email protected] • Internet: www.aspe.org
Copyright © 2003 by American Society of Plumbing Engineers
First Edition published in 1998 by American Society of Plumbing Engineers.
All rights reserved. No part of this book may be reproduced or transmitted in any form or by
any means, electronic or mechanical, including photocopying and recording, or by any infor-
mation storage or retrieval system, without permission in writing from the publisher.
ISBN 978-1-891255-18-2
Printed in the United States of America
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ILLUSTRATIONS
Figure 2.1 Weekday vs. Weekend Consumption . . . . . 20
Figure 2.2 Seasonal Variations, Weekend
Consumption . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
Figure 2.3 Seasonal Variations, Weekend
Consumption . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
Figure 2.4 Consumption curve. . . . . . . . . . . . . . . . . . 27
Figure 2.5 Comparison of DHW Peak Consumption . . 29
Figure 2.6 Parts of 3-Hour DHW Peak Consumption. . 29
Figure 2.7 Parts of Peak 60 Minutes DHW
Consumption . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Figure 2.8 Peak Demand Curve . . . . . . . . . . . . . . . . . 36
Fixture 14.1 Upfeed Hot Water System with
Heater at Bottom of System. . . . . . . . . . . . . . . . . 239
Figure 14.2 Downfeed Hot Water System with
Heater at Top of System. . . . . . . . . . . . . . . . . . . . 240
Figure 14.3 Upfeed Hot Water System with
Heater at Bottom of System. . . . . . . . . . . . . . . . . 240
Figure 14.4 Downfeed Hot Water System with
Heater at Top of System. . . . . . . . . . . . . . . . . . . . 241
Figure 14.5 Combination Upfeed and Downfeed
Hot Water System with Heater at
Bottom of System.. . . . . . . . . . . . . . . . . . . . . . . . 241
Figure 14.6 Combination Downfeed and Upfeed
Hot Water System with Heater at Top of System.. 242
Figure 14.7 Instantaneous Point-of-Use Water
Heater Piping Diagram. . . . . . . . . . . . . . . . . . . . . 243
Figure 14.8 Fixed Orifices and Venturi Flow Meters. 246
Figure 14.9 Preset Self-Limiting Flow Control
Cartridge. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247
Figure 14.10 Adjustable Orifice Flow Control Valve.. 248
Figure 14.11 Adjustable Balancing Valve with
Memory Stop. . . . . . . . . . . . . . . . . . . . . . . . . . . . 249
Figure 15.1 Construction of a Typical Heating Cable
for Hot Water Temperature Maintenance. . . . . . . 268
Figure 15.2 Components of a Hot Water Temperature
Maintenance System. . . . . . . . . . . . . . . . . . . . . . 269
Figure 15.3 Symbols Used to Indicate Components
of a Heat Traced Hot Water Supply System.. . . . . 273
Figure 15.4 Partial Simplified System Typical of
Hospitals, Correctional Facilities, and Hotels. . . . 276
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Figure 15.5 Typical Layout for 2 to 4-Story
Hospitals, Research Labs, Correctional Facilities,
and Dormitories. . . . . . . . . . . . . . . . . . . . . . . . . . 277
Figure 17.1 Indirect Water Heater Designs. . . . . . . . 292
Figure 17.2 Purdue Bulletin 74 Chart, Showing
the Relationship Between Lime Deposits and
Water Temperature . . . . . . . . . . . . . . . . . . . . . . . 294
Figure 18.1 A Typical Electric Water Heater.. . . . . . . 299
Figure 18.2 Electric Water Heater Element Types. . . 301
Figure 18.3 Electric Water Heater Element
Construction. . . . . . . . . . . . . . . . . . . . . . . . . . . . 301
Figure 18.4 Location of Controls—Residential and
Light-Duty, Commercial Electric Water Heaters. . 304
Figure 18.5 Location of Controls—Commercial
Electric Water Heaters. . . . . . . . . . . . . . . . . . . . . 307
Figure 18.6 Location of Controls—Booster Type,
Commercial Electric Water Heaters. . . . . . . . . . . 309
Figure 20.1 Location and Types of Flue. . . . . . . . . . . 316
Figure 20.2 Sacrificial Anode Installation in a
Residential Gas Water Heater Tank. . . . . . . . . . . 318
Figure 20.3 Example of Water Heater Fittings. . . . . . 318
Figure 20.4 The Principle of Operation of the
Dip Tube. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 319
Figure 20.5 Types of Gas Burner.. . . . . . . . . . . . . . . 320
Figure 20.6 Commonly Used Draft Hoods. . . . . . . . . 322
Figure 20.7 Downdraft Conditions in a Vertical
Draft Hood . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 323
Figure 20.8 Vent Connection to a Chimney. . . . . . . . 324
Figure 22.1 Recirculation System Piping and
Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339
Figure 23.1 A Closed Hot Water System Showing
the Effects as Water and Pressure Increase
from (a) P and T to (b) P and T .. . . . . . . . . . . . 344
1 1 2 2
Figure 23.2 Effects of an Expansion Tank in a
Closed System as Pressure and Temperature
Increase from (a) P and T to (b) P and T .. . . . . 345
1 1 2 2
Figure 23.3 Sizing the Expansion Tank. . . . . . . . . . . 353
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TABLES
Table 1.1 Hot Water Multiplier, P . . . . . . . . . . . . . . . . . 7
Table 1.1(M) Hot Water Multiplier, P. . . . . . . . . . . . . . 10
Table 1.2 Typical Delivered Hot Water Temperatures
for Plumbing Fixtures and Equipment. . . . . . . . . . 12
Table 1.2(M) Typical Delivered Hot Water
Temperatures for Plumbing Fixtures and
Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Table 1.3 Time/Water Temperature Combinations
Producing Skin Damage . . . . . . . . . . . . . . . . . . . . 14
Table 2.1 Occupant Demographic Characteristics. . . . 24
Table 2.2 Low, Medium, and High Guidelines:
Hot Water Demands and Use for Multifamily
Buildings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Table 4.1 School Grade Divisions . . . . . . . . . . . . . . . . 45
Table 4.2 Potential Areas of Hot Water Usage . . . . . . . 46
Table 4.3 Hot Water Demand per Fixture for Schools . 49
Table 4.4 General Purpose Hot Water
Requirements of Kitchen Equipment . . . . . . . . . . . 50
Table 4.5 Rinse Water (180–195°F)
Requirements of Commercial Dishmachines . . . . . 50
Table 4.5(M) Rinse Water (82–91°C)
Requirements of Commercial Dishmachines . . . . . 51
Table 6.1 General Purpose Hot Water
Requirements for Various Kitchen Uses. . . . . . . . . 87
Table 6.2 Usage Factors for User Groups . . . . . . . . . . 88
Table 8.1 General Purpose Hot Water
Requirements for Various Kitchen Uses. . . . . . . . 151
Table 8.2 Usage Factors for User Groups . . . . . . . . . 152
Table 10.1 Tank Size Selection Chart . . . . . . . . . . . . 199
Table 10.1(M) Tank Size Selection Chart. . . . . . . . . . 200
Table 10.2 Hot Water Requirements after
Initial Loading. . . . . . . . . . . . . . . . . . . . . . . . . . . 200
Table 10.2(M) Hot Water Requirements after
Initial Loading. . . . . . . . . . . . . . . . . . . . . . . . . . . 201
Table 11.1 Fixture/Equipment Table . . . . . . . . . . . . 209
Table 14.1 Water Contents and Weight of Tube
or Piping per Linear Foot. . . . . . . . . . . . . . . . . . . 235
Table 14.1(M) Water Contents and Weight of Tube
or Piping per Meter . . . . . . . . . . . . . . . . . . . . . . . 236
Table 14.2 Approximate Fixture and Appliance
Water Flow Rates . . . . . . . . . . . . . . . . . . . . . . . . 236
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Table 14.3 Approximate Time Required to Get
Hot Water to a Fixture. . . . . . . . . . . . . . . . . . . . . 237
Table 14.3(M) Approximate Time Required to Get
Hot Water to a Fixture. . . . . . . . . . . . . . . . . . . . . 237
Table 14.4 Minimum Pipe Insulation Thickness . . . . 250
Table 14.4(M) Minimum Pipe Insulation Thickness. . 250
Table 14.5 Approximate Insulated Piping Heat
Loss and Surface Temperature . . . . . . . . . . . . . . 251
Table 14.5(M) Approximate Insulated Piping Heat
Loss and Surface Temperature . . . . . . . . . . . . . . 251
Table 14.6 Heat Loss from Various Size Tanks
with Various Insulation Thicknesses . . . . . . . . . . 252
Table 14.6(M) Heat Loss from Various Size Tanks
with Various Insulation Thicknesses . . . . . . . . . . 252
Table 15.1 Time for Hot Water to Reach Fixture . . . . 270
Table 15.1(M) Time for Hot Water
to Reach Fixture (sec) . . . . . . . . . . . . . . . . . . . . . 271
Table 15.2 Water Wasted While Waiting for
Hot Water to Reach Fixture (oz) . . . . . . . . . . . . . 271
Table 15.2(M) Water Wasted While Waiting for
Hot Water to Reach Fixture (mL) . . . . . . . . . . . . . 272
Table 15.3 Nominal Maintenance
Temperatures, °F (°C) . . . . . . . . . . . . . . . . . . . . . 274
Table 18.1 Resistance of Element . . . . . . . . . . . . . . . 302
Table 23.1 Thermodynamic Properties of Water
at a Saturated Liquid . . . . . . . . . . . . . . . . . . . . . 347
Table 23.2 Nominal Volume of Piping . . . . . . . . . . . . 350
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ACRONYMS
ACEEE — American Council for Energy Efficient Economy
ADA — Americans with Disabilities Act
AGA — American Gas Association
ASHRAE — American Society of Heating, Refrigerating, and
Air-Conditioning Engineers
ASME — American Society of Mechanical Engineers
ASPE — American Society of Plumbing Engineers
CCU — Critical care unit
DHW — Domestic hot water
EPDM — Ethylene propylene diene monomer
ER — Emergency room
HBV — Hepatitis B virus
HIV — Human immunodeficiency virus
HVAC — Heating, ventilating, and air conditioning
ICU — Intensive care unit
LMH — Low, medium, and high
LPG — Liquid petroleum gas
NEC — National Electric Code
NFPA — National Fire Protection Association
NR — Nitrile rubber
NSF — National Sanitation Foundation
OB — Obstetrics
OHRD — Ontario Hydro Research Division
PSIG — Pounds per square inch gauge
SMACNA — Sheet Metal and Air Conditioning Contractors
National Association
TEMA — Tubular Exchange Manufacturers Association
UL — Underwriters’ Laboratories, Inc.
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CONTENTS
FOREWORD. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xvii
ACKNOWLEDGMENTS. . . . . . . . . . . . . . . . . . . . . . . . . xix
ACRONYMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxi
SECTION I — SYSTEM SIZING. . . . . . . . . . . . . . . . . . . . 1
1. FUNDAMENTALS OF DOMESTIC WATER
HEATING
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
Basic Relationships and Units. . . . . . . . . . . . . . . . . . . . 3
Thermal Efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
Heat Recovery—Electric Water Heaters . . . . . . . . . . . . . 5
Mixed Water Temperature. . . . . . . . . . . . . . . . . . . . . . . 6
Delivered Hot Water Temperature . . . . . . . . . . . . . . . . 12
Safety and Health Concerns . . . . . . . . . . . . . . . . . . . . 13
Scalding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Legionella Pneumophila (Legionnaires’ Disease). . . 14
Relief Valves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Thermal Expansion. . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
Storage and Recovery . . . . . . . . . . . . . . . . . . . . . . . . . 15
Stratification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Codes and Standards . . . . . . . . . . . . . . . . . . . . . . . . . 16
System Alternative Considerations . . . . . . . . . . . . . . . 17
2. MULTIFAMILY BUILDINGS
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Weekday Vs. Weekend Demand Patterns . . . . . . . . 19
Seasonal Demand Patterns . . . . . . . . . . . . . . . . . . 20
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Demand Flow Patterns . . . . . . . . . . . . . . . . . . . . . 21
Identification of Demand. . . . . . . . . . . . . . . . . . . . . . . 23
Demand Determination. . . . . . . . . . . . . . . . . . . . . . . . 24
Application of LMH Values . . . . . . . . . . . . . . . . . . . . . 26
Peak Demand Vs. Average Demand. . . . . . . . . . . . . . . 26
Potential of Generating Storage . . . . . . . . . . . . . . . 26
Time of Day of Peak Flows. . . . . . . . . . . . . . . . . . . 26
Peak Demand and Average Demand . . . . . . . . . . . 27
Retrofit to Existing Systems (Customized Sizing). . . . . 28
Research on Generation Rate and Storage
Capacity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30
Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Example 2.1 Traditional Multifamily Building . . . . 31
Example 2.2 Special Use Housing Facility. . . . . . . 35
Possible Traps. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
3. DORMITORIES
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Student Dormitories . . . . . . . . . . . . . . . . . . . . . . . . . . 39
Example 3.1 Student Dormitory . . . . . . . . . . . . . . 39
Institutional Dormitories. . . . . . . . . . . . . . . . . . . . . . . 42
Example 2.2 Institutional Dormitory. . . . . . . . . . . 42
4. ELEMENTARY AND SECONDARY SCHOOLS
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
Types of School. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
Information Gathering . . . . . . . . . . . . . . . . . . . . . . . . 47
General Considerations. . . . . . . . . . . . . . . . . . . . . . . . 47
Kitchen and Food Service . . . . . . . . . . . . . . . . . . . . . . 47
Showers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
School Population. . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
Calculating the Hot Water Demand. . . . . . . . . . . . . . . 49
General Purpose Demand . . . . . . . . . . . . . . . . . . . 49
Kitchen Demand . . . . . . . . . . . . . . . . . . . . . . . . . . 50
Shower Load . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
Example 4.1 Elementary School . . . . . . . . . . . . . . 52
Example 4.2 High School . . . . . . . . . . . . . . . . . . . 54
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
5. HOTELS AND MOTELS
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
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Hotel and Motel Classification. . . . . . . . . . . . . . . . . . . 59
Convention Hotel or Motel. . . . . . . . . . . . . . . . . . . 59
Business Travelers’ Hotel or Motel. . . . . . . . . . . . . 60
Resort Hotel or Motel. . . . . . . . . . . . . . . . . . . . . . . 60
General Occupancy Hotel or Motel . . . . . . . . . . . . 60
Guest Room Demand . . . . . . . . . . . . . . . . . . . . . . . . . 60
Questions and Assumptions . . . . . . . . . . . . . . . . . 60
Example 5.1 Guest Room Demand . . . . . . . . . . . . 62
Food Service Demand . . . . . . . . . . . . . . . . . . . . . . . . . 64
Questions and Assumptions . . . . . . . . . . . . . . . . . 64
Guide to Estimating Hourly Demand. . . . . . . . . . . 65
Example 5.2 Food Service Demand. . . . . . . . . . . . 65
Laundry Demand . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
Questions and Assumptions . . . . . . . . . . . . . . . . . 67
Example 5.3 Laundry Demand . . . . . . . . . . . . . . . 68
General Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69
System Considerations . . . . . . . . . . . . . . . . . . . . . 69
Design Criteria Considerations . . . . . . . . . . . . . . . 70
6. HOSPITALS
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
Design Considerations . . . . . . . . . . . . . . . . . . . . . . . . 71
Safety and Health Concerns . . . . . . . . . . . . . . . . . 71
User Group Analysis. . . . . . . . . . . . . . . . . . . . . . . . . . 72
General Outline. . . . . . . . . . . . . . . . . . . . . . . . . . . 72
User Groups . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
Worksheets and Tables . . . . . . . . . . . . . . . . . . . . . . . . 78
Worksheet 6.A—User Group . . . . . . . . . . . . . . . . . 78
Worksheet 6.B—User Group Totals . . . . . . . . . . . . 81
Worksheet 6.A—User Group—Example 6.1 . . . . . . 84
Table 6.1—General Purpose Hot Water
Requirements for Various Kitchen Uses . . . . . . 87
Table 6.2—Usage Factors for User Groups. . . . . . . 88
Questions for Owner or Client. . . . . . . . . . . . . . . . . . . 91
Patient Areas and Nurses’ Stations . . . . . . . . . . . . 91
Hydrotherapy . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91
Dietary and Food Service. . . . . . . . . . . . . . . . . . . . 92
Surgical Suite . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
Laundry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
Central Sterile Supply . . . . . . . . . . . . . . . . . . . . . . 92
Obstetrics/Nursery . . . . . . . . . . . . . . . . . . . . . . . . 93
Miscellaneous Areas (e.g., Lab, Administration,
Maintenance, Autopsy, the Morgue). . . . . . . . . 93