AO Smith Water Heater TC 049R3 User Guide

SERVICE HANDBOOK  
Residential  
Gas and Electric  
Water Heaters  
M O D E L S C O V E R E D  
Residential Gas Water Heaters that  
are atmospherically vented and use a  
thermocouple as their electrical source.  
Residential Electric Water Heaters  
having one or two heating elements  
and common wiring configurations  
for these models.  
Part No. TC-049R3 • $15.00 • Printed in the U.S.A. • 0505  
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RESIDENTIAL GAS AND ELECTRIC WATER HEATER  
SERVICE HANDBOOK  
TABLE OF CONTENTS  
Page  
Page  
Introduction  
Residential Electric Water Heaters  
Installation………………………………23  
Standard Illustrations………………….24  
Guidelines………………………………25  
Elements………………………………..26  
Thermostat….…………………….…..27  
C-2 Circuit…………………………….28  
C-2 Sequence of Operation…………29  
A-6 Circuit……………………………..30  
A-6 Sequence of Operation…….…..31  
A-7 Circuit…………………………….32  
A-7 Sequence of Operation…….……33  
A-7 – wiring – Post 1995………...… 34  
A-7 - Sequence of Operation ……….35  
Certification and Approvals….……….36  
Unbalanced 3 phase……………….…37  
C-2 Ohms Check……………………...38  
C-2 Ohms Check…………….………..39  
C2 No Hot Water……………….……..40  
C-2 Grounded Element Check………41  
A-6 Ohms Check – No Hot Water…..42  
A-6 No Hot Water Voltage Check…..43  
A-6 Lack of Hot Water Voltage Ck….44  
A-6 Grounded Element Test………...45  
A-7 Service……………………………46  
A-7 Ohms Test……………………….47  
A-7 Voltage Checks………………….48  
A-7 Lack of Hot ………………………49  
A-7 Grounded Element Test………50-51  
Miscellaneous and Ohms Table.……52  
Terms.................................................. 1  
Tools ................................................... 2  
Residential Gas Water Heaters  
General Information ............................ 3  
Installation........................................... 5  
Operations and Servicing  
Control................................................. 6  
Burner ................................................. 7  
Normal Operations.............................. 7  
Temperature........................................ 8  
Gas...................................................... 8  
Water Flow.......................................... 9  
Service .............................................. 10  
Procedures and Conditions............... 11  
Multiple Heater Piping....................... 14  
Exhaust Venting Notes...................... 15  
Flammable Vapor Ignition Design ……15  
Lint, Dust & Oil Screen……………... 16  
Flame Arrestor………………………...17  
Thermal Cut Off Switch………….…...18  
Pilot Burner Assembly……………..….19  
Sealed Combustion Chamber………..20  
Piezo Igniter…………………………….21  
Miscellaneous ……………………….....22  
Technical Bulletins …………….. 53-66  
RESIDENTIAL GAS AND ELECTRIC SERVICE HANDBOOK INTRODUCTION  
This service handbook is designed to aid in servicing and troubleshooting A.O. Smith  
Residential Gas and Electric water heaters in the field. No duplication or reproduction of this book  
may be made without the express written authorization of the A.O. Smith Water Products  
Company.  
The following text and illustrations will provide you with a step-by-step procedure to verify  
proper installation, operation, and troubleshooting procedures. Additional quick reference data is  
included to assist you in servicing this product.  
A.O. Smith Water Products Company  
©2005  
Technical Training Department  
Ashland City, TN  
1
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RESIDENTIAL GAS AND ELECTRIC WATER HEATER  
SERVICE HANDBOOK  
The information contained in this handbook is designed to answer commonly faced  
situations encountered in the operation of the Residential Gas and Electric product line and is not  
meant to be all-inclusive. If you are experiencing a problem not covered in this handbook, please  
contact the A.O. Smith Technical Information Center at 1-800-527-1953 or your local A.O. Smith  
Water Products Company representative for further assistance. Additional information is also  
available on the web site www.aosmithwaterheaters.com. This handbook is intended for use by  
licensed plumbing professionals and reference should be made to the instructional manual  
accompanying the product. This handbook contains supplemental information to the Residential  
Gas and Electric instructional manual.  
Qualifications  
Tools Required:  
For servicing gas models:  
Cross top screw driver  
3/8, 7/16, ¾ inch open end wrenches  
3/16 inch Allen wrench  
11/16 inch – 6 point – socket – for anode removal  
set of marked drill bits  
electrical multimeter  
gas pressure gauge or monometer  
water pressure gauge  
thermometer  
tubing cutter if pilot tube is to be replaced  
hose – to drain tank  
container – to measure gallons per minute flow  
For servicing electric models:  
1 1/16 inch – 6 point – socket (for anode removal)  
1 ½ inch deep socket – to remove an element  
electrical multimeter  
water pressure gauge  
thermometer  
hose – to drain tank  
container – to measure gallons per minute flow  
Rev 1 adds Technical Bulletins  
Rev 2 corrects illustration errors  
Rev 3 adds FVIR (C3) Technology product information  
2005 printing – revised cover  
A.O. Smith Water Products Company  
©2005  
Technical Training Department  
Ashland City, TN  
2
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RESIDENTIAL GAS AND ELECTRIC WATER HEATER  
SERVICE HANDBOOK  
GENERAL SECTION  
MISCELLANEOUS INFORMATION  
Draw efficiency is the quantity of hot water available to the consumer before the outlet water  
temperature decreases 25 degrees F. A 40 gallon water heater will typically provide 70% (28  
gallons) of this “usable” hot water. The burner or elements are allowed to operate during this test.  
Incoming, cold water mixes the remaining stored water below this 25 degree limitation.  
Energy Factor is an indicator of the combined thermal efficiency and standby efficiency of a  
water heater. The higher the energy factor, the more efficient the water heater will be.  
Recovery rate is the amount of water that is heated to a set temperature, per hour. An example  
might be that a water heater has a recovery rate of 30 gallons of water per hour at 80 degree F.  
(Fahrenheit) temperature rise.  
“R” Value is a measure of the resistance of a substance to heat flow.  
Thermal efficiency is approximately the amount of generated BTU (British Thermal Units),  
which enters the water. A percentage of the total BTU passes out through the vent piping.  
Temperature rise is the increase in the temperature from its coldest “inlet” water temperature to  
the desired hot (outlet) setting. Typically this is assumed to be 40 degrees entering water, 120  
degrees desired stored water or 80 degrees “temperature rise.”  
Standby efficiency – the water heater’s ability to contain heat in the tank. A minimum of tank  
water heat loss per hour is desired.  
Sample: temperature change = Btu/h loss/ square foot of tank surface  
“R” value  
Water cannot (for all practical purposes) be compressed.  
Water expands when it is heated.  
Water Hammer – is a concussion of moving water against the sides of a containing pipe or vessel  
on a sudden stoppage of flow.  
EX: 1/2 “copper pipe, 5GPM flow (7.2ft/sec.) – stop. Pressure rise of approximately 412 PSI.  
3/4” copper pipe, 5GPM flow (3.3ft/sec) – stop. Pressure rise of approximately 188 PSI  
Minerals and gases will separate from water as temperature increases.  
Formulas:  
BTU (British Thermal Unit) is the heat required to raise 1 pound of water 1°F  
1 BTU = 252 cal = 0.252 kcal  
1 cal = 4.187 Joules  
BTU X 1.055 = Kilo Joules  
BTU divided by 3,413 = Kilowatts  
To convert from Fahrenheit to Centigrade: (° F – 32) times 5/9, or .556, equals degrees C.  
A.O. Smith Water Products Company  
©2005  
Technical Training Department  
Ashland City, TN  
3
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RESIDENTIAL GAS AND ELECTRIC WATER HEATER  
SERVICE HANDBOOK  
One gallon of (120° F, 49°C) water weighs approximately 8.25 pounds.  
Pounds X .45359 = Kilogram  
Gallons X 3.7854 = Liters  
% of Hot = (Mixed Temp. – Cold) divided by (Hot Temp. – Cold)  
General Section – continued  
% Thermal Efficiency = (GPH X 8.25 X Temp. Rise X 1.0) divided by BTU/H Input  
BTU Output = GPH X 8.25 X Temp. Rise X 1.0  
GPH = (BTU/H Input X % Eff.) divided by (Temp. Rise X 8.25)  
One cubic foot of Natural Gas contains about 1000 BTU of heat.  
One “thermis equal to 100,000 BTU  
One cubic foot of Propane Gas contains about 2500 BTU of heat.  
One gallon of Propane gas contains about 91,250 BTU of heat.  
One pound of Propane gas contains about 21,600 BTU of heat.  
One pound of gas pressure is equal to 27.7 inches water column pressure  
Inches of Water Column X .036091 = PSI  
Inches of Water Column X .073483 = Inches of Mercury (Hg.)  
Centimeters = Inches X 2.54  
MM (millimeters) =Inches X 25.4  
Meters = Inches X .0254  
Doubling the diameter of a pipe will increase its flow capacity (approximately) 5.3 times.  
CONSTRUCTION: Tank is constructed of steel.  
The inside of the tank is constructed of a glass lining bonded to the steel. This prevents water  
to metal contact and rusting of the tank.  
An anode rod will be installed within the tank. The hex-head plug end of the anode is visible on  
the top of the water heater. This metal rod offers secondary protection of the tank against  
corrosion where the application of glass is not possible (threaded tank openings). These areas  
will have small areas of water to metal contact.  
All water heaters will contain at least one thermostat (to operate the heater) and one high  
limit (to prevent water temperatures approaching the “steam” level).  
A.O. Smith Water Products Company  
©2005  
Technical Training Department  
Ashland City, TN  
4
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RESIDENTIAL GAS AND ELECTRIC WATER HEATER  
SERVICE HANDBOOK  
INSTALLATION OF RESIDENTIAL GAS WATER HEATER  
Water  
Exhaust Vent to  
Shut Off  
Outside of Building  
Valve  
Union  
Union  
Expansion Tank  
Pressurize to Equal  
Supply Water  
Pressure  
See Manual and  
Labels For Installation  
Clearances  
Temperature And  
Pressure Relief  
Valve – Do Not  
Reuse Old Valve.  
Typical Model  
and Rating  
Plate Location  
Temperature and  
pressure relief valve  
tube piped to within 6”  
of drain.  
Maximum Gas Supply  
13.8” w.c. or ½ PSI  
Minimum  
Thermostat –  
4.5” w.c. –Natural Gas  
11.0” w.c. Propane Gas  
Recommending  
setting of 125°F.  
Safety Pan – Piped to  
Drain  
Drain  
Air Is Drawn In For  
Combustion. Keep  
Area Clean And Free  
From Flammables And  
Flammable Vapors  
Inner and  
Outer Doors –  
Reinstall After  
Lighting Pilot.  
Installation Must Follow Local Codes and Instruction Manual Guidelines  
A.O. Smith Water Products Company  
©2005  
Technical Training Department  
Ashland City, TN  
5
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