A.O. Smith TC-049R3 Anleitung zur Verwendung

MODELS COVERED

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.

SERVICE HANDBOOK

Residential

Gas and Electric

Water Heaters

Part No. TC-049R3 • $15.00 • Printed in the U.S.A. • 0505

RESIDENTIAL GAS AND ELECTRIC WATER HEATER

SERVICE HANDBOOK

TABLE OF CONTENTS

Page

Introduction

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

Page

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

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 Technical Training Department

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 Technical Training Department

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 Technical Training Department

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 “therm”is 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 Technical Training Department

RESIDENTIAL GAS AND ELECTRIC WATER HEATER

SERVICE HANDBOOK

INSTALLATION OF RESIDENTIAL GAS WATER HEATER

Typical Model

and Rating

Plate Location

Union

Minimum

4.5” w.c. –Natural Gas

11.0” w.c. Propane Gas

Maximum Gas Supply

13.8” w.c. or ½ PSI

Air Is Drawn In For

Combustion. Keep

Area Clean And Free

From Flammables And

Flammable Vapors Inner and

Outer Doors –

Reinstall After

Lighting Pilot.

Drain

Safety Pan – Piped to

Drain

Thermostat –

Recommending

setting of 125F.

Temperature and

pressure relief valve

tube piped to within 6”

of drain.

Water

Shut Off

alve

Temperature And

Pressure Relief

Valve – Do Not

Reuse Old Valve.

Expansion Tank

Pressurize to Equal

Supply Water

Pressure

See Manual and

Labels For Installation

Clearances

Union

Exhaust Vent to

Outside of Building

Installation Must Follow Local Codes and Instruction Manual Guidelines

A.O. Smith Water Products Company Technical Training Department

RESIDENTIAL GAS AND ELECTRIC WATER HEATER

SERVICE HANDBOOK

RESIDENTAL GAS WATER HEATER SERVICE

This portion of this manual applies to the Operations and Servicing of Residential Gas, Tank

Type, Water Heaters, which are vented atmospherically and use a thermocouple as their electrical

source.

Construction: See also “General” section of this

manual.

Control: There is one control on this style of water heater. The control has a main gas regulator,

pilot gas regulator, on-off-pilot knob, controls water temperature, has a temperature adjustment

knob, and a high water temperature limit safety.



(delta)

Note: The word “Hot”

may or may not be

present on the control

knob

A.O. Smith Water Products Company Technical Training Department

RESIDENTIAL GAS AND ELECTRIC WATER HEATER

SERVICE HANDBOOK

Residential Gas – continued

Burner: The burner assembly consists of the main burner, main burner orifice, main burner gas

supply tube, pilot burner, pilot burner orifice, pilot burner gas supply tube and thermocouple.

The pilot burner remains on once it is manually lit. When incoming cold water activates the

thermostat, gas flows to the main burner. The pilot flame ignites this gas. The main flame burns

until the tank reaches set temperature then the thermostat interrupts this main gas flow.

AFTER HAVING CONFIRMED THAT THE WATER HEATER HAS BEEN INSTALLED

PER THE INSTALLATION MANUAL INSTRUCTIONS:

Normal Operation

Electrical: The Pilot Flame heats the end of a thermocouple. As the thermocouple gets hotter,

it generates a small (cannot be detected without an electrical meter) electrical current to the

bottom of the control valve. This current powers the electromagnet and holds open the safety

valve as long as the pilot flame is heating the thermocouple. DANGER! If the pilot is

extinguished, it can take up to 180 seconds for the thermocouple to cool sufficiently to close the

safety valve.

See also C3 technology product information beginning on page .

A.O. Smith Water Products Company Technical Training Department

RESIDENTIAL GAS AND ELECTRIC WATER HEATER

SERVICE HANDBOOK

Residential Gas – continued

Temperature: Two metal probes mounted

onto the back of the control are immersed

inside the tank water. One probe (the

shorter) acts as a temperature high limit. If

water gets excessively hot, a sensor within

the probe opens, interrupts the small

electrical current to the gas valve, and gas

flow through the control is interrupted. If this

safety sensor opens, the entire control must

be replaced.

The longer probe contains a metal rod that

expands and contracts as water temperature

around the probe cools and heats. As the

rod expands, it pushes against a lever

actuated gas valve. If the regulator is

pushed sufficiently, gas flow is interrupted to

the main burner. Adjusting the temperature

dial changes the distance the rod must

expand or contract to open or close the gas

valve.

Gas: When you prepare to light the pilot,

you are instructed to turn the top

knob to the pilot position and depress

the knob. When the knob is

depressed gas will flow to the pilot

burner only. You then have to

(manually) ignite this pilot gas. When

the pilot is lit, the flame must heat the

thermocouple until it generates

sufficient electricity to the gas valve

to allow you to release the knob while

gas continues to flow to the pilot.

When the top knob is turned to the

“ON” position, gas is also available to

the main burner if the thermostat calls

for heat.

A.O. Smith Water Products Company Technical Training Department

RESIDENTIAL GAS AND ELECTRIC WATER HEATER

SERVICE HANDBOOK

Residential Gas - continued

Water Flow: When a hot water faucet is opened, water pressure from the well tank or street

main forces cold water into the water heater. This pushes hot water out of the tank.

Operation: A residential water heater is not a precise operating appliance. Because the water

heater relies on the expansion and contraction of a metal rod, when the thermostat dial is set at

an indicated setting (“” is recommended as a starting setting. This is approximately 120 degrees

F.) the heater may shut off at 110 to 130F. The heater will consistently shut off at this same

temperature. For this same reason, water temperature may drop 15 - 25F, around the

temperature probe, before the main burner is activated. Keep in mind that hot water in the upper

part of the tank will probably be very near the “shut off” temperature of the control while incoming

cold water drops the water temperature around the thermostat probe. Also, short repeating

heating cycles caused by small hot water uses can cause temperatures at the point of use to

exceed the thermostat setting by up to 30° F.

Setting Approximate Temperature (°F) Time To Cause Injury

Hot (▲) 120° ± 10° 5 Minutes

A 130° ± 10° 30 Seconds

B 140° ± 10° 5 Seconds

C 150° ± 10° 1.5 Seconds

Very Hot 160° ± 10° Under 1 Second

A.O. Smith Water Products Company Technical Training Department

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