Table Of Contents - A.O. Smith SERIES 120 Service Handbook

COMMERCIAL GAS WATER HEATER
INTRODUCTION ............................................................3
Qualifications ...........................................................3
Service Warning........................................................3
Service Reminder .....................................................3
REQUIREMENTS ...........................................................4
Instruction Manual ....................................................4
Tools Required ..........................................................4
Tools Optional ...........................................................4
INSTALLATION CONSIDERATIONS .............................5
Water Piping .............................................................5
Closed Water Systems ........................................5
Thermal Expansion .............................................5
Gas Pressure Requirements ....................................5
Air Requirements ......................................................6
Air Supply ............................................................6
Insufficient Make-up Air, Negative Air Pressure,
and Downdrafts ...................................................7
Make-up Air: Direct Communication with Out-
doors ...................................................................8
Contaminated Air ................................................9
Clearances (Water Heater) .......................................9
Clearances (Exterior) ..............................................10
Venting .................................................................... 11
OPERATION AND SERVICE .......................................12
Sequence of Operation ...........................................12
Electrical Sequence ................................................13
Wiring Diagram .......................................................14
Operating Sequence - Flow Chart ..........................15
Gas Control Valve ..................................................16
Measuring Gas Pressures ................................16
Manifold Pressure Adjustment ..........................17
Main Valve Solenoid Connections ....................17
Servicing should only be performed by a Qualifi ed Service Agent
SERVICE MANUAL

TABLE OF CONTENTS

TROUBLESHOOTING .................................................23
2
Gas Control Valve/Burner Area View ......................18
Blower Prover Switch - Settings .............................19
Thermostat and Ignition control Board View ...........20
White Rodgers Integrated Control - Thermostat .....21
White Rodgers Ignition Control Board ....................21
Pre-Service Checklist .............................................22
Ignition Control Board: Error Codes ........................23
1 Flash ..............................................................23
2 Flashes ..........................................................23
3 Flashes ..........................................................24
4 Flashes ..........................................................24
6 Flashes ..........................................................24
7 Flashes ..........................................................24
8 Flashes ..........................................................25
Continuous Flash ..............................................25
Continuous On ..................................................25
Integrated Heater Control: Display Lights ..............26
Test 1: 120 VAC to Heater Check ...........................27
Test 2: Polarity Check .............................................28
Test 3: Continuity Check of High Limit (ECO) .........29
Test 4: Upper Temperature Probe
Continuity Check .....................................................30
Test 5: Calling for Heat - No Blower Operation .......31
Test 6: Blower On, No Ignition ................................32
Test 7: Blower On, Blower Prover Switch Closed,
No Igniter Operation ...............................................33
Test 8: Igniter Heats, No Main Burner .....................34
Test 9: Igniter Heats, No Main Burner .....................35
Test 10: Main Burner Ignition for Less than
Five Seconds ..........................................................36
Test 11: Water Heater Shutting Off Below Setting ..37