Table Of Contents - A.O. Smith dre-52 Service Handbook

COMMERCIAL ELECTRIC WATER HEATER
INTRODUCTION ....................................................................... 2
Qualifications ...................................................................... 2
Service Warning ................................................................. 2
Tools Required.................................................................... 3
INSTALLATION CONSIDERATIONS ........................................ 4
Closed Water Systems ....................................................... 4
Thermal Expansion............................................................. 4
Electrical Requirements...................................................... 5
PRE SERVICE CHECKS........................................................... 6
Wiring Connections ............................................................ 6
Service Precautions............................................................ 5
WATER HEATER CONSTRUCTION ........................................ 7
Surface Mount Control Models ........................................... 8
Electronic Control Models................................................... 9
OPERATION & SERVICE........................................................ 10
Principles of Electricity...................................................... 10
Single And Three Phase Power ....................................... 12
Checking Single Phase Power .................................. 13
Checking Three Phase Power................................... 14
Phase Conversions - Surface Mount Control Models....... 15
Phase Conversions - Electronic Control Models .............. 16
Fuses ................................................................................ 17
Surface Mount Thermostats ............................................. 18
Thermostat & ECO Test............................................. 19
Heating Elements ............................................................. 20
Heating Element Construction.................................. 20
Heating Element Amperage Test............................... 23
Heating Element Voltage Test ................................... 24
Heating Element Resistance & Ground Test ............. 25
Replacing Heating Elements ..................................... 26
Element Sensors .............................................................. 27
Element Sensor Operation ........................................ 28
Contactors ........................................................................ 29
Contactor Configurations........................................... 30
Contactor Inspection.................................................. 31
Contactor Coil Voltage - At Contactor........................ 32
Contactor Coil Voltage - At CCB................................ 33
Transformers .................................................................... 34
120 VAC Control Circuit Transformer Wiring ............. 34
120 VAC Control Circuit Transformer Test................. 35
24 VAC Transformer Test .......................................... 36
Immersion Temperature Probes ....................................... 37
Temperature Sensor Resistance Test........................ 38
Temperature Sensor DC Voltage Test ....................... 39
ECO Continuity Test .................................................. 39
ECO Voltage Test ...................................................... 40
SERVICE MANUAL

TABLE OF CONTENTS

ELECTRONIC CONTROLS..................................................... 41
ELECTRONIC CONTROL SYSTEM ....................................... 48
TROUBLESHOOTING............................................................. 64
CCB - Central Control Board ............................................ 42
CCB Socket & Wiring Terminal Identification ............ 43
CCB Enable Disable Circuit(s) Test........................... 45
Checking Power And Ground To The CCB ............... 46
UIM - User Interface Module ............................................ 47
Control System Features.................................................. 48
Control System Navigation ............................................... 48
The Desktop Screen......................................................... 49
Status Icons............................................................... 50
Operating States........................................................ 51
Control System Menus .............................................. 51
Temperatures Menu.......................................................... 52
Temperature Settings ................................................ 53
Heater Status Menu.......................................................... 54
Economy Mode Setup Menu ............................................ 55
Setpoint Adjustment Value ........................................ 56
Time Clock Settings .................................................. 57
Daily Operating Mode Settings.................................. 58
Alarm Output Setup Menu ................................................ 59
Display Settings Menu...................................................... 60
Heater Information Menu.................................................. 61
Current Fault/Alert Menu .................................................. 62
Fault History Menu ........................................................... 62
Fault Occurrence Menu .................................................... 62
Restore Factory Defaults Menu........................................ 63
Factory Default User Settings ................................... 63
Common Service Problems.............................................. 64
Surface Mount Control Models ......................................... 64
Electronic Control Models................................................. 65
Fault Conditions ........................................................ 65
Alert Conditions ......................................................... 65
Resetting The Control System .................................. 65
Control System Unresponsive .......................................... 65
UIM Display Is Blank ................................................. 65
UIM Is Inoperable ...................................................... 66
Heating Cycle Disabled ............................................. 66
Fault & Alert Messages .................................................... 67
No Current Detected ................................................. 67
Temp Probe Open ..................................................... 68
Temp Probe Short ..................................................... 68
Energy Cut Out (ECO) .............................................. 69