A.O. Smith ATI-140H-N Service Handbook page 3

Service Procedures ......................................................................................................................................................................................................24
Verifying DIP Switch Settings .......................................................................................................................................................................24
Unit Draining and Filter Cleaning .................................................................................................................................................................24
Checking for a Crossed Connection .............................................................................................................................................................25
Checking for a Reversed Connection ...........................................................................................................................................................25
Checking Inlet Gas Pressure/Purging Air from Gas Line ..............................................................................................................................25
Checking and Adjusting the Manifold Gas Pressure ....................................................................................................................................25
Adjusting Minimum Manifold Pressure ....................................................................................................................................... 26
Checking the Overheat Cutoff Fuse (OHCF) .................................................................................................................................................27
Checking the Flow Sensor ............................................................................................................................................................................27
Cleaning the Rod Assembly (Flame Sensor and Air/ Fuel Ratio Rod) ..........................................................................................................28
Descaling the Unit .......................................................................................................................................................................................29
Draining and Hose Connection .................................................................................................................................................... 29
Pump And Descale ...................................................................................................................................................................... 29
Cleanse the System ..................................................................................................................................................................... 29
Cleaning the Combustion Components .......................................................................................................................................................29
Maintenance ..............................................................................................................................................................................................................35
Replacing the Heat Exchanger (Indoor Models) ..........................................................................................................................................37
Removing Heat Exchanger Components (Indoor Models) ...........................................................................................................................37
Preparing the New PRIMARY Heat Exchanger for Installation (Indoor Models) .........................................................................................40
Preparing the New SECONDARY Heat Exchanger for Installation (Indoor Models) .....................................................................................41
Installing the Heat Exchanger (Indoor Models) ..........................................................................................................................................41
Replacing the Heat Exchanger (Outdoor Models) .......................................................................................................................................46
Removing Heat Exchanger Components (Outdoor Models) ........................................................................................................................46
Preparing the New PRIMARY Heat Exchanger for Installation (Outdoor Models) ......................................................................................49
Preparing the New SECONDARY Heat Exchanger for Installation (Outdoor Models) .................................................................................50
Installing the Heat Exchanger (Outdoor Models) .......................................................................................................................................50
Flow Sensor/Control Valve Removal and Installation .................................................................................................................................55
Removal ...................................................................................................................................................................................... 55
Installation .................................................................................................................................................................................. 55
Burner Removal and Installation .................................................................................................................................................................56
Removal ..................................................................................................................................................................................... 56
Installation .................................................................................................................................................................................. 59
Gas Valve/Manifold Plate: Removal and Installation ...................................................................................................................................61
Removal ...................................................................................................................................................................................... 61
Installation .................................................................................................................................................................................. 62
Component Diagrams/Item Numbers .........................................................................................................................................................................67
Component Item Numbers ..........................................................................................................................................................................................71
Condensing Models: On-Demand Water Heater Service Handbook • 3