Takagi T-H3J-DV Service Handbook page 3

SERVICE PROCEDURES ................................................................................................................................................................................ 32
Unit Draining and Filter Cleaning ............................................................................................................................................................. 32
Checking for a Crossed Connection ......................................................................................................................................................... 33
Checking for a Reversed Connection ....................................................................................................................................................... 33
Checking the Inlet Gas Pressure and Pressure Drop ................................................................................................................................ 33
Checking and Adjusting the Manifold Gas Pressure ................................................................................................................................ 34
Checking the Manifold Gas Pressure ....................................................................................................................................... 34
Adjusting Maximum Manifold Pressure .................................................................................................................................. 35
Adjusting Minimum Manifold Pressure ................................................................................................................................... 35
Checking the Overheat Cutoff Fuse (OHCF) ............................................................................................................................................. 35
Checking the Flow Sensor ........................................................................................................................................................................ 36
Cleaning the Rod Assembly (Flame Sensor and Air/ Fuel Ratio Rod) ...................................................................................................... 36
Descaling the Unit ................................................................................................................................................................................... 38
Cleaning the Combustion Components ................................................................................................................................................... 39
Easy-Link Connections with Previous Models (540 [T-H3] Only) ............................................................................................................. 43
DIP Switch Setting on the 540 (T-H3) Computer Board ........................................................................................................... 43
Temperature Settings ............................................................................................................................................................... 44
Diagnostic Mode ...................................................................................................................................................................................... 45
Individual Unit ......................................................................................................................................................................... 45
Multiple Units in a Linked System (540 [T-H3] Models Only)................................................................................................... 45
MAINTENANCE ........................................................................................................................................................................................... 49
Flow Sensor/Control Valve Removal and Installation ............................................................................................................................. 51
Removal .................................................................................................................................................................................. 51
Installation .............................................................................................................................................................................. 51
Burner Removal and Installation ............................................................................................................................................................. 52
Burner Removal ....................................................................................................................................................................... 52
Burner Installation ................................................................................................................................................................... 54
Gas Valve/Manifold Plate: Removal and Installation ............................................................................................................................... 55
Gas Valve/Manifold Plate Removal .......................................................................................................................................... 56
Gas Valve/Manifold Plate Installation ...................................................................................................................................... 57
Replacing the Heat Exchanger ................................................................................................................................................................. 60
Preparing the New PRIMARY Heat Exchanger for Installation ................................................................................................ 65
Preparing the New SECONDARY Heat Exchanger for Installation ............................................................................................ 65
Installing the Heat Exchanger Assembly .................................................................................................................................. 66
Restarting the Unit................................................................................................................................................................... 70
COMPONENT DIAGRAMS/ITEM NUMBERS ............................................................................................................................................... 71
On-Demand Water Heater Service Handbook for 240, 340 & 540 Condensing Models • 3