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Service Manual
Singular Combi Boiler - BTC 439002301 A (12.2021)
7 Key Components Description
7.1 Pump
Part No.
7738007283
Function
Carries out combustion by circulating the water in the pipe.
Circulates the water when the water temperature is 59°F (15°C) or
below to prevent the boiler from freezing and bursting.
Failure Event
Unable to detect or measure water pressure change when the pump
operates.
Effects
The device may freeze.
The boiler does not operate.
Error Code
—
Diagnostic
Visual inspection : Check the circulation pump connection wire
Voltage check : Check range of voltage shown below
Color/Number of Wires
BLACK - WHITE
ON: AC 120 V ±
OFF: 0 V
Table 5
7.2 Turn Down Ratio (TDR) Solenoid valve
Part No.
7738007264
Function
To control the amount of mixed gas supplied with TDR of 10:1
It uses solenoid valve to control the amount of mixed gas
Failure Event
Solenoid valve not closing
Solenoid valve not opening
Effects
Frequent On/Off due to excessive heat.
Fail to reach the set temperature due to lack of heat
Error Code
—
Diagnostic
Visual inspection : Check the Solenoid valve connection wire
Voltage check : Check range of voltage shown below
Color/Number of Wires
RED - RED
DC : 120 V ±
Table 6
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