Navien NCB300-28K, Service Manual

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System Details 43
4.7.7 Main Gas Valve
Item Description
Function
1. Controls the amount of gas supplied to the burner based on fan speed.
2. When the unit experiences abnormal combustion, it automatically shuts off the gas supply to prevent
unsafe situations.
Fault Unable to open / close
Symptoms
1. No flame.
2. The boiler does not operate.
Error codes E003, E012
Diagnostics
1. Visual inspection: Check wire connections are secure and inspect for wire damage.
2. Check that the solenoid valve of Main Gas Valve works properly.
●
Voltage test: Test the voltage meets the specifications shown below.
Testing/inspection
information
WHITE - YELLOW/Connector Pin 1 and 5: DC 24 V