78 NPE Service Manual
Check method
Failure mode Cause Check method
Ignition failure
Gas supply error
1. Check if the main gas valve is open.
2. Check the gas supply pressure.
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NG: 3.5” - 10.5” W.C, LP: 8” - 13” W.C
●
LP pressure drop occurs frequently in the winter.
3. Check the flexible pipe diameter for compatibility with the water heater.
4. While the static pressure is normal, the use of another gas appliance may cause
a possible drop in gas pressure to the unit. Therefore, it is required to check the
dynamic pressure.
●
Static pressure: Gas pressure during stand by.
●
Dynamic pressure: Gas pressure at max combustion. (2nd stage MAX combustion
setting: DIP S/W 1-1 ON)
5. If a CSST connector has been used, check to ensure that it is not been overtightened
resulting in the seal obstructing gas flow.
6. Check the meter class (Example)
●
Gas meter Water heater Furnace Domestic gas stove
●
425 CFH (Gas Meter) ≥ 195 CFH (Water Heater)+ 58.8 CFH (Furnace)
+ 63.7 CFH (Domestic gas stove)
1 CFH = 1,020 Btuh
Digital pressure
manometer
Check gas supply pressure(Refer to page 24) A shifted seal narrows the inner diameter of CSST
connector
Defective electrode
gap and shape
Defective electrode gap and shape disables ignition.
●
Appropriate electrode gap: approx. 3~4mm(1/8") (replace if defective)
●
An ignition fail may occur due to improper gap, while discharge seems normal when
checked via the flame monitoring window. Therefore, it is required to check the gap
after disassembly.
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