90 NPE Service Manual
Fault Possible Causes Check method
Other trouble
Capacity setting
1. If the Max switch #1 of 1-1 is on,
Set the switch to the normal operation position.
2. PCB DIP S/W capacity setting error can suddenly increase the hot water
temperature.
●
Check the PCB DIP S/W capacity setting.(refer to page 21)
DIP SWITCH 1-1 DIP SWITCH 1-2
NPE-150
●
2-switch Panel:
Switch Function Setting
1 Cascade Vent
Common Vent 1-OFF
Individual Vent 1-ON
2 Gas Type
Natural Gas 2-OFF
Propane Gas 2-ON
1 2 3 4 5 6 7 8 9 10
ON ON
ON
1 2 3 4 1 2 3 4 5 6
ON
DIP S/W 1-1 DIP S/W 1-2
Primary heat
exchanger overheated
The surface temperature rises due to heavy scale deposits in the primary heat
exchanger.
●
Flush the primary heat exchanger.
Defective PCB If the issue continues despite checking the items above, the PCB is defective.