Navien NCB700-2S Plus 42K Installation & Operation Manual page 81

8. Remove the screw connecting the fan motor assembly
and the mixing chamber, and then remove the fan motor
assembly.
9. Remove the five bolts securing the chamber brackets.
10. Remove the two screws connecting the ignition transformer
to the heat exchanger and then remove the ignition
transformer.
11. Remove the rubber packing at the top of the cover and put
a Phillips screwdriver into the hole, and then loosen the
middle bolt located at the back of the burner.
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12. Remove the six bolts connecting the mixing chamber and
the heat exchanger, and then remove the mixing chamber,
burner and the chamber bracket.
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Maintaining the Boiler 81