Navien NCB300-28K Installation & Operation Manual page 65

8. Remove the screw connecting the fan motor assembly
and the mixing chamber, and then remove the fan motor
assembly.
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9. Remove the four bolts securing the chamber brackets.
64 Maintaining the Boiler
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10. 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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11. Remove the ten bolts connecting the mixing chamber and
the heat exchanger, and then remove the mixing chamber,
burner and the chamber bracket.
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