A.O. Smith 30 - Manual (Page 87)

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Instruction manual SGS 87
Heat exchanger and/or
chimney flue is blocked
3. Measure the pressure differential across the air pressure switch
4. Check the values
(2.4.6 "Pressure switch")
5. Check heat exchanger, condensation drainage and/or chimney
flue for blockages
6. Clear any blockage that may be present.
7. Reset appliance controller
Defective controller 1. Check that the controller is receiving power
2. Check that the controller is correctly connected
3. If there is no electrical power, check the power supply to the
terminal block, or replace the controller.
4. Rectify any incorrect connections.
5. Reset appliance controller
Code + Description Cause Solution Remark