A.O. Smith 500, GB/GW-300, 750 SERIES, 650 Fault Displayed Description Red LED Lockout, Hard, Soft

Page 17

TROUBLESHOOTING IGNITION SYSTEM

Fault Messages and Lockout Status (* = stage number: 1 or 2)

 

 

Fault Displayed

Description

Red LED

Lockout

“Display Fail”

Communications with UIM interrupted

Continuous

Auto Reset

Check communication cable to UIM. Try moving to other Internal Communications connector on CCB. Also check the connectors where the cable is plugged in for best connecting wires.

“Comm. Fail Stg.*” Communications with FCB interrupted

Continuous

Auto Reset

Same as above. Also try swapping FCB and UIM communications cables.

“Low AC Voltage”

Line voltage less than 90 vac

Continuous

Auto Reset

Check incoming power line for loss of voltage. May also be caused by a power line momentary loss of voltage.

“Low 24VAC”

Voltage from transformer less than 18 vac

Continuous

Auto Reset

Check transformer output. Should be over 24vac. May be caused by excessive current drain or a faulty transformer

“Brown Out Reset” Indicates a brown out reset occurred

- - - -

None

Caused by a momentary dip in voltage on the CCB +5vdc power bus. Contact factory. (Not considered a serious problem if it only occurs on very rare occasions.)

“Timeout Reset”

Indicates a watchdog reset occurred

- - - -

None

Caused when the micro executes the software in an improper way. Contact factory. (Not considered a serious problem if it only occurs on very rare occasions.)

“CCB Overflow”

Stack overflow - recorded in history only

- - - -

Immediate Reset

Caused when the micro overfills its memory stack. Contact factory. (Not considered a serious problem if it only occurs on very rare occasions.)

“CCB Underflow”

Stack underflow - recorded its history only

- - - -

Immediate Reset

Caused when the micro underfills its memory stack. Contact factory. (Not considered a serious problem if it only occurs on very rare occasions.)

“Sequence Err”

Incorrect flow of critical code

Flashing

HARD

Caused when the micro executes software code in an incorrect manner. Contact factory.

“A/D Fail CCB”

Error in analog input reading

Flashing

HARD

Caused when the Analog to Digital converter section of the micro operates improperly. Contact factory.

“EEProm Error”

Not implemented

- - - -

None

“ROM Failure Stg*”

ROM contents incorrect

Flashing

HARD

Caused when the Read Only Memory on one of the FCB micros operates improperly. Contact factory.

“ROM Failure CCB” ROM contents incorrect

Flashing

HARD

Caused when the Read Only Memory on the CCB micro operates improperly. Contact factory.

“Hdwr Short Stg**

FCB output pin shorted

Flashing

HARD

Caused when a pin on one of the FCB micros is not in the output state it should be in. Contact factory.

“Hdwr Short CCB” CCB output pin shorted

Flashing

HARD

Caused when a pin on the CCB micro is not in the output state it should be in. Contact factory.

“CPU Fail Stg**

FCB processor failed internal check

Flashing

HARD

Caused when one of the FCB micros does not pass its internal checks. Contact factory.

“CPU Fail CCB”

CCB processor failed internal check

Flashing

HARD

Caused when the CCB micro does not pass its internal checks. Contact factory.

“RAM Failure CCB” CCB Ram check failed

Flashing

HARD

Caused when the CCB micros Random Access Memory operates incorrectly. Contact factory.

“FCB Comm Timeout” FCB did not receive command from CCB

Continuous

SOFT

Caused when communications between the CCB and the FCB are interrupted. May occur when a surge of power on a nearby device (i.e. arc welder) creates an EMI burst. Not a serious problem if it occurs rarely.

“No Flow”

Water is not flowing

Continuous

SOFT

Caused by the flow switch being open when it should be closed. Check water lines, pump, flow switch

 

contacts, wiring.

 

 

“Blower Prov Stg*”

blower pressure is too low

Continuous

SOFT

Caused by either the High-Speed or Low-Speed blower prover switches being open when they should have been closed. Check blowers, switch contacts, wiring, and for air leaks.

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Contents 14-18 Series 400, 401, 402, 403, 404Lighting Instructions for the GB/W 300 through 750 models Risk of Scalds Lighting InstructionsInputs To CCB and FCB Burner SystemCCB Drawing #211758 FCB Drawing #211759 PDB Drawing #211760 Line Polarity Indicator & Fuse Protection CCB/FCB Indicator Lamps & FusesOutputs from CCB and FCBs IgnitersGB/LB FCB Eight position DipswitchStages 1 and 2 will turn on in sequence from 1 to Temperature Setpoints System Control AlgorithmUIM Operating Procedures Description of CCB control states Idle State Description of FCB control statesOperating Differential Setpoint Operating SetpointConnection Diagram Drawing #211769 Page UIM Touch Switches Soft Fault Displayed Description Red LED LockoutHard See below Other troubleshooting hints Page Page Page NEW Boiler Limited Warranty

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