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Technical Training Department
Ashland City, Tennessee
SBN TANK TYPE COMMERCIAL GAS WATER HEATER
SERVICE HANDBOOK
©2003
ELECTRICAL SEQUENCE OF SBN WATER HEATER OPERATION
120 VAC
Power to Heater
Green LED - On
Call for Heat
Green LED - On
Module Self Check
Low Gas Pressure
Switch is Closed
Draft Proving Switch
Is Open
High Limit is Closed
Inducer On
Blower Prover
Closes -1.6 to -2.60 ± .10 W.C. depending on heater model
Ignition Control Board –
120 VAC
HSI Warm Up
20 seconds
Variable Voltage
(80-120 VAC)
Gas Valve Open 3 Second Trial
HSI - Off
3 Seconds to Prove
Flame After HSI - Off
Flame Proves
No
Yes
Tank Heated to Set Temperature
20 Second Blower Purge
Gas Valve – Off
Call for Heat LED - Off
60 Second Blower Post Purge
Blower Prover - Opens
Standby LED - On
2 More Trials
To Prove Flame
Yes
No
Flash 8 Times On Diagnostic LED
Lock Out for 1 Hour
Then Retry
Minimum Millivolt for
4.25 seconds
Yes
No
Flash 7 Times
1 Hour Auto Reset
Natural Gas Models Only