WATER HEATING IGNITION SEQUENCE
(Make sure gas and electric power are connected properly)
1.The ignition control module is powered and monitors the system, waiting for a call for heat from the thermostat.
2.The thermostat calls for heat by reading a resistance value within a given range directly proportional to water temperature.
3.The control Module:
a.Checks the pressure switch for an open circuit.
b.Energizes the blower.
c.Checks the pressure switch for a closed circuit to prove draft.
d.Sends line voltage to the hot surface igniter with a 20 second warm up period.
e.Opens the gas valve and checks the sensing rod for flame.
4.The burner heats the water to the desired thermostat setting.
a.The resistance in the thermostat rises to the value selected by the temperature setting.
b.The control module closes the gas valve and 5 seconds later, removes power from the blower.
5.Cycle is completed.
FIGURE 29.
CONTROL SEQUENCE - HOT SURFACE DIRECT IGNITION
5 | seconds. | |
HSI | 20 seconds. | |
Ignition Activation Period | 4 | seconds. |
Flame Recognition Period | 1 | second. |
Ignition Trial | 4 | seconds. |
Interpurge | 5 | seconds. |
5 | seconds. | |
Retries | 2 |
|
Reset from Lockout | 1 | hr. |
Flame Sensing (Nominal) |
|
|
HSI Off/Run Mode | 4.0µ DC | |
|
|
|
HIGH ALTITUDE INSTALLATION
WARNING
INSTALLATIONS ABOVE 2000 (610 m) FEET REQUIRE REPLACEMENT OF THE BURNER ORIFICE IN ACCORDANCE WITH THE NATIONAL FUEL GAS CODE (ANSIZ223.1/NFPA 54).
FAILURE TO REPLACE THE ORIFICE WILLRESULTIN IMPROPER AND INEFFICIENT OPERATION OFTHE APPLIANCE, PRODUCING CARBON MONOXIDE GAS IN EXCESS OF SAFE LIMITS, WHICH COULD RESULT IN EXCESS OF SAFE LIMITS, WHICH COULD RESULT IN SERIOUS PERSONAL INJURY OR DEATH.
A.O. Smith builds models specifically for high altitude service. Please check the rating plate before making changes.
VENTING MANUAL RESET SWITCH
There is a venting manual reset switch located on the venting hood. If the switch is activated, it will not reset itself. Before resetting this reset switch, check for flue blockage and propriety of the venting systems. To reset, press the red button.
FIGURE 30.
MAINTENANCE
WARNING
DISCONNECT FROM ELECTRICAL SUPPLY BEFORE SERVICING UNIT.
FOR YOUR SAFETY, WATER HEATER SERVICE SHOULD BE PERFORMED ONLY BY A QUALIFIED SERVICE TECHNICIAN. READ THE GENERAL SAFETY INFORMATION SECTION FIRST.
14
