Groth 8391B - Manual (Page 6)

5
Note: The maximum thermocouple temperature that the pilot flame can achieve is dependent on various
factors; pilot fuel, fuel pressure, ambient temperature and wind conditions. The purpose of the thermocouple
is not to measure the flame temperature, but to determine if a flame exists. Therefore the upper switchpoint
can be adjusted to any temperature which meets the following criteria:
1.
Lower than the temperature achieved by a constant pilot flame under the worst gas and wind
conditions.
2. Greater than the temperature that can be achieved by ambient conditions or a weak, intermittent or
otherwise inadequate pilot.
The lower switchpoint should be set at approximately ambient temperature.
Burners equipped with a thermocouple [T/C] flame sensor normally take less than 3 minutes, but in some
cases may take 10 - 20 minutes to reach the upper switch point. Until that temperature is attained, the
ignition cycle will continue. Once established, the pilot will continue to burn, as long as the remote pressure
switch energizes the pilot control and power is supplied to the panel. The PILOT GAS ON indicator is
illuminated as long as the gas solenoid valve is open.
After a successful ignition, if the pilot flame is extinguished for any reason, the ignition electrode will begin
sparking when the "sensed" temperature drops below the upper switch point. Ignition will be attempted as
described above.
When ignition is initiated, either manually or automatically, an adjustable time interval begins, typically 10
minutes. If the time interval ends before a pilot flame is established, a flame failure indicator is illuminated on
the panel, however the ignition cycle continues. Additional contacts are provided for a remote alarm signal if
desired.
The flame failure interval should be set to provide the normal T/C heat-up time plus 20% to avoid nuisance
alarm signals.
If the Auto Shut Down / Manual Reset option is chosen, the ignition system will shut down after a pilot flame
failure indication. The system is manually reset at the control panel by turning the selector switch to OFF and
then returning it to AUTO or MANUAL. This option is enabled by removing the internal jumper between
terminals 5 and 8.
INSPECTION AND MAINTENANCE:
To ensure safe operation of your complete burner system, the following items need to be inspected periodically. See
table 3, page 7 for suggested maintenance intervals. Follow your own plant safety guidelines before performing the
inspection. We recommend the following:
MINIMUM SAFETY PROCEDURES
1. Disconnect and lock-out electric power to the control panel.
2. Shut off the supply of gas to the pilot line and lock-out.
3. Allow burner to cool to ambient temperatures or take precautions to deal with metal parts that are
exposed to the pilot and main burner flames.
AUTOMATIC IGNITION CONTROL
1. Open the ignition control panel enclosure door and check the condition of wiring, relays, switches, and the
flame monitor equipment. Look for evidence of loose wires at connections, burned components, loose
enclosures on relays, moisture, dirt or foreign materials, etc. Make sure that the proper range is selected
on all time delay relays. 1TR should be set for 10 seconds on and 3 seconds off. 2TR is typically set for 5-
10 minutes but may be longer [see operating instruction].
2. Open the transformer enclosure door and make sure the high voltage lug connection on the transformer is
tight. Check for loose wires, moisture, dirt or foreign materials, etc.
3. Remove the junction box cover from the electrode and disconnect the ignition wire and flexible conduit.
Remove [2] U-bolts and remove the electrode from the burner [see electrode maintenance]. Handle the