57
It may be necessary to adjust the sensor GAIN in order to keep the signal strength value on scale. If
so, observe and record the sensor GAIN value (1-31) selected. Perform this step for each sensor.
In the Manual Config Menu with the target flame OFF
(leaving other burners firing), observe
and record the sensor signal strength and stability at each of the twenty-one modulation BANDS: 23,
31, 39, 46, 54, 62, 70, 78, 85, 93, 101, 109, 117, 125, 132, 140, 148, 156, 164, 171 and 179Hz
Do not
adjust the sensor GAIN at this time.
Perform this step for each sensor.
At each of the twenty-one BAND settings, compare the recorded Flame ON signal strength to
the recorded Flame OFF signal strength.
Select the BAND setting that yielded the greatest Flame
ON to Flame OFF signal ratio and the greatest stability. Perform this step for each sensor.
Adjust the sensor gain
(1-31) so that the flame ON signal strength is well above the flame relay ON
THRESHOLD, and the flame OFF signal strength is well below the flame relay OFF THRESHOLD
(see “Flame Relay Thresholds”).
When
sensor select is “IR & UV”, the flame relay and 4-20 mA output operate on the SUM of the IR
and UV signals. When setting the GAIN adjustments, the user should favor the sensor (IR or UV)
which exhibited the greatest flame ON:OFF signal ratio, and/or greatest stability. The user may
choose to use the input from only one sensor by selecting “IR ONLY” or “UV ONLY”.
Note:
For best scanner operation, the total Flame ON Signal Strength (IR Signal St
UV Signal Strength) should be between 100 and 150 or higher even though the Flame Quality
display is capped at 100.
Each upward step in the User Gain setting will increase the Signal Strength number for the selected
sensor by approximately 50%. Each downward step in the User Gain setting will decrease the Signal
Strength number for the selected sensor by approximately 33%.
Example:
Assume that after selecting the best BAND settings for IR and UV, the flame signals are
as shown in Table 1. Assume that the Flame Relay ON threshold is 40 and the OFF is 20:
Table 1
In Table 1, the background flame signal (Target Burner OFF) is too high and is preventing the Flame
Relay from de-energizing. The User Gains should be reduced to drop the Flame Quality number
below the Flame Relay Flame OFF Threshold of 20.
Table 2 shows the results of lowering each User Gain setting by 4 steps (e.g. from User Gain=23 to
User Gain=19):
Table 2
Flame Relay Thresholds
The flame relay has a factory programmed FLAME ON threshold of 40, and a FLAME OFF thresh-
old of 20 (0-100 scale). With these settings, it is recommended that the flame ON signal normally be
at least 150. Other on and off thresholds may be selected to suit particular applications.
CAUTION: After selecting Sensor TYPES used, Sensor BANDS, Sensor GAINS, and Flame
Relay ON & OFF Thresholds, proper flame detection and flame discrimination must be
verified by starting and stopping the burner several times. The flame relay must reliably de-
energize for all flame out conditions. This testing should be done with various adjacent
burners on and off, and at various load levels. This is a requirement for proper operation.
Target Burner
Status
Flame Signal Strength (0-999)
Flame Quality
(0-100)
“FQ”
Flame Relay
Status
“IRFS
(IR)
“UVFS”
(UV)
“FS”
(Combined)
Burner ON
300
460
760
100
Energized
Burner OFF
40
10
50
50
Energized
Target Burner
Status
Flame Signal Strength (0-999)
Flame Quality
(0-100)
“FQ”
Flame Relay
Status
“IRFS
(IR)
“UVFS”
(UV)
“FS”
(Combined)
Burner ON
59
91
150
100
Energized
Burner OFF
8
2
10
10
De-energized
