Grain Systems PNEG-1928 - Manual (Page 9)

PNEG-1928 Page 9 of 9
UV Sensor Retrofit Instruction Manual for Portable Dryers
Operation
The UV sensor is highly sensitive to only UVC light that is present in flame. It can detect a small flame
from a lit match over 6' away. Because the particular wavelength “C” band of UV light this sensor is
sensitive to (180-230 nm) is normally absorbed by the ozone present in our atmosphere the sensor will
not be affected by normal sunlight.
The UV Sensor is powered up whenever the dryer controls are energized (orange and yellow wires). The
rectified output (black and red wires) of the UV flame sensor is only active when the sensor senses flame
through an internal relay. This is provided to the fenwal flame board between terminal S1 and the burner
ground or AC Neutral.
The Time delay relay provides a means of self checking to test whether or not the sensor has possibly
burned in a flame sense state. Or in other words the sensor has locked itself up by sensing UV flame
even when flame is not present. So every ten (10) hours the timer will open up the internal contacts that
provide the flame signal to the Vision Flame board J1-01. This interruption will force the controls to cycle
power to the fenwal board in an attempt to relight the burner.
Normally, if the UV sensor stops sensing flame then the fenwal will resume by relighting the burner. This
will cause a brief interruption in burner flame which will last for about five (5) seconds or so until the next
timer relay cycle (ten (10) hours).
If the UV sensor has burned in and continues to sense flame even with no flame present then the fenwal
board will go into a fault condition and will not allow the burner to relight. If the fenwal has a fault condition
then the LED will repeatedly flash two (2) times then pause then flash two (2) times again until power is
lost to the fenwal or the controls system shuts down with an error. This will occur after three (3) failed
relight attempts to the burner.
Life expectancy of the UV sensor is rated for approximately 10000 hours of continuous operation which
should provide many years of reliable use.
Testing
The sensor contains two (2) red LED lamps that will aid in troubleshooting flame sensing issues. One is
labeled “FLAME STATUS” and the other “FLAME RELAY”.
FLAME STATUS indicates the strength of the flame signal. The brighter the LED, the stronger the
flames signal.
FLAME RELAY turns on once the FLAME STATUS becomes strong enough. This is what activates the
flame rectification circuit going to the fenwal board used in the Vision control system.
If the sight tube is positioned too close to the spark or the reducing bushing is not used then the flame
sensor will falsely sense flame and activate the flame relay. This can be tested by dry firing the burner
with the gas turned OFF. You may rarely see the FLAME STATUS light flicker briefly during this test but
it should never be strong enough for the flame relay to become active.
If everything is working correctly the burner should attempt to relight three (3) times then controls will shut
the system down with an ignition failure warning on the screen.
NOTE: The ignition source (spark) is very rich in Ultraviolet light. This can cause the UV sensor to sense
flame if it can see the light that is emitted from the spark. This is the reason we choked the sight
tube down to a 1/8" NPT opening is to reduce this effect.
Do not reverse the Yellow and Orange wires on the UV sensor when hooking it up to 120 VAC.
The sensor is polarity sensitive and reversing these wires can destroy the sensor.