Weather-Rite TT Series, Installation, Operation & Service Manual

Page: 117 / 205

SECTION 22: D
IRECT
F
IRED
B
URNER
111 of 198
22.3 Direct Fired Burner Flame Provin g (Ultra
Violet Scanner)
The UV t ub e is made of q u artz and is filled w ith a gas
that ionizes w hen str u ck b y UV radiation from the
flame. In the a b sence of UV radiation, the gas acts
as an ins u lator b et w een t w o electrodes w hich are
mo u nted inside the t ub e. These electrodes are
energized contin u o u sly b y a high v oltage. D u ring
com bu stion, UV radiation ionizes the gas, ca u sing
c u rrent p u lses to flo w b et w een the electrodes. These
c u rrent p u lses res u lt in a flame signal w hich is
transmitted to the amplifier in the control w here it is
processed to energize or hold in the flame relay.
FIGURE 92: Ultra Violet Sensor
The flame rectification mod u le of the flame safeg u ard
control con v erts this signal to a D.C. v oltage. This
v oltage is the v al u e that is u sed to monitor the pilot
and the main flame of the bu rner. For the flame
safeg u ard control to recognize this signal the v al u e of
the v oltage m u st b e b et w een 5 to
10 v olts D.C. and it m u st b e steady. This signal is
meas u red at the flame relay, on the rectification
mod u le's test jacks; S1 (colored red) and S2 (colored
b lack). Upon recei v ing the correct signal, the flame
relay w ill accept this as proof that the bu rner is
f u nctioning correctly and w ill proceed w ith its
f u nctions.
FIGURE 93: Ultra Violet Scanner Mountin g