CB780/CB784 RELAY MODULES
32-00207—01
30
Fig. 24. Flame signal measurement.
3.
For all optical detectors, clean the detector viewing
window and inside of the sight pipe as applicable.
4.
With the burner running, check temperature at the
detector. If it exceeds the detector maximum rated
temperature:
a. Add a heat block to stop conducted heat travel-
ing up the sight pipe.
b. Add a shield or screen to reflect radiated heat.
c. Add cooling (refer to sight pipe ventilation in the
detector Instructions).
5.
Make sure the flame adjustment is not too lean.
6.
Make sure the detector is properly sighting the
flame.
7.
If necessary, resight or reposition the detector.
Initial Lightoff Check for Proved
Pilot
Perform this check on all installations that use a pilot. It
should immediately follow the preliminary inspection.
NOTE:
Low fuel pressure limits, if used, could be open. If
so, bypass them with jumpers during this check.
1.
Open the master switch.
2.
Make sure that the manual main fuel shutoff valve(s)
is closed. Open the manual pilot shutoff valve. If the
pilot takeoff is downstream from the manual main
fuel shutoff valve(s), very slightly open the manual
main valve to supply pilot gas flow. Make sure the
main fuel is shut off just up-stream from the burner
inlet, or disconnect power from the automatic main
fuel valve(s).
3.
Close the master switch and start the system with a
call for heat
by raising the set point of the operating
controller; see Fig. 19 or CB 780/CB 784 sequence.
The program should start the ten second INITIATE
sequence.
4.
Let the sequence advance through PREPURGE.
When the PILOT IGN status is displayed on the Key-
board Display Module, ignition spark should occur
and the pilot should light. If the pilot ignites, the
FLAME LED will be energized. Proceed to step 7.
5.
If the pilot flame is not established in ten seconds,
safety shutdown occurs. Let the sequence complete
its cycle. Consult the equipment operating manual
for further information.
6.
Push the reset pushbutton, and let the system recy-
cle once. If the pilot still does not ignite, make the
following ignition/pilot adjustments:
a. Open master switch and remove the CB 780/CB
784 from the subbase.
b. On the subbase, temporarily jumper terminal 4
to ignition terminals 8, 10 or 21; refer to the
appropriate wiring diagram to determine the
proper terminal. Disconnect the leadwire to the
pilot valve if it is connected to the same terminal.
c. Close the master switch to energize only the igni-
tion transformer.
d. If the ignition spark is not strong and continuous,
open the master switch and adjust the ignition
electrode spark gap setting to the manufacturer
recommendations.
e. Make sure the ignition electrodes are clean.
f.
Close the master switch and observe the spark.
g. After a continuous spark is obtained, open the
master switch and add a jumper on the subbase
from terminal 4 (L1) to the pilot terminal 8 or 21.
Reconnect the leadwire from the pilot valve if it
was disconnected in step b.
h. Close the master switch to energize both the
ignition transformer and the pilot valve.
i.
If the pilot does not ignite and if the ignition
spark is still continuous, adjust the pressure reg-
ulator until a pilot is established.
j.
When the pilot ignites properly and stays ignited,
open the master switch and remove the
jumper(s) from terminals 4-8, 4-10 and 4-21 of
the subbase.
k. Check for adequate bleeding of the fuel line.
l.
Reinstall the CB 780/CB 784 on the subbase,
close the master switch, and then return to step
4.
7.
When pilot ignites, measure the flame signal. If the
pilot flame signal is unsteady or approaching the
1.25 Vdc minimum value, adjust the pilot flame size
or detector sighting to provide a maximum and
steady flame signal.
8.
Recycle the system to recheck lightoff and pilot
flame signal.
9.
When the MAIN IGN period is displayed on the VFD,
make sure the automatic main fuel valve is open;
then smoothly open the manual main fuel shutoff
valve(s) and watch for main burner flame ignition.
When the main burner flame is established, proceed
to step 15.
10.
If the main burner flame is not established within ten
seconds, close the manual main fuel shutoff
valve(s).
11.
Recycle the system to recheck the lightoff and pilot
flame signal.
12.
Smoothly open the manual fuel shutoff valve(s) and
try lightoff again. (The first reattempt may have been
required to purge the lines and bring sufficient fuel
to the burner.)
13.
If the main burner flame is not established within
five seconds or the normal lightoff time specified by
the equipment manufacturer, close the manual main
fuel shutoff valve(s). Check all burner adjustments.
NEGATIVE (-)
METER LEAD
POSITIVE (+)
METER LEAD
ONE
MEGOHM/VOLT
METER
M7383C