750-166 1-29
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 de-
tector. If it exceeds the detector maximum rated temperature:
• Add a heat block to stop conducted heat traveling
up the sight pipe.
• Add a shield or screen to reflect radiated heat.
• 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 control-
ler; see Fig. 19 or CB780/CB784 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 Keyboard 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 recycle
once. If the pilot still does not ignite, make the following
ignition/pilot adjustments:
a. Open master switch and remove the CB780/CB784
from the subbase.
b. On the subbase, temporarily jumper terminal 4 to
ignition terminals 8, 10 or 21; refer to the appropri-
ate wiring diagram to determine the proper termi-
nal. 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. Recon-
nect the leadwire from the pilot valve if it was
disconnected in step b.
h. Close the master switch to energize both the igni-
tion transformer and the pilot valve.
i. If the pilot does not ignite and if the ignition spark
is still continuous, adjust the pressure regulator 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 CB780/CB784 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 re-
quired 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
valves(s). Check all burner adjustments.
14. If the main burner flame is not established after two
attempts:
a. Check for improper pilot size.
b. Check for excess combustion air at low fire.
c. Check for adequate low fire fuel flow.
d. Check for proper gas supply pressure.
e. Check for proper valve operation.
f. Check for proper pilot flame positioning.
15. Repeat steps 10 through 14 to establish the main
burner flame; then proceed to step 16.
16. With the sequence in RUN, make burner adjustments
for flame stability and Btu input rating.
17. Shut down the system by opening the burner switch or
by lowering the set point of the operating controller. Make
sure the main flame goes out. There may be a delay due to gas
trapped between the valve(s) and burner. Make sure all
automatic fuel valve(s) close.
CB780/CB784
CHECKOUT
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