CB780E/CB784E RELAY MODULES WITH VALVE PROVING
750-234
39
32-00150—03
NOTE:
Upon completing these tests, open the master
switch and remove all test jumpers from the sub-
base terminals, limits/controls or switches.
22.
Return the system to normal operation.
Pilot Turndown Test (All
Installations Using a Pilot)
Perform this check on all installations that use a pilot. The
purpose of this test is to verify that the main burner can be
lit by the smallest pilot flame that will hold in the flame
amplifier and energize the FLAME LED. Clean the flame
detector(s) to make sure that it will detect the smallest
acceptable pilot flame. If using AMPLI-CHECK™ or Self-
Checking Amplifier and 1M ohm/volt meter, the flame
signal will fluctuate every time the amplifier does a self-
check or a shutter check.
NOTE:
Low fuel pressure limits, if used, could be open. If
so, bypass them with jumpers during this test.
1.
Open the master switch.
2.
Close the manual main fuel shutoff valve(s).
3.
Connect a manometer (or pressure gauge) to mea-
sure pilot gas pressure during the turndown test.
4.
Open the manual pilot shutoff valve(s).
5.
Close the master switch and start the system with a
call for heat.
Raise the set point of the operating con-
troller. The program sequence should start, and
PREPURGE should begin.
6.
When the PILOT IGN begins, set the Run/Test
Switch to TEST position to stop the sequence. The
FLAME LED will come on when the pilot ignites.
NOTE:
If the sequence does not stop, reset the system
and make sure you set the Run/Test Switch to
TEST within the first eight seconds of the PILOT
IGN sequence.
IMPORTANT:
You have eight seconds or three seconds, depend-
ing on PFEP selected, to position the
Run/Test Switch to the TEST position to stop the
sequence after the start of the PILOT IGN period.
7.
Turn the pilot pressure down very slowly, reading the
manometer (or pressure gauge) as it drops. Stop
instantly when the FLAME LED goes out. Note the
pressure at the CB780E/CB784E flame relay drop-
out point. The pilot is at the minimum turndown
position. Immediately turn up the pilot pressure until
the FLAME LED comes on again or the flame signal
increases to 1.25 Vdc.
NOTE:
If there is no flame for fifteen seconds with the
sequence stopped at this point, the
CB780E/CB784E will lockout and flash a lockout
message; see Fig. 48.
8.
Repeat step 7 to verify the pilot gas pressure reading
at the exact point the FLAME LED light goes out.
9.
Increase the pilot pressure immediately until the
FLAME LED comes on, and then turn it down slowly
to obtain a pressure reading just above the dropout
point or until the flame signal increases to 1.25 Vdc.
10.
Set the Run/Test Switch in the RUN position and let
the sequence proceed. At ten seconds into the Igni-
tion Trial period, make sure the automatic main fuel
valve(s) open; then smoothly open the manual main
fuel shutoff valve(s) (or any other manually opened
safety shutoff valve(s), if used) and watch for main
burner ignition. If the main burner flame is estab-
lished, proceed to step 18.
NOTE:
This step requires two people, one to open the
manual valve(s) and one to watch for ignition.
11.
If the main burner flame is not established within ten
seconds, close the manual main fuel shutoff valve(s)
and open the master switch. If the lightoff was
rough, the pilot flame size is too small.
12.
Recycle the burner and stop the sequence in the
PILOT IGN period by using the Run/Test Switch.
13.
Increase the pilot flame size by increasing its fuel
flow until a smooth main flame is accomplished.
14.
Reposition the flame scanner sight tube or use ori-
fices until the pilot flame signal voltage is in the
range of 1.25 to 1.50 Vdc.
15.
When the main burner lights reliably with the pilot at
turndown, disconnect the manometer (or pressure
gauge) and turn the pilot gas flow up to that recom-
mended by the equipment manufacturer.
16.
If used, remove the bypass jumpers from the sub-
base terminals, limits/controls, or switches.
17.
Run the system through another cycle to check for
normal operation.
18.
Return the system to normal operation.
Fig. 48. Flame-out timer lockout.
Hot Refractory Saturation Test
(All Infrared Detectors)
Test to make certain that radiation from hot refractory
does not mask the flickering radiation of the flame itself.
Start the burner and monitor the flame signal during the
warm-up period. A decrease in signal strength as the
refractory heats up indicates hot refractory saturation. If
saturation is extreme, the flame signal will drop below
1.25 Vdc and the system will shut down as though a flame
failure occurred.
If hot refractory saturation occurs, the condition must be
corrected. Add an orifice plate in front of the cell to restrict
the viewing area, lengthen the sight pipe or decrease the
pipe size (diameter). Continue adjustments until hot
refractory saturation is eliminated.
M5001A
LOCKOUT #16 PFEP
* Flame-out Timer*
Condition at the
time of lockout . . .
PILOT HOLD:
(Run/Test Sw)
