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c. When the first stage burner flame is established,
watch for the automatic second stage fuel valve(s)
to open. Observe that the second stage lights off
properly.
d. Make burner adjustments for flame stability and
input rating.
e. Shut down the system by lowering the setpoint of
the operating controller. Make sure the burner flame
goes out and all automatic fuel valves close.
f.
Go to step 19.
19. Restart the system by closing the burner switch and/or rais-
ing the setpoint of the operating controller. Observe that the
burner flame is established during PILOT IGN, within the nor-
mal lightoff time specified by the equipment manufacturer.
20. Measure the flame signal. Continue to check for the proper
signal through the RUN period. Check the signal at both
high and low firing rate positions and while modulating. Any
pulsating or unsteady readings require further attention.
21. Make sure all readings are in the required ranges
before proceeding.
NOTE: On completing these tests, open the master switch
and remove all test jumpers from the subbase termi-
nals, 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 can hold in the flame amplifier
and energize the FLAME LED. Clean the flame detector(s) to
make sure that it detects the smallest acceptable pilot flame.
If using AMPLI-CHECK™ or self-checking amplifier and
1M ohm/voltmeter, the flame signal fluctuates 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 measure
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 setpoint of the operating controller.
The R7120D sequence should start, and PREPURGE
should begin.
6. After the PILOT LED turns on in interrupted pilot appli-
cations, set the Run/Test Switch to the TEST position to
stop the sequence. The FLAME LED comes 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 0.8 second or three seconds, depending
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 down the pilot pressure very slowly, reading the
manometer (or pressure gauge) as it drops. Stop
instantly when the FLAME LED goes out. Note the pres-
sure. 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 15 seconds with the Run/Test
switch in the TEST position, the relay module locks out.
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 (if used)
and let the sequence proceed. When the MAIN LED
turns on, make sure the automatic main fuel valve(s)
opens; 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 established, go to step 18.
NOTE: This step requires two people, one to open the man-
ual valve(s) and one to watch for ignition.
11. If the main burner flame is not established within five
seconds, or within the normal lightoff time specified by
the equipment manufacturer, close the manual main
fuel shutoff valve(s) and open the master switch. If the
lightoff is rough, the pilot flame size is too small.
12. Close the master switch to recycle the burner and stop
the sequence in the PILOT 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 orifices
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 up the pilot gas flow to that recom-
mended by the equipment manufacturer.
16. If used, remove the bypass jumpers from the subbase
terminals, limits/controls, or switches.
17. Run the system through another cycle to check for
normal operation.
18. Return the system to normal operation.
Ignition Interference Test
(All Flame Rods)
Ignition interference can subtract from (decrease) or add to
(increase) the flame signal. If it decreases the flame signal
enough, it causes a safety shutdown. If it increases the flame
signal, it could cause the FLAME LED to come on when the
true flame signal is below the minimum acceptable value.
Start the burner and measure the flame signal with both
ignition and pilot (or main burner) on, and then with only the
pilot (or main burner) on. Any significant difference (greater
than 0.5 Vdc) indicates ignition interference.
15
R7120D BURNER CONTROL MODULES
66-1196EF—01
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