R7140G,L,M BURNER CONTROL MODULES
31 66-1153—03
6. After the PILOT LED turns on in interrupted pilot
applications, 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 pressure. 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
manual 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 light-
off 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.
To Eliminate Ignition Interference
1. Make sure there is enough ground area.
2. Be sure the ignition electrode and the flame rod are on
opposite sides of the ground area.
3. Check for correct spacing on the ignition electrode:
a. 6000V systems—1/16 to 3/32 in. (1.6 to 2.4 mm).
b. 10,000V systems—1/8 in. (3.2 mm).
4. Make sure the leadwires from the flame rod and ignition
electrode are not too close together.
5. Replace any deteriorated leadwires.
6. Try wrapping the ignition wire with an insulated wire (No.
18 stranded, for example). See Fig. 13.
7. Strip the insulation nearest the ignitor and ground it;
also, strip the insulation nearest the ignition transformer
and ground it.
8. If the problem cannot be eliminated, consider changing
the system to an ultraviolet flame detection system.
Fig. 20. Eliminating ignition interference.
Hot Refractory Saturation Test
(All Infrared Detectors)
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 drops below 1.25 Vdc
and the system shuts down as though a flame failure occurred.
IGNITION
TRANSFORMER
IGNITION
LEAD
M19423B
BURNER ASSEMBLY
BURNER
MODULE
FLAME ROD
LEAD