Fig. 30-Flame-Out Timer Lockout - Honeywell 7800 Series Manual

NOTE: Low fuel pressure limits, if used, could be open. If so,
bypass them with jumpers during this test. These steps
may require two people—one to open the manual valves
and one to watch the ignition.
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 the purge sequence will
begin.
6. When "PURGE HOLD: T21" appears on the display,
press the Start Switch and 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, the
Alarm will stop.
IMPORTANT: You have eight seconds to position the Run/
Test Switch to the TEST position to stop the sequence
after the start of the PILOT IGN period (first three
seconds if configuration jumper CJ1 is clipped).
7. Turn down the pilot pressure very slowly, reading the
manometer (or pressure gauge) as it drops. Stop when the
FLAME LED goes out or the flame signal drops below
1.25 Vdc. Note the pressure at the RM7838B flame relay
dropout point. The pilot is at the minimum turndown posi-
tion. Immediately turn up pilot pressure until the FLAME
LED comes on again or flame signal increases to 1.25 Vdc.
NOTE: If there is no flame for 15 seconds with the sequence
stopped at this point, the RM7838B will lockout and flash
a lockout message, see Fig. 30.
Fig. 30—Flame-out timer lockout.
LOCKOUT #16 PFEP
* Flame-out Timer*
Condition at the
time of lockout . . .
PILOT HOLD:
(Run/Test Sw)
8. Repeat step 7 to verify the pilot gas pressure reading is
at the exact point the FLAME LED light goes out.
9. Increase 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 Ignition Trial
period, make sure the automatic main fuel valve(s) open (if
configuration jumper JR3 is clipped). Smoothly open the
manual main fuel shutoff valve(s), open the Pilot Valve
Hold Switch (if closed) and close the Manual Open Valve (if
used) and watch for main burner ignition. If the main burner
flame is established, 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 four
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 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 can be 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 or 1.25 Vdc flame signal strength, turn up the pilot
gas flow to that recommended by the equipment manufacturer
and disconnect the manometer (or pressure gauge).
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)
Test to make certain that a false signal from a spark
ignition system is not superimposed on the flame signal.
Ignition interference can subtract from (decrease) or add
to (increase) the flame signal. If it decreases the flame signal
enough, it will cause 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 .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
M5001
opposite sides of the ground area.
3. Check for correct spacing on the ignition electrode:
4. Make sure the leadwires from the flame rod and
ignition electrode are not too close together.
5. Replace any deteriorated leadwires.
6. If the problem cannot be eliminated, the system may
have to be changed to an ultraviolet flame detection system.
39
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).
RM7838B
CHECKOUT
65-0120—1