7800 SERIES EC7885A/RM7885A RELAY MODULE
65-0203
26
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:
These steps may require two people, one to open
the manual valve(s) and one to watch for ignition.
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, allow ten seconds for the
INITIATE period of the 7885A, then press the Start
Switch and the Ignition Transformer will be energized.
After a two-second delay for the 7885A to complete its
Safe-Start Check, PILOT IGNITION should begin.
6. After the pilot has been established, turn down the pilot
gas pressure very slowly, reading the manometer (or
gauge) as the pressure drops. Stop immediately when
the FLAME LED goes out. Note the pressure at this
point.
7. Slowly increase the pilot pressure until the FLAME LED
comes on, and then turn it down slowly to obtain a
pressure reading just above the dropout point.
8. Release the Start Switch to shut off the Ignition
Transformer. Make sure that the automatic main fuel
valve(s) is open. Smoothly open the manual main fuel
shutoff valve(s) and watch for main burner lightoff.
9. If the main flame is not established within five seconds
or the normal lightoff period specified by the burner
manufacturer, close the manual main fuel shutoff
valve(s) and open the master switch. If the burner flame
is established in the normal lightoff period, proceed to
step 11.
10. Restart the system and increase the pilot flame size by
increasing its fuel flow until a smooth main flame is
accomplished.
11. Observe the flame signal voltage. It should be
approximately 1.25-1.50 Vdc. Reposition the flame
scanner sight tube or use orifices until the pilot flame
signal voltage is approximately 1.25-1.50 Vdc.
12. 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 meet
equipment manufacturer recommendations.
13. If used, remove the bypass jumpers from the subbase
terminals, limits/control or switches.
14. Run the system through another cycle to check for
normal operation.
15. Return the system to normal operation.
Ignition Interference Test (All Flame Rods)
Test to be sure 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, the 7885 will not recognize a flame. 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.
Shut the manual main fuel valve. Press the Start Switch and
measure the flame signal with both ignition and pilot on. Then
release the Start Switch and measure the pilot flame only.
Any significant difference (greater than .5 Vdc) indicates
ignition interference.
Open the manual main fuel valve when ignition interference is
or was reduced to less than .5 Vdc.
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.
6,000V 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. If the problem cannot be eliminated, the system may
require changing to an ultraviolet or infrared flame
detection system.
Hot Refractory Saturation Test
(All Infrared Detectors)
Test to be sure 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
has 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. You can also try to lengthen the sight pipe or
decrease the pipe size (diameter). Continue adjustments until
you eliminate hot refractory saturation.
Hot Refractory Hold-In Test (Rectifying
Photocell Or All Infrared Detectors)
Test to be sure hot refractory is not delaying the flame
detection system response to a flameout. This condition can
delay response to flame failure and also can prevent a
system restart as long as hot refractory is detected.
