Honeywell 7800 Series Manual page 27

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 Ampli-
fier and 20 kohm/voltmeter, 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 RM7885, then press the Start Switch
and the Ignition Transformer will be energized. After a two-
second delay for the RM7885 to complete its Safe-Start
Check, PILOT IGNITION should begin.
6. After the pilot has been established, turn the pilot gas
pressure down 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 Ingition Trans-
former. 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 manu-
facturer, 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 accom-
plished.
11. Observe the flame signal voltage. It should be approxi-
mately 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 the pilot gas flow up to that recommended by the
equipment manufacturer.
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 RM7885 will not recognize a flame. If it in-
creases 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) indi-
cates ignition interference.
Open the manual main fuel valve when ignition interfer-
ence is or has been 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
have to be changed to an ultraviolet or infrared flame detec-
tion system.
HOT REFRACTORY SATURATION TEST (ALL IN-
FRARED 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 refrac-
tory 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 (RECTIFY-
ING PHOTOCELL OR ALL INFRARED DETEC-
TORS)
Test to be sure hot refractory will not delay 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.
To check rectifying photocells for hot refractory hold-in,
operate the burner until the refractory reaches its maximum
temperature. Then terminate the firing cycle by pressing the
Stop Switch. Do not open the master switch. Visually observe
when the burner flame or FLAME LED goes out. If this takes
longer than .8 or 3 seconds (depending on the FFRT of the
amplifier), the photocell is sensing hot refractory. This con-
27
RM7885A
CHECKOUT
65-0107