RM7895A RELAY MODULE
17
32-00122-01
Table 8. Flame Signal.
a
This minimum or a stronger signal should easily be obtained if the detector is correctly installed and positioned to prop-
erly sense the flame. This voltage must be obtained before completing checkout.
Fig. 14. Flame signal measurement.
Measure the flame signal at the appropriate times defined
in the following checkout tests. Read the flame signal volts
dc at the flame amplifier test jacks + and - (Com).
1.
Use a 1 Megohm/volt meter with a 0 to 10 Vdc
capability.
2.
Set the meter to the 0 to 10 Vdc range.
3.
Insert the positive (red) probe into the + jack of the
flame amplifier. Insert the negative (black) probe
into the - (Com) jack of the flame amplifier. See Fig.
14.
4.
Allow a few seconds for the meter reading to stabi-
lize.
5.
The meter reading must be as specified in Table 8
after all tests are completed and all adjustments are
made.
As an option, the flame signal can be checked by using the
optional Keyboard Display Module.
If the signal is unstable or less than the minimum
acceptable voltage, check the flame detector installation
and circuitry.
1.
Check the supply voltages at terminals 5 (L1) and
L2(N). Make sure the master switch is closed,
connections are correct, and the power supply is of
the correct voltage and frequency and is sinusoidal.
2.
Check the detector wiring for defects including:
Incorrect connections.
• Wrong type of wire.
• Deteriorated wire.
• Open circuits.
• Short circuits.
• Leakage paths caused by moisture, soot or
accumulated
dirt.
3.
For flame rod, make sure:
• Ground area is large enough.
• Flame rod is properly located in the flame.
• Temperature at the flame rod insulator is no greater
than
500°F (260°C).
4.
For all optical detectors, clean the detector viewing
window and inside of the sight pipe as applicable.
5.
With the burner running, check the temperature at
the detector. If it exceeds the detector maximum
rated temperature:
• Add a heat block to stop conducted heat traveling up
the sight pipe.
• Add a shield or screen to reflect radiated heat.
• Add cooling (refer to sight pipe ventilation in the
detector
instructions).
6.
Make sure that the flame adjustment is not too lean.
7.
Make sure that the detector is properly sighting the
flame.
8.
If necessary, resight or reposition the detector.
Initial Lightoff Check for Proved
Pilot
Perform this check on all installations that use a pilot. It
should immediately follow the preliminary inspection.
NOTE:
Low fuel pressure limits, if used, could be open. If
so, bypass them with jumpers during this check.
1.
Open the master switch.
2.
Make sure that the manual main fuel shutoff valves
are closed. Open the manual pilot shutoff valve. If
the pilot takeoff is downstream from the manual
main fuel shutoff valve(s), very slightly open the
manual main valve to supply pilot gas flow. Make
sure the main fuel is shutoff just upstream from the
burner inlet, or disconnect power from the automatic
main fuel valves.
Flame Detector
Acceptable Flame Signal
Amplifier
Minimum Maximum
Steady dc Voltage
a
Expected dc Voltage
Flame Rod
C7012A,C
R7847A
1.25 Vdc
5.0 Vdc at the Keyboard
Display Module
or
5.0 Vdc at a 1 Megohm/volt
meter.
C7027A
C7035A
C7044A
R7849A
1 MEGOHM/VOLT
METER
M20281
POSIIVE (+)
METER LEAD
NEGATIVE (–)
METER LEAD
