Honeywell 7800 SERIES EC7895A Product Data page 21

Flame Signal Measurement (Fig. 18 and Table 5)
Flame Detector
Flame Rod Photocell
C7012A,C
C7012E,F
C7015A
C7027A
C7035A
C7044A
C7061
C7076A,D
a
This minimum or a stronger signal should easily be obtained if the detector is correctly installed and positioned to properly
sense the flame. This voltage must be obtained before completing checkout.
b
The flame amplifiers are AMPLI-CHECK® type.
c
The flame signal amplifier circuitry is tested one-half second every five seconds during burner operation and shuts down the
burner if the amplifier fails (all installations).
d
Requires seperate stepdown power transformer. See Fig. 14.
e
Use with RM7895A Only.
NEGATIVE (-)
METER LEAD
Fig. 18. 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 1M ohm/voltmeter with a 0 to 10 Vdc capability.
2. Set the 1M ohm/voltmeter 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. 19.
4. Allow a few seconds for the meter reading to stabilize.
5. If using AMPLI-CHECK® or shutter check amplifiers,
read the average stable voltage, disregarding the peaks
caused by the self-checking operation.
6. The meter reading must be as specified in Table 5 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.
Table 5. Flame Signal.
Acceptable Flame Minimum Maximum
Signal Amplifier Steady DC Voltage
b
R7847A,B
c
R7847C
b
R7848A,B
b
R7849A,B
d
R7861A
e
R7886A
POSITIVE (+)
METER LEAD
ONE
MEGOHM/VOLT
METER
M7382
7800 SERIES EC7895A, RM7895A RELAY MODULE
a
1.25 Vdc
5.0 Vdc at the Keyboard Display Module
5.0 Vdc at a 1M ohm/volt meter
If the signal is unstable or less than the minimum ac-ceptable
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 a 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.
21
Expected DC Voltage
OR
65-0205