Honeywell 7800 SERIES Manual page 20

RM7890A,B,C
CHECKOUT
Flame Detector
Flame Rod
Photocell
C7012A,C
C7012E,F
C7015A
C7027A
C7035A
C7044A
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 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).
c
The flame amplifiers are AMPLI-CHECK™ type.
FLAME SIGNAL MEASUREMENT
Fig. 17—Flame signal measurement.
NEGATIVE (-)
METER LEAD
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 20 kohm/voltmeter with a 0 to 10 Vdc capability.
2. Set the 20 kohm/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. 17).
4. Allow a few seconds for the meter reading to stabilize.
5. If using AMPLI-CHECK™ or shutter check amplifi-
ers, read the average stable voltage, disregarding the peaks
and valleys 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.
If the signal is unstable or less than the minimum accept-
able voltage, check the flame detector installation and cir-
cuitry.
65-0126—2
TABLE 5—FLAME SIGNAL (see Fig. 17).
Flame Signal Amplifier
c
R7847A,B
b
R7847C
c
R7848A,B
c
R7849A,B
R7886A
POSITIVE (+)
METER LEAD
1 MOHM/
VOLT METER
M10683
Minimum Acceptable
a
Steady dc Voltage
1.25 Vdc
1. Check the supply voltages at terminals 3 (L1) and
L2 (N). Make sure the master switch is closed, connections
are correct, and the power supply is of the correct voltage,
frequency and is sinusoidal.
2. Check the detector wiring for defects including:
• Deteriorated wire.
• Incorrect connections.
• Leakage paths caused by moisture, soot or accumu-
lated dirt.
• Open circuits.
• Short circuits.
• Wrong type of wire.
3. For a flame rod, make sure:
• Flame rod is properly located in the flame.
• Ground area is large enough.
• 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 tempera-
ture:
• 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.
20
Maximum Expected
dc Voltage
5.0 Vdc at the Keyboard
Display Module.
or
5.0 Vdc at a 20
kohm/voltmeter.