Honeywell 7800 Series Manual page 36

RM7800E,G,L,M
CHECKOUT
Flame
Detector
Flame Rod
Photocell
C7012A,C
C7012E,F
C7015A
C7027A
C7035A
C7044A
C7076A,D
a
This minimum or 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.
Fig. 33—Flame signal measurement.
NEGATIVE (-)
METER LEAD
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. 33.
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 7, after
all tests are completed and all adjustments made.
As an option, the flame signal can be checked by using the
Keyboard Display Module.
If the signal is unstable or less than the minimum accept-
able voltage, check flame detector installation and cir-
cuitry.
TABLE 8—FLAME SIGNAL.
Flame Signal
Amplifier
c
R7847A,B
b
R7847C
c
R7848A,B
c
R7849A,B
R7886A
POSITIVE (+)
METER LEAD
ONE
MEGOHM/VOLT
METER
M7383
Minimum
Acceptable
Steady dc
a
Voltage
1.25 Vdc
1. Check the supply voltages at terminals 4 (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:
• Incorrect connections.
• Wrong type of wire.
• Deteriorated wire.
• Open circuits.
• Short circuits.
• Leakage paths caused by moisture, soot or accu-
mulated dirt.
3. For a flame rod, make sure:
• There is enough ground area.
• The flame rod is properly located in the flame.
• The 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 temperature at the de-
tector. 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 the flame adjustment is not too lean.
7. Make sure 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.
36
Maximum
Expected
dc Voltage
5.0 Vdc at
Keyboard Display
Module
OR
5.0 Vdc at
20 kohm/volt meter