Honeywell 7800 Series Manual page 23

FLAME SIGNAL MEASUREMENT
Acceptable
Flame
Detector
Flame Rod
Photocell
C7012A,C
C7012E,F
C7015A
C7027A
C7035A
C7044A
C7076A,D
a
This minimum or a stronger signal should be easily 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.
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.
4. Allow a few seconds for the meter reading to
stabilize.
5. If using AMPLI-CHECK™ or shutter check am-
plifiers, you should read the average stable voltage, disre-
garding 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.
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 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 accumu
lated dirt.
TABLE 6—FLAME SIGNAL.
Maximum
Flame signal
Amplifier
c
R7847A,B
b
R7847C
c
R7848A,B
c
R7849A,B
R7886A
window and inside of the sight pipe as applicable.
detector. If it exceeds the detector maximum rated tempera-
ture:
flame.
INITIAL LIGHTOFF CHECK FOR PROVED PILOT
should immediately follow the preliminary inspection.
NOTE: These steps may require two people, one to open the
NOTE: Low fuel pressure limits, if used, could be open. If so,
is closed. Open the manual pilot shutoff valve. If the pilot
takeoff is downstream from the manual main fuel shutoff
valve(s), slightly open the manual main valve to supply pilot
gas flow. Make sure the main fuel is shut off just upstream
23
Steady dc
Voltagea
1.25 Vdc
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
5. With the burner running, check the temperature at the
• 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
8. If necessary, resight or reposition the detector.
Perform this check on all installations that use a pilot. It
manual valve(s) and one to watch for iginition.
bypass them with jumpers during this check.
1. Open the master switch.
2. Make sure that the manual main fuel shutoff valve(s)
RM7885A
CHECKOUT
Expected
Dc voltage
5.0 Vdc at the
Keyboard Display
Module
or
5.0 Vdc at a
Volt ohmmeter
65-0107