12
PRELIMINARY INSPECTION
Perform this inspection to avoid common problems.
Make certain that:
1. Wiring connections are correct and all terminal screws
are tight.
2. The flame detector(s) is (are) clean and installed and
positioned properly. Consult the Installation Instructions
for the flame detector.
3. The burner is completely installed and ready to fire
(consult the manufacturer instructions); fuel lines are
purged of air.
4. Combustion chamber and flues are clear of fuel and
fuel vapors.
5. Power is connected to the master disconnect switch.
6. Lockout switch is reset (push in and release the
reset button).
7. RUN/TEST switch is in the RUN position (in-
terrupted pilot models only).
8. System is in the standby condition.
9. All limits and interlocks are reset.
FLAME SIGNAL MEASUREMENT (Figs. 9 and 10)
(All Installations)
The flame signal measurement is the best indicator of
proper flame detector application. This check should be
performed when:
• The system is initially set up.
• Any service is done to the system.
• At least once a month while the system is in operation.
This will prevent shutdowns due to poor flame signal.
Use the 196146 Meter Connector and a W136A Meter (or
equivalent). Connect the RED plug-in tip to the RED (+)
meter lead and the BLACK plug-in tip to the BLACK (-)
meter lead. Insert the gray plug into the amplifier flame
current jack on the R7795 amplifier board (see Fig. 9).
The minimum flame current must be an average of
two microamperes for the R7795B,D models and an aver-
age of 3.5 microamperes for the R7795A,C models (refer
to Table 3).
If the minimum average current level cannot be ob-
tained, one or more of the following conditions may exist:
1. Check the supply voltage at terminals L1-L2 on the
wiring subbase. Make sure the master switch is closed,
connections are correct, and the power supply is the correct
voltage and frequency.
2. Check the flame detector wiring for defects, including:
• incorrect connections.
• wrong type or size of wire.
• deteriorated wire.
• open circuits.
• short circuits.
• high resistance shorts caused by accumulated mois-
ture, soot or accumulated dirt.
3. For a flame rod, make sure that:
• there is enough ground area.
• the flame rod is properly located in the flame.
• temperature at the flame rod insulator is no greater
than 500
°
F [260
°
C].
• there is no ignition interference (see the Ignition
Interference Test in this section).
4. For all other detectors, clean the detector lens, fil-
ter, viewing window, and the inside of the sight pipe, as
applicable.
5. With the burner running, check the temperature at
the detector. If it exceeds the detector’s maximum rated
temperature:
• add additional insulation between the wall of the
combustion chamber and the detector.
• add a shield or screen to reflect radiated heat away
from the detector, or
• add cooling. Refer to Sight Pipe Ventilation in
the Detector Instructions.
6. Make sure that the flame adjustment is not too lean.
R7795A,B,C,D
CHECKOUT
Fig. 10—Measuring the flame signal.
TABLE 3—FLAME SIGNAL.
Minimum Acceptable Average
Maximum Current
Flame Detector
R7795 Model
Current (microamperes)
Expected (microamperes)
C7027, C7035, C7044
A, C
3.5
7.5
Ultra-violet Minipeeper
Rectifying Flame Rod or
B, D
2
5
Rectifying Photocell
C7012A,C Ultraviolet
2
6
(Purple Peeper)