Honeywell 7800 Series Installation Instructions Manual page 21

Fig. 17. Flame signal measurement.
1 . Use a one megohm per volt meter with a 0 to 10 Vdc capa-
bility.
2 . Set the one megohm per volt meter to the 0 to 10 Vdc
range.
3 . Insert the positive (red) probe into the + jack of the flame
amplifier and 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
the average stable voltage, disregarding the peaks and val-
leys caused by the self-checking operation.
6 . The meter reading must be as specified in Table 10 after all
tests are made and all adjustments are made.
As an option, check the flame signal by using the optional
KDM.
If the signal is unstable or less than the minimum acceptable
voltage, check the flame detector installation and circuitry.
1 . Check the supply voltages at terminals 3 (L1) and L2 (N)
for the RM7890 and terminals 5 (L1) and L2 (N) for the
RM7895. Make sure the master switch is closed, connec-
tions are correct and the power supply is of the correct
voltage, frequency and is sinusoidal.
2 . Check the detector wiring for defects:
a . Deteriorated wiring.
b . Incorrect connections.
c . Leakage paths caused by moisture, soot or accumulated
dirt.
d . Open circuits.
e . Short circuits.
f . Wrong type of wire.
3 . For a flame rod, make sure:
a . Flame rod is properly located in the flame.
b . Ground area is large enough.
c . Temperature at the flame rod insulator is no greater
than 500°F (260°C).
4 . Make sure that the flame adjustment is not too lean.
5 . If necessary, reposition the flame detector.
TM
or shutter check amplifiers, read
Initial Lightoff Check for Proved Pilot
Perform this check immediately following the preliminary in-
spection on all installations that use a pilot:
NOTE: Low fuel pressure limits, if used, could be open; if so,
bypass with jumpers during this check .
1 . Open the master switch.
2 . Make sure the manual main fuel shutoff valve(s) is closed.
3 . 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
from the burner inlet, or disconnect power from the auto-
matic main fuel valve(s).
4 . Close the master switch and start the system with a call
for heat by raising the setpoint of the operating controller,
see Fig. 15 or the relay module sequence. The sequence
should start the ten-second INITIATE sequence.
5 . Let the sequence advance through STANDBY and SAFE-
START CHECK (PREPURGE in the RM7895). Ignition spark
should occur and the pilot should light. If the pilot ignites,
the FLAME LED will be lighted. Proceed to step 8.
6 . If the pilot flame is not established in 15 or 30 seconds,
safety shutdown occurs. Let the sequence complete its
cycle. Consult the equipment operating manual for further
information.
7 . Push the reset pushbutton and let the system recycle once.
If the pilot still does not ignite, make the following ignition/
pilot adjustments.
a . Open the master switch and remove the relay module
from the subbase.
b . On the subbase, jumper terminal 3 on the RM7890
(terminal 5 on the RM7895) to ignition terminal 8 or 10,
refer to the appropriate wiring diagram (Fig. 4 through
7) to determine the proper terminal. Disconnect the
leadwire to the pilot valve if it is connected to the same
terminal.
c . Close the master switch to energize only the ignition
transformer.
d . If the ignition spark is not strong and continuous, open
the master switch and adjust the ignition electrode
spark gap setting to the manufacturer recommenda-
tions.
e . Make sure the ignition electrodes are clean.
f . Close the master switch and observe the spark.
g . After a continuous spark is obtained, open the master
switch and add a jumper on the subbase from terminal 3
(L1) (RM7890) or terminal 5 (L1) (RM7895) to the pilot
terminal 8. Reconnect the leadwire from the pilot valve if
it was disconnected in step b.
h . Close the master switch to energize both the ignition
transformer and the pilot valve.
i . If the pilot does not ignite and if the ignition spark is still
continuous, adjust the pressure regulator until a pilot is
established.
j . When the pilot ignites properly and stays ignited, open
the master switch and remove the subbase jumper(s)
from terminals 3 to 8 or 3 to 10 (terminals 5 to 8 or 5 to
10 on the RM7895).
k . Check for adequate bleeding of the fuel line.
l . Reinstall the relay module on the subbase, close the
master switch and return to step 4.
21
RM7890, RM7895 100 Vac
32-00216-01