Product Overview

RM7890; RM7895 100 VAC 7800 SERIES RELAY MODULES
66-1195—01 22
8. When the pilot ignites, measure the flame signal. If the
pilot flame signal is unsteady or approaching the 1.25
Vdc minimum value, adjust the pilot flame size or
detector position to provide a maximum and steady
flame signal.
9. Recycle the system to recheck lightoff and pilot flame
signal.
10. When the RUN period (MAIN IGN period for the
RM7895) is displayed by the MAIN LED, make sure the
automatic main fuel valve is open; then smoothly open
the manual main fuel shutoff valve(s) and watch for
main burner flame ignition. When the main burner flame
is established, proceed to step 17.
11. If the main burner flame is not established within five
seconds or the normal lightoff time specified by the
equipment manufacturer, close the manual main fuel
shutoff valve(s).
12. Recycle the system to recheck lightoff and pilot flame
signal.
13. Let the relay module recycle to the RUN period (MAIN
IGN period for the R7895). Smoothly open the manual
fuel shutoff valve(s) and try lightoff again. (The first
attempt may have been required to purge the lines and
bring sufficient fuel to the burner.)
14. If the main burner flame is not established within five
seconds or the normal lightoff time specified by the
equipment manufacturer, close the manual fuel shutoff
valve(s). Check all burner adjustments.
15. If the main burner flame is not established after two
attempts:
a. Check for improper pilot size.
b. Check for excess combustion air.
c. Check for adequate fuel flow.
d. Check for proper gas supply pressure.
e. Check for proper valve operation.
f. Check for proper pilot flame positioning.
16. Repeat steps 11 through 15 to establish the main
burner flame, then proceed to step 17.
17. With the sequence in RUN, make burner adjustments
for flame stability and BTU input rating.
18. Shut down the system by opening the burner switch or
by lowering the setpoint of the operating controller.
Make sure the main flame goes out. There may be a
delay due to gas trapped between the valve(s) and the
burner. Make sure all automatic fuel valve(s) close.
19. Restart the system by closing the burner switch and/or
raising the setpoint of the operating controller. Observe
that the pilot is established during PILOT IGN and the
main burner flame is established during RUN (MAIN
IGN for RM7895) within the normal lightoff time.
20. Measure the flame signal. Continue to check for the
proper signal, see Table 10, through the RUN period.
21. Run the burner through another sequence, observing
the flame signal for:
a. Pilot flame alone (unless using direct spark ignition).
b. Pilot and main flame together. Also observe the time
it takes to light the main flame. Ignition of the main
flame should be smooth.
22. Return the system to normal operation.
23. Make sure all readings are in the required ranges before
proceeding.
NOTE: Upon completing these tests, open the master
switch and remove all test jumpers from the
subbase terminals, limits/controls or switches.
Initial Lightoff Check for Direct Spark
Ignition (DSI)
Use this check for gas and oil burners that do not use a pilot
immediately following the preliminary inspection. Refer to the
appropriate sample block diagram of field wiring for the
ignition transformer and fuel valve(s) hookup.
NOTE: Low fuel pressure limits, if used, could be open;
if so, bypass them with jumpers during this
check.
1. Open the master switch.
2. Complete the normal checkout of the fuel supply and
equipment as recommended by the equipment
manufacturer.
3. Close all manual main fuel shutoff valve(s). Check that
the automatic fuel valve(s) are closed. Make sure fuel is
not entering the combustion chamber.
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 operating
sequences. The primary sequence should start with the
10-second INITIATE sequence.
5. Let the sequence advance through STANDBY and
SAFE-START CHECK for the RM7890 (PREPURGE for
the RM7895) to Ignition Trial. Ignition spark should
occur. Listen for the click of the first stage fuel solenoid
valve(s).
6. Let the program sequence complete its cycle.
7. Open the manual fuel shutoff valve(s).
8. Push the reset button and recycle the program
sequence through STANDBY and SAFE-START
CHECK for the RM7890 (PREPURGE for the RM7895).
9. Watch for the FLAME LED to help determine when the
first stage burner flame is established. If it is estab-
lished, go to step 15.
10. If the first stage burner flame is not established within
four seconds, or within the normal lightoff time specified
by the equipment manufacturer, close the manual fuel
shutoff valve(s) and open the master switch.
11. Check all burner adjustments.
12. Wait about three minutes. Close the master switch,
open the manual fuel shutoff valve(s), and try again to
light off the burner. The first attempt may have been
required to purge the lines and bring sufficient fuel to the
burner.
13. If the first stage burner flame is not established within
four seconds or within the normal lightoff time specified
by the equipment manufacturer, close the manual fuel
shutoff valve(s) and open the master switch.
14. If necessary, repeat steps 8 through 13 to establish the
first stage burner flame. Then proceed to step 15.
15. When the first stage burner flame is established, the
sequence will advance to RUN. Make burner adjust-
ments for flame stability and input rating. If a second
stage is used, proceed to step 18.
16. Shut down the system by opening the burner switch or
by lowering the setpoint of the operating controller.
Make sure the burner flame goes out and make sure all
automatic fuel valves close.
17. If used, remove the bypass jumpers from the low fuel
pressure limit and subbase.
18. If a second stage is used, make sure the automatic
second stage fuel valve(s) opened, and check the
lightoff as follows (otherwise proceed to step 19):