RUN
1. A ten second stabilization period occurs at the
beginning of the RUN period.
2. The firing rate motor releases to modulation
(RM7840E,G,L).
3. The RM7840 is now in RUN and will remain in
RUN until the controller input, terminal 6, opens, indicat-
ing that the demand is satisfied or a limit has opened.
POSTPURGE
The RM7840 provides a fifteen second POSTPURGE
following the completion of the RUN period. The blower
motor output is powered to drive all combustion products
and any unburned fuel from the combustion chamber. It
also supplies combustion air to burn fuel being purged
from the fuel line downstream of the fuel shutoff valve.
1. The main fuel valve and intermittent pilot valve,
terminals 9 and 21, are de-energized and the firing rate
motor is commanded to the low fire position to begin the
POSTPURGE period.
2. The Preignition Interlock closes within the first five
seconds of POSTPURGE.
3. After the fifteen second POSTPURGE period is
completed, the RM7840 reenters STANDBY.
19 65-0087—2
RM7840E,G,L,M
OPERATION
Fig. 17—RM7840E,L sequence.
RM7840E,L
POWER
00
OPERATING
CONTROLS
AND
INTERLOCKS
BURNER
FLAME
SIGNAL
FIRING
RATE
MOTOR
INITIATE
POWER
STANDBY
POWER
PREPURGE
DRIVE TO
HIGH FIRE
POWER
PILOT
FLAME
MAIN
POWER
PFEP
4 OR 10 SEC
PILOT
FLAME
MAIN
POWER
MFEP
PILOT
FLAME
MAIN
RUN
POWER
POSTPURGE
POWER
STANDBY
00
00 10 25 00 1520
RM7800E,L SWITCHING
MOTOR ACTION
BURNER/BLOWER MOTOR
IGN.
15 SEC. PILOT
LIMITS AND BURNER CONTROLLER CLOSED
LOCKOUT INTERLOCKS CLOSED
PREIGNITION INTERLOCK CLOSED
LOW FIRE SW.
SAFE START CHECK
FLAME PROVING
10 SEC. IGN./PILOT
8
10
5
5 SEC.
21
6
TO
7TO
20
TO
5
18
TO
13 15
TO
13 12
TO
M3357
INTERLOCK. CHECK
HIGH FIRE SW.
19
TO
13
14
TO
13 14
TO
5
4
6
L1
MAIN VALVE
9
FOR THE RM7840E: THE HIGH FIRE SWITCH MUST BE WIRED CORRECTLY TO PERFORM ENERGY SAVING PURGE
FUNCTIONS. THE BURNER/BLOWER MOTOR DOES NOT START UNTIL THE HIGH FIRE SWITCH HAS BEEN MADE.
1
1
1
TIMED
PURGE
POWER
FLAME
MAIN
PILOT
ALARM
POWER
FLAME
MAIN
PILOT
ALARM
ALARMALARMALARM
PREPURGE
DRIVE TO
LOW FIRE
00
IC
PII
SSC
LED
DISPLAY
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