Operation - Honeywell 7800 Series Product Data

OPERATION

Sequence of Operation
The RM7896 has the following operating sequences (see
Fig. 15, 16 and 18).
INITIATE
The RM7896 enters the INITIATE sequence when the Relay
Module is powered. The RM7896 can also enter the INITIATE
sequence if the Relay Module verifies voltage fluctuations of
+10/-15% or frequency fluctuations of +/- 10% during any part
of the operating sequence. The INITIATE sequence lasts for
ten seconds unless the voltage or frequency tolerances are
not met. When the tolerances are not met, a hold condition
will be initiated and will be displayed on the optional VFD for
at least five seconds. When the tolerances are met, the
INITIATE sequence will restart. If the condition is not
corrected and the hold condition exists for four minutes, the
RM7896 will lockout. Causes for hold conditions in the
INITIATE sequence are:
• AC line dropout is detected.
• AC line frequency error caused by using a 60 Hz device
on a 50 Hz line, or vice versa.
• AC line noise that can prevent a sufficient reading of the
line voltage inputs.
• Brownouts caused by a low line voltage.
LED
DISPLAY
BURNER
START
OPERATING
CONTROLS
AND
INTERLOCKS
FLAME
SIGNAL
1
00
INITIATE STANDBY START
POWER POWER POWER
BURNER/BLOWER MOTOR
LIMITS AND BURNER CONTROLLER CLOSED
1 AIRFLOW SW. CHECK AIRFLOW INTERLOCK CLOSED
SAFE START CHECK
AIRFLOW SWITCH CHECK FEATURE IS FOR THE RM7896B.
Fig. 15. RM7896A,B sequence.
7800 SERIES RM7896A,B,C,D RELAY MODULE
The INITIATE sequence also delays the burner motor starter
from being energized and de-energized from an intermittent
AC line input or control input.
STANDBY
The RM7896 is ready to start an operating sequence when the
operating control input determines a call for heat is present.
The burner switch, limits, operating limit control and all
microcomputer monitored circuits must be in the correct state
for the RM7896 to continue into the PREPURGE sequence.
NORMAL START-UP
PREPURGE
The RM7896 provides a selectable PREPURGE timing from
two seconds to 30 minutes with power applied and the
RM7896 operating control indicating a call for heat .
a. Airflow Interlock, burner switch, Run/Test Switch and all
microcomputer monitored circuits must be in the correct
operating state.
b. The blower motor output, terminal 4, is powered to start
the PREPURGE sequence.
c. The Airflow Interlock input must close ten seconds in
PREPURGE or within the specified purge card timing;
otherwise, a recycle to the beginning of PREPURGE or
lockout will occur depending on how the airflow switch
selectable jumper is configured.
00 00
TIMED PFEP
PURGE 4 OR 10 SEC RUN
POWER POWER POWER
PILOT
PILOT PILOT
FLAME
FLAME FLAME
MAIN
MAIN MAIN
ALARM ALARM ALARM
4
1
IGN.
10
IGN./ PILOT 8
MAIN VALVE
L1 TO 6
6 TO 7
FLAME
PROVING
17
POST PURGE
15 SEC
STANDBY
POWER POWER
9
AFSC
SSC
M7549
65-0193