Honeywell 7800 Series Manual page 25

Fig. 20— RM7888A Relay Module Pilot Sequuence timing diagram.
PV Return and MV Lo Fire
STANDBY
INPUT &
OUTPUT
SIGNALS
STANDBY-
PURGE
POWER
POWER
PILOT
FLAME
MAIN
ALARM
IGNITION- T10
PILOT- T8
MAIN- T9
AIR VALVE-T5
FLAME PROVEN- T21
ALARM- T3
MOTOR POSITION- T12-T15 L/H/MOD
@ LOW FIRE INPUT- T18
LIMITS COMPLETE- T7
SF1 SPECIAL FUNCTION- T6
SF2 SPECIAL FUNCTION- T17
SF3 SPECIAL FUNCTION- T19
SF4 SPECIAL FUNCTION- T20
FLAME SENSED
High/Low Stepfire sequence is used when the applica-
tion requires the burner flame to be switched, on command,
between a Low Fire and a High Fire Run state.
Off/On Stepfire sequence is used when the application
requires the burner flame to be switched, on command,
between a Standby state and a Main Flame state.
Each DSI operating sequence has several states. See
Table 7 for the state names, the text as shown on an S7800A
Keyboard Display Module, and a brief description of the
state purpose. All three sequences have the Standby state in
common.
PILOT
PILOT- MAIN BURNER
FUEL VALVE
IGNITION TRAIN
LAST 5- FUEL ON OPEN-PILOT
IGNITION
INFINITE TIMEOUT
SECONDS
0-INFINITE
TIME
1ST 10 SEC
POWER POWER
POWER
PILOT PILOT PILOT
FLAME FLAME FLAME
MAIN
L L L
RELEASE TO
BURNER
MODULATION
FUEL VALVE
OPEN-PILOT
TIMEOUT
LAST 5 TO RUN: 0 TO
1ST 10 SEC
INFINITE INFINITE SEC
POWER POWER
POWER
PILOT
PILOT PILOT
FLAME
FLAME FLAME
MAIN MAIN MAIN
L L MOD
WARNING
The user of the RM7888A is responsible for pro-
viding the correct signal to each special function
input terminal and must make sure that safety is
not compromised if an incorrect special function
input is applied.
25
PV Return Only
PILOT RELIGHT
PILOT DRIVE TO LOW
RELIGHT AFTER 10 SEC FIRE POSITION
WAIT FOR LOW
2 TO 5 SEC.
OFF FOR 5 SEC
(WITH 2-3 SEC.
AT LOW
5 TO INFINITE
10 SEC
SEC STABILIZE)
POWER POWER
POWER
PILOT PILOT PILOT
FLAME FLAME FLAME
MAIN
L MOD L
RM7888A
OPERATION
RETURN
TO MAIN
TRAIN
FUEL ON
STATE
M9497
65-0175