Sequence Of Operation - Honeywell RM7838B Installation Instructions Manual

RM7838B,C 7800 SERIES RELAY MODULE
3. PURGE Period
a. Preignition Interlock opens anytime during purge.
b. Flame signal detected during purge .
c. High Purge Rate Switch fails to close within four
minutes, fifteen seconds after the firing rate motor is
commanded to drive to high fire position.
d. Low Fire Start Switch fails to close within four min-
utes, fifteen seconds after the firing rate motor is
commanded to drive to low fire position.
e. Lockout Interlock does not close within five sec-
onds.
f. Lockout Interlock opens during purge .
g. Ignition/pilot valve/intermittent pilot valve terminal is
energized.
h. Main valve terminal is energized.
i. Internal system fault.
j. Purge card is not installed or removed.
k. Purge card is bad.
4. Purge Hold: T21
a. Preignition Interlock opens.
b. Flame is detected.
c. Lockout Interlock opens during Hold.
d. Ignition/pilot valve/main valve is energized.
e. Internal system fault.
f. Purge card is removed.
g. Purge card is bad.
5. PILOT FLAME ESTABLISHING Period (PFEP)
a. Low Fire Switch opens.
b. Lockout Interlock opens .
c. Ignition/pilot valve/intermittent pilot valve terminal is
not energized.
d. No flame is present at end of PFEP.
e. Internal system fault.
f. Purge card is not installed or removed.
g. Purge card is bad.
6. MAIN FLAME ESTABLISHING Period (MFEP)
a. Low Fire Switch opens.
b. Lockout Interlock opens .
c. Ignition/pilot valve/intermittent pilot valve terminal is
not energized.
d. Main valve terminal is not energized.
e. No flame is present at end of MFEP.
f. Internal system fault.
g. Purge card is not installed or removed.
h. Purge card is bad.
7. RUN Period
a. Flame is present.
b. Lockout Interlock opens.
c. Main valve terminal is de-energized.
d. Internal system fault.
e. Purge card is not installed or removed.
f. Purge card is bad.
8. Pilot Valve Hold
a. Low Fire Switch opens.
b. Lockout Interlock opens.
c. Ignition/pilot valve terminal is not energized.
d. No flame is present at end of PFEP.
e. Internal system fault.
f. Purge card is not installed or removed.
g. Purge card is bad.
h. Non Shutter Check Amplifier/Detector used.
66-1094—08
OPERATION

Sequence of Operation

The RM7838B,C has the operating sequences listed below.
The RM7838B,C LED provide positive visual indication of the
program sequence: POWER, PILOT, FLAME, MAIN and
ALARM. Fig. 5 and 6 show the operating sequences not using
pilot valve hold and using pilot valve hold, respectively.
Initiate
The RM7838B,C enters the INITIATE sequence when the
Relay Module is initially powered. The RM7838B,C can also
enter the INITIATE sequence if the Relay Module verifies
voltage fluctuations of +10/-15 percent or frequency
fluctuations of ±10 percent 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 is initiated and
displayed on the KDM for at least five seconds. When the
tolerances are met, the INITIATE sequence restarts. If the
condition is not corrected and the hold condition exists for four
minutes, the RM7838B,C locks out. Causes for hold
conditions in the INITIATE sequence:
a. ac line dropout detection.
b. ac line noise that prevents a sufficient reading of the
line voltage inputs.
c. Low line voltage brownouts.
The Alarm, terminal 3, is energized during INITIATE
(RM7838B only).
Standby
The RM7838B,C remains in STANDBY until the Burner
Control Switch is closed. Two seconds before leaving
STANDBY, the shutter circuit is energized and verifies that no
flame is present. The Alarm, terminal 3, is energized until
flame is sensed (RM7838B only).
Purge
The RM7838B,C provides PURGE timing selectable from two
seconds to thirty minutes. The RM7838C requires the
ST7800C Purge Timer for correct operation. The ST7800C
Purge Timer will not fit into an RM7838B.
1. Closing the burner control switch starts the recirculating/
exhaust blower. PURGE sequence begins when power
is applied to the RM7838B,C through the recirculating/
exhaust blower airflow switch, Stop Station, and the limit
string to terminal 6. The Run/Test switch and all
microcomputer-monitored circuits must also be in the
correct operating state.
2. The RM7838B,C Relay Module commands the firing
rate motor to the high purge rate position by closing a
circuit between terminals 12 and 13. PURGE timing
begins when the High Fire Switch closes, providing
input to terminal 19. Four minutes, 15 seconds are
provided for the High Fire Switch to close. A jumpered
High Fire Switch adds 30 seconds to the PURGE
timing.
3. When the PURGE timing is complete, the RM7838B,C
commands the firing rate motor to the low fire position
by closing a circuit between terminals 13 and 14 (termi-
nals 13 and 15 for the C1020). Four minutes, 15 sec-
onds are provided for the motor to reach the low fire
position.
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