RM7838B,C 7800 SERIES RELAY MODULE
15 66-1094—08
4. When the Low Fire Proving Switch is proven (input on
terminal 18), the RM7838B,C commands the Combus-
tion Blower to turn on through terminal 5. A jumpered
Low Fire Switch adds 30 seconds to the PURGE timing.
5. The RM7838C will wait indefinitely for the Combustion
Airflow Switch , terminal 7, to close. Once closed, five
seconds are provided for it to stabilize. Safety shutdown
occurs if the Combustion Blower Airflow Switch opens
after this five-second period, during ignition trials or
RUN.
6. The RM7838B,C waits indefinitely for the Start Input to
terminal 21.
7. The Preignition Interlock must remain closed throughout
PURGE timing or a safety shutdown occurs.
8. The Alarm is powered during PURGE timing (RM7838B
only).
Ignition Trials
Ignition trials begin when the momentary Start input is
received at terminal 21 of the RM7838B,C. The RM7838B,C
locks out if the Start Switch is not released.
1. Pilot Flame Establishing Period (PFEP):
a. When the PFEP begins:
(1) The pilot valve and ignition transformer,
terminals 8 and 10, are energized.
(2) Five seconds into PFEP, Ignition terminal 10 is
de-energized.
(3) Flame must be proven by the end of the ten
second PFEP (four seconds if Configuration
Jumper JR1 is clipped); to allow the sequence to
continue. If a flame is not proven by the end of
PFEP, a safety shutdown occurs.
(4) During PFEP, the Low Fire Switch must remain
closed. If it opens, a safety shutdown occurs.
(5) The Preignition Interlock input is ignored
throughout the Ignition Trial state.
(6) The alarm output stops when flame is proven.
(RM7838B only)
(7) The RM7838B,C (except C1020):
(a)holds indefinitely, waiting for Manual Open
Valve command (terminal 17).
(b)holds indefinitely with a Pilot Valve Hold
command present on terminal 16.
(c)automatically sequences to Main Flame
Establishing Period (MFEP) if the
configuration jumper JR3 was clipped and the
Pilot Valve Hold Command is not present.
Manual Open Valve input, terminal 17, must
be closed at the end of MFEP.
b. With flame proven, the alarm, terminal 3, is
de-energized (RM7838B only).
2. Main Flame Establishing Period (MFEP) (except C1020
as it does not have a manual open valve switch input):
a. With the configuration jumper JR3 intact, the
RM7838B,C waits for Manual Open Valve Switch
input to terminal 17 through a Manual Open Valve
Switch. With the configuration jumper JR3 clipped
and the Pilot Valve Hold command on terminal 16
open, the RM7838B,C initiates immediate MFEP.
(1) Main valve terminal 9 is energized by the
RM7838B,C and the relay module is in the RUN
period.
(2) If configuration jumper JR2 is clipped, ten sec-
onds after terminal 9 is energized (15 seconds
for the C1004, 5 seconds for the C1020), the
pilot valve terminal 8 is de-energized. If flame is
lost during this MFEP, safety shutdown occurs
and the ALARM sounds.
(3) If configuration jumper JR3 is clipped, a Manual
Open Valve Switch input must be present at ter-
minal 17 at the end of the MFEP or safety shut-
down occurs and the Alarm sounds.
b. The C1020 proceeds immediately to a 5 sec MFEP.
Run
1. The RM7838B,C releases the firing rate motor to
modulation (terminals 13 and 15 are closed) (terminal
13 and 14 for C1020).
2. The RM7838B,C is now in RUN and remains in RUN
until the controller input, terminal 6, opens (burner
control opens, Stop Switch is pushed, running interlocks
open, a limit opens, Run/Test is switched to Test),
indicating that the demand is satisfied or a limit opened,
or the Pilot Valve Hold (terminal 16) is energized.
Pilot Valve Hold (except C1020)
Pilot Valve Hold (switched line voltage input to terminal 16)
allows the burner to be cycled back to Pilot from the Run
position without the need to do a complete burner startup.
This allows for batch loading in process applications.
A shutter-type flame detection system is required to use the
Pilot Valve Hold function.
Pilot Valve Hold can also be used to hold the burner at the end
of PFEP if configuration jumper JR3 was clipped.
A switch closure to the RM7838B,C terminal 16 while in the
Run position initiates the Pilot Valve Hold:
1. RM7838B,C commands the firing rate motor to Low Fire
position.
2. Once Low Fire is proven (input to terminal 18 through
Low Fire Switch), the pilot valve terminal is energized.
3. Forty-five seconds later, the main valve terminal is
de-energized and the ignition terminal is energized for
ten seconds, then shut off.
4. Pilot valve, terminal 8, remains energized throughout
Pilot Valve Hold.
5. RM7838B,C remains in Hold as long as a Pilot Valve
Hold input is present on terminal 16.
6. Opening the Pilot Valve Hold input to terminal 16 puts
the RM7838B,C ready to initiate MFEP.
The RM7838B,C goes into safety shutdown and sounds the
Alarm if flame is lost at any time during this sequence.
NOTE: A Shutter Check Detection System must be in place
to use the Pilot Valve Hold function. Fault 46 occurs
along with safety shutdown.
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