Honeywell 7800 Series Manual page 23

WARNING
The Flame Proven output is an RM7888 safety out-
put, whose output status is monitored by RM7888A.
This output is to be used by external equipment that
can respond to the signal. The end user must assure
that the Flame Proven output cannot be misinter-
preted. Misinterpretation of this signal could create
a hazardous situation, resulting in fire or explosion
that can cause damage, serious injury or death.
Pilot Ignition-(Hold)
After the five second period following the ten-second
pilot establishing period has expired, the RM7888A will
respond to special functions 2 and 3. If special functions 2
and 3 are both de-energized, or if special function 2 is de-
energized and special function 3 is energized, the pilot state
will continue indefinitely. If, after four minutes, special
function 2 does not become energized, the alarm will be
commanded on. If special function 2 is still de-energized
after an additional four minutes (eight minutes total), a lock-
out will occur.
If special function 2 becomes energized and special func-
tion 3 is de-energized, the pilot state will sequence to the
Main Train Fuel On state. If special functions 2 and 3 both
become energized at the same time, the pilot state will se-
quence to the Burner Fuel Valve Open/Pilot Timeout state,
bypassing the Main Train Fuel On state.
Main Train Fuel On
At Main Train Fuel On, the Air Valve and the Main Fuel
are commanded on. The motor position will continue at Low
Fire, and the pilot valve will stay on. The sequence will lock-
out if either the Low Fire input, or the Limits Complete de-
energize, or a flame failure occurs.
The Main Train Fuel On state will proceed to the Burner
Fuel Valve Open/Pilot Timeout state as soon as special
function 3 becomes energized in addition to special func-
tion 2. If special function 2 becomes de-energized after the
first two seconds while in the Main Train Fuel On state, a
lockout will occur. After four minutes, if special function 3
does not become energized, the alarm will be commanded
on. After an additional four minutes, if special function 3 is
still de-energized, a lockout will occur.
Burner Fuel Valve Open/Pilot Timeout (Main Flame
Establishing)
During Burner Fuel Valve Open/Pilot Timeout, the
main flame will be established and the pilot extinguished.
When the Burner Fuel Valve Open/Pilot Timeout state
is entered, the pilot, main, and Air Valve will be com-
manded on, the ignition commanded off, the motor position
to low fire, and a ten second timer starts.
A lockout will occur if the Low Fire input or the Limits
Complete becomes de-energized, or a flame failure occurs,
or Flame Proven output is de-energized. After the first two
seconds, a lockout will occur if the special function 2 or 3
de-energize.
At the end of the ten second period, the pilot is com-
manded off and a five second minimum flame stabilization
period begins. When the stabilization period is completed,
the RM7888A will respond to the status on special function 4.
If special function 4 is energized, the sequence will proceed
to the Release to Modulation state (Run state).
If special function 4 is de-energized, the sequence will
remain indefinitely at the Main Flame Low Fire state. A lock-
out will occur if the Pilot, Ignition or Main Valve outputs are
not in the commanded states, if the flame is lost, if special
function 2 or 3 becomes de-energized, or Flame Proven output
is de-energized.
Release to Modulation State (Run State)
When the Release to Modulation state is entered, the
only change in the commanded output status is the motor
position; it is commanded to Modulate instead of Low Fire.
The sequence will lockout if the Limits Complete be-
comes de-energized, a flame failure occurs, special function
2 or 3 becomes de-energized, or Flame Proven output is de-
energized.
If the site configurable jumpers are configured to in-
clude Pilot Relight (PV Return Sequence) Pilot Relight is
initiated as follows. When the motor position is Modulate
and the Low Fire input is energized during the Release to
Modulation state for a continuous time period of ten sec-
onds, the sequence will proceed to the Pilot Relight state.
Normally, the requirements of the process will be sufficient
to keep the modulating control above the Low Fire position.
If the site configurable jumpers are configured to ex-
clude Pilot Relight (MV Lo Fire Sequence), Pilot Relight
will not be initiated; the burner modulates to Low Fire
during the Run state and remains there until the RM7888A
is commanded off (Standby).
Run-Low Fire(part of Run State)
If special function 4 becomes de-energized during the
Run state, the sequence will command the motor position to
Low Fire and start a 240-second timer. If the @Low Fire
input fails to energize or becomes de-energized after the time
period has expired while special function 4 remains de-
energized, the alarm output will be made active. If special
function 4 becomes energized, the time period measurement
will end and the normal Release to Modulation (Run) state
will be active.
Pilot Relight—PV Return Sequence Only
When the Pilot Relight state is entered, the Ignition, Pilot,
Main, and Air Valve will be commanded on, the motor posi-
tion will be commanded to Low Fire and a ten second timer
will be started. Flame Proven remains on.
The sequence will lockout if the Limits Complete de-
energizes or a flame failure occurs. Lockout will also occur
if the Low Fire input or special function 2 or 3 becomes de-
energized during Pilot Relight.
At the end of the ten-second period, the Wait for Low
Off state is entered. The ignition, main valve and Air Valve
are commanded off, the Pilot remains commanded on, and
23
RM7888A
OPERATION
65-0175