Honeywell 7800 Series Installation Instructions Manual page 22

RM7888A 7800 SERIES RELAY MODULE
Pilot Configuration Ignition Trials
(PV Return and MV Lo Fire
Sequences)
Pilot Ignition State
Pilot Ignition is entered only from the Standby state with
the Limits Complete and Low Fire input signals energized,
Special Function input 1 (terminal 6) energized and the Air
Valve either on or off, depending on which Standby state
preceded the Pilot Ignition state.
At the start of the Pilot Ignition state, the ignition and pilot
outputs are commanded on, Low Fire is commanded, and
the Air Valve is commanded off. The RM7888A will lockout
if the Low Fire input becomes de-energized after the first
two seconds of the Pilot Ignition state. A one- to two-
second transition state precedes the Pilot Ignition state so
Special Function 2
(Terminal 17)
De-energized De-energized
De-energized De-energized
De-energized Energized
Energized Energized
De-energized Energized
Energized De-energized
Energized De-energized
Energized Energized
WARNING
The Flame Proven output is an RM7888 safety
output, 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 misinterpreted.
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
deenergized 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 lockout will occur.
If special function 2 becomes energized and special
function 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 sequence to the Burner Fuel Valve Open/Pilot Timeout
state, bypassing the Main Train Fuel On state.
32-00214—01
Table 8. Special Function Inputs/Output States During Standby.
Special Function 3 Special Function 4
(Terminal 19)
De-energized
Energized
Energized
Energized
De-energized
De-energized
Energized
De-energized
the Low Fire switch has at least three seconds to stabilize.
This reduces the possibility of a contact bounce causing a
lockout. The RM7888A will lockout if the Limits Complete
input becomes de-energized.
For the first ten seconds, the Pilot Ignition state attempts
to establish a pilot flame. If, at the end of ten seconds, a
pilot flame has not been established, a lockout will occur.
Otherwise, with a flame established, the igniter is
commanded off, the Flame Proven output is commanded
on and the pilot flame continues. This pilot state, with only
the pilot output on and a pilot flame proven, will continue
for at least five seconds, but may continue indefinitely
depending on the status of the special function input
terminals.
If a flameout occurs any time after this point in the burner
sequence, a lockout will occur.
(Terminal 20)
De-energized
Energized
Energized
Energized
Energized
Energized
Energized
Energized
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
lockout if either the Low Fire input, or the Limits Complete
deenergize, 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
function 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 commanded
on, the ignition commanded off, the motor position to low
fire, and a ten second timer starts.
22
Air Valve Motor Position
Output Commanded
Low Fire
High Fire
Modulate
Low Fire
Modulate
Low Fire
Low Fire
Low Fire