Honeywell 7800 Series Installation Instructions Manual page 26

RM7888A 7800 SERIES RELAY MODULE
WARNING
The user of the RM7888A is responsible for
providing an effective purge that meets the
approval of the authority having jurisdiction for a
particular installation. The RM7888A does not
directly monitor the presence or absence of
airflow and cannot guarantee that the air valve
or fan is working. Failure to provide an effective
purge can result in a fire or explosion, causing
damage, serious injury or death.
NOTE: When special function 1 is energized, the
RM7888A will sequence to the initial DSI state
based on the setting of the configuration jump-
ers. A hold, as previously defined, will prevent the
sequence from exiting the Standby state.
Normal—Part 1
The Normal—Part 1 state is entered only from the Standby
state with the Limits Complete signal and @Low Fire input
on, and special function 1 energized. On entry, the Air
Valve will be commanded off, the Ignition and Pilot (Low
Fire Valve) outputs are commanded on, and Low Fire
position is commanded. The Main Valve and Flame Proven
outputs are commanded off. The RM7888A will lockout if
the @Low Fire input becomes de-energized after the first
two seconds of the Normal—Part 1 state. A one- to
twosecond transition state precedes the Normal—Part 1
state so the Low Fire switch has at least three seconds
(total) to stabilize. This reduces the chance of a nuisance
lockout due to a contact bounce on the @Low Fire input.
The RM7888A will lockout if the Limits Complete is de-
energized.
For the first four seconds, the Normal—Part 1 state
attempts to establish a Pilot (Low Fire Valve) flame. At the
end of the first four seconds, the Ignition output is
commanded off. If flame has not been established, a
lockout will occur. With flame established, an indefinite
hold will occur if special function 2 is de-energized and
the Flame Proven output is commanded on. Otherwise,
with flame established and special function 2 energized,
the Normal— Part 2 state is entered.
WARNING
The Flame Proven output is an RM7888A safety
output with an output status monitored by the
RM7888A. This output is used by external
equipment which 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.
Normal—Part 2
Upon entry, the igniter is commanded off, the Flame
Proven output is commanded on, and the Main Fuel Valve
and Air Valve are commanded on. The Pilot (Low Fire)
Valve remains on. The commanded Low Fire motor
position is unchanged. This state will continue for five
seconds. A flame failure will result in a lockout. A lockout
will also occur if the @Low Fire input becomes de-
energized during this state. Special function terminal 2 is
32-00214—01
ignored during this timed period. At the end of the timed
period, the sequence will go back to the end of the
Normal—Part 1 state if special function 2 is de-energized.
If special function 2 is energized and special function 4 is
de-energized, a Hold will occur. If special function 4 is
energized, the sequence will proceed to the Normal—Part
3 state.
Normal—Part 3
All commanded outputs remain unchanged. The igniter is
commanded off and Flame Proven output, Pilot (Low Fire
Valve), Main Fuel Valve and Air Valve are commanded on.
The sequence will lockout if the Limits Complete is de-
energized or a flame failure occurs. The sequence will
lockout if special function 2 is de-energized. and special
function 4 is energized. If special functions 2 and 4 are
energized , the motor position will be Modulated. If special
function 2 is energized and special function 4 is de-
energized, the commanded motor position will be the Low
Fire position and an alarm will occur if the Low Fire input
is de-energized after four minutes. If special functions 4
and 2 are both de-energized, an alarm will occur if the Low
Fire input is de-energized anytime after four minutes and
a lockout will occur after a total of eight minutes has
elapsed. If special functions 2 and 4 are de-energized, the
sequence will return to the end of the Normal—Part 1 state
when the Low Fire input is energized (after a two- to
threesecond Debounce period). Otherwise, the Normal—
Part 3 state will proceed to Standby when special function
1 becomes de-energized.
NOTE: For High/Low Stepfire and Off/On Stepfire
sequences, the @Low Fire input (Low Fire switch)
is not used but must be jumpered to prevent a
Hold condition in Standby.
High/Low Stepfire—Part 1
High/Low Stepfire—Part 1 is entered only from the
Standby state with Limits Complete and @Low Fire inputs
energized and special function 1 energized. Upon entry to
this state, the Igniter and the Pilot (Low Fire Valve) are
commanded on, and the motor position is commanded to
Low Fire. The Main Valve, Air Valve and Flame Proven
outputs are commanded off.
HIGH/LOW STEPFIRE—PART 1 LASTS FOR FOUR
SECONDS.
The @Low Fire input is ignored during this state, and
special functions 2, 3 and 4 are ignored. If, at the end of
the timed period, the flame has not been established, a
lockout will occur. Otherwise, with flame established, the
High/ Low Stepfire—Part 2 is entered.
High/Low Stepfire—Part 2
Upon entry to this state, the Pilot (Low Fire) Valve is
commanded on, the Igniter and Main Valve are
commanded off, the Flame Proven output is commanded
on, the commanded motor position is Low Fire and a two-
second timer is started. A lockout will occur if a flame
failure occurs. Special functions 3 and 4 are ignored.
The High state will be entered if special function 2 is
energized and the two-second timer has expired.
Otherwise, High/Low Stepfire—Part 2 continues. The
@Low Fire input is ignored during this state.
26