Honeywell 7800 Series Installation Instructions Manual page 27

High State
Upon entry to High State, the Main and Air Valves are
commanded on, and the Pilot (Low Fire Valve) and Flame
Proven outputs are commanded on. A two-second timer is
started. The commanded motor position is changed from
Low Fire to Modulate. A lockout will occur if a flame failure
occurs. The @Low Fire input and special functions 3 and 4
are ignored.
The High/Low Stepfire—Part 2 state will be re-entered if
special function 2 is de-energized and the two-second
time has expired. Otherwise, High State will continue until
special function 1 is de-energized, causing entry to
Standby.
Off/On Stepfire—Part 1
Off/On Stepfire—Part 1 is entered only from the Standby
state, with Limits Complete, @Low Fire and special
function 1 energized. When Off/On Stepfire—Part 1 is
entered, the igniter, Pilot (Low Fire Valve) and Air Valve are
commanded on, while the Main Valve and Flame Proven
are commanded off. The commanded motor position is
Modulate. Part 1 lasts for four seconds.
The flame signal and @Low Fire inputs are ignored during
this state while a Pilot/Low Fire (flame) is being
established. The sequence will lockout if Limits Complete
RM7888A 7800 SERIES RELAY MODULE
becomes de-energized. Special functions 2, 3 and 4 are
ignored. At the end of the time period, if the flame has not
been established, a lockout will occur. Otherwise, with the
flame established, Off/On Stepfire—Part 2 is entered.
Off/On Stepfire—Part 2
When On/Off Stepfire—Part 2 is entered, the igniter is
commanded off and the Pilot (Low Fire) Valve, Main Valve
and Flame Proven are commanded on. The commanded
motor position remains at modulate. Special functions 2,
3 and 4 are ignored. The RM7888A will lockout if a flame
failure occurs. The @Low Fire input is ignored during this
state. The sequence will lockout if the Limits Complete
becomes de-energized. Off/On Stepfire—Part 2 proceeds
to Standby if special function 1 becomes de-energized.
Lockout
Lockout is entered when a timed sequence hold expires or
a signal is not in the required state. The RM7888A DSI
configuration sequence description details the conditions
under which the sequence will lockout.
Figs. 22 through 24 show the timing relationship between
the RM7888A inputs and outputs for each sequence state
during DSI Normal, DSI High/Low Stepfire and DSI Off/On
Stepfire sequences.
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