![Daikin FC Series Скачать руководство пользователя страница 15](http://html.mh-extra.com/html/daikin/fc-series/fc-series_installation-and-maintenance-manual_502014015.webp)
Typical Sequence of Operation (3-1 gas burner)
with no MicroTech III Control System
When the rooftop unit is energized, 120 V power is supplied
through the System ON-OFF switch (S1) to the Heat ON-OFF
contacts . Upon a call-for-heat, the Heat ON-OFF contact will
close, energizing the Relay (R20) which supplies power to
the Burner ON-OFF switch (S3) . The Burner ON-OFF switch
(S3) will power the Modulating Gas Valve Actuator (VM1) and
Terminal 5 (L1) on the Flame Safeguard (FSG) .
When the 120 V power is furnished through the System ON-
OFF switch (S1) through the Burner ON-OFF switch (S3),
Relay (R20) contacts, High Limit Control (FLC) and Terminal 6,
the Flame Safeguard (FSG) is powered . The Flame Safeguard
(FSG) energizes its Terminal 4 which powers the Burner
Combustion Air Blower Motor (BM) . The Blower operation is
sensed by the Air Switch (AS) which initializes Terminal FSG-6
and FSG-7 for a prepurge cycle . Whenever power is supplied
to the Flame Safeguard, it will go through a 10 second initiation
period before the prepurge begins .
The Burner Air Control Valve is at the minimum position during
OFF cycles . Upon a call-for-heat or any other time a prepurge
cycle occurs, the Air Control Valve is set to the maximum
position for prepurge operation . It is returned to the minimum
position for a Low-Fire Start . Blower operation sensed by the
Air Switch (AS) initializes Terminals 6 and 7 and after a 30
second prepurge period, Terminal 8 (Pilot Gas Valve [GV1])
and Terminal 10 (Ignition Transformer [IT]) will energize . If the
process is complete, the pilot flame will ignite and be detected
by the Flame Safeguard (FSG) through the Flame Rod (FD) .
Terminal 10 (Ignition Transformer [IT]) will de-energize when
the pilot flame is detected. Terminal 9 (Main Gas Valve [GV2])
energizes and the main flame will ignite. The Flame Safeguard
(FSG) contains an LED at the lower left corner which will glow
to indicate operation. The firing rate of the burner is determined
by a 2–10 vDC signal (field-supplied) to the Gas Valve Actuator
(VM1). This actuator positions a butterfly gas valve and
combustion air damper. It sets the firing rate between 33% and
100% of the normal rate .
A Low-Fire Start is controlled by Relay (R23) and the Gas
Valve Actuator Auxiliary contacts (VM1–AUX) . Relay (R23)
sets the Gas Valve Actuator (VM1) to the minimum firing rate
position and holds the position until a flame has been detected.
When the Gas Valve Actuator is at the minimum firing position,
the Gas Valve Actuator Auxiliary contacts (VM1–AUX) are
closed, Relay (R22) is energized and the R22 contacts are
closed . Gas Valve Actuator (VM1) is required to be at the
minimum firing position for pilot ignition.
Terminals 4, 8, 9, 10 and the Burner are de-energized if the
pilot flame fails to ignite or the Flame Safeguard (FSG) fails to
detect a pilot flame within 10 seconds. The Flame Safeguard
(FSG) switches to safety lockout and must be manually reset .
This failure will energize the Heat Alarm Relay (R24) and
send a fail signal to the Heat Fail contacts located on the main
control schematic .
If the unit overheats, a High Limit Control (FLC) cycles the
Burner, limiting the furnace temperature to the limit control
setpoint .
Start-Up and Operating Procedures
www .DaikinApplied .com 15
IM 684-6 • ROOFTOP SYSTEMS