Weather-Rite TT Series, Инструкция по установке, эксплуатации и обслуживанию

Страница: 105 / 205

SECTION 20: S
EQUENCE OF
O
PERATION
99 of 198
options; See Page 98, Figure 85 and Page 98, Table
39 . If necessary, clip the site-config u ra b le j u mpers
w ith side c u tters and remo v e the resistors from the
relay mod u le.
IMPORTANT
Clipping and remo v ing a j u mper after 200 ho u rs of
operation ca u ses a non-resetta b le Fa u lt 110. The
relay mod u le m u st then b e replaced.
The follo w ing w ill descri b e the internal operation of
the flame safeg u ard and the external f u nctions that
w ill take place. We w ill j u st trace the
electromechanical steps and not the electronic
net
w ork.
• Initiate
• The flame safeg u ard enters the INITIATE
seq u ence w hen the relay mod u le is initially
po w ered. The INITIATE seq u ence lasts for ten
seconds.
• Stand b y
• The flame safeg u ard is ready to start an operating
seq u ence w hen the operating control inp u t,
Terminal #6 recei v es po w er.
• Normal Start-Up Pre-p u rge
• The flame safeg u ard pro v ides PREPURGE
timing, w ith the ST7800 P u rge Timer card, for
se v en w ith po w er applied to Terminal #6.
• Ignition Trials
Pilot Flame Esta b lishing Period (PFEP):
A. When the PFEP b egins:
1. The pilot v al v e and ignition
transformer, terminals 8 and 10 are
energized.
2. Flame m u st b e pro v en b y the end
of the ten second PFEP to allo w the
seq u ence to contin u e. If a flame is not
pro v en b y the end of PFEP, a safety
sh u tdo w n occ u rs.
Main Flame Esta b lishing Period (MFEP):
After PFEP, and w ith the presence of flame,
the main f u el v al v e, terminal 9, is po w ered. If
a flameo u t occ u rs, the flame safeg u ard
recycles w ithin 0.8 or 3 seconds, depending
on the Flame Fail u re Response Time (FFRT)
of the amplifier.
R u n
The flame safeg u ard is no w in RUN and remains in
RUN u ntil the controller inp u t, terminal 6, opens,
indicating that the demand is satisfied or a limit has
opened.
20.5 Air Volume Control Options
20.5.1 Volumatic Dampers
This is a control option for v arying the total deli v ered
air v ol u me do w n to 20% of the air handler's
maxim u m airflo w capacity. It is u sed w hen the space
demands for make- u p air are not at a constant v al u e
d u e to exha u st fan cycling or en v ironmental changes.
The standard Vol u matic control option allo w s the air
handler's discharge damper to mod u late, w hich in
t u rns deli v ers the req u ired airflo w .
Methods of control for this option are b y a man u al
damper position controller (standard w ith this option),
Space Press u re controller w hich senses the space
press u re and makes v ol u me changes as req u ired.
The minim u m air position is preset from the factory
and may b e readj u sted in the field b y the u se of the
minim u m air damper positioner, located on the air
handlers control panel. It is adj u sted to pre v ent the
air handler from going b elo w the minim u m airflo w
req u ired for proper com bu stion. The profile damper
motor w hich maintains the proper air press u re drop
across the bu rner is electrically interlocked w ith the
discharge damper (master/sla v e operation). As the
discharge damper opens, the profile damper opens
proportionally to maintain the proper press
u re drop
across the bu rner. As the discharge damper closes,
the profile damper closes.
20.5.2 Volumatic Variable Fre q uency Drive
This is a control option for v arying the total deli v ered
air v ol u me do w n to 25% of the air handler's
maxim u m airflo w capacity. It is u sed w hen the space
demands for make- u p air are not at a constant v al u e
d u e to exha u st fan cycling or en v ironmental changes.
The VFD control option allo w s the air handler's
b lo w er v ary its speed, w hich in t u rns deli v ers the
req u ired airflo w .
Methods of control for this option are b y a Keypad
(standard w ith this option) or Space Press u re
controller w hich senses the space press u re and
makes v ol u me changes as req u ired.
The minim u m air position is preset from the factory
and may b e readj u sted in the field b y the u se of the
VFD's Keypad. It is adj u sted to pre v ent the air
handler from going b elo w the minim u m airflo w
req u ired for proper com bu stion. The profile damper
motor w hich maintains the proper air press u re drop
across the bu rner is electrically interlocked w ith VFD