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

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SECTION 20: S
EQUENCE OF
O
PERATION
97 of 198
• All interlocks, control relays and safety limits are
closed. Po w er is s u pplied to terminal #7 of the
flame safeg u ard.
• The Operating Control LED ill u minates.
• The electronic net w ork is no w po w ered u p w hich
ill u minates the Air Flo w LED.
NOTE: The airflo w circ u it of the safeg u ard control is
not u sed and is j u mped. This is w hy the Air Flo w LED
ill u minates w ith the Operating Control LED.
• Follo w ing a time delay period (p u rge cycle) 7
seconds. The electronic net w ork closes a contact
that po w ers u p terminal #3 and terminal #4 in the
safeg u ard control.
• Terminal #3 po w ers u p the eq u ipment's pilot gas
solenoid v al v e w hich opens allo w ing gas to flo w .
• Terminal #4 po w ers u p the ignition mod u le
creating the spark at the bu rner.
• This lasts for 10 seconds. This cycle is called trial
for ignition. D u ring this time period, the PTFI LED
is ill u minated.
• When the flame sensor detects a pilot flame, the
signal is sent b ack to the safeg u ard control. The
electronic net w ork ill u minates the FLAME LED.
• It closes an internal contact, w hich po w ers u p
terminal #5 in the control. This terminal po w ers u p
the main gas v al v es allo w ing the main bu rner to
come on.
• At the same time that the contact in step b closes,
the electronic net w ork opens a contact, w hich
po w ers terminal #4. This sh u ts off the po w er to
the ignition mod u le, w hich stops the spark at the
bu rner. The safeg u ard control at this point
monitors the flame.
NOTE: If a pilot flame is not detected d u ring the 10
second trial for ignition, the pilot gas solenoid v al v e
and the ignition mod u le are t u rned off. A safety
locko u t occ u rs w hich sh u ts do w n the electronic
net w ork. The only LED that w ill b e ill u minated at this
time w ill b e the OPERATING CONTROL. 30 seconds
after the locko u t has acti v ated, the alarm circ u it is
po w ered u p, ill u minating the ALARM LED. Man u al
reset is no w req u ired. Wait 10 seconds b efore
resetting the control to allo w the locko u t s w itch to
cool do w n.
NOTE: If the flame signal is lost w hile the bu rner is
on, the pilot and main gas v al v es w ill b e t u rned off. A
safety locko u t occ u rs w hich sh u ts do w n the
electronic net w ork. The only LED that w ill b e
ill u minated at this time w ill b e the OPERATING
CONTROL. Thirty seconds after the locko u t has
acti v ated, the alarm circ u it is po w ered u p,
ill u minating the ALARM LED. Man u al reset is no w
req u ired. Wait 10 seconds b efore resetting the control
to allo w the locko u t s w itch to cool do w n.
FIGURE 8 4: Honeywell RM7 8 97
20.4.3 Honeywell RM7 8 97 Flame Safe g uard
The color of this control is b l u e and it has a reset
bu tton extending o u t from it. It consists of three
components, w hich are:
1. The RM7897 chassis contains the main hard-
w are. It also has mo u nted on its exterior, fi v e
(5) lights w hich indicate the operating stat u s of
the control.
2. The ST7800 P u rge Timer Card w hich deter-
mines the pre-p u rge time for the control -
defa u lt is 7 seconds.
3. The R7847 (flame rod) or R7849 ( u ltra v iolet)
rectifier/amplifier mod u le pro v ides the flame
scanning capa b ility and the flame fail u re
response time. On its exterior are test jacks,
w hich permit flame signal meas u rement d u ring
operation.
The f u nctions of the indicator lights, w hich are
located on the main chassis, are as follo w s. They are
listed in the order yo u w ill find them on the flame
safeg u ard. This is also the order in w hich they w ill
occ u r in the seq u ence.
1. Power - this indicator is on w hen po w er is
present at terminal #5 of the flame safeg u ard.
BUR N ER CO N TROL
BUR N ER FLAME CO N TROL
FLAME AMPLIFIER
+
-
- N egative + Positive
5.0 V DC