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36. After proper air pressure is received in the air
plenum, the air pressure switches will close.
37. If there is insufficient air pressure and the air pres-
sure switch does not close, a 24 VAC signal is sent
to the Universal Diagnostics Board to indicate the
fault.
38. A 24 VAC signal is now sent to the blower LED’s
on the status board.
39. Power is applied to the optional equipment inter-
lock connection (normally jumpered).
40. The 24 VAC signal is then sent to the 24 VAC safe-
ty connector.
41. 24 VAC is now sent to the pressure switch (P.S.)
terminal on the ignition modules.
42. Once the pressure switch signal is received at
ignition module one, the heater performs a 15 sec-
ond pre-purge, then hot surface igniter one is
energized by a 120 VAC signal from S-1 on igni-
tion module one for approximately 30 seconds.
(The hot surface igniter must draw greater than
3.1 amps while being energized or ignition lockout
will occur after three tries.)
43. Once ignition module one determines that hot sur-
face igniter one has heated up and operating
properly, a 24 VAC signal is output from pin GV on
module one.
44. 24 VAC signal is received at gas valve 1 thus ener-
gizing it.
45. The stage 1 LED on the status display board is
now illuminated.
46. The coil of relay K-2 is now energized with the
N.O. contacts closing downstream of the stage 2
and upstream of the stage 3 connections.
47. The gas coming through the burners should ignite
from the heat of hot surface igniter one and the
flame should carry over from one burner to the
other burners of stage 1. Remote flame sensor
one is now trying to sense the flame. If the flame
is not sensed within 4 seconds, the ignition mod-
ule will shut down gas valve 1 and retry hot
surface igniter one. During ignition retry the heater
must perform a 15-second pre-purge and approx-
imately a 30-second igniter warm-up before
opening gas valve 1 again. The standard ignition
module will attempt ignition a maximum of three
times prior to ignition lockout.
48. If ignition module one locks out, a signal will be
sent to the Universal Diagnostics Board and to the
status display board to indicate an ignition fault.
49. When power is sent to gas valve 1 it is also sent to
time delay relay 1 (TD-1) which starts a 5-second
countdown.
50. After the 5-second countdown from TD-1, 24 VAC
is waiting at pin 3 of the stage 2 connections on
the CPW board.
51. After closure of the stage 2 contacts Gas valve 2
is energized.
52. The stage 2 LED on the status display board is
now illuminated.
53. Power is applied to pin 5 of the stage 3 connec-
tions on the CPW board.
54. The temperature controller closes the stage 3 con-
tacts at J3 on the CPW board.
55. Power is applied to the “TH” terminal of ignition
module 2.
56. Once the “TH” signal is received at ignition module
2, the heater performs a 15 second pre-purge,
then hot surface igniter 2 is energized by a 120
VAC signal from S-1 on ignition module 2 for
approximately 30 seconds. (The hot surface ignit-
er must draw greater than 3.1 amps while being
energized or ignition lockout will occur after three
tries.)
57. Once ignition module 2 determines that hot sur-
face igniter two is operating properly, a 24 VAC
signal is sent to energize gas valve 3.
58. The stage 3 LED on the status display board is
now illuminated.
59. The gas coming through the stage 3 burners
should ignite from the heat of hot surface igniter
two and the flame should carry over from one
burner to the other burners of stage 3. Remote
flame sensor two is now trying to sense the flame.
If the flame is not sensed within 4 seconds, the
ignition module will shut down gas valve 3 and
retry the hot surface igniter. During ignition retry
the heater must perform a 15-second pre-purge
and approximately a 30-second igniter warm-up
before opening gas valve 3 again. The standard
ignition module will attempt ignition a maximum of
three times prior to ignition lockout.