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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 and the
internal contacts close, time delay relay 2 (TD-2 )
receives 24 VAC.
51. Gas valve 1a is energized allowing the remainder
of stage 1 to fire.
52. After the 5-second countdown from TD-2 the inter-
nal contacts close allowing 24 VAC to sit at pin 3
of the stage 2 connection on the CPW board.
53. After closure of the stage 2 contacts Gas valve 2
is energized.
54. The stage 2 LED on the status display board is
now illuminated.
55. The temperature controller closes the stage 3 con-
tacts at J3 on the CPW board.
56. Power is applied to pin 5 of the stage 3 connec-
tions on the CPW board.
57. Power is applied to the “TH” terminal of ignition
module 2.
58. Once the “TH” signal is received at ignition module
2, the heater will perform a 15-second pre-purge,
and 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.)
59. If ignition module two locks out, a signal will be
sent to the Universal Diagnostics Board and to the
status display board to indicate an ignition fault.
60. Once the ignition module determines that the hot
surface igniter has heated up and operating prop-
erly, a 24 VAC signal is output from pin GV on the
module.
61. 24 VAC signal is received at gas valve 3 thus ener-
gizing it.
62. The stage 3 LED on the status display board is
now illuminated.
63. The coil of relay K-5 (N.O.) is now energized with
the (K-5) contacts closing downstream of the
stage 4 connections.
64. Remote flame sensor 2 is trying to rectify flame.
65. Power is now applied to time delay relay 3 and the
contacts of TD-3 located upstream of the stage 4
connection close after 5 seconds.
66. The stage 4 controller contacts close.
67. Power is applied to gas valve 4.
68. The stage 4 LED on the status display board is
now illuminated.
69. The heater is now operating at full fire.