the 120 VAC pilot duty terminals, located at
29.The 120 VAC signal continues to the coil of relay
30.The 120 VAC signal continues to the 120 VAC safety terminals located at
31.When the coil on relay
32.After proper air pressure is received in the air plenum, the air pressure switches will close.
33.Power is applied to the optional equipment inter- lock connection (normally jumpered).
34.The 24 VAC signal is then sent to the 24 VAC safe- ty connector.
35.24 VAC is now sent to the pressure switch (P Switch) terminal on the ignition modules.
36.Once the pressure switch signals are received at both ignition modules, hot surface igniter 1 is ener- gized by a 120 VAC signal from
37.Once ignition module 1 determines that hot sur- face igniter 1 has heated up and operating properly, a 24 VAC signal is output from terminal “valve” on module 1.
38.24 VAC signal is sent to gas valve 1.
39.The blue LED on the front of the unit is now illumi- nated.
40.The coil of relay
41.The gas coming through the burners should ignite from the heat of hot surface igniter 1 and the flame should carry over from one burner to the other burners of stage 1. The remote sensor is now try- ing to sense the flame. If the flame is not sensed within 4 seconds, the ignition module will shut down the gas valve and retry the hot surface ignit- er. During ignition retry the heater must perform a
42.After gas valve 1 opens and flame rectification is received, time delay relay 1
43.After the 5 second countdown from
44.After 5 seconds gas valve 1a is now energized allowing the remainder of stage 1 to fire.
45.After the
46.The temperature controller closes the stage 2 con- tacts and gas valve 2 in energized.
47.The temperature controller closes the stage 3 con- tacts at
48.24 VAC signal is received at gas valve 3 (Model 1259B only).
Models 1529B–2339B Only
49.Power is applied to the “TH” terminal of ignition module 2.
50.Once the “TH” signal is received at ignition module 2, hot surface igniter 2 is energized by a 120 VAC signal from
51.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 “valve” on the module.
52.24 VAC signal is received at gas valve 3.
53.The coil of relay
54.Remote flame sensor 2 is trying to rectify flame.
55.Power is now applied to time delay relay 3 and the contacts of
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