Furnace Section Controls And Ignition System; Normal Furnace Operating Sequence - Rheem RRNA-B SERIES Installation Instructions Manual

TABLE 6
FIELD WIRE SIZE FOR 24 VOLT THERMOSTAT CIRCUITS
SOLID COPPER WIRE - AWG.
3.0 16
2.5 16
2.0 18
50
(1) The total wire length is the distance from the furnace to the
thermostat and back to the furnace.
NOTE: DO NOT USE CONTROL WIRING SMALLER THAN NO. 18
A WG.
22
14 12 10
14 12 12
16 14 12
100 150 200 250
Length of Run – Feet (1)
X. FURNACE SECTION CONTROLS AND

NORMAL FURNACE OPERATING SEQUENCE

This unit is equipped with an integrated direct spark ignition control.
1. The thermostat calls for heat.
2. The control board will run a self check to verify that the limit control and manual reset
overtemperature control are closed and that the pressure switch is open. If so, the
induced draft blower (inducer) begins a prepurge cycle.
3. The air proving negative pressure switch closes.
4. 15 seconds after the pressure switch closes, the gas valve opens and the spark is
initiated for a 7 second trial for ignition.
5. Burners ignite and flame sensor proves all burners have lit.
6. The circulating air blower is energized after 30 seconds.
7. The control board enters a normal operation loop in which all safety controls are moni-
tored continuously.
8. Thermostat is satisfied and opens.
9. The gas valve is de-energized and closes, shutting down the burner flame.
10. The control board will de-energize the inducer after a five second post purge.
11. The circulating air blower is de-energized after 90 seconds.
• The integrated control board has a three ignition system.
• After a total of three trials for ignition without sensing main burner flame, the system
goes into a 100% lockout mode.
• After one hour, the ignition control repeats the prepurge and ignition cycles for 3 tries
and then goes into 100% lockout mode again.
• It continues this sequence of cycles and lockout each hour until ignition is successful or
power is interrupted.
• During the lockout mode, neither the spark ignition control or gas valve will be energized
until the system is reset by turning the thermostat to the "OFF" position or interrupting
the electrical power to the unit for 3 seconds or longer.
• The induced draft blower and main burner will shut off when the thermostat is satisfied.
• The circulating air blower will start and run on the heating speed if the thermostat fan
switch is in the "ON" position.
The integrated furnace control is equipped with diagnostic LED. The LED is lit continuously
when there is power to the control, with or without a call for heat. If the LED is not lit, there
is either no power to the control or there is an internal component failure within the control,
and the control should be replaced.
If the control detects the following failures, the LED will flash on for approximately 1/4 sec-
ond, then off for 3/4 second for designated failure detections.
1 Flash: Failed to detect flame within the three tries for ignition.
2 Flash: Pressure switch or induced draft blower problem detected.
3 Flash: High limit or auxiliary limit open.
4 Flash: Flame sensed and gas valve not energized or flame sensed with no "W" signal.
5 Flash: Overtemperature switch open.
10 10
12 10
12 10
300
IGNITION SYSTEM