Manual

035-16329-002 Rev. B (0304)
2. When the furnace control
board isactivated, the combus-
tionair blower isturned on.
3. As the combustion air blower
increases in speed, the con-
tactsofthe pressure switchwill
close and complete the electd-
cal circuitto the ignitioncircuit.
4. Duringthe next 40 to 50 sec-
onds, the combustionair
blowerwill bringfresh air into
the heat exchanger and the
ignitorwillbeginto glow. At the
end of this pedod,the gas
valve wi!l openand the burner
will light.
5. After the burner lights, a sepa-
rate sensor acts as a flame
probe to check for the pres-
ence of flame. As long as flame
is present, the system will
monitor it and hold the gas
valve open.
6. If the burner fails to light within
6-8 seconds after the gas valve
opens, the gas valve willclose
and the ignitor will be turned
off. After a short pause, the
systemwill recycle and try
again for ignition. If the burner
fails to light atler three tdes, the
ignition system will lock out.
The system will remain in lock-
out mode for a period of one
hour, then the furnace will try
for ignition again.
7. The lapsed time from the
moment the roomthermostat
closesto when the burner
lightsmay be 45-60 seconds.
This delay is caused by:
a. The timerequired for the
ignitorto heat up and
b. The time requiredfor fresh
air to be brought intothe
heat exchanger.
8. Approximately 60-90 seconds
after the burnerlights,furnace
air circulationblower will run.
9. When roomthermostat issetis-
fled, the circuitto the furnace
control board isopened. The
circuittothe combustionair
blowerand the gas valve is
opened and the burnerisextin-
guished.Then the furnace con-
trolboard willkeep the
circulatingblower running for a
fixed pedod oftime to allow
additionalheat to be drawn
from the heat exchanger.
DIAGNOSTIC LIGHT
If furnace does not maintain home
temperature as set, check the light
indicator, visible through a small
window in the dght side of the fur-
Racecontrolbox.
The electronic furnace control is
equipped with a diagnostic light
which flashes when there is a ser-
viceproblem.The diagnosticcodes
are;
Steady on: Normal operation.
ONE flash: Ignition failure.
TWO flashes: Pressure switch
failedclosed.
THREE flashes: Pressure switch
failedopen.
FOUR flashes: Limitswitchopen.
FIVE flashes: Gas valve energized
with no call for heat
SIX flashes or
rapid flash: Reversed poladty
If a problem is indicated, contact
your authorizedservice person.
THE FURNACE CONTROLS
AND THEIR FUNCTION
1. System Switch - This system
switchturns=ON"or "OFF"the
120 volt electdcal circuitthat
powersthe furnace controls
and the blower motor.The sys-
tem switch mustbe turned
"ON" for the furnace to oper-
ate. Turn the switchto "OFF"
when cleaningthe blower,etc.
2. Limit Control - This furnace is
protected bytwo (2) hightam-
perature limitswitches.The
lowerlimitswitch isan auto-
maticreset type.
3. Gas Valve - The gas valvefor
the gas furnaces are a 100%
shut-offtype and willfail safe if
for somereason the gas is
turned off.
Unitary Products Group 5