291891-YUM-A-0207
Unitary Products Group
3
After combustion airflow is estab-
lished, the air proving pressure
switch “PS” closes, the ignitor is
energized and the pilot valve opens
igniting the pilot flame.
The flame rod senses a flame and
de-energizes the ignitor opening
the main gas valve and the main
burners light.
30 seconds after the main burners
light the circulating fan is energized
at the heating speed.
When the thermostat is satisfied,
terminal W is de-energized, de-
energizing the ignition system clos-
ing the gas valve.
After a 30 second postpurge timing
period, the combustion air blower is
de-energized and the heat fan off
timing begins.
When this field selected heat fan
off timing is completed the circulat-
ing fan is de-energized.
If the limit switch “LS”, auxiliary
limit switch “ALS” or the rollout
switch “RS” open, the ignition sys-
tem is de-energized and the gas
valve closes. The combustion
blower and the circulating fan are
energized.
The combustion blower remains
energized for the 30 second post-
purge timing period if the limit
switch “LS”, auxiliary limit switch
“ALS” or the rollout switch “RS”
contacts reset (the rollout “RS” and
auxiliary limit switch “ALS” must be
manually reset). The circulating fan
remains energized for the selected
heat delay off timing.
Normal operation of the system
resumes.
COOLING
When the thermostat calls for
“COOL”, the thermostat signals the
compressor and outdoor fan to run.
The circulating fan is immediately
energized at cooling speed.
When the thermostat is satisfied,
the compressor and outdoor fan is
de-energized.
After a cool fan off delay timing of
30 seconds the circulating fan is
de-energized.
CIRCULATING FAN
When the thermostat calls for
“FAN”, the thermostat terminal sig-
nals the circulating fan to run at the
cool speed.
If a call for “COOL” occurs, the cir-
culating fan continues to run at the
cool speed.
If a call for “HEAT” occurs, the cir-
culating fan switches to heat speed
after a 30 second delay.
When the thermostat ends the call
for “FAN”, the thermostat is de-
energized, de-energizing the circu-
lating fan.
INPUT
The correct heat capacity of the fur-
nace is regulated by the burner ori-
fices and the gas pressure. The
proper orifices are furnished but
the gas pressure regulator must be
adjusted by the installing service-
man or gas company. This is a
“one-time” adjustment.
FOR YOUR SAFETY, READ
BEFORE OPERATING
A.
BEFORE OPERATING, smell all
around the appliance area for gas.
Be sure to smell around the base
of the unit because some gas is
heavier than air and will settle in
the area.
WHAT TO DO IF YOU
SMELL GAS
•
Do not try to light any appliance.
•
Do not touch any electrical
switch.
•
Do not use any phone in your
building.
Should overheating occur,
shut off the manual gas
valve external to the appli-
ance before shutting off the
electrical supply.
WARNING
Flue hood surface and
immediate area is designed
to operate at high tempera-
tures during the heating
cycle. Special attention
must be given to keep all
human contact and debris
away from this area.
Incorrect installation of the
flue vent hood could cause
personal injury or property
damage.
WARNING
V E N T O U T L E T S C R E E N
F L U E V E N T O U T L E T
A I R H O O D
WARNING
If you do not follow these
instructions exactly, a fire
or explosion may result,
causing property dam-
age, personal injury or
loss of life.
WARNING
