66324-YIM-B-1004
Unitary Products Group
15
SEQUENCE OF OPERATION
The unit is controlled by a conventional four wire heating/
cooling thermostat common to this class of equipment.
HEATING
When the thermostat calls for HEAT, the thermostat terminal
W is energized, energizing the combustion air blower.
After airflow is established, the air proving switch closes, the
hot surface 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 closing the gas valve.
After a 5 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
circulating fan is de-energized.
If the primary, rollout and auxiliary limit switches open, the
thermostat and ignition system is de-energized and the gas
valve closes. The combustion blower and the circulating fan,
at heat speed, are energized.
The combustion blower remains energized for the 5 second
postpurge timing period if the primary, rollout and auxiliary
limit switches remake the contact (the rollout and auxiliary
limit switches 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 termi-
nals G and Y are energized signaling the compressor and
outdoor fan to run.
After a cool fan on delay timing of 2 seconds, the circulating
fan is energized at cooling speed.
When the thermostat is satisfied, terminals G and Y are de-
energized, de-energizing the compressor and outdoor fan.
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 G
is energized signaling the circulating fan to run at the heat
speed 2 seconds after the G terminal is energized.
If a call for HEAT occurs, the circulating fan continues to run
at the heat speed.
If a call for COOL occurs, the circulating fan switches to cool
speed after a 4 second delay.
When the thermostat ends the call for FAN, the thermostat
terminal G is de-energized, de-energizing the circulating fan.
START-UP
PRE-START CHECK LIST
Complete the following checks before starting the unit.
1.
Check the type of gas being supplied. Be sure that it is
the same as listed on the unit nameplate.
2.
Make sure that the vent outlet air hoods has been prop-
erly installed.
OPERATING INSTRUCTIONS
1.
STOP! Read the information on the unit safety label.
2.
Set the thermostat to the OFF position.
3.
Turn off all electrical power to the unit.
4.
DO NOT try to light the burners by hand. This appliance
is equipped with an ignition device which automatically
lights the burners.
5.
Remove the access panel.
6.
Turn the gas valve switch to the OFF position.
7.
Wait five (5) minutes to clear out any gas. If you then
smell gas, STOP! Follow B in the information on the unit
safety label. If you don't smell gas, go to the next step.
8.
Turn the gas valve switch to the ON position.
9.
Replace the control access panel.
10. Turn on all electric power to the unit.
11. Set the thermostat to the desired setting.
12. If the unit will not operate, follow the instructions To Turn
Off Gas To Appliance and call your service technician or
gas supplier.
TO TURN OFF GAS TO UNIT
1.
Set the thermostat to the OFF position.
2.
Turn off all electric power to the appliance if service is to
be performed.
