GCSS96 Installation Manual

36
PRIMARY LIMIT
The primary limit control is located on the partition panel and
monitors heat exchanger compartment temperatures. It is a
normally-closed (electrically), automatic reset, temperature-ac-
tivated sensor. The limit guards against overheating as a result
of insufficient conditioned air passing over the heat exchanger.
AUXILIARY LIMIT
The auxiliary limit controls are located on or near the circulator
blower and monitors blower compartment temperatures. They
are a normally-closed (electrically), manual-reset sensors. These
limits guard against overheating as a result of insufficient con-
ditioned air passing over the heat exchanger.
ROLLOUT LIMIT
The rollout limit controls are mounted on the burner/manifold
assembly and monitor the burner flame. They are normally-
closed (electrically), manual-reset sensors. These limits guard
against burner flames not being properly drawn into the heat
exchanger.
PRESSURE SWITCHES
The pressure switches are normally-open (closed during opera-
tion) negative air pressure-activated switches. They monitor
the airflow (combustion air and flue products) through the heat
exchanger via pressure taps located on the induced draft blower
and the coil front cover. These switches guard against insuffi-
cient airflow (combustion air and flue products) through the heat
exchanger and/or blocked condensate drain conditions.
FLAME SENSOR
The flame sensor is a probe mounted to the burner/manifold
assembly which uses the principle of flame rectification to de-
termine the presence or absence of flame.
T ROUBLESHOOTING
ELECTROSTATIC DISCHARGE (ESD) PRECAUTIONS
NOTE: Discharge body’s static electricity before touching unit.
An electrostatic discharge can adversely affect electrical
components.
Use the following precautions during furnace installation and ser-
vicing to protect the integrated control module from damage.
By putting the furnace, the control, and the person at the same
electrostatic potential, these steps will help avoid exposing the
integrated control module to electrostatic discharge. This pro-
cedure is applicable to both installed and uninstalled (ungrounded)
furnaces.
1. Disconnect all power to the furnace. Do not touch the
integrated control module or any wire connected to the
control prior to discharging your body’s electrostatic
charge to ground.
2. Firmly touch a clean, unpainted, metal surface of the
furnace away from the control. Any tools held in a
person’s hand during grounding will be discharged.
3. Service integrated control module or connecting wiring
following the discharge process in step 2. Use caution
not to recharge your body with static electricity; (i.e., do
not move or shuffle your feet, do not touch ungrounded
• R,Y, G thermostat contacts close, initiating a call
for cool.
• Integrated control module performs safety circuit
checks.
• Outdoor fan and compressor are energized.
• Circulator blower is energized on the cool speed.
• 96% models 115 VAC EAC terminal is energized.
• Furnace circulator blower and outdoor cooling unit
run their appropriate speeds, integrated control
module monitors safety circuits continuously.
• R,Y, G thermostat contacts open, completing the
call for cool.
• Outdoor fan and compressor are de-energized.
• Circulator blower continues running during a cool
off delay period of 45 seconds.
• Furnace awaits next call from thermostat.
FAN ONLY MODE
The normal operational sequence in fan only mode is as follows:
• R and G thermostat contacts close, initiating a call
for fan.
• Integrated control module performs safety circuit
checks.
• Circulator blower is energized on heat speed.
• 96% models 115 VAC EAC terminal is energized.
• Circulator blower runs, integrated control module
monitors safety circuits continuously.
• R and G thermostat contacts open, completing the
call for fan.
• Circulator blower is de-energized.
• EAC terminal is de-energized.
• Furnace awaits next call from thermostat.
O PERATIONAL C HECKS
The burner flames should be inspected with the burner compart-
ment door installed. Flames should be stable, quiet, soft, and
blue (dust may cause orange tips but they must not be yellow).
Flames should extend directly outward from the burners without
curling, floating, or lifting off. Flames must not impinge on the
sides of the heat exchanger firing tubes.
S AFETY C IRCUIT D ESCRIPTION
A number of safety circuits are employed to ensure safe and
proper furnace operation. These circuits serve to control any
potential safety hazards and serve as inputs in the monitoring
and diagnosis of abnormal function. These circuits are continu-
ously monitored during furnace operation by the integrated con-
trol module.
INTEGRATED CONTROL MODULE
The integrated control module is an electronic device which, if a
potential safety concern is detected, will take the necessary pre-
cautions and provide diagnostic information through an LED.