Check the burner flames for:
1.Good adjustm ent
2.Stable, soft and blue
3. Not curling, floating, or lifting off.
Burner Flame
AUXILIARY LIMIT CONTROL
Auto reset limits are located on or near the blower. To access this auxiliary limit, disconnect the electrical power and remove the blower door. If the limit control opens, the air circulation blower will run continuously. The diagnostic light will flash four times. These symptoms are identical to a trip of the primary limit control. The auxiliary limit control is designed to prevent furnace operation in case of main blower failure on horizontal and counterflow installations. It may also open if the power supply is interrupted while the furnace is firing. The auxiliary limit control is suitable for both horizontal right and horizontal left installations. Regardless of airflow direction, it does not need to be relocated.
WARNING
TO AVOID PERSONAL INJURY OR DEATH, DO NOT REMOVE ANY INTERNAL COMPARTMENT COVERS OR ATTEMPT ANY ADJUSTMENT. ELECTRICAL COMPONENTS ARE CONTAINED IN BOTH COMPARTMENTS. CONTACT A QUALIFIED SERVICE AGENT AT ONCE IF AN ABNORMAL FLAME APPEARANCE PREVENT PROPERTY DAMAGE, PERSONAL INJURY OR DEATH DUE TO FIRE,
PRIMARY LIMIT
The primary limit control guards against overheating resulting from insufficient conditioned air passing over the heat exchanger. If the primary limit control does not function during this test, the cause must be determined and corrected. Function of this control should be verified by gradually blocking the furnace return air after the furnace has been operating (burners firing) for approximately ten minutes. Check the control as follows:
1.Allow the furnace to operate with burners firing continuously for approximately ten minutes.
2.Gradually block the return air to furnace. Remove airflow blockage when limit control is activated and turns off burners. Airflow blockage causes unit overheating and will produce the following reactions:
•The gas valve to close and extinguish flame,
•The induced draft blower to be de-energized after a fifteen second postpurge, and
•The circulator blower to remain energized continuously until limit control resets.
3.Remove the return air blockage to clear overheating condition. After an acceptable temperature is reached during the cool down period, the limit control will reset and allow the furnace to resume normal operation.
WARNING
TO PREVENT PREMATURE FAILURE OF HEAT EXCHANGER, PROPERTY DAMAGE, PERSONAL INJURY OR DEATH, DO NOT ADJUST THE LIMIT CONTROL (FACTORY SET).
IMPORTANT NOTE: This unit must not be used as a construction heater during the finishing phases of construction of a new structure. This type of use may result in premature failure due to extremely low return air temperatures and exposure to corrosive or very dirty atmospheres.
These checks establish that the primary limit control is functioning and will respond to a restriction in the return air, or a circulator blower failure. If the primary limit control does not function during this test, the cause must be determined and corrected.
XIV. SAFETY CIRCUIT DESCRIPTION
GENERAL
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 continuously monitored during furnace operation by the integrated control module.
INTEGRATED CONTROL MODULE
The integrated control module is an electronic device which controls all furnace operations. Responding to the thermostat, the module initiates and controls normal furnace operation, and monitors and addresses all safety circuits. If a potential safety concern is detected, the module will take the necessary precautions and provide diagnostic information through an LED.
PRIMARY LIMIT
The primary limit control is located on the partition panel and monitors heat exchanger compartment temperatures. It is an automatic reset, temperature sensor. The limit guards against the overheating as a resulting of insufficient air passing over the heat exchanger.
AUXILIARY LIMIT
The auxiliary limit control is located either on or near the circulator blower and monitors heat exchanger compartment temperatures. The control is a temperature sensor. It guards against overheating resulting from insufficient air passing over the heat exchanger.
ROLLOUT LIMITS
The rollout limit controls are mounted on the burner/manifold assembly and monitor the burner flame. They are manual-reset, temperature sensors. This limit guards against burner flames not being properly drawn into the heat exchanger.
PRESSURE SWITCHES
The pressure switches are normally-open, 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. These switches guard against insufficient airflow (combustion air and flue products) through the heat exchanger.
FLAME SENSOR
The flame sensor is a probe mounted to the burner/manifold assembly which uses the principle of flame rectification to determine the presence or absence of flame.
XV. TROUBLESHOOTING
ELECTROSTATIC DISCHARGE (ESD) PRECAUTIONS
NOTE: Discharge body’s static electricity before touching unit. An electrostatic discharge can adversely affect electrical components.
