Amana VR8205 Figure Auxiliary Limit Control, Burner Box, Auxiliary Limit Control Figure

BURNER BOX

This furnace must use indoor air for combustion. It is not a direct vent furnace, and it cannot be installed as a direct vent furnace. The burner box (on some models) is present only to reduce the burner sound transmission.

AUXILIARY LIMIT CONTROL (FIGURE 35)

A manual reset limit is located on the blower side of the blower deck, near the center. 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. See Section X, Abnormal Operation - Integrated Ignition Control for diagnosis.

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 direc- tion, it does not need to be relocated.

WARNING

To prevent death, personal injury or property damage due to fire, follow these directions for the auxiliary limit control. If the auxiliary limit control opens, it may be reset one time only.

(SERVICER’S NOTE: If it becomes necessary to slide the blower assembly out of the furnace, the auxiliary limit control should be removed first. After the blower assembly is reinstalled, the auxiliary limit must be reinstalled.)

Figure 35

Auxiliary Limit Control

ABNORMAL OPERATION - INTEGRATED IGNITION CONTROL

The following presents the probable causes of question- able furnace operation and how to fix them. Look through

the observation window in the blower access door and make a note of the number of flashes in sequence between pauses. Next, refer to the Diagnostic Signal Chart for an interpretation of the signals and to this section for a descrip- tion.

1.Internal Control Failure with Integrated Ignition Control

An internal control failure occurs when the integrated ignition control senses an internal problem and stops the unit.

To solve this problem, replace the ignition control.

2.System Lockout

A system lockout occurs when the integrated ignition control determines that a measurable combustion can- not be established or maintained after three consecu- tive tries (four, if flame is established then lost) to turn on the furnace.

If a flame is not sensed during the first six seconds after a gas valve has been energized, the ignition control will internally turn off the gas. After 60 seconds, during which time the induced draft blower purges the heat exchanger, the ignitor will re-energize and preheat for 27 seconds. The gas valve is then re-energized. If a flame is not sensed again in six seconds, the gas valve will de-energize and another purge is performed. The ignition control will cycle the gas valve three times before it determines it cannot establish measurable combustion and enter a lockout state. If a flame is sensed but lost after 10 seconds, the control will cycle four more times before locking out. A lockout stops ignition attempts and causes the air blower to run continuously. The diagnostic light will indicate either condition with one short flash followed by a longer off.

The control can be reset and brought out of lockout mode by turning the thermostat off and then back on. It can also reset by turning off the electrical disconnect switch to the furnace for 30 seconds. The control will reset after one hour.

IMPORTANT: If you have to frequently reset your furnace, it means that a problem exists that should be corrected. Contact a qualified servicer for further information.

3.Pressure Switch Stuck Closed

A sticking pressure switch can be caused by either a faulty pressure switch, faulty wiring, a disconnected hose, or a restricted intake or flue piping. In the case of a pressure switch sticking closed, the probable cause is a faulty pressure switch or wiring.

If the ignition control senses that the pressure switch is closed and the induced draft blower is off, it will shut down the unit until the fault is corrected. The light code for this problem is two short flashes followed by a longer pause.

4.Pressure Switch Stuck Open

A sticking open pressure switch can be caused by a faulty pressure switch, a disconnected hose to the pressure switch, a restricted air intake or flue piping, or a faulty wiring.

If the ignition control senses that the induced draft blower is energized but the pressure switch is not closed, the control will keep the blower on and wait for the switch to close. The diagnostic light code for this problem is three short flashes followed by a pause.

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