Thermostat Control - Indesit New electronic cold platform 2005 Service Manual

Refrigerator

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Table Of Contents

Table of Contents

In alarm status the appliance forces operation utilising specific On / Off parameters that control the tem-

perature in the freezer compartment at specific values depending on the type of alarm. To reset the alarm

and restore normal operation, the appliance must be set to LOGICAL OFF (freezer knob set to minimum).

Control of freezer compartment temperature is continuous during operation of the appliance, by means of

the freezer air temperature sensor; this control will proceed even if the appliance is in one of the two

available alarm conditions. In the event of a freezer air sensor fault, the alarms will no longer be displayed.

Temperature control is not performed for a time parameterised in the EEPROM memory to prevent false

alarms both during the testing process and at the time of power-on immediately after the appliance has

been purchased.

Temperature control and alarm signalling are managed by means of three thresholds: Check Threshold

(the control strategy becomes more intensive when this threshold is exceeded); Threshold A1: when ex-

ceeded, alarm A1 is activated; Threshold A2: when exceeded, alarm A2 is activated. The values of the three

thresholds are parameterised in the EEPROM memory.

If the control temperature exceeds the Check Threshold but does not exceed the A1 Alarm threshold, a

delay time T1 is activated (parameterised in the EEPROM) before performing the next control, to prevent

the generation of alarm signals when the placement of large quantities of warm food in the freezer compart-

ment near the freezer air sensor causes unreliable transient temperature readings. At the same time an-

other time interval T2 is activated (parameterised on the EEPROM) after which, if the temperature is con-

stantly maintained between the Check Threshold and the Alarm A1 Threshold, alarm A1 is forced because

the persistence of a temperature in this range for this period of time is anyway a symptom of faulty operation

and constitutes a risk for the correct preservation of the food.

At the time of activation of alarm A1 also a time interval T3 is activated (parameterised in the EEPROM)

after which, if an alarm reset has not been executed, alarm A2 is forced, since in the situation of alarm A1

the freezer compartment is set to a temperature that may not be the same as the temperature selected by

the user. This time interval is reset also when power is restored after a mains power failure.

N. B.: The time and temperature values shown in this graph are EEPROM parameters and as such they are subject to modification