Not sure that 60 deg. Fahrenheit is the lowest temperature that room air conditioners are normally designed to cool to, but assume that that is correct. What I want to do is, in a simple way, to make the conditioner's compressor not stop running until after a "room" temperature of about 40 deg. Fahrenheit has been reached.
In other words, the room (window) air conditioner will be used to make a walk-in refrigerator.
Assume that the air conditioner has a thermistor-type room air temperature sensor. A thermistor can be either postive or negative temperature coefficient (ptc or ntc). Another given is that the temperature setting of the air conditioner (the desired room temp) is 60 deg. F.
If the temperature sensor is a ptc, then I would connect a rheostat in series with the thermistor. In that way, assuming a correct resistance value of the rheostat, resistance of the thermistor is less than normal when the compressor is shut off as room temperature reaches 40 deg. F.
If the temperature sensor is ntc, then I would connect a rheostat in parallel with the thermistor. Where the resistance of the rheostat is correct, then resistance of the thermistor must be greater than normal before the compressor is shut off and room temp. again equals 40 deg. F. Given a 40 deg F. room temperature, the total resistance of the thermistor in parallel with the resistor is equal to the resistance of the thermistor with respect to room temp. equal to 60 deg. F lacking the rheostat connected in parallel with it.
These two different possible circuits are shown in the drawing below.
Over the past two days I have been trying to understand the workings of air conditioners, but I have previously done very little with them. So I'm looking for advice from anyone who is experienced with them as to whether or not what I have in mind is practical and not cause damage to an A.C. .
In other words, the room (window) air conditioner will be used to make a walk-in refrigerator.
Assume that the air conditioner has a thermistor-type room air temperature sensor. A thermistor can be either postive or negative temperature coefficient (ptc or ntc). Another given is that the temperature setting of the air conditioner (the desired room temp) is 60 deg. F.
If the temperature sensor is a ptc, then I would connect a rheostat in series with the thermistor. In that way, assuming a correct resistance value of the rheostat, resistance of the thermistor is less than normal when the compressor is shut off as room temperature reaches 40 deg. F.
If the temperature sensor is ntc, then I would connect a rheostat in parallel with the thermistor. Where the resistance of the rheostat is correct, then resistance of the thermistor must be greater than normal before the compressor is shut off and room temp. again equals 40 deg. F. Given a 40 deg F. room temperature, the total resistance of the thermistor in parallel with the resistor is equal to the resistance of the thermistor with respect to room temp. equal to 60 deg. F lacking the rheostat connected in parallel with it.
These two different possible circuits are shown in the drawing below.
Over the past two days I have been trying to understand the workings of air conditioners, but I have previously done very little with them. So I'm looking for advice from anyone who is experienced with them as to whether or not what I have in mind is practical and not cause damage to an A.C. .