Method of control for a refrigerated merchandiser

1. A method of controlling a refrigerated merchandiser, comprising:

providing a case defining a product display area and an air passage having an inlet that receives air from the product display area and an outlet that delivers air to the product display area;

positioning an evaporator in the air passage to refrigerate the air;

positioning a fan in the air passage to move the air through the passage;

logging a first temperature value during frost-free operation of the evaporator, the first temperature value associated with at least one of the air entering the inlet of the air passage, the air exiting the outlet of the air passage, and saturated evaporator temperature;

logging a second temperature value during frosted operation of the evaporator, the second temperature value associated with at least one of the air entering the inlet of the air passage, the air exiting the outlet of the air passage, and saturated evaporator temperature;

calculating a difference of the first and second temperature values; and

defrosting the evaporator when the difference exceeds a pre-determined value.

2. The method of claim 1 , further comprising comparing the difference of the first and second temperature values with the pre-determined value.

3. The method of claim 1 , wherein logging the first and second temperature values includes logging at least one of an inlet air temperature, outlet air temperature, and saturated evaporator temperature.

4. The method of claim 1 , wherein logging the first and second temperature values includes logging at least one of a difference between outlet air temperature and inlet air temperature, and a difference between saturated evaporator temperature and inlet air temperature.

5. The method of claim 1 , wherein the product display area defines a highest temperature zone and a lowest temperature zone, and wherein the method further includes

generating a first signal representative of the temperature of products positioned in the highest temperature zone of the product display area using a first product simulator;

generating a second signal representative of the temperature of products positioned in the lowest temperature zone of the product display area using a second product simulator; and

adjusting an outlet temperature set point in response to the first and second signals generated by the first and second product simulators.

6. The method of claim 5 , further comprising positioning the first product simulator adjacent to the inlet of the air passage.

7. The method of claim 5 , further comprising:

providing a rear wall in the case separating in part the product display area from a vertical portion of the air passage, the rear wall having a plurality of apertures to communicate the air passage and the product display area; and

positioning the second product simulator adjacent to the rear wall.

8. The method of claim 1 , wherein the evaporator refrigerates the air in the air passage according to an outlet temperature set point, and wherein the method further includes

detecting an outlet temperature of the air discharged from the outlet of the air passage;

calculating a temperature difference between the outlet temperature and the outlet temperature set point; and

adjusting flow of refrigerant through the evaporator to decrease a magnitude of the temperature difference.

9. The method of claim 8 , wherein detecting the outlet temperature of the air discharged from the outlet of the air passage occurs about every 1 to 3 seconds of operation of the refrigerated merchandiser.