초록 ▼

A demand defrost controller employs temperature measurements taken at the outlet of the discharge air curtain and the inlet of the air return to determine the need for defrost. If the difference between these temperature measurements exceeds a set point for a predetermined sustained period of time a

A demand defrost controller employs temperature measurements taken at the outlet of the discharge air curtain and the inlet of the air return to determine the need for defrost. If the difference between these temperature measurements exceeds a set point for a predetermined sustained period of time and a minimum amount of time has elapsed since the last defrost of the case, defrost is initiated. Regardless of the value of the temperature difference, defrost is initiated if elapsed time since the last defrost exceeds a specified maximum time between defrosts for the case. Defrost can be terminated on the basis of time and/or temperature. The demand defrost controller can also control display case temperature and can be applied to independently control multiple display case circuits.

대표청구항 ▼

Demand defrost control apparatus for automatically controlling defrost of a refrigerated display case, comprising: first temperature sensing means located near an outlet of the discharge air curtain of the display case for measuring discharge air temperature; second temperature sensing means located

Demand defrost control apparatus for automatically controlling defrost of a refrigerated display case, comprising: first temperature sensing means located near an outlet of the discharge air curtain of the display case for measuring discharge air temperature; second temperature sensing means located near an inlet of the air return of the display case for measuring return air temperature; and control means, connected to said first and second temperature sensing means, for ascertaining a temperature difference between the measured return air temperature at the inlet and the measured discharge air temperature at the outlet and for determining whether said temperature difference exceeds a temperature difference setting for a predetermined sustained period of time.