US 6,629,422 B2Granted

Sequential defrosting of refrigerated display cases

OwnerKeith E. Wellmaninventor

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Abstract

The invention is a method and a defroster control circuit to sequentially defrost a series of refrigerated display cases. The method begins by operating the series of refrigerated display cases during a normal refrigeration mode. At the beginning of the refrigeration mode, a refrigeration time is set to zero and an elapsed refrigeration time is subsequently monitored. When the refrigeration time equals an activation time, a defrost mode begins and a defrost cycle for the first case starts. The defrost mode for the first case terminates based either on a defrost time criterion or a defrost temperature criterion. After the first refrigerated display case is defrosted, a refrigeration mode is restarted for the first case. After the first refrigerated display case is defrosted, the other refrigerated display cases in the series of refrigerated display cases are then sequentially defrosted.

Claims14

Dependent claims

For a series of refrigerated display cases each having an evaporator coil and operated in a refrigeration mode and a defrost mode, wherein each refrigerated display case operates in a refrigeration mode and a defrost mode independent of the refrigeration modes and defrost modes of the other display cases in the series, a method for controlling the operation of the series of refrigerated display cases to sequentially defrost the evaporator coils of the refrigerated display cases, the method comprising steps of:

(a) starting a normal refrigeration mode for all of the display cases in the series of refrigerated display cases and setting a refrigeration time equal to zero wherein, during the refrigeration mode, each display case in the series of refrigerated display cases is operating a refrigeration mode;
(b) monitoring the refrigeration time elapsed from the start of the refrigeration mode;
(c) when the refrigeration time elapsed equals an activation time, starting a defrost mode wherein, during the defrost mode, the following steps are performed:
(c1) for a first refrigerated display case, starting a defrost mode;
(c2) for the first refrigerated display case, terminating the defrost mode based on a selected one of a defrost time criterion or a defrost temperature criterion;
(c3) for the first refrigerated display case, restarting the refrigeration mode;
and
(c4) repeating the steps (c1) through (c3) for each successive refrigerated display case in the series of refrigerated display cases, such that no more than one refrigerated display case is in a defrost mode at any one time;
and
(d) terminating the defrost mode, setting the refrigeration time equal to zero and returning to the normal refrigeration mode at step (b).

7 more elements

(a) starting a normal refrigeration mode for all of the display cases in the series of refrigerated display cases and setting a refrigeration time equal to zero wherein, during the refrigeration mode, each display case in the series of refrigerated display cases is operating a refrigeration mode;
(b) monitoring the refrigeration time elapsed from the start of the refrigeration mode;
(c) when the refrigeration time elapsed equals an activation time, starting a defrost mode wherein the following steps are performed:
(c1) for a first refrigerated display case, starting a defrost mode comprising:
(c1i) melting the frozen condensation on the evaporator coil with a defroster heater;
and
(c1ii) terminating the refrigeration mode by stopping the flow of refrigerant through the evaporator coil of the display case;
(c2) for the first refrigerated display case, terminating the defrost mode based on a selected one of a defrost time criterion or a defrost temperature criterion;
(c3) for the first refrigerated display case, restarting the refrigeration mode;
and
(c4) repeating the steps (c1) through (c3) for each successive refrigerated display case in the series of refrigerated display cases, such that no more than one refrigerated display case is in a defrost mode at any one time;
and
(d) terminating the defrost mode, setting the refrigeration time equal to zero and returning to the normal refrigeration mode at step (b).

10 more elements

For a series of refrigerated display cases having a refrigeration mode and a defrost mode, wherein each refrigerated display case operates in a refrigeration cycle and a defrost cycle, a method for controlling the operation of the series of refrigerated display cases and for sequentially defrosting the evaporator coils of the refrigerated display cases using a defroster control circuit, the method comprising steps of:

(a) starting a refrigeration mode for the series of refrigerated display cases and setting a refrigeration time equal to zero wherein, during the refrigeration mode, each case in the series of refrigerated display cases is operating in a refrigeration mode;
(b) monitoring the refrigeration time elapsed from the start of the refrigeration mode;
(c) starting a defrost mode when the refrigeration time elapsed equals an activation time, wherein, during the defrost mode, the defroster control circuit performs steps of:
(c1) starting a defrost mode for a first refrigerated display case by heating frozen condensation on the evaporator coil;
(c2) terminating the defrost mode for the first refrigerated display case based on either a defrost time criterion or a defrost temperature criterion;
(c3) restarting the refrigeration mode for the first refrigerated display case ;
and
(c4) repeating the steps (c1) through (c3) for each successive refrigerated display case in the series of refrigerated display cases, such that no more than one refrigerated display case is in a defrost cycle at any one time;
and (d) returning to the refrigerator mode at step (b) when the last display case has competed the defroster mode and setting the refrigeration time equal to zero.

6 more elements

A refrigerated display case system, comprising:

(a) a series of refrigerated display cases, each having an evaporator coil;
and
(b) a defroster control circuit to control the operation of the refrigerated display case system and to sequentially defrost the evaporator coils by steps of:
(i) starting a normal refrigeration mode for the series of refrigerated display cases;
(ii) at a beginning of the normal refrigeration mode, setting a refrigeration time equal to zero and subsequently monitoring an elapsed refrigeration time;
(iii) when the elapsed refrigeration time equals an activation time, performing the steps of:
(iiiA) for a first refrigerated display case, starting a defrost mode to melt condensation from the evaporator coils;
and
(iiiB) for the first refrigerated display case, terminating the defrost mode based on either a defrost time criterion or a defrost temperature criterion;
(iiiC) for the first refrigerated display case, restarting the refrigeration mode;
and
(iiiD) repeating steps (iiiA) to (iiiC) for successive refrigerated display cases in the series of refrigerated display cases;
and
(iv) terminating the defrost mode, setting the refrigeration time equal to zero and returning to the normal refrigeration mode at step (ii).

11 more elements

Dependencies are inferred from the claim text.