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US 4,850,204 AGranted
Adaptive defrost system with ambient condition change detector
AssigneeParagon Electric Company, Inc.
InventorsPeter J. Bos, John J. Allard
Life of this patent
Estimating the term…
Abstract
A defrost system adapted for use with refrigeration or heat pump systems wherein an evaporator coil defrost cycle is adaptively modified in response to changing environmental conditions. Under normal conditions, a defrost operation is effected at the end of a period of frost accumulation. The period of frost accumulation is adjusted in accordance with deviation of the time required to defrost a coil from a desired defrost time. During the frost accumulation period, the differential between the temperature of the coil and ambient temperature is determined, and the frost accumulation period terminated and a defrost operation initiated if temperature differential exceeds a target differential.
Claims50
A method for controlling the defrosting of a heat transfer unit of a temperature conditioning system by initiating a defrost operation when a predetermined amount of frost has accumulated on the unit during a frost accumulating period that occurs between defrost operations, a predetermined desired defrost time being required to defrost said unit when it has the predetermined amount of frost accumulated thereon, said method being of the type comprising the steps:
- determining the time required to actually defrost said unit during an actual defrost operation;
- increasing the frost accumulating period before initiating the next defrost operation if the time to complete the last defrost was less than said desired defrost time period;
- or
- decreasing the frost accumulating period before initiating the next defrost operation if the time to complete the last defrost was greater than said desired defrost time period;
- improved wherein said method further comprises the steps of:
- sensing ambient temperature in the vicinity of said heat transfer unit;
- determining if the temperature of said unit has stabilized;
- determining if the system operation is within a first predetermined portion of said frost accumulation period;
- determining the temperature differential between said unit and ambient;
- and
- if said unit temperature has stabilized and said system operation is within said first predetermined portion of said frost accumulating period, initiating said defrost operation upon said temperature differential exceeding a threshold value.
8 more elements
A method of selectively defrosting a heat transfer unit, said method comprising the steps of:
- a. selectively effecting a defrost operation at the end of a period of frost accumulation of a duration adjusted in accordance with the deviation from a desired defrost time required to defrost said unit in a previous defrost operation;
- b. determining if the temperature of said unit has stabilized;
- c. determining if the system operation is within a first predetermined portion of said frost accumulation period;
- d. determining the temperature differential between said unit and ambient;
- e. if said unit temperature has stabilized and said system operation is within said first predetermined portion of said period of frost accumulation, selectively effecting a defrost operation responsive to said temperature differential exceeding a threshold value.
2 more elements
A method of selectively defrosting a heat transfer unit, said method comprising the steps of:
- selectively effecting a defrost operation at the end of a period of frost accumulation of a duration adjusted in accordance with the deviation from a desired defrost time required to defrost said unit in a previous defrost operation;
- determining the temperature differential between said unit and ambient;
- during at least a first portion of said period of frost accumulation, selectively effecting a defrost operation responsive to said temperature differential exceeding a threshold value;
- and
- during a second portion of said period of frost accumulation, selectively effecting a defrost operation responsive to said temperature differential exceeding a second threshold differential.
2 more elements
A system for selectively generating a defrost control signal to controllably defrost a heat transfer unit, said system comprising:
- temperature sensor means for providing indicia of the temperature of said unit and of the ambient temperature in the vicinity of said heat transfer unit;
- storage means for accessibly storing indicia of:
- a frost accumulation period duration;
- and
- a target temperature differential value;
- timer means, receptive of indicia of a time period communicated thereto, for providing indicia of temporal advancement through said time period;
- means, cooperating with said storage means, for selectively communicating said indicia of said frost accumulation period duration to said timer means, whereby said timer means provides indicia of temporal advancement through said frost accumulation period;
- means for determining if the temperature of said heat transfer unit has stabilized;
- means for determining if the system operation is within a first predetermined portion of said frost accumulation period;
- temperature differential actuation means, cooperating with said storage means, responsive to the difference between the temperature of said unit and ambient temperature exceeding said target temperature differential when said heat transfer unit temperature has stabilized and said system operation is within said first predetermined portion of said frost accumulation period, for initiating generation of said defrost control signal;
- means, cooperating with said timer means, responsive to indicia of the expiration of said frost accumulation period, for initiating generation of said defrost control signal;
- means for selectively terminating generation of said defrost control signal;
- and
- means for adjusting said frost accumulation period in accordance with the deviation, from a desired value, of the time required to defrost said unit.
11 more elements
A system for selectively generating a defrost control signal to controllably defrost a heat transfer unit, said system comprising:
- temperature sensor means for providing indicia of the temperature of said unit and of the ambient temperature in the vicinity of said heat transfer unit;
- storage means for accessibly storing indicia of:
- a frost accumulation period duration;
- and
- a target temperature differential value;
- timer means, receptive of indicia of a time period communicated thereto, for providing indicia of temporal advancement through said time period;
- means, cooperating with said storage means, for selectively communicating said indicia of said frost accumulation period duration to said timer means, whereby said timer means provides indicia of temporal advancement through said frost accumulation period;
- temperature differential actuation means, cooperating with said storage means, responsive to the difference between the temperature of said unit and ambient temperature exceeding said target temperature differential during a first portion of said frost accumulation period, for initiating generation of said defrost control signal;
- means cooperating with said timer means, responsive to indicia of the expiration of said frost accumulation period, for initiating generation of said defrost control signal;
- means for selectively terminating generation of said defrost control signal;
- means for adjusting said frost accumulation period in accordance with the deviation, from a desired value, of the time required to defrost said unit;
- and
- second temperature actuation means, responsive to the difference between the temperature of said unit and ambient temperature exceeding a second target differential during a second portion of said frost accumulation period, for initiating generation of said defrost control signal.
10 more elements
A system for regulating the temperature of an area, said system comprising:
- a compressor, responsive to compressor control signals applied thereto;
- first and second heat transfer units, fluidically coupled to said compressor, said first heat transfer unit being disposed in said area, said second heat transfer unit being disposed outside of said area;
- defrost means, responsive to defrost control signals applied thereto, for controllably defrosting said second heat transfer unit;
- a first temperature sensor, disposed to provide indicia of the temperature of said second heat transfer unit;
- a second temperature sensor, disposed to provide indicia of the ambient temperature in the vicinity of said second heat transfer unit;
- storage means for accessibly storing indicia of:
- a frost accumulation period duration;
- and
- a target temperature differential;
- timer means, receptive of indicia of a time period communicated thereto, for providing indicia of temporal advancement through said time period;
- means, cooperating with said storage means, for selectively communicating said indicia of said frost accumulation period duration to said timer means, whereby said timer means provides indicia of temporal advancement through said frost accumulation period;
- means for determining if the temperature of said heat transfer unit has stabilized;
- means for determining if the system operation is within a first predetermined portion of said frost accumulation period;
- temperature differential actuation means, cooperating with said storage means, responsive to the difference between the temperature of said unit and ambient temperature exceeding said target temperature differential when said heat transfer unit temperature has stabilized and said system operation is within said first predetermined portion of said frost accumulation period, for initiating generation of said defrost control signal;
- means, cooperating with said timer means, responsive to indicia of the expiration of said frost accumulation period, for initiating generation of said defrost control signal;
- means for selectively terminating generation of said defrost control signal;
- and
- means for adjusting said frost accumulation period in accordance with the deviation, from a desired value, of the time required to defrost said unit.
15 more elements
A system for regulating the temperature of an area, said system comprising:
- a compressor, responsive to compressor control signals applied thereto;
- first and second heat transfer units, fluidically coupled to said compressor, said first heat transfer unit being disposed in said area, said second heat transfer unit being disposed outside of said area;
- defrost means, responsive to defrost control signals applied thereto, for controllably defrosting said second heat transfer unit;
- a first temperature sensor, disposed to provide indicia of the temperature of said second heat transfer unit;
- a second temperature sensor, disposed to provide indicia of the ambient temperature in the vicinity of said second heat transfer unit;
- storage means for accessibly storing indicia of:
- a frost accumulation period duration;
- and
- a target temperature differential;
- timer means, receptive of indicia of a time period communicated thereto, for providing indicia of temporal advancement through said time period;
- means, cooperating with said storage means, for selectively communicating said indicia of said frost accumulation period duration to said timer means, whereby said timer means provides indicia of temporal advancement through said frost accumulation period;
- temperature differential actuation means, cooperating with said storage means, responsive to the difference between the temperature of said unit and ambient temperature exceeding said target temperature differential during a first portion of said frost accumulation period, for initiating generation of said defrost control signal;
- means, cooperating with said timer means, responsive to indicia of the expiration of said frost accumulation period, for initiating generation of said defrost control signal;
- means for selectively terminating generation of said defrost control signal;
- and
- means for adjusting said frost accumulation period in accordance with the deviation, from a desired value, of the time required to defrost said unit;
- means for sensing the on/off state of said compressor;
- wherein said means for terminating generation of said defrost control signal comprises:
- means for selectively communicating indicia of a maximum defrost period to said timer means, whereby said timer means provides indicia of temporal advancement through said maximum period;
- means for selectively restarting temporal advancement through said maximum defrost period in said timer means responsive to said compressor assuming an off state;
- means for terminating generation of said defrost control signal responsive to the first to occur of:
- said second heat transfer unit attaining a predetermined temperature indicative of a defrosted condition;
- or
- expiration of said maximum defrost period.
21 more elements
A method of selectively defrosting a heat transfer unit, said method comprising the steps of:
- selectively effecting a defrost operation at the end of a period of frost accumulation;
- determining the temperature differential between said unit and ambient;
- if, during at least a first portion of said period of frost accumulation, said temperature differential exceeds a target differential, terminating said period of frost accumulation and effecting said defrost operation;
- storing indicia of the temperature differential occurring just prior to initiating a defrost operation;
- determining the deviation of the time required to defrost said unit from a desired defrost time;
- adjusting said predetermined duration of said period of frost accumulation in accordance with said deviation;
- if there is no deviation, establishing a target temperature differential in accordance with said temperature differential occurring just prior to initiating said defrost operation.
4 more elements
Dependencies are inferred from the claim text.