US 5,123,252 AGranted

Method of operating a transport refrigeration unit

AssigneeThermo King Corporation

InventorJay L. Hanson

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Abstract

A method of operating a transport refrigeration unit with microprocessor based control. The microprocessor automatically selects an operative control algorithm, according to system configuration, with each algorithm having one or more operating conditions. Return air and discharge air temperature sensors provide inputs to the microprocessor. First, second and third sets of look-up tables are accessed by the microprocessor to determine which conditions are in the selected algorithm, and the high and low trip points of each condition. The first set of tables is accessed when the return air sensor is functional, the second set is accessed when the discharge air sensor is functional and the discharge air sensor is not, and the third set is accessed when both the return air and the discharge air sensors are not functional and the conditioned load is frozen. Failure of both sensors when the load is fresh shuts the unit down.

Claims9

Dependent claims

A method of operating a transport refrigeration unit to condition the air of a load space to a selected set point temperature, with the unit having a refrigerant compressor driven by a prime mover, return air and discharge air temperature sensors, and a plurality of control algorithms each comprised of predetermined unit operating conditions, comprising the steps of:

providing a first set of look-up tables associated with return air control;
providing a second set of look-up tables associated with discharge air control,
providing a third set of look-up tables,
providing a plurality of look-up tables in each of said first, second and third sets of look-up tables, with said plurality of look-up tables defining low and high trip points for each operating condition, and the next potential low and the next potential high operating conditions for each operating condition, of each of the plurality of algorithms,
detecting the conditions of the return air and discharge air sensors,
using the first set of look-up tables when the detecting step indicates the return air sensor is functional,
using the second set of look-up tables when the detecting step indicates the return air sensor is not functional and the discharge air sensor is functional,
and using the third set of look-up tables when the detecting step indicates both the return air and discharge air sensors are not functional.

5 more elements

Dependencies are inferred from the claim text.