Abstract: Both a system and method are provided for achieving temperature control in a refrigeration circuit by providing a bypass flow of saturated, gaseous refrigerant from the receiver tank to a point in the circuit downstream of the evaporator coil. The system includes a bypass conduit for conducting a bypass flow of saturated, gaseous refrigerant from an upper portion of the receiver tank to a point in the circuit between the evaporator coil and a suction line throttling valve to partially offset the cooling of the evaporator coil from the expansion valve. The bypass conduit includes a valve mechanism for modulating this flow to achieve a desired temperature setpoint. The system also includes a temperature monitoring sensor located in a space conditioned by the refrigeration circuit, as well as a microprocessor. The input of the microprocessor receives an electrical signal generated by the monitoring sensor indicative of the temperature of the space.

Abstract: A method of controlling refrigerant pressure during elevated ambient temperature conditions in a refrigeration unit having a refrigerant compressor driven by a prime mover, and controllable suction line modulation. The method includes the steps of detecting the actual load PML on the prime mover, sensing the ambient temperature AA, and providing a dynamic load limit DLL as a function of the ambient temperature AA. The actual load PML is compared with the dynamic load limit DLL, and the suction line modulation is changed as a function of the comparison step to cause the actual load PML to follow the changing dynamic load limit DLL. The invention also includes a method of preventing excessive on-off cycling of a refrigeration unit during low ambient temperature conditions, with the refrigeration unit operating in a cycling start-stop mode to control the temperature of a conditioned space to a selected set point temperature SP.

Abstract: A belt tension indicating system for indicating the belt tension of a belt driven machine includes a belt tension indicating assembly and a hydraulic ram assembly to provide the belt tension. The hydraulic ram assembly is connected between an idler wheel of the machine and the belt tension indicating assembly. When the belt tension decreases below a predetermined value, the belt tension indicating assembly activates a switch which then activates a horn, light or other device to alert the machine operator.

Abstract: A method of operating a transport refrigeration system having a compressor driven by a prime mover at a selected one of high and low speeds, an evaporator, and an evaporator blower driven by the prime mover. Refrigeration control provides an error value which controls the temperature of a load space to a predetermined set point via heating and cooling modes. The method includes the steps of driving the compressor at high speed during pull down, and injecting hot gas into the evaporator when the error is reduced to a predetermined value. The prime mover is maintained at high speed, to keep evaporator air flow at a high rate, continuing a relatively rapid temperature pull-down across the entire load space. The speed of the prime mover is reduced to low speed when the error is further reduced to a second value, which also initiates suction line modulation while maintaining hot gas injection.

Abstract: A refrigeration distribution arrangement which improves the uniformity of coil temperature distribution along the length of an evaporator coil. The distribution arrangement is particularly beneficial when an evaporator coil is operating partially flooded with refrigerant, such as when refrigeration capacity is being reduced with a suction line modulation valve. Distributor tubes from a refrigerant distributor are inserted for at least first and second different dimensions into coil tubes which initiate a plurality of refrigerant circuits in the evaporator coil. In an exemplary embodiment, the first dimension is a relatively short dimension, and the second dimension is a relatively long dimension, such as about one-third of the coil length. The refrigerant thus expands at different locations across the coil length, initiating coil cooling at different coil locations. The discharge temperature of air (flowing across the evaporator coil into a served space is thus more uniform across the coil length.

Abstract: A method of controlling a refrigeration system by determining an average air temperature by sensing and averaging evaporator return and discharge air temperatures, and developing an average error by using the average air temperature and a selected set point temperature. The average air temperature is then used to calculate a proportional error and an integral error, and the discharge air temperature is used to calculate a floor error. The proportional error, integral error and floor error are weighted by predetermined gain factors and then summed to provide an error signal which is used to modulate the capacity of the refrigeration system, with the control mode depending upon the location of the error signal relative to set point.

Abstract: Transport refrigeration apparatus including a condenser section containing an inverted U-shaped refrigerant condenser coil which defines a central opening which functions as a fan chamber having a vertically oriented air discharge side. A propeller fan is disposed in the central opening of the condenser coil which draws air through the condenser coil and discharges it through the vertically oriented discharge side of the opening. A metallic grille is disposed across the air discharge side of the central opening, with the grille having a plurality of horizontally spaced, vertically oriented louvers which straighten the discharge air flow in vertical planes and reduce short circuiting of the discharge air back into the condenser coil. The louvers are spaced by a dimension selected to enable the metallic grille to perform the function of a protective or safety grille across the fan chamber.