The Frigitek® controller is designed to reduce the energy used by evaporator fans in refrigeration systems by reducing the speed of the fans whenever there is no demand for cooling.
Refrigeration systems use forced air evaporators to cool the air, or more correctly, to remove the heat. The air is moved across the evaporator coils with fans. These fans are also used to destratify the air to provide even temperatures throughout the room. The fans on smaller units such as walk-in coolers and freezers in supermarkets are typically powered by one of three different kinds of single-phase motors: shaded-pole, permanent split capacitor, and electronically commutated motors (ECMs). Shaded-pole motors are available in only fractional horsepower sizes, have low torque and low efficiency. The efficiency of a shaded-pole motor ranges between 10- 35%. Permanent split capacitor motors have a larger range of sizes and a higher efficiency than shaded-pole motors, ranging between 55-60%. ECMs have the best efficiencies of these single-phase motors – at about 70%.
The Frigitek controller is used to reduce the speed of the evaporator fan motor when the evaporator is not actively cooling. This is accomplished by modifying the voltage waveform with proprietary circuitry. Under normal operation the fans operate continuously, even when the evaporator is not actively cooling. Reducing the speed of the fan motor reduces both the energy used by the motor and the additional heat generated by the motor. The heat added to the space from the motor has to be removed from the space by the evaporator. Typically, the single-phase motors operate at 1750 rpm and the controller reduces the speed to 350 rpm and reduces the voltage to 33%.
The Frigitek controller senses whether refrigerant is flowing through the evaporator by one of two means. One sensor is called a Signal Sensor Tee, which is used to sense the state of a solenoid operated control valve in the refrigerant line to the evaporator. The second sensor is called a Temperature Differential Sensor, which detects the temperature difference across the expansion valve of the evaporator coil. This method is used if there is not a solenoid or if the solenoid is inconveniently located. These methods used to control the fan motors are patented.
The Frigitek controller comes in various models for a variety of situations. The models cover ranges for single and three-phase systems in multiple voltages and amperages. The various models allow for use of a Frigitek controller on virtually any refrigeration system, including reach-in, walk-in, and industrial-sized coolers and freezers.
The three-phase Frigitek model allows control for multiple evaporators through one controller. Each evaporator is connected to its own power unit, and each power unit is daisychained to the next power unit with control wiring. One control module is connected to the first power unit in the chain and controls all of the power units for each evaporator. Three-phase motors have typical speeds of 1100-1200 rpm and 1600-1800 rpm. With the controller these speeds are reduced to 20% of full speed and 33% of full voltage. Electronically commutated motors (ECMs) are relatively new compared to the other motors available for evaporator fans. They have much higher efficiencies than either shaded-pole or permanent split capacitor motors. Replacing shadedpole and permanent split capacitor motors with ECMs is considered an excellent energy efficiency measure. Frigitek has an ECMotor controller that is specifically designed for the ECM. The ECMotor controller is designed to be used with two-speed Regal-Beloit ECMs. These motors have a full speed of 1750 and a reduced speed of 500 rpm. This means that the Frigitek can be combined with an ECM retrofit for additional savings. This method of controlling ECMs is currently patent pending.
The Frigitek controller saves energy in two ways. First, the speed of the motor is reduced when the evaporator is not cooling. The reduction in the speed of the motor decreases the energy needed by the motor. Secondly, the heat generated by the motor is reduced when the speed of the m motor heats up the space and has to be removed by the evaporator, adding to the cooling load. The amount of energy saved relates directly to the size and type of fan motor being used, the number of fan motors, how the cooler or freezer is operated, and the duty cycle of the compressor. Slowing the fan speed reduces the heat generated by the fans and thus the duty cycle of the compressor. Frigitek estimates the duty cycle reduction of the compressor to be 20% for shaded-pole motors, 15% for permanent split capacitor motors, and 25% for ECMs. Slowing the fan speed also reduces the energy used by the motor. Frigitek calculates the reduction in energy used by the motor at slow speed to be 80% for shaded-pole motors, 72% for permanent split capacitor motors, and 95% for ECMs.
All of these reductions were determined by tests performed in the manufacturer's motor laboratory. Based on an average compressor duty cycle of 40% and a typical installation, Frigitek savings are in the range of 25-35% of the energy used to operate a refrigerated walk-in cooler or freezer.
Three non-energy benefits have been identified by Frigitek:
The Frigitek controller has typical savings ranging from 25% to 35%, which is a reasonable amount of savings given the reduction in both energy used by the motor and the reduction in heat from the motors, if installed in an appropriate application.
The more often the compressor is off, the more savings will occur. If the compressor is oversized for the load, then the compressor is off more of the time. When this is the case, as is typical of new installations, the fans can run at a reduced speed more of the time. This is one product that actually saves more energy when the system has good efficiency than when it has poor efficiency. Frigitek recommends that a pre-inspection of the application be done before a decision is made to purchase this product.
Most cooler and freezer walk-ins can use a Frigitek controller, but each situation should be evaluated for applicability.
Rebates are available from most electric utilities.