Modulation Technologies
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Modulation Technologies

Copeland Scroll Digital Compressors

The Copeland Scroll Digital™ compressor utilizes axial scroll compliance to achieve modulation by forcing the scrolls to separate, causing compression of the refrigerant to stop without stopping the compressor motor. In this “unloaded” state, the compressor output is zero capacity. When the scrolls are engaged in the “loaded” state, compressor output is 100% capacity. The scrolls are separated in a periodic cycle (15 seconds) to obtain a time-averaged compressor capacity based on the ratio of loading and unloading times. This allows the compressor to achieve infinite capacity modulation between 10% and 100%.

 Advantages

  • Modulation Capability: Most precise capacity matching capability provides continuous modulation between 10% and 100% capacity, the widest available capacity modulation range available.
  • Electromagnetic Interference Issues: Negligible, since no motor frequency variation is needed.
  • Oil Management Issues: Negligible, since compressor motor runs at constant speed.
  • Efficiency: High system efficiency is obtained by matching capacity with cooling/heating demand.
  • Temperature Control: Precise and smooth control is achieved, limiting any fluctuations in setpoint.
  • Humidity Control: Precise and smooth control is achieved, limiting any fluctuations in setpoint.

Copeland Scroll UltraTech Compressors
The Copeland Scroll™ UltraTech™ compressor is typically used on split and packaged systems under 5 HP. The compressor runs at either 67% or 100% capacity, depending on cooling/heating demand. When partial load is needed, bypass ports inside the compression chamber open which partially unloads the compressor. This allows the compressor to pump only the refrigerant needed to achieve 67% capacity, making this more efficient than hot-gas bypass.

Advantages

  • Installation Costs: Less expensive than inverter systems or Copeland Scroll Digital systems, most cost effective method of modulation for systems under 5HP
  • Electromagnetic Interference Issues: None
  • Oil Management Issues: None
  • Reliability: Comparable to fixed scroll systems
  • Efficiency: More efficient than hot-gas bypass, more efficient than inverters or Copeland Scroll Digital at 67% load, less efficient than inverters or Copeland Scroll Digital at full load
Multiple Compressor Systems
System capacity can be modulated by using multiple refrigeration circuits or by using multiple compressors in single-circuit systems. In a four circuit system, commonly used in packaged rooftops, individual compressors can be turned on and off to achieve a specific output.

Advantages

  • Installation Costs: Least expensive form of modulation
  • Electromagnetic Interference Issues: None
  • Oil Management: No extra oil management hardware needed
  • Reliability: Comparable to fixed compressor systems
Inverter System
Inverter systems modulate refrigerant flow by varying the speed of the compressor motor.

The compressor motor speed determines the refrigerant flow speed. Therefore, by varying the motor frequency, capacity can be modulated. Capacity output increases and decreases with motor speed. Although this allows precise temperature and humidity control, oil management hardware and electronics are needed to ensure enough oil is in the compressor during slow motor conditions and to ensure that too much oil does not get pushed out of the compressor during fast motor conditions.

Advantages

  • Modulation Capability: More capacity output possibilities than hot-gas bypass
  • Temperature Control: Precise control is achieved
  • Humidity Control: Precise control is achieved
  • Efficiency: High system efficiency is obtained by matching capacity with cooling/heating demand

Disadvantages

  • Installation Costs: Most expensive of modulation technologies
  • Modulation Capability: More capacity steps than hot-gas bypass or multiple circuit systems, but capacity range is limited by minimum motor speed. Capacity change is slow because motor frequency changes must be performed slowly to avoid damage due to insufficient compressor lubrication.
  • Electromagnetic Interference Issues: High electromagnetic interference from varying motor frequency
  • Oil Management: Extra hardware and electronics needed to control compressor oil level
  • Reliability: More complex electrical and mechanical hardware
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