Modulation Technologies

Modulation Technologies

Modulation technologies have the ability to modify compressor performance and therefore perform more efficiently at different ambient temperatures.  The capacity of the compressor changes to meet the cooling demand and therefore reduce energy consumption.  Modulation technology leads to many benefits including increased humidity and temperature control, efficiency, reliability and comfort.  Copeland Scroll compressors utilize this technology to offer the best possible solution for residential and commercial applications.

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%.By offering a capacity range of 10%–100%, the Copeland Scroll Digital compressor doesn't need to start-stop as often as a traditional compressor. That means enhanced reliability and less maintenance because of the reduced wear and tear on the compressor.


  • Modulation Capability: Precise capacity matching capability provides continuous modulation between 10% and 100% capacity, the widest available capacity modulation range available
  • 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
  • Efficiency: High system efficiency is obtained by matching capacity with cooling/heating demand
  • Oil Management Issues: None, since compressor motor runs at constant speed
  • Electromagnetic Interference Issues: None, since no motor frequency variation is needed


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. Field testing shows improved temperature and humidity control provided by Copeland Scroll UltraTech compressors compared to fixed compressors. But, more importantly, inside comfort levels are maintained, regardless of how hot or cold it is outside.


  • Installation Costs: Less expensive than inverter systems or Copeland Scroll Digital systems, most cost effective method of modulation for systems under 5HP
  • Reliability: Comparable to fixed scroll systems
  • Efficiency: More efficient than hot-gas bypass, more efficient than inverters or Copeland Scroll Digital at 67% load
  • Oil Management Issues: None
  • Electromagnetic Interference Issues: None


    Copeland Scroll™ Variable Speed Compressors

    Variable speed 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. Emerson's new Copeland Scroll variable speed compressors are optimized for high efficiency (21+SEER) air conditioning and heat pump applications. Our newest compressor technology innovation delivers superior system performance.


    • Modulation Capability: Up to 6:1 turndown ratio achievable
    • Efficiency: High system efficiency is obtained by matching capacity with cooling/heating demand. Highest part-load efficiencies of any modulation technology
    • Reliability: Capable of superior reliability due to active protection provided by the motor control drive
    • Temperature Control: Precise control is achieved
    • Humidity Control: Precise control is achieved


    Multiple Compressors (Tandems/Trios)

    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. Six to eight compressors per unit can be used, which means, depending on the even or uneven combination, up to 12 capacity steps available to match the load by cycling the compressors on and off.


    • Efficiency: High system efficiency at both full-load and part-load
    • Installation Costs: Least expensive form of modulation
    • Reliability: Comparable to fixed compressor systems
    • Flexibility: Wide and smooth system lineup with a limited number of compressor models
    • Oil Management: No extra oil management hardware needed
    • Electromagnetic Interference Issues: None
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