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Air-to-Water Cascade Heat Pump System for High Temperature Heating

Air-to-Water Cascade Heat Pump System

Air-to-Water Cascade Heat Pump System for High Temperature Heating

Innovation that achieves the impossible.

The fully packaged Air-to-Water Cascade Heat Pump System delivers efficient, precise, high temperature heating performance for buildings with heating and cooling needs.

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  • Versatile to meet high temperatures that traditional boilers operate at

    Trane's cascade heat pump design provides precise, simultaneous heating and cooling temperature control.

    Additionally, the system provides a wide turndown range with a minimum of 20% heating unloading capabilities, designed to match building heating loads when multiple water-to-water heat pumps are used.

  • Simplifies electrified heating system retrofits

    Our system extends air-to-water heat pumps to higher temperature ranges. Air-to-water heat pumps and water-to-water heat pumps work together to achieve high hot water supply temperatures up to 165°F with 0°F ambient temperature, making them ideal for building retrofits.

    The system’s high temperature enables buildings to leave distribution and infrastructure (i.e. piping, terminal coils) in place while reducing building occupant disruption when electrifying heating systems.

  • Streamlines system design and high-performance operation

    Our fully integrated tools deliver all the necessary equipment, control sequences, and specifications to reduce the system’s complexity while enhancing performance.

    Implement electrified HVAC systems even faster with Trane’s applications guide and educational resources. 

  • Improves heating efficiency and reduces energy costs

    Trane’s cascade heat pump system extends multiple, large-capacity, highly efficient heat pump chillers to higher temperature performance. 

    Our system is twice as efficient as traditional boilers. Advanced control algorithms and Trane energy services save energy even further.

  • Achieve sustainability goals and meet local building requirements

    Our low-GWP heat pump systems provide efficient electrified heating and cooling with optional back-up electric heating.

    Trane local system experts help ease the transition from traditional heating systems to sustainable systems. We collaborate with building owners, contractors, and engineers to understand their goals and applications from the start. Our commitment continues through the entire process, ensuring the system operates as expected. In addition, our local experts understand local laws and can help meet local requirements.

The Air-to-Water Heat Pump Cascade System is a fully packaged heating system that dramatically eases the transition to efficient, electrified heating by using the same high temperatures that non-condensing boilers operate today, which helps reduce the high upfront cost to replace building infrastructure, such as piping.

Part of the Trane Comprehensive Heat Pump Chiller System portfolio, the Air-to-Water Heat Pump System option delivers higher hot water supply temperatures up to 165°F. The high temperature avoids replacement of building infrastructure and distribution (i.e. piping, terminals) when converting boilers to heat pumps. Its flexible design provides cooling, heating, and simultaneous loads with or without dedicated heat recovery units and accommodates dedicated air-cooled chillers.

  •  Air-to-Water Heat Pump (60 to 230 tons; 800 to 2500 MBH) operates in heating or cooling mode. Fluid temps up to 140°F. Heating down to 0°F ambient. Meets ASHRAE® AWHP efficiency requirements.
  • Water-to-Water Heat Pump (600 to 3000 MBH) operates in heating mode to immediately heat the building; Achieves leaving water temperatures up to 165°F (74°C) with R-515B. Meets ASHRAE® booster efficiency requirements.
  • Tracer® Controls applied control sequences balance multiple priorities: reliability, carbon reduction, efficiency, and cost savings, during heating, cooling, and simultaneous modes. Advanced algorithms enhance intermediate loop temperature based on load, outdoor ambient, and units selected.
  • Intermediate loop buffer tank provides a mechanism to manage volume to prevent defrost disruption.
  • Auxiliary boiler option available to provide backup heat

System Applications

Explore our Air-to-Water Heat Pump System Options

We offer multiple options and variations that work with many existing hydronic airside systems, offering configurations and options to fit a variety of applications.

Base Systems

Air-to-Water Cascade Heat Pump System

The base system features advancements in air-to-water heat pumps to meet lower ambient temperatures using low temperature hot water supply for enhanced efficiency and energy cost savings. 

Comprehensive Chiller-Heater System with Hydronic Branch Controls
model RTWD

Water-to-water heat pump (model RTWD)

The RTWD increases the air-to-water heat pump leaving water temperatures up to 165°F, which is distributed throughout the building’s heating system.

Explore the RTWD
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Frequently Asked Questions

A cascade heat pump system integrates an air-to-water heat pump, water-to-water heat pump, and controls to deliver higher temperature ranges for efficient low carbon heating and cooling.

The system works by utilizing a water-to-water heat pump to increase the leaving hot water temperature from the air-to-water heat pump. The system can produce up to 165°F hot water at ambient temperatures as low as 0°F. 

A dual temperature heating configuration enables the system to produce multiple hot water setpoints to increase system efficiency and match heating capacity to the building’s heating needs.

Precise hot water temperature controls help deliver consistent hot water temperatures. In addition, the hot water temperature controls help the heat pumps stay online without cycling at low loads.

The primary reasons for choosing a cascade system are to lower retrofit costs and improve efficiency. The system uses multiple heat pumps to reach temperatures that non-condensing boilers operate at, which allows the building to leave infrastructure (i.e. piping, terminal coils) in place, helping to  reduce labor and material to convert to electrified heating while reducing building occupant disruption. For existing buildings with aging heating or cooling equipment looking for a more efficient solution, the Cascade Heat Pump System helps meet efficiency requirements with a heating COP of 2 at low ambient conditions, making the system twice as efficient as non-condensing boilers.

The water-to-water heat pump model RTWD is a key component of the Cascade System. It increases the temperature from the air-to-water heat pump model ACX up to 165°F, which is distributed throughout the building's heating system. The RTWD modulates its heating capacity to match the building's heating needs, which improves system reliability and reduces heat pump cycling.

Yes, the system uses familiar, easy-to-install, and maintain technologies that are commonly used today. For example, the system’s air-to-water heat pumps are similar to commonly used air-cooled chillers with the addition of a reversing valve to enable the unit to provide cooling or heating. The water-to-water heat pumps are proven water-cooled chillers featuring R-513A or R-515B refrigerant but are controlled by hot water setpoints. Together, the air-to-water heat pumps and water-to-water heat pumps provide hot temperatures like traditional boiler heating systems, so there is no need to change the building’s heating infrastructure and distribution (i.e. piping, terminal coils). 

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