AReCoS
U.S. patent allowed

Since the 1940s, frost has stopped heat pumps. Ours are designed not to.

Keep the heat on without relying on backup gas or electric heat, with the optimizer built into the unit—not the cloud. Rooftop heat pumps up to 10 tons, with a ground-loop option later.

Reserve a place in the first units See the rooftop unit Read our story

Free · no deposit · no commitment.

Controller: U.S. patent allowed · Air–water heat exchanger: patent pending · ORNL: our controller is being tested with Oak Ridge National Laboratory under a research agreement (CRADA) supported by the U.S. Department of Energy, 2025 to 2027

Where we are: the controller has run a vapor-compression system in a hardware test and is now being tested with Oak Ridge National Laboratory · rooftop unit in design · chamber tests before 2027 pilots

One rooftop unit for every season A rooftop unit on a low commercial building, designed to send cool air into the building in summer and warm air in winter. Inside it, the AReCoS air–water heat exchanger, designed to keep frost to a thin, cleared layer, sits beside the embedded controller. Its water loop leaves the unit at two connections; a dashed loop runs from them into the ground, the ground loop it can take later. Its embedded controller is designed to extend to grid signals passed through the building's automation system, shown as a dashed line to the building. Embedded controller Rooftop unit Air–water heat exchanger DESIGNED TO KEEP FROST THIN Grid signal WATER LOOP Ground loop later Summer: cooling Winter: heating

Our rooftop unit: one unit for summer and winter.

What defrost costs a conventional unit Heat delivered to a building over time. A conventional air-source unit loses output as frost builds and then stops heating briefly during each defrost, twice in the period shown. A dashed line holds near full output without the interruptions: what our air–water heat exchanger is designed to deliver. WITH OUR HEAT EXCHANGER A CONVENTIONAL UNIT DEFROST DEFROST time heat into the building
What defrost costs on a winter day.

Refrigeration or chiller plant? Our controller is available for evaluation today

Heat pump products

What we're building

First the rooftop unit, up to 10 tons. Then a residential size, up to 5 tons, and small chillers.

Our products

All-season heat pump RTU

Light commercial · up to 10 tons · ground-ready

Air source, with our air–water heat exchanger (patent pending) and controller inside.

  • 22.1IEER
  • 13.4EER
  • 3.72COP at 47 °F
  • 2.57COP at 17 °F

10-ton unit. Projected ratings, not certified. Heating COP does not yet include water-loop pump and frost-clearing power.

Design basis

  • WinterDesigned to deliver 100% of its heating capacity rated at 47 °F at 0 °F, and at least 70% at −15 °F.
  • Backup heatOptional electric, used only below the heat pump's capacity or for emergency heat.
  • SummerDesigned to keep cooling up to 115 °F.
  • Ground-readyDesigned to connect to a ground loop later, without replacing the unit.
  • ControlsBACnet or a standard thermostat · on-unit fault codes · manual service mode. No cloud required.
More of the design basis
  • GridDesigned to accept demand-response signals through the building automation system (OpenADR), with capacity cap, setpoint shift and pre-heat modes.
  • ComponentsDesigned around standard compressors, valves and fans from several suppliers.
  • RefrigerantR-454B (A2L, GWP 466), with a refrigerant detection system and leak mitigation to UL 60335-2-40.
  • StandardsDesigned for UL 60335-2-40 listing, AHRI 340/360 ratings (AHRI 1340, IVEC and IVHE, when required) and ASHRAE 90.1. Full list

Inside the unit

Winter, heating: the pumped water–antifreeze loop in the air–water heat exchanger is active around the outdoor coil, which is the evaporator; hot refrigerant goes to the indoor coil. Winter: heating WATER–ANTIFREEZE LOOP ACTIVE OUTDOOR AIR AIR–WATER HEAT EXCHANGER Outdoor coil (evaporator) WATER PUMP ON T AMBIENT Compressor Indoor coil (condenser) EXV P, T P, T WARM AIR TO THE BUILDING Summer, cooling: hot refrigerant goes to the outdoor coil, which is the condenser, and rejects its heat through the water–antifreeze loop to the outdoor air; cold refrigerant goes to the indoor coil. Summer: cooling WATER–ANTIFREEZE LOOP ACTIVE OUTDOOR AIR AIR–WATER HEAT EXCHANGER Outdoor coil (condenser) WATER PUMP ON T AMBIENT Compressor Indoor coil (evaporator) EXV P, T P, T COOL AIR TO THE BUILDING
  • Hot refrigerant
  • Cold refrigerant
  • Water–antifreeze loop
  • Sensor
  • AReCoS embedded controller sets compressor · reversing valve · EXV · fan · blower · water pump together

In every season, heat moves between the outdoor air and the refrigerant through the water–antifreeze loop: air to loop to refrigerant when heating, and back out the same way when cooling.

More: sensors, actuators and the controller All-season heat pump rooftop unit, simplified schematic A rooftop unit with an outdoor side and an indoor side. Outdoors: the air–water heat exchanger, designed to keep frost to a thin, cleared layer (patent pending), the outdoor fan, the compressor and the reversing valve. Indoors: the indoor coil and blower. Outdoor air passes through the air–water heat exchanger and leaves the outdoor section; return air from the building enters the indoor section, passes the indoor coil and leaves as supply air, so the two airstreams are separate. An expansion valve joins the two sides. Pressure and temperature sensors on the refrigerant line at each coil, and outdoor-air and supply-air temperature sensors, feed the AReCoS embedded controller, which is designed to set the compressor, reversing valve, expansion valve, outdoor fan, blower and water pump together. OUTDOOR SIDE INDOOR SIDE Air–water heat exchanger DESIGNED TO KEEP FROST THIN PATENT PENDING Outdoor fan Compressor Reversing valve EXV Indoor coil and blower P, T P, T T T AReCoS embedded controller PATENT ALLOWED REFRIGERANT SENSOR SIGNAL COMMAND

Simplified. The controller is designed to read every sensor and set every actuator together.

Residential heat pump: air source first, ground loop later An outdoor heat pump unit beside a house draws heat from the outside air. A dashed pipe below the unit shows a ground loop that could be added later; the unit is designed to connect to it without being replaced. Same air–water heat exchanger as the rooftop unit First: air source Later: add a ground loop

Residential heat pump, ground-ready

Up to 5 tons

The rooftop unit's platform in a home size.

  • 23.8SEER2
  • 10.9HSPF2

5-ton ducted split. Projected ratings, not certified. HSPF2 does not yet include water-loop pump and frost-clearing power.

  • WinterDesigned to deliver at least 70% of its heating capacity rated at 47 °F at 0 °F.
  • GridDesigned to accept demand-response signals through the building automation system (OpenADR), with capacity cap, setpoint shift and pre-heat modes.
  • StandardsDesigned for UL 60335-2-40 listing and AHRI 210/240 ratings, with R-454B and leak detection.

How we make money

One platform. Three revenue paths.

AReCoS plans to sell all-season rooftop heat pumps, license its embedded controller to HVAC and refrigeration manufacturers, and selectively offer performance-based agreements where energy savings can be measured and verified.

  1. Unit salesAll-season rooftop heat pumps, initially 5–10 tons.
  2. Controller licensingPer-unit licensing and integration fees from manufacturers of heat pumps, chillers and refrigeration systems.
  3. Performance-based agreementsFor selected pilots and customers, pricing may include a share of independently verified energy savings.

What is different

One controller, designed to optimize the whole unit and set every actuator at once.

It is designed to run a physics model of the whole refrigerant cycle on the unit and set every actuator together. No cloud.

More on how the controller works

Equipment controls often give each actuator its own loop, and those loops interact. In the architecture described in U.S. application 18/592,624, the controller is designed to estimate the states its sensors can't measure and set the actuators together in real time, with a second model designed to screen its commands for likely component failures. The building still sets the goals, such as setpoints and schedules.

  • Startup and shutdown — designed to bring the unit up without liquid floodback, and to track where the refrigerant settles as it stops, so the next start begins from a known state.
  • Changeover — designed to sequence the compressor, reversing valve and expansion valve through each switch between heating and cooling.
  • Winter — designed to need no reverse-cycle defrost in normal operation; if the frost-clearing system faults, the unit falls back to standard defrost and reports it.
Patent pending

Hardware

Air–water heat exchanger, designed to keep frost thin while it heats

More about the air–water heat exchanger

Like any air-source heat pump, it draws its heat from the outdoor air; in our unit that heat passes from the air to the water–antifreeze loop and then to the refrigerant, and in summer it leaves the same way in reverse. A new electromechanical system is designed to limit frost to a thin, controlled layer and clear it continuously, so in normal operation the unit is designed to keep heating without a reverse-cycle defrost stop; if the frost-clearing system faults, it falls back to standard defrost and reports it. The water–antifreeze loop is sealed inside the unit and freeze-protected, including after a ground loop is connected. Details under NDA: request the technical brief. U.S. provisional application on file; the allowed patent covers the controller.

Patent allowed

Controller

Embedded controller, designed to set every actuator together

U.S. application 18/592,624, allowed July 2026. Its hardware test is published in US 2024/0295337 A1 (FIGS. 4–7).

The full record Check status at the USPTO

  • Optimizes itself

    Designed to set the compressor, valves and fans together for the lowest total power, around the clock.

  • Units work together

    Designed to share the load and agree on the best setpoints among themselves over the local network or BACnet, with no smart supervisory system. The cloud is optional, for monitoring only.

  • Finds its own faults

    A physics model of the refrigerant cycle is designed to flag faults such as low charge or a sticking valve, so contractors finish each call faster and fit in more of them.

  • Keeps heating in winter

    Our air–water heat exchanger is designed to keep frost thin, so the unit keeps heating without leaning on backup heat.

First units

Reserve a place in the first units.

Pilot units targeted for 2027 and commercial units for 2028, planned for production with established manufacturing partners.

  • Priority for the first units. The list decides where the first units go.
  • First to hear pricing and schedules. Shared with reservation holders before anyone else.
  • Shape the first builds. Early sites help set configurations and pilot plans.
  • No cost, no obligation. No deposit and nothing to sign.

Owning, installing, warranty and verification: answers for owners, contractors and utilities.

Add details (optional)

No payment, no obligation. Your details are used only to plan the first units. Privacy.

Team

Ahmed Hussein, founder and CEO of AReCoS

Ahmed Hussein, PhD

Founder and CEO. Inventor of the AReCoS controller (U.S. patent allowed) and air–water heat exchanger (patent pending). Twelve years of control design in automotive and aerospace, with strong experience in fluid mechanics modeling: a PhD on unsteady flow and fluid–structure interaction, and physics-based fluid-thermal models of electric-vehicle battery and cabin heating and cooling.

More · Google Scholar · LinkedIn

Ahmed Atallah, physics modeling lead at AReCoS

Ahmed Atallah, PhD

Physics modeling lead. PhD in control, UC San Diego. Working with the founder since 2022, and co-leading the physical models and control algorithms at AReCoS. Ten years of physics-based modeling, estimation and optimal control: high-precision numerical integrators and orbit propagators, uncertainty quantification, nonlinear model predictive control, and sensor-fusion estimation for autonomous machines. Best Paper Award, 2019 AAS/AIAA Space Flight Mechanics Meeting.

Google Scholar

Chief technology officer

Joining soon. A vice president from the automotive industry, name to be announced: 25 years of industrial leadership, 30+ global products, close to 40 patents, PhD in control engineering.

How it started: read our story, from a garage test bench to rooftop units.

Collaborator: Oak Ridge National Laboratory · Funding agency: U.S. Department of Energy

Investors: request the deck.

Roadmap

From a controller today to heat pumps for every season.

  1. Embedded controller for chillers and refrigeration

    Available for evaluation, fitted to your system.

    Product brief

    Evaluation today

  2. All-season heat pump RTU

    Light commercial, up to 10 tons.

    See the rooftop unit

    Pilots 2027 · commercial 2028

  3. EV heat pump

    Our heat pump and controller for the cabin and battery, for vehicle programs.

    EV heat pump

    Pilots summer–fall 2027

  4. Residential heat pump

    Up to 5 tons, on the same platform, ground-ready.

    See the residential heat pump

    Pilots early 2028

Dates after today are targets.

Let's talk.

Pilot sites for our heat pump RTU, manufacturing partners for our first builds, or our controller for your system.

Email info@arecos.net
625 Kenmoor Ave SE, Suite 350
Grand Rapids, Michigan 49546