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Refrigeration Evaporators

Custom Evaporators - Heat Pump Evaporators


A heat pump is a system that transfers heat from one place to another using refrigeration technology, providing both heating and cooling for buildings by absorbing heat from outdoor air. An evaporator heat pump is an air source heat pump designed with the capability of switching between cooling and heating mode.

At Colmac Coil, we manufacture industrial air source heat pumps available in V-bank, flat deck horizontal air flow, flat deck vertical air flow, insulated penthouse, and other customizable configurations.

Heat pump systems are increasingly gaining adoption in certain parts of the world due to the expanding availability of equipment, environmental regulations mandating low global warming potential (GWP) refrigerants, and growing demand for sustainable and high-performance heating and cooling solutions. Natural refrigeration heat pump systems are attractive to end users who want a future proof, sustainable, and high-performance heating and cooling system. 

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Outdoor installation: Colmac heat pump evaporators feature robust construction and durable materials for outdoor installations, ensuring longevity, reliability, and weather resilience.

Casing material options:

  • G235 galvanized steel
  • Stainless steel


  • Stainless steel: Utilizing stainless steel tubes ensures resistance to corrosion and longevity, maintaining optimal heat transfer efficiency over the system's lifespan.

Fin material options:

  • Aluminum
  • Epoxy coated aluminum.
  • CuNi
  • Stainless steel

Drain pan material options (if required):

  • Galvanized steel
  • Stainless steel
  • Aluminum (inner material)
  • All drain pans are heated

Defrost options:

  • Hot gas
  • Electric
  • Interlaced glycol
  • Air
  • Water

Efficient defrost: reducing escape heat during the defrost cycle significantly lowers power consumption.

Several options are available to improve defrost efficiency on Colmac Heat Pump Evaporators:

  • Louvers: louvers that close during the defrost cycle to minimize heat loss to improve the defrosting of the evaporator heat pump.
  • Air inlet hoods: Air inlet hoods prevent the ingress of cold air during the defrost cycle
  • Defrost dampers: Defrost dampers regulate airflow during the defrost cycle, optimizing system performance and energy efficiency.

Fans: EC or AC

  • EC fan motors: Equipped with electronically commutated (EC) fan motors as standard, EC fans offer lower sound pressure levels, remote fan control, and variable fan speed without a variable frequency drive (VFD)
  • AC fan motors: Reliable performance and cost-effective operation, AC fan motors are suitable for a wide range of applications.

CO2 Design:

  • High tube pressure rating up to 1800 PSIG.
  •  Safety certifications: UL207, CRN, ASME “U” Stamp
  •  Stainless steel tubes
  • Electric ring heaters for both AC and EC fans
  • Mounting legs
  • Factory wired fans to individual disconnect switches

How does a Heat Pump Evaporator work?

A heat pump's evaporator can switch from heating to cooling by reversing the flow of the refrigerant through the system.

Heating Mode: In heating mode, the heat pump absorbs heat from the outside air (even in cold temperatures, there is heat energy present) using the outdoor unit's evaporator coil. The refrigerant in the coil evaporates, absorbing heat energy from the outdoor air. This heated refrigerant is then compressed by the compressor, raising its temperature even higher. The hot refrigerant then flows through the indoor unit's coil (the condenser coil) where it releases heat into the inside air.

Cooling Mode: When switching to cooling mode, the flow of refrigerant is reversed. The outdoor unit's coil now acts as a condenser, rejecting heat to the outside air. The refrigerant is still compressed by the compressor, but now it's absorbing heat from the indoor air. This process cools down the inside air. The cooled refrigerant then flows through the indoor unit's coil (the evaporator coil) where it absorbs heat from the indoor air, further cooling it down. The now-warmed refrigerant returns to the outdoor unit to repeat the cycle.

The reversing valve in the heat pump system is what facilitates this change in the direction of refrigerant flow. By shifting the position of the reversing valve, the heat pump changes whether the indoor or outdoor coil functions as the evaporator or condenser. This allows the heat pump to provide both heating and cooling capabilities.


District Heating & Cooling Systems

Industrial Heating & Cooling

Waste Heat Recovery

HVAC Systems

Drying Processes

Cold Storage

Food Processing

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