Modine Manufacturing Company was recently granted a patent for its hot gas reheat (HGRH) system option used in its Atherion Commercial Packaged Ventilation units. The technology manages and reduces the refrigerant charge required in an (HGRH) system while taking advantage of efficiency and performance improvements through the use of a full height HGRH coil for heating dehumidified air in a Dedicated Outdoor Air System (DOAS).

Additionally, the patent provides ... 

  • the ability to adjust the total volume of the system. If low reheat capacity is required, one circuit is disabled to lower the system’s internal volume and keep more refrigerant flowing through the system. 
  • the ability to vary the internal volume and allow for reduced fan energy consumption.
  • fully modulating adaptive control for precise supply air temperature control in a wide range of operating conditions.

“We are excited how this technology delivers on our global commitment to provide sustainable and efficient products that transform the industry and exceed our customers’ expectations,” says Mike Schires, senior product manager at Modine. Here's what the patent means for the company and technology's future:

How does the Hot Gas Reheat System save energy. If you were to explain the process to customers (not technicians) how would you explain it? 

It saves energy a couple ways. First, it is reclaimed energy for reheat which meets the ASHRAE 90.1 requirement that reheat be at least 75 percent site reclaimed. The heat transferred from the conditioned airstream by the evaporator coil typically is rejected to the outside atmosphere through the condenser coil.  With hot gas reheat, some of that hot refrigerant gas from the cooling process is diverted from the condenser to the hot gas reheat coil in the conditioned airstream to reheat the dehumidified air off the evaporator. Second, we use a larger coil than most manufacturers which reduces static pressure drop, thus saving supply fan energy.

How long has this technology been around? Is it completely new or is it a play on what already exists?

Hot gas reheat is a proven technology to save energy and can be as simple as on/off control to multi-stage control, to more sophisticated modulating control. While there are manufacturers that offer fully modulating hot gas reheat control, Modine takes that one step further with our patented fully modulating multi-stage design that adjusts total coil volume by disabling a circuit in low reheat load conditions. The system is still fully modulating, but by controlling total reheat coil volume, in addition to modulating, we provide greatly improved hot gas reheat performance over smaller single circuit modulating control strategies.

Explain what you mean by the “ability to vary the internal volume and allow for reduced fan energy consumption.”

Unlike smaller coils that have a higher static pressure drop, our reheat coil is full height, thus reducing required supply fan power. We overcome the internal volume challenges in low reheat conditions by reducing the internal volume through disabling half the coil when not needed.

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