ASHRAE Journal Highlights Common Problem Solved by Marlo Humidity Control Coils

March 20, 2024

The cover story in the November issue of the ASHRAE Journal (the publication of the American Society of Heating, Refrigeration and Air Conditioning Engineers) focused on a common problem in healthcare facilities: excess moisture creating wet and moldy conditions in HVAC systems. The story, entitled “Avoiding Wet and Moldy AHUs in Critical-Care Facilities,” draws attention to a major, but not well known, issue that affects many hospitals and other healthcare buildings.

At Marlo, we were happy to see this major, international coverage of a problem we’ve been solving for many years. The issue stems from condensate and moisture carryover collecting on air filters in air handling units – often very expensive HEPA and ULPA filters. This not only drastically shortens the life of the filters, but also reduces overall system performance and, most importantly, creates a breeding ground for dangerous pathogens like mold and bacteria.

The ASHRAE Journal article discusses the dangers of mold and microbial growth in hospital settings, where patients and other building occupants can be exposed to both airborne and surface contaminants. Pathogens like mold, fungi and bacteria can become aerosolized and distributed via the hospital’s ductwork to various areas, including operating rooms. This presents and obvious indoor air quality concern, with serious potential consequences for all occupants – especially already compromised patients.

The Marlo Solution – HCC Coils

Fortunately, Marlo has already developed a cost-effective solution to this serious problem: our Humidity Control Coils (HCCs). Sometimes referred to as “de-saturation” (or “de-sat”) coils, these coils remove excess humidity in the hospital’s airstream, eliminating moisture buildup in the filters, which prevents the conditions that lead to the development of mold and bacteria. In addition, stopping the excess moisture problem before it begins allows the system to run more efficiently and extends the life of the filters.

One of the traditional ways to solve this problem would be to use a cooling coil and a separate heating coil to eliminate carryover condensate and moisture. However, the Marlo Humidity Control Coil offers a more cost-effective solution by using just one coil, requiring just one supply and one return header, which saves the significant costs involved with plumbing hot water or steam to a reheat coil.

Our innovative Humidity Control Coil is a cooling coil that recirculates the warm fluid leaving the coil to, in turn, heat and desaturate the air exiting the coil. Advantages of the Marlo HCC include:

  • Eliminates excessive moisture in the airstream
  • Prevents development of a breeding ground for mold and bacteria
  • Stops damage to filters, extending filter life
  • Combines two coils into one, reducing installation and plumbing costs
  • Re-heat circuits on the air exit side of the coil reduce humidity and minimize carryover
  • Intermediate drain pans further eliminate condensate management problems

In addition to healthcare facilities, Marlo Humidity Control Coils are also ideal for other critical environments that utilize expensive HEPA and ULPA filtration, such as laboratories and clean room manufacturing facilities.

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