How to route dehumidifier ductwork (VIDEO)

How to route desiccant dehumidifier ductwork is the most common question in the food processing industry when it comes to managing humidity.  

That’s why Quest engineers have spent hours upon hours (seriously, like, an unsettling amount of time) fine-tuning what they have found to be the best approach. 

Why’s all this matter? Because it’s critical to get your ductwork installed correctly to prevent frost in walk-in freezers and coolers, loading docks and other small spaces. If you don’t capture all that moisture from the air, the problem is only going to get worse – leading to safety and quality issues. 

But FirstDesiccant Basics … 

It’s important to note how desiccant dehumidifiers work because it’s what dictates ductwork placement. 

A desiccant wheel, which spins inside the unit, is a honeycomb material coated in silica gel. As air blows through it, the wheel pulls moisture from the air. 

“To get the best performance from our desiccant dehumidifier, we want the most humid air possible, so it can absorb the most moisture,” said Dan Dettmers, applications engineer, Quest Dehumidifiers. 

How to Route dehumidifier ductwork 

  1. First things first, determine the moisture source.  

Almost 100% of the time, the moisture that’s causing frost problems isn’t coming from frozen product. The moisture is coming from warm, humid environments outside the space you’re trying to control. 

That outside space could be adjacent rooms or the great outdoors; regardless, both will cause issues.  

And the reason humidity sneaks in? Most the time it’s from doors being opened again and again … and again. And then one more time just to be safe.  

“In rushes the warm air, out rushes the cold air,” Dettmers said. “Then, we immediately have moisture in the space, where frost can quickly form.” 

  1. Ductwork placement 

When the doors open, warm air runs across the ceiling. In a perfect world, that humid air makes its way to the evaporator, where it’s dried. The problem is that rarely happens, Dettmers said. 

More often, the warm air cools and settles as frost on the ceiling, or it settles in the space, ultimately condensing and freezing on the floor or products. Additionally, evaporators are rarely capable of meeting dehumidification needs. 

To solve this, Dettmers recommends placing the return inlet right above the door, where the air is warmest and contains the most moisture. From there, the air is pumped through the desiccant dehumidifier outside the room. 

But, where that air is returned matters, too.  

“We don’t want to put it in the middle of the room and thaw our food or desiccate produce,” Dettmers said. 

The dry air is pumped back into the space directly behind the evaporator and dispersed as cool, dry air. As a bonus, this process helps reduce the amount of time the evaporator needs to spend in defrost mode – meaning the room temperature remains consistent.  

Want to get into specifics for your project? Send us an email or call us any time.