Dehumidifiers all have the same job: pull moisture out of the air. How they do it, and how well they perform under different conditions, varies a great deal. On a large water damage job, a construction site or an industrial facility, choosing the wrong type can add days to a project or leave materials wetter than they should be.
Three main types of dehumidifiers are used for professional drying: conventional refrigerant units, low grain refrigerant units, known as LGR, and desiccant units. This article explains how each type works, where each performs best and how drying professionals decide which to use, particularly on larger commercial and industrial projects.
What this covers
- Why Dehumidifier Type Matters
- How Refrigerant Dehumidifiers Work
- Conventional Refrigerant Units
- Low Grain Refrigerant Units
- How Desiccant Dehumidifiers Work
- The Three Types Side by Side
- Temperature and Humidity Ranges
- Large Losses and Trailer-Mounted Systems
- Choosing the Right Type for a Job
- What Equipment Comparisons Often Miss
- Short Answers on Dehumidifier Types
Why Dehumidifier Type Matters
Drying a building depends on keeping the air dry enough that wet materials continue to release moisture. As a drying job progresses, the air gets drier and the remaining moisture becomes harder to remove. A dehumidifier that works well at the start of a job may struggle near the end.
Temperature matters too. Some dehumidifiers lose much of their capacity in cool conditions, which is a problem in unheated warehouses, parking structures, basements and buildings under construction. Matching the dehumidifier type to the conditions is one of the most important decisions in a drying plan.
How Refrigerant Dehumidifiers Work
Refrigerant dehumidifiers work much like an air conditioner. A fan draws humid air across a cold coil. Moisture in the air condenses on the coil, drips into a collection pan and is pumped or drained away. The air is then warmed slightly as it passes over a hot coil and returned to the room, drier than before.
This process works best when the air is warm and humid, because there is more moisture to condense. As the air gets cooler or drier, less water condenses and performance drops.
A useful way to picture this is to think about a cold glass of water on a summer day. In humid weather, water beads quickly on the outside of the glass. In dry weather, the glass stays nearly dry. A refrigerant dehumidifier’s cold coil behaves the same way, collecting a great deal of water when the air is humid and much less when it is not.
Refrigerant units also release a small amount of heat into the room as they run. In a warm space, that added heat can help drying by warming wet materials slightly, which encourages evaporation. In an already hot space, it can add to discomfort for occupants, which is one reason equipment placement is planned with the people in the building in mind.
Conventional Refrigerant Units
Conventional refrigerant dehumidifiers are the simplest professional units. They perform well in the early stages of drying, when humidity is high. They are generally less expensive to rent, simple to set up and common on smaller residential jobs such as a single wet room or a small leak caught early.
Their limitation appears as the job progresses. Once the air reaches moderate humidity, conventional units remove much less water. On jobs with dense materials or large amounts of water, they may not be able to bring conditions low enough to finish drying efficiently.
Low Grain Refrigerant Units
LGR dehumidifiers are refrigerant units engineered to keep removing moisture at lower humidity levels. The name refers to grains of moisture per pound of air, a measure drying professionals use. LGR units can pull the air down to lower moisture levels than conventional units, which helps wet materials continue to dry late in a project.
Because of this, LGR units have become the standard choice for many water damage jobs. One Los Angeles equipment provider lists the Dri-Eaz LGR 7000XLi, rated to remove up to 29 gallons of water per day, alongside other high-capacity LGR units rated for large square footage.
How Desiccant Dehumidifiers Work
Desiccant dehumidifiers work differently. Instead of cooling air to condense moisture, they pass air through a slowly rotating wheel coated with a moisture-absorbing material. The wheel picks up moisture from the air. A separate stream of heated air then dries the wheel and carries the moisture outside the building, usually through a duct.
Because they do not rely on condensation, desiccant units keep working in cold conditions where refrigerant units struggle. They can also reach very low humidity levels, which is useful for drying dense materials such as concrete, hardwood and plaster.
Desiccant units need a power supply and ductwork to exhaust the moist air, and some large units run on high-voltage circuits or generators. Setup is more involved than plugging in a portable refrigerant unit, which is part of why they are used selectively.
The Three Types Side by Side
|
Feature |
Conventional refrigerant |
LGR refrigerant |
Desiccant |
|
How moisture is removed |
Condensation on a cold coil |
Condensation, optimized for drier air |
Absorption on a rotating wheel |
|
Best conditions |
Warm, very humid |
Warm to moderate, humid to moderately dry |
Cool or cold, very dry target |
|
Performance late in drying |
Declines |
Continues |
Continues |
|
Moisture discharge |
Drained or pumped as water |
Drained or pumped as water |
Exhausted as warm, moist air through a duct |
|
Typical use |
Small or early-stage jobs |
Most water damage jobs |
Cold spaces, dense materials, large losses |
Temperature and Humidity Ranges
Each type has a range where it performs best. Refrigerant units, both conventional and LGR, generally work well in normal indoor temperatures. As temperatures fall, ice can form on the cold coil and capacity drops sharply. Desiccant units maintain performance in cooler conditions and can be the better choice for unheated buildings, cold storage areas or winter work.
In Los Angeles, most interior spaces stay warm enough for refrigerant units, but certain locations, such as parking structures, large warehouses, building shells under construction and crawl spaces, can fall into ranges where desiccant equipment performs better.
Large Losses and Trailer-Mounted Systems
Very large losses, such as flooded warehouses, multi-story buildings, hospitals and schools, sometimes call for trailer-mounted desiccant systems. These units sit outside the building and push dry air in through large ducts, while humid air is exhausted. They can handle volumes of air far beyond what portable units can manage.
Large projects often combine equipment types. A plan might use trailer-mounted desiccant systems to dry the main space, LGR units to handle specific rooms and air movers to keep air circulating across wet materials.
|
Project type |
Common equipment approach |
|
Single flooded room |
One or two LGR units with air movers |
|
Several rooms or a small commercial suite |
Multiple LGR units with air movers |
|
Cold or unheated structure |
Desiccant units, sometimes with supplemental heat |
|
Large warehouse or multi-floor building |
Trailer-mounted desiccant systems plus portable units |
Choosing the Right Type for a Job
Drying professionals weigh several factors when choosing equipment:
- The size of the space and volume of air
- The amount of water and the types of wet materials
- The temperature of the space, now and overnight
- How low humidity must go to dry the materials fully
- Available power and ventilation for desiccant exhaust
- How quickly the space must return to use
These factors often point to a mix of equipment rather than a single type. Plans are also revisited during the job. A project that starts with conventional units while the air is very humid may switch to LGR or desiccant equipment once the easy moisture is gone, keeping drying on pace through the final days.
What Equipment Comparisons Often Miss
Many comparisons focus on the gallons-per-day rating. That rating reflects specific test conditions and may not match real conditions on a job. A unit rated for high capacity in warm, humid air may remove far less in cooler, drier air.
Comparisons also tend to miss the discharge difference. Desiccant units exhaust moist air rather than water, so they need a path to the outdoors. That affects setup in sealed or multi-story buildings.
Finally, comparisons rarely address monitoring, which is the only way to confirm a choice was right. Whatever equipment is used, daily moisture readings are what show whether it is working.
Short Answers on Dehumidifier Types
Contractors and facility managers comparing industrial dehumidifier hire for Los Angeles job sites can ask which types are available and how quickly they can be delivered. LA Restoration Rentals, listed on its Google Business Profile, is one of the local suppliers offering high-capacity LGR units, desiccant units and trailer-mounted systems for large losses, on daily, weekly and monthly terms with delivery across Los Angeles County.
What does LGR stand for?
Low grain refrigerant, a design that keeps removing moisture as air becomes drier.
When is a desiccant dehumidifier used?
In cold spaces, for dense materials and on very large projects.
Why do refrigerant units struggle in the cold?
Their cold coils can ice up and condense less moisture at low temperatures.
Do large projects use one type of dehumidifier?
Often not. Many combine desiccant, LGR and air movers.
Choosing between conventional, LGR and desiccant dehumidifiers comes down to conditions and goals. Understanding how each works, and where each performs best, helps drying projects finish faster and more completely.
