Quick answer: A ceiling mounted dehumidifier hangs from the roof structure or sits above a suspended ceiling, so it removes moisture without taking floor space. Commercial models range from about 26 L/day to 960 L/day. Choose direct-air units to dry the room they hang in, and ducted units to dry rooms away from the unit or to hide it completely. Before buying, check the structure can carry the weight, the condensate can drain, and technicians can reach it.
Quick answer
- Best where floor space is valuable: warehouses, greenhouses, grow rooms, pools, food plants, basements.
- Direct-air: unit blows dry air straight into the room. Ducted: supply and return ducts connect the unit to one or more rooms.
- Size by moisture load and airflow, then check external static pressure if you add ducts.
See our ceiling-mounted and ducted dehumidifier range for full model data.
Where do ceiling dehumidifiers make sense?
- Warehouses and cold rooms: racking and forklifts need the floor.
- Greenhouses and grow rooms: benches and crops fill the floor, and high units help mix air above the canopy.
- Indoor pools and spas: ducted units keep the machine out of the humid, chlorinated hall.
- Food processing: overhead units keep wash-down areas clear.
- Basements, archives and shops: units hidden above the ceiling keep the space usable.
A floor-standing or portable unit is simpler when floor space is free, the space changes often, or the roof cannot carry extra load.
Direct-air or ducted?
| Direct-air | Ducted | |
|---|---|---|
| How it works | Draws room air in, blows dry air back into the same room | Return and supply ducts connect the unit to the rooms it serves |
| Best for | Open halls, greenhouses, warehouses | Several rooms from one unit; pools; hidden installations |
| Key check | Air throw reaches the working zone | Duct pressure loss stays within the unit's external static pressure |
| Installation | Simpler, fewer parts | Needs duct design and balancing |
Every RYDZ model lists its airflow and external static pressure, so you can size the ductwork before ordering. Our guide to ducted dehumidifier systems covers duct layout in detail.
Ceiling dehumidifier models and capacities
All capacities are rated at 30 °C/80 % RH. Pints per day are converted at the same condition (1 L = 2.113 pints).
| Model | Removal | Pints/day | Airflow | External static pressure | Supply |
|---|---|---|---|---|---|
| RYDZ-26DM | 26 L/day | 55 | 260 m³/h | 40–60 Pa | 220 V, 1-phase |
| RYDZ-58DM | 58 L/day | 123 | 550 m³/h | 40–60 Pa | 220 V, 1-phase |
| RYDZ-90DM | 90 L/day | 190 | 1,000 m³/h | 50–80 Pa | 220 V, 1-phase |
| RYDZ-138DM | 138 L/day | 292 | 1,300 m³/h | 50–80 Pa | 220 V, 1-phase |
| RYDZ-7S | 168 L/day | 355 | 1,800 m³/h | 100 Pa | 380 V, 3-phase |
| RYDZ-10S | 240 L/day | 507 | 2,500 m³/h | 100 Pa | 380 V, 3-phase |
| RYDZ-12S | 288 L/day | 609 | 3,000 m³/h | 120 Pa | 380 V, 3-phase |
| RYDZ-22S | 480 L/day | 1,014 | 5,600 m³/h | 150 Pa | 380 V, 3-phase |
| RYDZ-30S | 720 L/day | 1,521 | 7,400 m³/h | 200 Pa | 380 V, 3-phase |
| RYDZ-40S | 960 L/day | 2,028 | 10,000 m³/h | 200 Pa | 380 V, 3-phase |
R290 refrigerant is available on request. Read R290 vs R410A dehumidifiers for the differences.
How to size a ceiling dehumidifier
- Estimate the moisture load in litres per day: people, plants, open water, wet products, and outdoor air entering through doors and ventilation. Our sizing guide shows the method.
- Correct for your room condition. The rated L/day applies at 30 °C/80 % RH; cooler, drier rooms give less. See how much water a dehumidifier collects in a day.
- Check air changes. As a rule of thumb, the units' combined airflow should turn over the room air several times an hour so that all areas are dried.
- Split large spaces into zones with one unit each, so a single failure does not leave the whole space uncontrolled.
Installation checklist
| Check | What to confirm |
|---|---|
| Structure | The roof steel or slab can carry the unit's operating weight plus hangers; a structural engineer approves the fixing points. Never hang a unit from a suspended ceiling grid. |
| Vibration | Spring or rubber hangers between unit and structure; flexible duct connectors. |
| Drainage | A gravity drain with the fall and trap shown in the installation manual, or a condensate pump with overflow alarm. Insulate or heat-trace drain lines in unheated spaces. |
| Air path | Supply and return far enough apart that dry air crosses the working zone; outlets aimed away from people and crops. |
| Ducts (if used) | Total pressure loss of ducts, bends, grilles and filters at design airflow is within the unit's external static pressure. |
| Service access | A platform, lift or access panel reaching the filter, electrical box and drain pan. |
| Controls | Humidity sensor in the working zone, or a remote sensor if return air is not representative. |
| Corrosive spaces | Stainless or coated hangers in pools, greenhouses and wash-down areas. |
FAQ
Frequently asked questions
What is the difference between a ceiling mounted and a ducted dehumidifier?
"Ceiling mounted" describes where the unit hangs. "Ducted" describes how air reaches it. A ceiling unit can blow directly into the room or connect to ducts.
How high can a ceiling dehumidifier be mounted?
High enough to clear racking or crops, as long as the dry air still reaches the working zone and technicians can reach the unit. In tall halls, ducts or downward-angled outlets bring the air to the working level.
Do ceiling dehumidifiers need a drain?
Yes. At commercial capacities they run on continuous drainage, by gravity or by condensate pump.
Can one ceiling unit serve several rooms?
Yes, with a ducted layout, as long as the rooms need similar conditions and the duct pressure loss is within the unit's external static pressure.
Are ceiling dehumidifiers noisy?
The compressor and fans make some noise, which travels through the structure if the unit is rigidly fixed. Anti-vibration hangers, flexible duct connectors and placing the unit away from quiet rooms reduce it.
References
- ASHRAE Handbook—HVAC Systems and Equipment, Dehumidification and pressure drying equipment.
- ASHRAE Handbook—Fundamentals, Duct design.
