Rules of
thumb formulas

Quick Reference Guide

In many cases it is not strictly necessary to perform all the extensive calculations described on these pages. Experience allows you to use some shortcuts when selecting a mobile dehumidifier. This empirical data is presented in the table below with easy rules of thumb formulas referring to the problems solved in the examples here. 

W refers to the amount of water drawn from the air in g/hour.

V refers to the volume of the room in m3 

Problemrequirementtypical locationassumed air change raterules of thumb
Excess water content in the air Establish good indoor climate Office buildings, domestic houses, conference rooms, etc. 0.5 per hour W=V*2.0 (g/hour)
 Excess water content in the air Preserve and protect goods and materials  Museums and exhibitions storage rooms for sensitive goods, water works, etc.  0.3 per hour   W=V*1.2 (g/hour)
 Excess water ontents in the materials  Repair water damage* Floods, fires, burst water pipes   As low as possible W=V*4.0 (g/hour) 

* = Based on a drying period of 8-12 days

Please note that concerning drying out a newly constructed building it all comes down to the specific nuilding materials used for walls, floors and roofs. The water content of various building materials differ so much that a simple rule of thumb would not make sense. 

1. Establishing a comfortable indoor climate

If the desired RH-value is to be approx. 50% RH use this formula:

W = V * 2.0 (g/hour)

Example: V = 500m3> W = 2.0 * 500 = 1,000 g/hour.

Recommendation: Two CDT 40 units. Capacity: 0.65 litre/hour at 20oC/50% RH. 

2. Preserve and protect goods and materials

If the desired RH-value is to be approx. 50% RH use this formula:

W = V * 1.2 (g/hour)

Example: V = 450 m3 > W = 1.2 * 450 = 540 g/hour

Recommendation: CDT 40. Capacity: 0.65 litre/hour at 20oC/50% RH. 

3. Repair water damage

Assuming a drying process of 8-12 days and an average condition of t = 20oC/50% RH (starting at 60% RH ending at 40% RH) use this formula:

W = V * 4.0 (g/hour)

Example: V = 280 m3 > W = 4 * 280 = 1,120 g/hour

Recommendation: Two CDT 40 S units. Capacity pr. unit: 0,60 litre/hour at 20oC/50% RH. We recommend that you use S-models with extra air volume and built-in 1kW heaters to force the evaporation and speed up the dehumidification process when dealing with water damage.

Room volume (V)CDT 30 (S)CDT 40 (S)CDT 60CDT 90
< 200 m3  2 units 1 unit  1 unit 1 unit 
200 - 300 m3 3 units 2 units 2 units  1 unit 
300 - 500 m3 5 units 3 units  3 units  2 units 

500 - 750 m3

 7 units 4 units  3 units 2 units 


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