+44 203 286 8189 steve.jones@westside-int.com

Electric Dehumidifier


Instruction Manual

M-1J1R / M-2J1R / M-3M1R / M-3J1R M-5J1R / M-7J1R / M-10J1R


– Please read this manual before you use ROSAHL and use it correctly.

– Please keep this manual for the person who operates, manages, and maintains ROSAHL.


For correct usage

– Supply 3V DC to ROSAHL. DO NOT reverse the polarity.

– Dehumidification changes to humidification if you reverse the polarity and may result in an adverse effect on items stored in the enclosure. Moreover, it will damage the electrode and cause the ROSAHL membrane to fail.

– Confirm the dehumidifying / humidifying direction of the ROSAHL membrane before installation.

– DO NOT expose the membrane directly to wind and rain. When using outdoors, use a rain cover or moisture-permeable sheet to prevent it from getting wet.

– DO NOT touch or damage the surfaces of the membrane or it may deteriorate.

– DO NOT use ROSAHL with vapour phase corrosion inhibitors or insect repellents.

– DO NOT use ROSAHL near high density organic gases or V.O.Cs as it will quickly reduce the performance of the ROSAHL membrane.

– DO NOT attempt to disassemble, repair, or modify ROSAHL. It may cause an electric shock and reduce the membrane’s performance.


Make the moisture discharging hole and mounting holes of the enclosure using the following dimensions, insert the gasket and attach ROSAHL using the recommended screws. Note 1) Refer to Table 1 for mounting holes and moisture discharging hole. Note 2) Refer to Table 2 for mounting holes for the standard ROSAHL rain cover.  
Table 1. Installation dimensions (mm)
Model nameM-1J1RM-2J1RM-3M1RM-3J1R
Discharge hole20 x 2535 x 25 35 x 3555 x 30
Screws4 x M34 x M34 x M34 x M3
Model nameM-5J1RM-7J1RM-10J1R
Discharge hole55 x 5575 x 75105 x 105
Screws4 x M34 x M48 x M4
Table 2. Optional rain cover installation dimensions
Model nameM-1J1RM-2J1RM-3M1RM-3J1R
Cover modelRDH/C-3J1
Screws4 x M4
Model nameM-5J1RM-7J1RM-10J1R
Cover modelRDH/C5J1RDH/C-7J1RDH/C-10J1
Screws4 x M44 x M44 x M4

Precautions when using ROSAHL

1. Attach a protective cover to avoid contact and prevent damaging the dehumidifying / humidifying surface of a membrane.

2. Confirm the dehumidifying direction of the membrane to avoid damaging the enclosure contents.

3. Ensure the correct electrical connections to the ROSAHL membrane.

3.1 Do not reverse the polarity or the membrane will be irreparably damaged within minutes.

3.2 ROSAHL usually has a big inrush current when applying power, therefore we recommend the use of an appropriate current limiting power supply.

3.3 Use a dedicated power supply for each membrane. When connecting multiple membranes, best practice is for each to have a power source.

3.4 When unpowered, the membrane will allow water vapour to return to the enclosure until over many hours, balance is restored.

4. For the best performance, the enclosure should be airtight otherwise the results may be lower than expected

5. Attach ROSAHL vertically in the centre of the inner side surface of a enclosure with a gasket. Do not attach it on a top or bottom surface.

6. Do not use ROSAHL with gaskets containing an antioxidant as crystal materials may form on the surface of a membrane.

7. Do not use silicon-based sealing materials to improve airtightness of an enclosure as the outgassing can adhere to the membrane and reduce its performance. When using other sealants, attach ROSAHL after sealing materials has fully cured. Modified silicon caulks are acceptable.

8. Do not expose the moisture discharging side of a membrane to water. When using outdoors, attach a rain cover or vent filter to protect a membrane from water or insects.

9. Attach a moisture-permeable sheet to a membrane to protect ROSAHL from dust or oil mists.

10. Keep the moisture discharging side of a membrane well ventilated.

11. Do not use ROSAHL with vapour phase corrosion inhibitors or insect repellent, high density organic gases or V.O.Cs.

12. Do not modify ROSAHL or it may be damaged.

13. When you prepare a gasket, we recommend a sponge packing having closed-cell structure (hardness: Durometer Shore A of ten or lower) of the EPT rubber (ethylene propylene rubber). Using harder materials may cause gaps that lower the performance of ROSAHL. Please evaluate it carefully. Additionally, when using a silicon rubber gasket, vulcanize it at (200° C for 6 hours) to avoid degrading membrane performance.

Recommended Power supply specifications

Rated voltage 3 - 3.3V DC
Output current1A1.5A2A2A3A5A10A
Overcurrent protectionRequired
Overvoltage protection Required
Overvoltage variation<0.1 V
Ripple noise<0.2 V
OthersAccording tocommerciallyavailable powersupplies

Note : Use a constant or fold-back current limiting regarding overcurrent protection function.
You cannot use the power supply with the Hiccup mode current limiting type  as the voltage more than 2V DC is necessary for ROSAHL when an overcurrent protection function worked. Also ROSAHL may not work correctly depending on a characteristic of fold-back current limiting.


Confirmation items before using ROSAHL

Please confirm the following items surely before turning on the power.

  1. Is the power supply 3V DC?
  2. Is the polarity of ROSAHL correct?
  3. Does not a membrane get wet?


  1. Please supply 3V DC to
  2. Please adjust a supply voltage in the range of 2.9 ~ 3.3V DC across the terminals 5-20 minutes from turning on the power at the first time of installation. ROSAHL naturally causes a high inrush current when applying power, but this is normal.)

Membrane specifications

Image of Rosahl M-Series membrane dehumidifier
Dehumidifying (grams/day)*112.02.9481629
Applicable volume m³ *20.125 m³<0.25 m³<0.35 m³<0.5 m³<1 m³<2 m³<4 m³
Element voltage 3V DC
Power consumption (W) *31.01.5223612
Dimensions (mm) *452.5 x 50 x 16.567.5 x 50 x 16.5
65 x 62 x 16.5
74 x 58 x 16.5
89 x 84 x 116.5
117 x 105 x 17.5
162.5 x 155 x 17.5
Weight (g)70859095150340580
Operating temperature-10 to +50C-10 to +50C-10 to +50C-10 to +50C-10 to +50C-10 to +50C-10 to +50C
TerminalsPush connectorPush connectorPush connector Push connectorPush connectorPush connectorPush
Notes *1 The initial value at the temperature of 30° C and humidity 60% relative humidity (RH). (The dehumidifying performance will reduce during use depending on the operating environment and conditions. If observing any signs of abnormality, consider early replacement of the membrane.) *2 The applicable volume is for a sealed, moisture-impermeable container, and may vary depending on the material of the container, state of sealing and required humidity. *3 The annual average power consumption in average condition in Japan. *4 Dimensions show the values of H × W × D in the figure below.


Version RB-OP21004-BE