Using a dehumidifier on board during the winter

Chris Michael, managing director of Meaco (U.K.) Limited, has advice for choosing and getting the best out of a dehumidifier.

It is not uncommon for people to use a dehumidifier to protect their boat and their belongings over winter. Organic material in particular is prone to damage from excess moisture, which explains why cushions and bedding often smell musty when you return to your boat in spring. Furthermore, anything paper based like books or pictures can absorb moisture and curl up, not forgetting that wood and veneer can also be attacked.

If your boat is laid up near to a power supply you can use a dehumidifier to keep humidity levels down and to prevent potential damage.

Choosing your dehumidifier

  • The boat will be unheated over winter and not all dehumidifiers work well in the cold.
  • You are likely to be carrying this dehumidifier between a car and the boat, so weight comes into consideration.
  • If your boat is still on the water then avoid a dehumidifier with castors as it will roll around.
  • Choose a dehumidifier that has the ability to drain water away continuously.

A desiccant dehumidifier operates better in cold conditions and extracts more water than a compressor. As it has an internal heater a desiccant will also add warmth to a space, ideal when there is no heating, plus they tend to be lighter and do not have castors.

The Meaco DD8L Junior, for example, is an energy efficient, light weight desiccant dehumidifier, with no castors. When the target relative humidity on the boat is reached it runs its fan for five minutes to check that all is ok and then it turns itself off to save energy. 30 minutes later it turns its fan back on and samples the air again for five minutes. If the relative humidity has increased above its target it starts dehumidifying again, otherwise it goes back to sleep for another 30 minutes. In a well-sealed boat this will mean that the fan will run for just 10 minutes an hour. It has a hose for continuous emptying and, if the power fails, when it comes back on it will start again in the mode it was left in.

The dehumidifier needs to be on a level surface

Getting the best out of it

  • Place the dehumidifier on a level surface, the galley side.
  • Use a RCD because you are using an electrical appliance on your boat and it will be unattended most of the time. The boat owner must still clean the filter and check the quality of the RCD and power supply.
  • Drain the water away using a hose into a sink (otherwise the dehumidifier will turn itself off when it is full).
  • Use as little hose as possible and do not leave excess curled up in the sink. Too much hose will create a negative air pressure and the water will not flow down the hose, the tank will fill and the dehumidifier will turn off.
  • Do not use a plug-in timer switch with your dehumidifier. This is like giving your appliance a power cut twice a day and will damage it in the long run.
  • Seal the boat up the best you can.
  • Leave the internal doors open so that the damp air in the boat can migrate towards the dehumidifier and be dried.

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