Dehumidifying 8 hours a day

[Cat-a-tonic]

I run a small unattended desiccant dehumidifier (Pre-I-Air DD122FW Mk 3) on shore power during the winter haul out. Currently running about 7 hours a day via a timer socket with the unit set to "On". Trouble is the unit is designed for the fan to run on for a couple of minutes after switch off to cool the heating element which doesn't happen when the timer socket powers off. The unit has its own 2, 4 or 8 hour setting but this is only set manually after you switch on the unit. The setting is not "sticky" so is lost when next powered on. In fact, if using the 8 hour setting for example, the unit powers off after the cool down period and willl not power up again when the timer socket next switches on.



Any ideas ?

[GordMay]

With an average maximum temperature of ±8°C (47°F), in winter, I wouldn’t be overly concerned with overheating [which requires the 2 min. fan cooldown].
At those temperatures, it will cool down, without the 2 min. fan.
Evidently, in Surrey, the average daytime temperatures, from December to February, are between 7°C and 9°C.

Or, you could leave the dehumidifier powered on, and rely on the humidistat to control the operation.


DD122FWMK3 Manual
http://www.theultimatefinish.co.uk/D...tionManual.pdf

... Keep the dehumidifier running continuously in Auto mode and it will then decide how much drying is required using it's humidistat and a mixture of the Low and High fan speeds. The unit automatically keeps room humidity at 55 -60% RH, in Auto mode.
In High super dry mode, the unit automatically keeps room humidity at 40 - 45% RH, to prevent dew in the room ...

[GordMay]

The Dewpoint, at 8°C (46.4°F) ambient air temperature:
60% RH = 1.8°C (35.3°F)
45% RH = -3.2°C (26.2°F)

The dew point is the temperature to which the air must be cooled, in order for it to become saturated, and, at which, moisture will condense on a surface. It provides a measure of the actual amount of water vapor in the air. So, the higher the dew point, the more moisture in the air.

Relative humidity increases, as the air temperature drops to the dew point, or the dew point rises to the air temperature (since the humidity is relative to the air temperature). Once the air temperature and dew point meet, the air becomes saturated, and the relative humidity reaches 100%. The dew point can never be higher than the air temperature.

[Pete7]

Other than Southern England has just had 2 months of biblical rain and a bloke down the road is building something big measured in cubits, I wonder do you really need to run a de-humidifier that much?

We run ours once a week when down the boat for a few hours, which produces lots of water but then the volume drops. Same if we go sailing in the winter, first 24/48 hours the de-humidifier does wonders, but then as the boat warms ups and dries out, we only run it occasionally.

The auto function Gord found looks interesting.

[deblen]

I run a dehumidifier year round in my Canadian house. It is a smaller portable on wheels unit with a drain hose running to floor drain.
As Gord suggests,set the onboard humidistat to desired relative humidity an forget it.
It will cycle on/off as and when required-year round.
I don't bother with one in my boat.I just leave some vents open,as at winter temps of 15C or lower,no condensation seems to occur-or at least,no mold occurs.
Edit: I don't live on boat during winter storage.



Cheers/Len

[s/v Jedi]

I have a unit much like this one that you can put on a timer like you wish or just let it cycle on humidity level.

I just had it run for two years on solar/battery/inverter.

https://www.amazon.com/dp/B07XKGLMR8

[Cat-a-tonic]

Thanks for all your feedback and experiences. I'm going to follow Gord's advice and try running on "Auto" and relying on its humidistat to control humidity instead of stoppng/starting on a timer.