Friday, 21 October 2016

The Dehumidifier Experiment

Jan rediscovered the stored dehumidifier today.  It’s been in deep storage since her winter on shore power at Rugby several years ago.  We’re now starting to get some condensation on the mushroom vents and Jan thought it might be a good idea to run the dehumidifier when we were cruising and the inverter was on.  Obviously the dehumidifier needed to be checked before we plugged it in and that’s when i had the idea it might be possible to run it off the boat 12V system.  It has a ‘power brick’ so I inspected the information on the label.


The first thing I noticed was the input and output power.

Input is 240V and 1.5A = 360W

Output 12V and 6A = 72W

80% of the electricity is lost in the power brick.  It’s definitely worth attempting to eliminate the power brick and run the dehumidifier directly off the 12V.

The other useful piece of information was at the bottom of the label where the pos and neg wiring for the plug was displayed.

I needed a few things to complete the conversion.


Pliers, soldering iron, solder and a spare 12V plug.

The first step was to cut the cable between the power brick and the dehumidifier using the pliers


You will note I’m not going to cut it at the power brick.  If the experiment doesn’t work I’ll need to reconnect the original wiring so I’m leaving a ‘tail’ if that happens.

I cut the cable and soldered the 12V plug onto the end before connecting the dehumidifier to the 12V system.

It didn’t work!   Obviously the power brick produces 12V AC and the boat system is 12V DC.  So I removed the 12V plug and reconnected the cable to the power brick.  Nothing ventured…. nothing gained!

By 10.30 the weather was looking slightly better and Jan helped me apply masking tape to the starboard handrail.  I then gave the red paint a light sanding ensuring I carefully removed the paint lines from earlier patch repairs to the paint.  It Then received a first top coat of Alpha Red.  I think my painting might be improving Towpath Bill.

IMG_1022IMG_1023We had some rain at 5pm but I think the surface of the paint already had a skin on it so I’m hoping there won’t be a problem.  If the weather is fine tomorrow I’ll apply the final coat.


Halfie said...

But the symbol between "12V" and "6A" indicates DC, as does the +/- for the plug.

Tom and Jan said...

Can't trust those chinese manufacturers! 😁

Don McCoskrie said...

If you have a diode connect this in series with the power supply output and your multi-meter. On a DC range you will be able to read approx 12v with the diode either way around if AC is present. If DC it will only read in one orientation of the diode. Maybe the picture is showing the polarity of the socket not the cord.

Tom and Jan said...


The polarity is a possibility but I don't think repeating the experiment is worth the effort.

Chas and Ann said...

Perhaps the size of cable produced a volt drop on start up. The symbol === indicated DC 12V. Hope you are keeping dry n warm this winter.
Regards Chas n Ann. Moore to Life

Tom and Jan said...

Chas I can see there will shortly be a referendum on whether I should repeat the experiment! 😁 Rather than taking a beating I'll make a second attempt.

We're fine inside a very dry and warm boat. Hope you are both well!


Paul (from Waterway Routes) said...

The will be power lost in the brick, possibly quite a lot but not 80% as you suggest.

The input current will allow for the inrush surge when you switch it on, rather than the steady state current.