I have always been a big advocate of using a dehumidifier to keep a boat dry and fresh during the winter. I started with an old-fashioned refrigerant type, which was not only heavy, but also not very good at dehumidifying when the ambient temperature approaches freezing. With the advent of desiccant types, I thought all of my prayers had been answered. A lightweight unit, that works in cold temperatures, and that also gives out some heat.
Unfortunately I found out the hard way that they had one flaw. They don't like to be operated on a time switch. If you have an unmetered supply of electric this isn't a problem, as you can just leave it running on an appropriate continuous setting. If, however you are paying per unit, they can be surprisingly expensive to run, and running for around six hours per day keeps the boat dry and the electric bills low. I broke two desiccant type dehumidifiers by running them on a timeswitch, the problem being that they have to go through a shut down procedure to cool them, something that doesn't happen when the power is suddenly killed.
The DD8L Zambezi from Meaco is unique as it comes with a built in timer, which will allow it to run down properly before turning off. We've been running one for a couple of months onboard our Sealine. Could this be the ultimate boat dehumidifier? Operationally, the Zambezi is, on first glance at least, a little more complicated to use. This is due to its digital controls and LCD display. Once you get your head around navigating the menu and changing settings, it becomes as easy as any other model.
"The Zambezi gives out a fair amount of heat and can befitted with a permanent drain hose"
The controls let you enter all sorts of parameters, including fan speed, humidity setting, louvre operation and timer settings. You can also run the unit for a single pre-determined length of time of between one and eight hours. For a really damp situation you could use the laundry mode, which ramps everything up to the max until the humidity falls below 35%. It will then go into a sleep mode and monitor the humidity, ready to fire up again if it rises over 40%. You also get an ioniser setting that removes germs, bacteria, mould spores and odours from the air.
Powerwise, the Zambezi is not too hungry. In standby mode it uses as little as 45W and, when dehumidifying, it seems to draw between 350 and 700W, depending upon the setting chosen. I have always liked the ability for desiccant dehumidifiers to provide some background heat, and on my current one this is quite controllable by choosing different settings. With the Zambezi, the heat seemed to be permanently on. Even on its lowest setting, the air being blown out was a constant 30°C, and this went up to 35° on higher settings.
A dehumidifier will help to keep the boat dry. You can use chemical ones if you have no power, but an electric version does a much better job. One with a built-in timer, set for 6 hours a day, will save electricity.
Just occasionally, I would have liked to have had the ability to dehumidify, without too much additional heat, but this really is the only criticism I can dish out.
So is it the perfect boat dehumidifier? In terms of the inbuilt timer controls, I would say yes. It is larger and a bit heavier (9kg compared to 6.5kg) than the Ecoair DD122, which is probably one of the most popular desiccant dehumidifiers for boat owners.
It is also a bit more expensive than the standard DD8L, but with electricity rates the way they are, the difference could easily be saved in a short time by using the in-built timer. We clearly are not the only ones taken by the Zambezi. It has also been awarded the "2016 Which? Best Buy".
Reading a recent article in the section about winter boat lay up advice, I was glad to notice that you recommend running a dehumidifier. For years, I have run a compressor dehumidifier on a timer for 6 hours every other day to keep the damp at bay, and also a small tube heater to prevent the dehumidifier from freezing.
However, through some research I decided to purchase a desiccant dehumidifier which produces some heat, therefore eliminating the need for the tube heater. The plan was to set it up on a time switch to run for less time per day. I purchased the suggested and popular Meaco DD8L desiccant dehumidifier. But I was shocked to read a warning in the user manual which stated that the dehumidifier must not be turned off at the mains, as it has to run through a cool down procedure.
The dehumidifier can only be turned off on the power button on the unit, putting it into cool down mode for a few minutes so the fan inside removes the excess heat from the unit. I contacted Meaco and the company's technical department confirmed that it is essential to leave the dehumidifier to run through its cool down and that it should definitely not be used with any form of electric timer.
They went on to say that if the unit isn't allowed to cool down it will have a very short life. They also mentioned that the unit is designed to run permanently with the lowest humidity level. I tried this but was quite concerned with the amount of electric units consumed, and so I decided to go back to my old compressor unit and tube heater method which uses around $15-$20 electric per month. I just wanted to inform your readers of my findings.
I have suffered a broken Meaco in the past, that I now believe was caused by using it with a time switch. I am currently leaving mine on permanently on a low setting, but it does indeed seem to use quite a bit of power. As much as I hate to admit it, it seems like the old technology might be better suited to this application. I do think the Meaco is brilliant when on board though, as the heat it gives out is a very useful by product.
I noticed your product review on the Meaco DD8L Zambezi and it prompted me to go to the boat and remove the timer as I was unaware of the problem they could cause. Alas too late, my old EcoAir had died, so your review was even more timely as I've just ordered the Zambezi to replace it.
Editor replies: Sorry my advice came too late to save your old dehumidifier, but I think you'll be pleased with the Zambezi. I understand that dehumidifiers that have become faulty due to use with a time switch can be repaired for a fixed cost by the supplier. It's not cheap, especially with postage added, but may be worth considering if the unit is fairly new.
If you have the corrosion protection and feel leaving the power on isn't a problem, then you'll probably also be considering leaving either a heater or a dehumidifier on permanently.
However, it's worth noting that the time you really benefit from having an electric dehumidifier is when you're on board, as your breath is the biggest creator of condensation, followed closely by the use of gas appliances.
By all means put a small (200W) bar heater or oil-filled radiator on board, just to keep it from getting too cold and to create a small movement of air, but don't be tempted use a fan heater, even one with a thermostat, they present a serious fire risk if they fall over and they're horrendously expensive to run.
If you do decide to leave a dehumidifier on permanently:
Close all fresh-air vents for maximum efficiency or you'll be trying to dehumidify the entire atmosphere.
The ideal boat dehumidifier should have a permanent drainage option, so that you don't need to keep visiting the boat to empty the internal water reservoir. The drainage pipe can simply be put into a sink or permanently plumbed into the sink drain.
Some dehumidifiers don't automatically switch back on if the mains power is disconnected, which could prove pointless if, like many, your shore power frequently trips out.
Keep the filters clean - this is the single biggest cause of dehumidifiers overheating and causing fires - and check on them every few weeks at least.
Buy a dehumidifier with a built-in humidistat, which will switch off to save power when a pre-set humidity level is reached.