The reliability of these units has been appalling. Of the four units we originally bought, all four had to be replaced under warranty. Of our second order for three units, two of these were also replaced under warranty. So in total we bought seven and had received thirteen. I’d also resurrected three units, two being out-of-warranty and one being a warranty return that they didn’t want back, so we should now have eight working units. We actually had four fully working and two in “work-emulation mode” - that’s where you pretend to work but don’t actually achieve anything – plus one in pieces for spares and one awaiting a post-mortem.
So WTF is going on here?
Let’s just start by saying that we work these things hard. We have a huge property, with unheated outbuildings and the West Wing has no central heating. The conservatory roof leaks, as does the old kitchen ventilation system and even the house windowsills are rotten, so water gets inside the cavity walls.
All these dehumidifiers are either connected to permanent drains or run into 25Litre drums, so they don’t get to switch off when their internal tanks are full.
Most are set to 60% humidity, which is slightly higher than ideal but a good compromise between managing the electric bill and protecting the structure and contents.
All of the original units failed with the same fault. The motor unit that drives the disc got very noisy, due to failure of the internal bearing. This is as discussed above and replacement of these motors is how I resurrected three units.
Actually, one of these had skipped through “stage 1” of this failure mode, as in “making lots of noise” straight to “stage 2”, which is one of the “work emulation modes”. The first I knew of this was a bloom of mildew across the RX-8 and the Alfa, parked together in one of the outbuildings.
It’s worth taking some time out here to delve into how these things work and how they can fail.
The core of the unit is a vertically rotating honeycomb disc that room air is blown through to collect moisture – all very simple.
The disc is coated in Zeolite which becomes saturated and has to be heated to dry it out. As the disc slowly rotates there’s a pizza slice shaped heater that boils off the water and blows the vapour into a plastic condenser matrix, which is cooled by the incoming airflow, this condensate is then drained away.
Our “simple” device therefore needs the rotation motor, which is a unit that engages on the outside of the disc, just like a starter motor drives the engine flywheel ring-gear. However, it’s permanently engaged and the disc needs to turn really slowly. Even the reduction of the tiny drive gear onto the ring isn’t sufficient and the motor unit has an internal gear reduction, which means that its output is only ~5rpm, the disc turning at a fraction of that. However, it’s the bearing of this output gear that fails, making the internal gear reduction noisy – or it just seizes solid as “stage 2” failure.
Once the disc stops turning everything appears to still be working. The main fan still blows air through the unit, switching on and off as required. The heater, with its own fan, still heats the pizza sliced section of the disc, but it’s just the same section all the time, which stays really dry, while the rest of the disc stays really wet and there’s no drying of the circulating air. It’s taking just the same amount of power for no good use.
Replacement of the motor got this unit working again, though it’s not quite as efficient as it was, maybe because that one section of the disc has been damaged by overheating.
Talking about over-heating, there are lots of fuseable links in the design of these units. They look like little resistors or diodes but they go permanently open-circuit if heated above their rated temperature. They’re located where failure of another component could create a fire risk. For example, if the fan that blows air through the heater were to fail then that area would get very hot very quickly. The fuseable links cut the power and prevent fire.
One of our units completely died, with no response from the control panel, and the autopsy found that many of the links were open-circuit. I tried a controlled test, shorting the links to determine what was working and what had failed but it looked like there had been a cascade that had affected the relays that control all the motors and the heating element. We now have a second unit with a total system failure, so it will be interesting to see what’s going on inside that.
The two remaining units that are in work emulation mode must have a different failure, as their discs are still rotating. The obvious conclusion is that, as everything else appears to be working, it must be a problem with the heater; either the element or the blower fan (which would blow the over-heat on the element) or the related relays. More open-heart surgery required.
The original four units were Amcor, which were replaced like-for-like. These are the ones that have responded well to disc motor replacement surgery, but two of these models are the ones mentioned directly above. I’ve lost track of which is which, so won’t know if these specific ones still have original or replacement motors, until I open them up.
For the second order we bought three Devola branded units. Two of these also suffered from disc drive motor clacking. The first within a week and the second just before the one-year warrant expired. As these were the same batch as all those that the supplier had in stock, they agreed to provide a different unit as a replacement, this being a Meaco. The Meaco is the DD8L Junior, which is the same capacity as the previous ones but doesn’t have either the ioniser or output deflector motor – neither of which we used anyway.
It’s two of the Devola units that have completely died, the second outside warranty.
Last weekend I purchased two more Meaco units, as the one we had is (was?) working well and these now come with a 3-year warranty – with an option to extend to 5-years.
We still have the supplier on speed-dial…
Actually, the supplier (AirconCentre – part of the Love Shopping Group) has been very good with the warranty replacements, never quibbling and always arranging free collection of the faulty units, or just agreeing for us to dispose of them.
If you’re not put off by this saga and thinking of buying one (or more) then I’d recommend the Meaco DD8L Junior
and hopefully the code DEV5
will still get you 5% discount – it worked for me last week.