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Re: Dehumidifier for the garage?

Posted: Thu Dec 14, 2017 2:32 pm
by PeteH
I suspect the heat energy comes from the room itself, and the air in the room probably ends up fractionally colder than it otherwise would be, whilst the water captured in the desicant is slightly warmer than ambient. The cold air in the room will then require heat transfer to equilibriate. It will suck heat from where ever is warmer, and that means the desicant. You may suck a tiny bit of heat from outside the garage, but I suspect it is unmeasurably small. And the dehumidifier will have all it's usual losses, meaning the 600W is a direct heat source, that is ultimately lost to the outside.

You may have the beginnings of a heat pump, but one with so many losses that it is bound to be a net loss of heat and energy.

Potential energy? If you dehumidify at a height then your fan has to draw denser humid air from the lower level. The fan will always do more work than the amount you can recover through your turbine arrangement.

Entropy is a bu##er!

Re: Dehumidifier for the garage?

Posted: Thu Dec 14, 2017 5:29 pm
by Rotary Potato
No such thing as a free lunch as far as energy is concerned. A bit like lawyers in that respect! :lol:

Re: Dehumidifier for the garage?

Posted: Wed Jul 31, 2019 11:37 am
by warpc0il
Just bringing this thread up-to-date...

First some context

Our home is huge and "The West Wing" is unheated, as are the outbuildings.
My '68 Alfa and '04 RX-8 sit in a garage that's a converted stable, with a straight on-the-dirt concrete floor and no dpc in the walls.

Damp is therefore a serious problem for us, not helped by the weather in Northern Ireland and the sea being only 200 yards away :roll:

Our first batch of desiccant dehumidifiers were so effective, much better than the old compressor versions, and despite the issues with disc motors, that we decided to buy same more.

The original Amcor product was no longer available so we bought three Devola Fast Dry 8L ... ier-dvfd8l
taking advantage of a 10% discount code plus another 2% for buying 3 off.

These proved to be better than the Amcor in that they were even quieter, just the "fan" sound, and just as effective.
Well, two of the three were good but one kept stopping with the alarm light lit.
The alarm indicates an internal fault, usually overheating, and resets when the power is removed.

When we went round to check the dehumidifiers, emptying the tanks on those without remote drainage, this one unit would be sitting silent with only half a tank of water and the alarm lit on [-X

The supplier - AirConCentre (part of the LoveShopping group) - was very helpful and arranged to have the faulty unit collected.
Within a few days we had a new replacement :thumleft:
Within a week the replacement started exactly the same behaviour, so we wondered if it was a problem with the airflow in the location or the electricity supply to the socket.
Anyway, we swapped units around and the same (new) one had the same problem, in a different building.
Repeat the process with AirConCentre and we get another new replacement.
We checked the production batch on the label and the replacement was from the same batch as all the others; including the original two that were still happy and the first failure and it's replacement.
A month later and the second replacement is also playing silly buggers. :evil:
Back on the phone to AirConCentre and they're happy to swap yet again but they've checked their stock and all of that model are from the same batch. :roll:
They offer to upgrade us to the Meaco brand product for just the difference in retail price, in the hope that this will resolve the problem permanently. In the end they do better than that as they also apply a Customer Services discount code and free NI shipping on the new order, to ensure that we're not out-of-pocket.
God know how much all this cost them.

Anyway the replacement Meaco arrives via DPD and there a slight crump in the corner of the box.

I take a quick look inside before signing for the delivery and all appears fine.

Take the new unit out of the packaging and find that the water tank has got a big crack across the front #-o
Back on the phone to AirConCentre and they suggest running the unit, with the drain into a bucket, to confirm if everything else is working, while they check to see if they've got a spare tank in stock.
It all worked and the replacement tank arrived next day.

It's been nearly a week now and the new unit is happily running, still into a 20L external tank so it can go for days without emptying.

So, this is the new unit we have ... dd8ljunior and I'm happy to recommend. There's also a discount code NET1819 for 5% until 20th August (though it might still be worth trying after that date).

You may think that a dehumidifier is unnecessary in warm weather but you only have to check under the car after a run to see how much excess water the a/c is pulling from the air. Also consider that rusting is much more aggressive in warm conditions than in the cold.

Re: Dehumidifier for the garage?

Posted: Thu Aug 01, 2019 9:13 am
by zippyonline
warpc0il wrote:
Wed Jul 31, 2019 11:37 am
They offer to upgrade us to the Meaco brand product for just the difference in retail price, in the hope that this will resolve the problem permanently. In the end they do better than that as they also apply a Customer Services discount code and free NI shipping on the new order, to ensure that we're not out-of-pocket.
God know how much all this cost them.
Great service. FWIW, my parents have a Meaco compressor unit in their house and it's been working nicely for a few years now, and I've got a dessicant Meaco in the garage, and that's been faultless since, ermm, this post in fact:
zippyonline wrote:
Sun Jan 08, 2017 7:15 pm
Just thought I'd mention that I bought a Meaco DD8L last night via amazon warehouse deals.

Re: Dehumidifier for the garage?

Posted: Sun Sep 22, 2019 6:21 pm
by warpc0il
Did I ever mention the house that my parents went to see, many years ago when they were looking to move?
It had a big garage/workshop at the bottom of the garden but, for some strange reason, the power and lights only worked when the streetlights were on in the road behind :? :-k :roll: [-X

Anyway, this post is just an excuse for a quick "bump" as we approach the time of year that a dehumidifier could make all the difference in the garage.

Re: Dehumidifier for the garage?

Posted: Sun Sep 22, 2019 9:11 pm
by bigpete8
My brother used to rent a garage workshop with student accommodation above.
After her messed around with the wiring one day the landlord came in enquiring if everything was okay with his electrics. As students complaining theirs was off. Turned out there was only one meter for building and he'd left their circuit isolated as couldn't see what it switched off...
Needless to say he wasn't impressed at being charged for their electricity...

Re: Dehumidifier for the garage?

Posted: Thu Feb 20, 2020 1:11 pm
by warpc0il

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. :thumleft: