Demumidifier not working as well expected

Just bought a Delonghi DEM10 dehumidifier. The humidity in my house has consistently been between 60 - 70% humidity over the past few weeks and with winter coming on, it's not going to get much better.

I had the demumidifier left running in my hallway over a period of 12 hours last night during which time, it collected about 1.5 litres of water. The measured humidity started off at 65% and this morning it had fallen to 63%.

The dehumidifier is specified as being able to collect 10 litres of water in

24 hours (at 70% relative humidity). I was therefore expecting to collect substantially more than 1.5 litres over 12 hours.

Am I being unrealistic in my expectation?

Reply to
Mr. Benn
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It's not doing too badly. If you can find a collection curve for varying RH, you'll see that it will collect a lot less at 65% than at

70%. This is particularly at so lower temperatures, when the corresponding absolute humidity is lower.

In the Winter, the big problem with dehumidifiers is that their efficiency falls to near-zero with falling temperature. Their cold evaporator runs at a fairly constant temperature, so the temperature differential with the room (and thus "dehumidifying capacity") is reduced.

At this time of year though, a likely problem is draughts. If your outside air is at 65% and the air is continually exchanging between indoors and outdoors, then it's hardly likely to dehumidify the whole local climate. Effective dehumidification depends on first having effective draught control.

Really though, I wouldn't worry about it, and I wouldn't even worry about trying to dehumidify below 65%. That's already avoiding damp problems, you don't (usually) need to go drier than that.

Reply to
Andy Dingley

Persevere.

There's a whole lot of factors. Airflow in your house. Proximity to damp sources. The amount of trapped water in the building fabric - and how readily it can escape to the atmosphere. Etc.

I would expect to run a dehumidifier 24/7 for several days before making a significant impact, and to keep the whole place warm, and to have to move it from room to room.

What is the source of moisture? Have you done anything to cure the problem at source?

Reply to
dom

Are you sure your humidistat is accurate, analog units need calibration every year, most digital units are a bit more stabil, at lower humidity units dont reach their rating. Your unit may be defective, I bought and returned a humidifier that didnt work as advertised, I have 2 units that work as stated. Is it warm inside your home, for the humidifier to work as stated it has an operating temp, at cooler temps it will remove less moisture. try to find at what temp the uniit is rated at, but removing only 30% of stated rating I would return it and try another brand.

Reply to
ransley

In the Winter we sometimes use a dehumidifier to accelerate clothes drying and prevent condensation associated with it.

In my experience "yield" is massively improved by having a secondary fan (small oscillating desktop type) in the same room stirring the air up.

Try leaving an additional fan on and see if it make a difference.

Reply to
Vortex7

That's actually pretty good.

The

At what temperature?? The water vapour content of air increases exponentially with temperature and most dehumidifiers are rated at 30c or more to produce the most impressive statistics. You won't get anywhere close at normal house temps of 20c or so.

I was therefore expecting to collect

Yes very. My own rather antiquated 20 y/o 180W Tatung dehumidifier pulls a couple of litres of water a day out of the house most of the time compared with a quoted 7.5lt extraction at 30c and 80% relative humidity which of course it never sees. Your 3 litres compared with 10 stated per day is about the same performance.

You need to be aware that humid air actually rises not falls because it is less dense than dry air so put the dehumidifier upstairs even if the main problem is damp downstairs. Up on a shelf or table on an upstairs landing is good (as close to the ceiling as possible) with the drain running into a big bucket so you don't have to empty it so often. As the machine dries the air upstairs this will sink back down and be replaced by fresh humid air from downstairs. This creates a circulation of air which will help performance and dry the house faster.

Even a couple of litres of water a day makes a massive improvement to any damp or mould problem. All my leather goods (watch straps, belts, jackets) had gone mouldy before I dragged the dehumidifier out of the workshop last winter and fired it up in the house for the first time and it cured the problem within days.

Reply to
Dave Baker

Thanks for the words of advice Andy.

Reply to
Mr. Benn

Thanks, that's a useful suggestion. I will try it.

Reply to
Mr. Benn

Sorry, I can't remember.

The water vapour content of air increases

Thanks Dave for your comments and suggestions. Like the other people who responded, they were very useful and interesting. It sounds like the unit I have is working ok and I won't need to return it.

Reply to
Mr. Benn

Actually once the central heating in it will get dryer. Internal RH for the summer months here is somewhere between 50 and 60%. Back in Feb/Mar with outside temps barely getting above 0C and the heating working hard the RH was about 35%.

Why do you think you need a dehumidifier? Have you problems attributable to damp? If so the dehumidifier is only treating the symptom not the root cause of the problem.

Reply to
Dave Liquorice

That's only true in an unheated space where the temp falls to 12C or less. Not many of us live like that these days. For those of us with heating the above described issue doesnt exist.

NT

Reply to
Tabby

I winter, I need to slop water in plants to get the humidity UP.

Reply to
The Natural Philosopher

Many of us in uk.d-i-y do - or at least our sheds do, which we consider to be just as important.

I don't have a damp problem in the house because it's already warm and dry. The place where I have the damp is also the place that's cold.

Reply to
Andy Dingley

I get problems with condensation on windows building up during the colder weather and during the winter, I keep windows closed!

Reply to
Mr. Benn

Lack of ventilation for the amount of moisture you or your activities are producing. Do you have extractors in any kitchen and bath/shower rooms and do you use them? Do you dry clothes indoors (how effective is the spin cycle of your washing machine?)

Our kitchen had a recirculating cooker hood, condensation on the 6mm gap double glazed windows was terrible. Ducted the cooker hood outside and the reduction in condensation is very marked. We still get it when cooking pasta, ie an large open pan boiling away but nothing like we used to for ordinary cooking.

Reply to
Dave Liquorice

Hi Dave

I do dry clothes inside during the winter so it's not really surprising that the humidity is high. There is no air extraction in the kitchen or bathroom. If I owned the house, I'd fit extractors but because it's rented while I find a property to buy (and while I watch the prices go down hopefully), it's probably a bit pointless paying to install extractors and I don't think I'd be able to persuade the landlord to pay for these things.

Reply to
Mr. Benn

pan with lid? simples ;>)

Jim K

Reply to
Jim K

Room for a tumble dryer?

Reply to
ARWadsworth

That explains the damp then.

Ahhh...

Well you aren't going to get the long term benefit and it really is the landlords responsibilty IMHO.

Are you suffereing mold on walls or having stuff get mildew? Noticable mould could be considered a health hazard. If you have it on walls it'll also be damaging the decoration and possibly the walls both may be the landlords responsibilty, the walls will be for sure. A gently gently approach letting them know there is a damp problem and that fitting extractors to the kitchen and bathroom will improve things may get a positive response.

Reply to
Dave Liquorice

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