dehumidifier - what uses less energy running on high or low?

PollySouthend

Hi,

Now winter is here I'm using my dehumidifier. I turn it on when I leave for work and when I'm back its full. So what would use less energy? Running on low or high? Or just the same?

Thanks

macman

High will use more power, not surprisingly.
Leaving it off will use least...
Sounds like you need to address the source of the humidity: treat the cause, not the symptoms.

busybee100

Hi
I've just switched ours on. I'll leave it on full for a couple of days then drop it down or leave on automatic for the rest of winter. Humidity currently 83% - it's Cornwall and an old house.

savemoney

I leave mine on all time but have humidity set to 60%. As said if you run it on high it will use more energy. They don't normally use that much any way unless the property is really bad ie suffer from humidity a lot.

When I first use mine for Autumn it runs quiet a lot but after a few days it hardly comes on unless we dry any washing. Cooking and showering doesn't make much difference as we have fans on for those

footyguy

PollySouthend wrote: »

Hi,

Now winter is here I'm using my dehumidifier. I turn it on when I leave for work and when I'm back its full. So what would use less energy? Running on low or high? Or just the same?

Thanks

Depends.

Presumably it turns itself off when it is full.

So if on high it fills itself up in 1 hour and then if off for 7 hours, that probably uses less energy than saying being left on low for 8 hours and not filling up.

I would say turning it off completely (and perhaps opening a window instead) would be the way to use the least energy.

But something is seriously wrong if it fills up just in a few hours. :eek:

Look into the cause of the problem, rather than attempting to treat the effects.
If it proves necessary to run a dehumidifier after treating the cause (e.g. whilst the fabric of the building then dries out) and it is still filling up whilst you are at work, then look to get a permanent drainage facility installed for it.

PollySouthend

Thanks, think I will stick to running it on high for the next few days.

Well the cause is living in the south west, old house, CWI, windows without vents and in. A damp country!

Usually it goes on full for a a couple of days to start with, then just needs a few hours each day throughout the winter. It did fill up 2l in 3 hours. But this is at the start, will dry out. House is currently 72%

Isn't it just normal to run a dehumidifier in the winter? Esp as I don't have central heating and keep it coolish

pogofish

Running on low uses the least electricity - 27W vs 165W or even @400W on its very highest setting.

I tend to run mine on low for a couple of hours on the morning, then depending on humidity (get a hygometer too!) another 2-4 hours in the evening and 4hrs overnight. Will turn up high when cooking and bathing, letting it run-on for approx an hour after then back to low

The reduction in my bills over the year from last winter is massive. You need so much less heating with a dehumidifier!

CashStrapped

A dehumidifier should be a stop gap measure. If you are using it as a permenant solution there is somthing wrong. They are also very expensive to run, especially all day!

The cause is not the weather. The weather can just exacerbate an existing problem and make it seem like it is the cause.

Why do you need a dehumidifier permenantly on? How is the damp presenting itself?

PollySouthend

Surely lots of people use them as a perminant solution?

Mine uses 500w on high, but it outputs heat so I save on heating. Don't have central heating and don't like heating a whole house just because its just me here.

Well everything gets damp in the winter if I don't use it and the windows look like a steam room in the morning

macman

So the cause is most likely the south west climate, but lack of heating, and fundamentally, a lack of ventilation. Cold air carries less water in suspension than warm air, so without heating you'll get more condensation without the dehumidifier.
It's certainly not 'normal' to run one in winter: most properties don't even have them.

CashStrapped

They should only be used as a permenant solution if there is a fundimental problem that could never be solved.

In most situations, they should be used as a stop gap measure, untill the issue is resolved.

They are a very in-efficient and expensive form of "heating". The issue is, people do not realise why damp/condensation forms and what causes it. So they choose an easy but expensive method to reduce the issue. But this is not fixing the cause of the problem, which is usually living habits.

People produce far more water vapour than one would think. Houses used to be draughty enough to cope with this. An average family can put 15 litres of water vapour into the air per day.

As we have insulated our houses people do not realise that ventilation becomes even more important. The more one insulates, the more mechancial ventilation you need to put in.

Condensation is caused by warm moist air (warm air can hold more water vapour than cold air) cooling. As the warm air cools the water vapour turns to water and condensation is formed. So that 15 litres an average family put in the air during the day, cools when the heating goes off (usually at night) and condensates where it can.

In the days of single glazed windows, the coldest surface in the house was always the windows. They acted like natural dehumidifiers. Attracting all the water vapour to form on them.

However as we have begun upgrading to double glazed windows, they are no longer the coldest surface in the house. To make matters worse, they are more airtight, meaning more water vapour is trapped in the house for longer.

So, the water vapour now condenses on the next coldest surface in the house, which is usually the walls! With enough water vapour in the air and depending on the outside temperature, double glazing windows can still end up having water vapour condensate on them.

If you have cavity wall insulation this can also exacerbate (not cause) damp issues on the walls as the condensation can be concentrated on to small focused cold spots on the walls where the insulation may have missed. This is usually around doors, windows, corners of rooms and where pipes maybe coming through the wall from outside!

So you get spots of damp forming on the walls because these are the coldest spots in the house, and much more prone to attracting the vapour.

So, all people experiencing damp should look at their living habits:

Look at ways to increase ventilation. Especially in areas where a lot of water vapour is created.

Do you have a mechanical ventilation in the bathroom and kitchen?

How does the extractor fan in the bathroom operate? Does it always come on? Is it controlled by the light? Does it stay on after you finish your bath/shower? Is it powerful enough? Do you open windows as well?

Do you have an extractor in the kitchen?

Do you have the windows on the night lock (open a crack but locked). We produce a lot of water vapour in our bedrooms just breathing at night.

Do you dry clothes on radiators under the assumption this is cheaper and more healthy. This is a big no no. Weigh your clothes before and after, all that water in your clothes is now water vapour in your house. Use the laundrette or your tumble dryer if you have one. It costs around 30p/hour (that is for an old model).

Better control of your heating can help too. Do not let your heating go on/off on/off/on/off. Quick changes in temperature can cause air cool and condensate. Try keeping a very low background temperature, and turn it up when you need a boost.

This is one of the better guides I have found:

http://www.bolton.gov.uk/sites/DocumentCentre/Documents/Condensation%20and%20Mould.pdf

Read it!