Laundry drying with a dehumidifer

[Lootman]

My one has a laundry 'mode' which we'll be testing out tomorrow.

Does it need to be a warm/heated room? (we have a small unused bedroom in mind for the laundry function).

It's not a cold room, but we rarely use the heating in it.

The non-dessicant dehumidifiers like ours will work better in warmer rooms

By "work better" do you mean that the laundry dries quicker? Or that it dries with a minimum of power consumption?

The air in a warm room can contain more moisture, and so can be harder to dry out. I notice my dehumidifier works harder on warm days than cold days.

But part of what dries laundry is also warmth. In fact three factors contribute to drying: warmth, ventilation and a lack of humidity.

In our house we have 4 ways of drying. The gas-fired dryer is fast but expensive. The utility room with a dehumidifier takes longer but is cheaper. The south-facing conservatory (when it is sunny) is fast and free. The washing line in our south-facing rear garden on a hot, sunny day with a breeze is fastest and free.

[UncleEbenezer]

But part of what dries laundry is also warmth. In fact three factors contribute to drying: warmth, ventilation and a lack of humidity.

The effect of warmth is to lower the relative humidity ('cos warm air has much more capacity for moisture). That's why warmth helps with drying. It's the direct opposite to water condensing from the air on a cold surface. A dehumidifier supplies the breeze, as well as lower humidity.

But radiation also supplies energy to evaporate moisture away. Strong radiation (sunlight) is indeed the best dryer.

[Itsallaguess]

The non-dessicant dehumidifiers like ours will work better in warmer rooms

By "work better" do you mean that the laundry dries quicker? Or that it dries with a minimum of power consumption?

Covered by the chart in RC's post earlier in the thread -

https://www.lemonfool.co.uk/viewtopic.php?f=14&t=45473&start=40#p703391

It should be acknowledged that desiccant dehumidifiers generally use more power than the non-desiccant types, so that needs to be taken into account when reading the chart on the above linked post.

When we've been using our bathroom for dehumidifier drying days, I'd say it's a fairly cold room when starting off, with no additional heat added other than the running of the dehumidifier through the approximate 7-hour drying period, so the temperature-based performance of our non-desiccant model is not something that's proving to be prohibitive for our particular use-case.

Cheers,

Itsallaguess

[GoSeigen]

Accrding to the manual, it draws 165w per hour, so for a 6 hour cycle it's consume just under a kW - right?

Almost. It draws 165W (capital W, no "per hour" involved, power in W is itself a measure of energy use per unit time), in six hours it will consume just under a kWh (an amount of energy).


GS

[Tedx]

Currently we're running it overnight on the standard setting and it pretty much fills up the 2.5l tank in that 10 hour period. The humidity reading is in the high 50s and it cuts out occasionally as it drops below 55.

We've run 6 hour drying cycle once and that worked well. We left it on the dryer overnight on the standard cycle as well and it was bone dry by the morning. Most of that was fairly light stuff though.

Bathroom Towels and the like today should prove a bit more of a challenge. We might use an extra spin cycle to shake more of the water out before hanging it.

Saying that it is currently minus 3 outside and there isn't a breath of wind so no chance of hanging it out. Your only other option would just be to let it hang in the house (we don't have a tumble dryer).

Overall though, the house feels much much better. We have only had a little condensation on the bedroom window but it has been quite cold outside lately. I guess the condensation migrates to the cold bedroom window first. The dehumidifier is downstairs although all the doors are wide open.

What's worrying is the amount of water it has taken out of the air in such a short period of ownership. Where has it all been going in the last quarter of a century that we've owned the house?

Probably best not to think about it!

[funduffer]

We use a dehumidifier to dry clothes as I described earlier.

viewtopic.php?f=14&t=45473&p=702942#p702942

We also have installed thermal blinds in the bedroom which has a large bay window. These are amazingly effective. I have also purchased 2 cheap digital hygrometers (which I recommend to anyone who has a condensation problem). I place one in front of the blind and one behind by the window pane at bedtime and look at the results in the morning. When it was around freezing outside, the room temperature in the morning was at 16C and 69% rel humidity, but behind the blind it was 10C and 100% humidity with the window covered in condensation. We now have more comfortable nights, but a mop op operation every cold morning!

To solve the latter I have purchased a small window cleaning vac. In the morning, after drawing the blind, I suck up all the condensation with it, and it goes down the sink. I could use the dehumidifier I suppose, but it is a quicker and simpler method of removing the moisture from the bedroom and the relative humidity soon reverts to a normal level as the bedroom temperature evens out.

The other advantage is that condensation is now confined to the window bay behind the blind, so inhibits the creation of mould anywhere else in the bedroom.

Condensation is older houses can be a tricky problem, particularly with indoor clothes drying, but there are some useful tools out there to address it.

FD

[swill453]

Condensation is older houses can be a tricky problem, particularly with indoor clothes drying, but there are some useful tools out there to address it.

It's not for everyone but we have a PIV (Positive Input Ventilation) unit in the attic, gently blowing not-quite-as-cold-as-outside air into the house. It necessitates leaving internal doors open, and having trickle vents open at all windows.

In north-central Scotland it has literally removed all condensation issues (which used to be terrible) and relative humidity rarely gets above 55%.

It costs pennies of electricity to run, and the heating bill has reduced, if anything.

The model we got was https://www.amazon.co.uk/dp/B00NIV51RU

Scott.

[swill453]

I have also purchased 2 cheap digital hygrometers (which I recommend to anyone who has a condensation problem).

You can buy multipacks very cheaply https://www.amazon.co.uk/dp/B094N2KM7B

Scott.

[servodude]

I have also purchased 2 cheap digital hygrometers (which I recommend to anyone who has a condensation problem).

You can buy multipacks very cheaply https://www.amazon.co.uk/dp/B094N2KM7B

Scott.

True... but are they as much fun as these: https://amzn.eu/d/4g1sFAD

- they do go on special every so often and it can be handy/interesting to see what's going on remotely

[ReformedCharacter]

I have also purchased 2 cheap digital hygrometers (which I recommend to anyone who has a condensation problem).

You can buy multipacks very cheaply https://www.amazon.co.uk/dp/B094N2KM7B

Scott.

Just a word of caution... They may well be good enough for your purpose but don't rely on getting an accurate reading with these, the specs suggest ±5%RH. I have a relatively expensive Tecpel handheld hygrometer which I trust to be more or less accurate. I also have a cheaper handheld hygrometer which seems to be both inaccurate and inconsistent.

I've also assembled a number of weather stations (but use them indoors for temperature and RH%) using the details from Explaining Computers here:

https://www.explainingcomputers.com/pi_pico_w_weather.html

These use Bosch BME280 modules which claim an accuracy tolerance of ±3% RH. In use I find them to be pretty inaccurate, if I place two units side by side I can find a difference of as much as 8% RH between them. They do seem fairly consistent though, so I think they work well enough if the output is adjusted for the estimated inaccuracy. Hygrometers can be calibrated (or at least the degree of inaccuracy measured) using salt:

https://www.youtube.com/watch?v=sbAv9m_o0dI

I'd be interested to see how the individual units in the multipack vary in RH%, I suspect quite a lot!

RC

[swill453]

I'd be interested to see how the individual units in the multipack vary in RH%, I suspect quite a lot!

I bought the set of 8 put them down in one place. Five pretty much agreed with each other, and three were outliers.

I used the five and ignored the others. Worth it for the few quid, I thought.

Scott.

[Tedx]

Well I have to say I'm impressed.

It is totally grim outside with snow, sleet, freezing temperatures and today's laundry (bedding) has been over the drier next to the dehumidifier for about 3 hours and its almost dry. Room humidity is around 60%. Previously, it would still be on the drier but blocking radiators etc.

It also I'm still running it overnight and it's only filling up the water tank to about half now and the house just feels better It also dried off my wet boots overnight too. Again, they'd probably be upside down on a radiator somewhere before the humidifier.

[Itsallaguess]

As an aside I think I'm going to set up a small 'cold-setting' desk-fan to help maintain an improved air-flow of the dry air across my airer whilst the dehumidifier is on, to see if that can help improve the drying time, so I'll report back on that if there's any benefit being seen in the next few weeks.

As discussed above, yesterday I set up a small 'cold-setting' desk-fan to blow sideways into our airer, whilst the dehumidifier sat in it's usual position underneath, blowing it's dry-air upwards into the hanging laundry.

Given how cold a day it was, which I will assume had some level of negative effect on the whole drying process, I was very impressed by what a difference having the additional 'cold-setting' fan blowing into the drying made, with some heavier tops and towels drying out quicker and more evenly than the previous processes without the fan, and where I've had cause to flip over some of the heavier pegged articles on previous drying days, this time I left everything as it was, and just rotated the airer every now and then, to make sure everything was getting a good blast-through from both directions at various times.

With our large three-arm airer being easy to rotate in the room we're using to dry in, it feels like having this improved air-flow around and through the various bits of hanging washing helps the dehumidifier process quite considerably, so I think I'll continue with the additional cold-setting fan given these good results.

Cheers,

Itsallaguess