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This is a window air conditioner.

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And this is a dehumidifier.

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What's the difference?

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This one's got a bucket.

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Hello.

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You're about to learn a lot about dehumidifiers.

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You're probably looking at this video's length and thinking

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How the heck is there that much to talk about dehumidifiers?

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Well, it's simple.

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I'm a nerd!

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But I'm making this video because these machines have a simple mission with perplexingly confusing side effects.

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Most everyone knows what they do:

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they remove water from the air and decrease humidity.

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But the ramifications of that are, I'd wager, not very well understood.

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I myself didn't realize something pretty profound about these until quite recently,

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so today I'd like to talk about how dehumidifiers work.

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They're actually doing something pretty amazing,

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and when you understand the details, it might cause you to reevaluate where and how best to use them.

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This video is kind of all over the place, so rather than bury the tack too deep,

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I'll get right to the brass ledes.

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The purpose of these machines is not to make you comfortable

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or even to help your air conditioning system.

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They absolutely will not do that.

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This might rub against your intuition.

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We all know from experience that humid air sucks when it's hot outside

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and make air less humid is like... its job.

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But before you run out and grab one of these things thinking it'll help in the next heatwave,

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there's a giant catch you need to be aware of:

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The process of dehumidifying the air generates heat,
and it's a lot more heat than you might expect.

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This little machine can put out as much heat as a space heater,

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and larger ones will easily exceed that.

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And you probably don't want to be running a space heater during a heatwave.

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Now where that heat comes from is fascinating,

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and it creates some really interesting implications when you use a dehumidifier alongside an air conditioning system.

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Those implications are really the main point of this video.

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But to fully understand them, 
we have to get pretty deep into the weeds.

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Which we will.

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Hence the runtime.

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But long story short,

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if you don't have a significant and chronic humidity problem somewhere in your home which requires attention,

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there's really no point to having a dehumidifier.

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It's just going to make a lot of heat, 
a lot of noise and waste your money.

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So... what qualifies as a humidity problem?

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Well, as a general rule,

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if indoor relative humidity persistently stays above about 65%, 
(though, you'll find disagreement on the exact number)

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that's bad.

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That can lead to mold and mildew growth which is unpleasant and dangerous.

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In addition to that, high humidity can accelerate corrosion on things that corrode

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and quick and material degradation in materials that degrade

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so it can ruin your belongings.

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And if that's not enough, high moisture environments are more likely to attract certain pests.

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And if the damp gets real bad, it can even cause structural issues.

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So if you live where the air gets mmmmoist, a lot,

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dehumidifiers are common.

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They're practically a staple of Midwestern basements and crawl spaces during the summer months,

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especially when people have problems with stormwater seepage down there.

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Did you catch, though, that I said basements and crawl spaces?

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There's something unique about those areas.

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They're not generally conditioned.

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Or if they are, such as with a finished basement, 
they're often poorly conditioned compared to the rest of a home.

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The main issue down there is that since those areas are partially underground,

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in the warm months of the year, 
they're typically cooler than the outside air temperature.

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And that leads to persistently elevated humidity.

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Now, it's important to understand why that is the case.

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When we talk about how much water vapor is in the air,
 we usually discuss relative humidity.

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Fun fact, though...

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relative humidity doesn't actually tell us how much water vapor is in a given volume of air.

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But that's fine.

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We don't actually need to care about

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how many water molecules are in a cubic meter of air.

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Relative humidity tells us what's usually more important:

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Air's current ability to absorb more moisture.

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It's expressed as a saturation percentage,

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meaning air with 50% relative humidity is 50% saturated,

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and thus it has absorbed
half as much water vapor as it theoretically can.

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But there's a wrinkle to this.

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Air's total capacity to absorb moisture depends on its temperature.

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Air can absorb more moisture the warmer it is.

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So if you take a known volume of air 
with a known saturation percentage and heat it,

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its relative humidity will actually fall.

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It has exactly as much water vapor in there as it did before we warmed it up,

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but the air's increase in temperature 
unlocked more capacity for it to absorb water vapor,

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which ultimately lowered its relative humidity.

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This is why the indoor air is usually 
very, very dry in the winter months.

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Elevating the indoor air temperature causes relative humidity to fall.

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But of course, the opposite is also true.

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If you take air and cool it down, 
it loses its ability to hold on to moisture.

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And that means the same volume of air, when chilled -

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even though we haven't added any water vapor - 
becomes more saturated and thus its relative humidity goes up.

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What this means for a house or structure 
is that when there's any air exchange at all

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between the cool basement or crawl space and the outside air
(or even just the rest of the house),

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relative humidity will be persistently higher in those cooler spaces.

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That means it's harder for liquid water to evaporate down there,

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which in turn means wet stuff dries out more slowly.

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And that's the problem.

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If humidity levels are elevated enough stuff will dry out so slowly that you risk damage to whatever's down there,

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or even your home itself.

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So what do you do in that situation?

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You conditioned the air.

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Dehumidifiers technically are a form of air conditioning, 
but they don't provide cooling.

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They simply extract moisture from the air and collect it in a bucket, 
or send it down a hose to a drain.

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That makes them less energy intensive than cooling.

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And for a space that's already kind of cool but a little too damp, they make perfect sense.

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Simply pick a humidity percentage you'd like it to maintain,

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and it will switch on when the air's too humid, 
begin extracting water from the air

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and then switch back off once humidity is back in range.

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Now, I don't have a basement or crawl space at home,

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but I do have a garage.

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And that space is not conditioned at all -

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which isn't necessarily a problem 
and genuinely isn't in the winter months.

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But I live in the Midwest, and in the summer months 
it can get quite humid outside.

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I store a good deal of stuff in my garage
which I don't want to be damaged from that humidity,

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and that's why I have this little dehumidifier.

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It keeps the air in the garage from exceeding 50% humidity,

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and thus keeps all the stuff out there nice and dry.

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Even when I come home in the rain and park a very wet car 
in the same space with all that stuff.

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As the car drips water onto the floor and starts to dry out, 
the air in the garage starts to get very wet.

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But, the dehumidifier always notices 
"it's getting a little bit damp in here" and switches on.

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And that is the point of a dehumidifier.

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It keeps the air dry to protect your stuff.

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That's what it's for.

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Though it does have the side benefit 
of helping the car dry off a lot faster.

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That's pretty neat.

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Before we explore how they work, 
I want to give two pieces of advice.

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First, if you are in actual need of a dehumidifier,

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for it to be any good at all it needs to cost more than $100 
and it needs to be a fairly heavy and cumbersome machine.

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This little one, which is the smallest 
capacity you can get from a mainstream brand,

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came with casters because it weighs about 30 pounds.

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I'll show you what's making it so heavy shortly, 
but please know and share with your friends

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that cheap machines
 that you can easily pick up are useless junk.

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This thing from Amazon, as far as I'm concerned,

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is a piece of e-waste which should not exist.

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This has no business calling itself a dehumidifier,

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as it can't even counteract the added moisture 
from your average human breathing.

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There are a lot of purported "dehumidifiers" just like this for sale these days which simply do not, in fact, do that.

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And they're starting to show up in mainstream hardware stores, too.

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In the US, dehumidifiers are rated 
in pints of moisture removal per day.

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I know.

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And this unit, which I will remind you is the smallest capacity you can get from a mainstream brand,

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is rated at 22 pints per day.

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Yet Home Depot will gladly sell you this 
3.2 pint unit from Magic Chef for 63 bucks,

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and Menards will sell you this one pint machine for 70 bucks.

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So will Lowe's.

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Don't waste your time 
with anything like that and put it back on the shelf.

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And if you'd rather not waste your time 
emptying the bucket from a real dehumidifier

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but you also don't have access 
to a drain where you need to put it

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before you resign yourself to the bucket brigade, 
look into getting one of these.

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This is called a condensate pump.

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It's a tiny, self-contained sump pump which you can drain a dehumidifier into using an abridged garden hose.

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And once the dehumidifier fills the sump with extracted water,

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a float switch is tripped and the pump will turn on.

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Then it pumps that water...

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somewhere else.

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You can easily hook vinyl tubing up to these things,

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and if you've got a reasonable way to run that tubing to another room with a sink or drain, or even through an outside wall,

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it will make your life a lot easier.

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Some dehumidifiers are now being sold with built in pumps,

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but in my experience they don't work that well.

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I bought one some years ago 
and its pump broke after less than a year.

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So I ended up having to get one of these for it anyway.

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These dedicated pumps are much more robust, though they can still fail.

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So if you're using one 
where an overflowing pump would cause a mess,

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you should periodically check on it to confirm it's working.

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But with that out of the way, 
why is this such a heavy and cumbersome machine?

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We should probably take a look inside.

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And through the magic of having a broken one, 
I could tear this bigger fella apart with reckless abandon.

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And what we find inside is...

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an air conditioner.

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These are all the same parts we find 
in a small window air conditioner like this.

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In the dehumidifier, they're simply rearranged.

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Here's the compressor.

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Here's a blower fan to move air through the evaporator coil.

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Here's the evaporator coil itself.

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And then sitting right behind the evaporator is the condenser coil.

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That's... hmm.

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If you know anything about air conditioners, this arrangement will seem more than a little strange.

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But it actually makes sense given what the purpose of this device is.

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It's not an air conditioner.

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It's a dehumidifier.

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But wait.

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Don't air conditioners also dehumidify?

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Why, yes they do.

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And that's why this is weird and complicated

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This dehumidifier

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literally is an air conditioner.

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But it's controlled by a humidity that rather than a thermostat.

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And it has provisions to collect the condensate that an air conditioner typically sends down a drain or simply lets drip outside.

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Other than the different controls and the float switch that will shut it down when the bucket is full,

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this is the same machine that cools air, 
except it doesn't cool the air.

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In fact, it makes the air very hot 
when it's running in a humid environment.

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I suppose I should demonstrate that.... 
[snaps fingers]

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I know! I'll set up a wireless hose!

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I put this dehumidifier in an enclosed bathroom,

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and then put one of my temperature data loggers on top of it in the airstream of its exhaust.

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Then I switched it on and let it run nonstop for an hour.

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When operating, this small unit only consumes about 300W 
of power, which is not very much.

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If we were releasing that into the room as heat,

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it would raise the air temperature a little bit, but not a whole lot.

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And that's what we see -

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over an hour of adding 300W of heat to the room,

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the exhaust temperature slowly rose and by the end
it had reached about 90°F, roughly 32 Celsius.

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But then I switched on the arch nemesis of a dehumidifier:

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a humidifier.

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And in fact, two of them.

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Working together in that little bathroom they dramatically increased humidity levels.

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But the dehumidifier worked diligently to undo that,

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which you can see as this fairly steady drip of water coming out of the hose.

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But notice what happened to the dehumidifier's 
exhaust temperature once the battle began:

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it climbed significantly.

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In just 15 minutes, it was above 100°F.

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And by the end of the hour, it was tickling 105 (about 40 Celsius).

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That might not seem like a huge increase in temperature,

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but these machines move a ton of air through them.

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So it's actually quite a lot of heat energy being expelled.

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And that's despite only using about 300W the entire time.

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How and why is there so much extra heat all of a sudden?

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Well, it's because of two things:

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Latent heat and latent heat.

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To help explain this, I want to set the dehumidifier aside for a moment and go over how an air conditioner works.

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And I promise, this isn't just another chance
for me to explain the refrigeration cycle.

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It's actually very important to understanding the whole picture here.

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But if you're not a newcomer to this channel and already know the basics of heat pumps

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and what coefficient of performance means,

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then you can go ahead and skip to

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if you'd like.

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So an air conditioner is a machine which is exploiting the physical properties of a chemical known as a refrigerant

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in order to move heat energy from one location to another.

228
00:16:16,909 --> 00:16:22,715
And when you do that, the location which is getting energy removed from it becomes cooler.

229
00:16:23,682 --> 00:16:30,689
We can do this because refrigerants have very useful relationships between their boiling points and their pressure.

230
00:16:31,690 --> 00:16:38,364
The refrigerant inside this air conditioner, 
difluoromethane or R32 is normally a gas.

231
00:16:38,464 --> 00:16:43,902
And at atmospheric pressure its boiling point is about -35°F.

232
00:16:44,603 --> 00:16:50,642
In other words, you'd need to get it that cold
 in order for the gas to transition to a liquid.

233
00:16:51,477 --> 00:16:54,546
But we've trapped some of this gas,

234
00:16:54,580 --> 00:16:58,417
in fact, 7.58oz, or 215g of it

235
00:16:58,417 --> 00:17:01,286
inside a big loop of piping.

236
00:17:01,920 --> 00:17:05,024
And that allows us to do some very interesting things.

237
00:17:05,924 --> 00:17:09,762
When this machine is operating, a mechanical compressor

238
00:17:09,762 --> 00:17:11,521
(that's this fella here)

239
00:17:11,521 --> 00:17:16,568
squeezes our gaseous refrigerant and forces it into this maze of piping.

240
00:17:17,436 --> 00:17:19,338
This is what's called a heat exchanger.

241
00:17:19,738 --> 00:17:27,813
All of those fins attached to the copper pipe looping back and forth help to quickly transfer heat energy from those pipes to the air.

242
00:17:28,180 --> 00:17:35,639
And a fan helps speed up that process even further by moving lots and lots of air through these fins.

243
00:17:35,639 --> 00:17:40,321
[compressor starts buzzing] 
We need to do this because once the refrigerant exits the compressor,

244
00:17:40,321 --> 00:17:45,297
it's under very high pressure - typically above 300 PSI.

245
00:17:46,365 --> 00:17:50,736
All that pressure is squeezing the refrigerant molecules together,

246
00:17:50,969 --> 00:17:56,041
which has the effect of dramatically elevating the refrigerant's boiling point to temperature.

247
00:17:56,942 --> 00:18:04,283
In fact, under these sorts of pressures, the refrigerant boiling point becomes higher than outdoor air temperature.

248
00:18:04,550 --> 00:18:07,219
Typically by about 20°F.

249
00:18:08,487 --> 00:18:11,790
This ultimately means that after it leaves the compressor,

250
00:18:11,857 --> 00:18:14,660
the refrigerant cannot remain a gas.

251
00:18:14,960 --> 00:18:20,332
The pressure in these pipes is too high 
and the ambient air temperature is too cold,

252
00:18:20,799 --> 00:18:26,004
so the refrigerant inside begins condensing into a liquid.

253
00:18:26,939 --> 00:18:30,042
That's why we call this heat exchanger the condenser.

254
00:18:30,742 --> 00:18:32,911
And as the refrigerant condenses,

255
00:18:33,078 --> 00:18:36,915
it releases lots and lots of heat.

256
00:18:38,050 --> 00:18:39,799
Why?

257
00:18:39,799 --> 00:18:40,719
Hold that thought.

258
00:18:41,487 --> 00:18:45,958
Once sufficiently cooled down
 by all the air being forced through the condenser,

259
00:18:46,492 --> 00:18:53,932
liquid refrigerant begins to stack up at the end of the condensers piping thanks to a restriction known as a metering device.

260
00:18:54,800 --> 00:19:01,773
That's there to limit flow and maintain a pressure imbalance between the two sides of the refrigeration circuit.

261
00:19:02,708 --> 00:19:09,756
After the liquid refrigerant passes through the metering device, 
it moves into a second heat exchanger.

262
00:19:09,756 --> 00:19:16,588
And thanks to the suction created by the intake of the compressor inside here the pressure is relatively low,

263
00:19:16,922 --> 00:19:19,124
perhaps 120 PSI.

264
00:19:20,225 --> 00:19:29,360
That causes the refrigerant's boiling point to plummet, 
landing somewhere around 40°F (about 5 Celsius).

265
00:19:29,601 --> 00:19:32,671
That's much colder than room temperatures.

266
00:19:32,871 --> 00:19:37,093
So once the refrigerant makes its way into here,

267
00:19:37,093 --> 00:19:43,549
the air in a room is actually hot enough 
to cause it to boil off and become a vapor again.

268
00:19:44,650 --> 00:19:49,354
Since the refrigerant vaporizes in this heat exchanger, 
we call it the evaporator.

269
00:19:49,955 --> 00:19:56,528
And when the liquid refrigerant starts boiling inside of these pipes, it gets very, very cold.

270
00:19:57,462 --> 00:19:58,664
Why is that?

271
00:19:59,097 --> 00:20:02,034
Well, key to understanding the refrigeration cycle

272
00:20:02,167 --> 00:20:08,507
is that the refrigerant cannot boil away 
until it absorbs its latent heat of vaporization.

273
00:20:09,308 --> 00:20:15,113
That's the heat energy a substance must absorb 
to change phases from a liquid to a gas.

274
00:20:16,315 --> 00:20:19,484
Now, latent heat is very strange.

275
00:20:20,085 --> 00:20:24,389
Unlike sensible heat, which we experience as temperature,

276
00:20:24,389 --> 00:20:28,627
we can't feel latent heat 
or even detect it with a thermometer.

277
00:20:29,528 --> 00:20:32,598
For instance, when boiling water on a stove,

278
00:20:32,598 --> 00:20:36,356
if you're measuring the temperature of the liquid water with a thermometer,

279
00:20:36,356 --> 00:20:40,672
you will see it slowly and continuously rise as the water absorbs heat.

280
00:20:41,006 --> 00:20:42,241
And that's what you would expect.

281
00:20:42,908 --> 00:20:47,872
But then it will get stuck at its boiling point temperature.

282
00:20:47,872 --> 00:20:49,815
Which is kind of weird, right?

283
00:20:50,415 --> 00:20:53,986
I mean, boiling water is very hot to us fragile humans,

284
00:20:54,186 --> 00:20:59,791
but compared to the temperature of a flame 
or a glowing heating element, it's quite cold.

285
00:21:00,158 --> 00:21:03,462
And so it's still going to absorb lots of heat energy from a stove.

286
00:21:04,329 --> 00:21:07,866
Yet despite the fact that it's absorbing lots of heat,

287
00:21:08,233 --> 00:21:10,302
it's not getting any hotter.

288
00:21:10,736 --> 00:21:12,771
The temperature is just stuck.

289
00:21:14,039 --> 00:21:17,342
Now, the reason is that once it's at its boiling point,

290
00:21:17,576 --> 00:21:21,813
the only heat energy the water can absorb is latent heat.

291
00:21:22,481 --> 00:21:25,917
And rather than increase the temperature of the liquid water,

292
00:21:26,385 --> 00:21:32,391
that heat energy is transforming the liquid water 
into its gaseous form: water vapor.

293
00:21:33,358 --> 00:21:36,862
We can observe this as violent bubbling at the bottom of the pot.

294
00:21:37,362 --> 00:21:39,598
But the thermometer doesn't show us this.

295
00:21:40,032 --> 00:21:44,803
All it sees is the fact that the water is at its boiling point temperature.

296
00:21:45,370 --> 00:21:51,710
Now, very importantly, 
all the latent heat energy which turned the water into a vapor

297
00:21:51,710 --> 00:21:54,513
is now stored in that water vapor.

298
00:21:54,946 --> 00:21:56,181
It didn't disappear.

299
00:21:56,915 --> 00:22:01,553
That heat energy is what's 
keeping the water at a higher state of matter.

300
00:22:02,321 --> 00:22:05,023
So let's bring this back to the air conditioner.

301
00:22:05,023 --> 00:22:07,759
When the liquid refrigerant enters the evaporator,

302
00:22:08,193 --> 00:22:14,266
the pressure inside is so low that its boiling point falls below ambient air temperature,

303
00:22:14,266 --> 00:22:16,768
meaning the refrigerant cannot remain a liquid.

304
00:22:17,602 --> 00:22:22,174
But to actually vaporize it has to absorb latent heat energy.

305
00:22:23,342 --> 00:22:25,811
It first gets this energy from itself.

306
00:22:26,211 --> 00:22:29,181
This is why it immediately becomes so cold.

307
00:22:29,848 --> 00:22:32,851
It will use its excess heat energy to begin boiling,

308
00:22:32,951 --> 00:22:38,357
which causes its sensible temperature to fall until it's at its new boiling point temperature.

309
00:22:38,423 --> 00:22:42,294
And like the water on a stove, it gets stuck there.

310
00:22:43,028 --> 00:22:48,066
But the refrigerant needs much, much more heat energy to completely vaporize.

311
00:22:48,834 --> 00:22:52,137
That's why the evaporator is also a heat exchanger.

312
00:22:52,738 --> 00:22:57,909
We need all these fins to help transfer heat energy from the air in the room

313
00:22:57,909 --> 00:23:01,847
into the cold refrigerant boiling inside the pipes.

314
00:23:02,748 --> 00:23:09,554
And when heat is transferred from the air into a colder substance, the air itself gets colder.

315
00:23:10,655 --> 00:23:13,492
Once the refrigerant has completely boiled away,

316
00:23:13,492 --> 00:23:18,196
the now gaseous refrigerant contains lots more energy than it did moments ago.

317
00:23:18,764 --> 00:23:25,370
It's still holding on to its latent heat energy that it just took from the room's air to become a gas.

318
00:23:26,371 --> 00:23:28,455
And, here's the amazing thing,

319
00:23:28,455 --> 00:23:31,777
simply by taking another spin through the compressor,

320
00:23:31,777 --> 00:23:35,280
we can force the refrigerant to get rid of that heat energy.

321
00:23:36,314 --> 00:23:40,790
Once re pressurized by the compressor and sent back to the condenser,

322
00:23:40,790 --> 00:23:48,293
the refrigerant's under high pressure again, and its boiling point is back up in the well above ambient air temperature range.

323
00:23:49,194 --> 00:23:55,233
Since it's once again not possible for it to remain a gas, 
it will spontaneously condense.

324
00:23:55,801 --> 00:24:01,440
And as it does that, 
it releases the latent heat energy it just absorbed.

325
00:24:02,174 --> 00:24:04,142
Which means it gets hot.

326
00:24:04,709 --> 00:24:13,552
at a pressure of 350 PSI the refrigerant's condensing temperature will be about 105°F or 40 Celsius.

327
00:24:13,885 --> 00:24:17,222
So it's gonna be that hot once it starts to condense.

328
00:24:17,789 --> 00:24:23,428
And to allow it to keep condensing, we need to help it get that heat out as quickly as possible.

329
00:24:23,628 --> 00:24:25,530
Hence, all the fans and the fan.

330
00:24:26,531 --> 00:24:29,201
And of course, once it's condensed,

331
00:24:29,201 --> 00:24:32,737
it ends up back at the evaporator and the whole process repeats.

332
00:24:33,338 --> 00:24:35,907
The refrigerant is simply traveling in a loop,

333
00:24:36,141 --> 00:24:40,412
and the process runs continuously
so long as the compressor is operating.

334
00:24:41,213 --> 00:24:43,281
Now I want you to notice two things.

335
00:24:43,715 --> 00:24:48,453
One, the condenser has the same basic structure as the evaporator.

336
00:24:49,321 --> 00:24:57,896
This is because it will be releasing just as much heat from the condensing refrigerant as the evaporator absorbs when the refrigerant boils.

337
00:24:58,864 --> 00:25:05,070
And two, notice that the condenser 
is in a very different location from the evaporator.

338
00:25:06,171 --> 00:25:09,338
This is the basic principle behind a heat pump.

339
00:25:10,108 --> 00:25:12,143
Air conditioners are heat pumps,

340
00:25:12,143 --> 00:25:19,701
and they use the refrigerant as a working fluid to capture heat energy from indoors and move it outside,

341
00:25:19,701 --> 00:25:22,454
which results in the indoor air getting colder.

342
00:25:23,522 --> 00:25:30,295
When installed in a window, this machine's heat absorbing evaporator coil ends up inside the home,

343
00:25:30,629 --> 00:25:34,332
and the heat rejecting condenser coil ends up outside.

344
00:25:34,766 --> 00:25:40,438
So it pumps heat from inside to outside, 
which cools the indoor air.

345
00:25:41,239 --> 00:25:43,508
This is also how your refrigerator works, by the way.

346
00:25:43,775 --> 00:25:47,612
Though it's just got to get heat 
from inside the box to outside the box.

347
00:25:48,246 --> 00:25:51,516
And the hot new thing is for heat pumps to be reversible.

348
00:25:51,917 --> 00:25:58,290
That way they can also absorb energy from outside air 
and bring it inside to produce heating.

349
00:25:59,057 --> 00:26:03,428
It's actually not new at all, but we've gotten much better at making them work in cold climates.

350
00:26:04,296 --> 00:26:07,566
But anyway, there's one last thing to know about heat pumps.

351
00:26:08,333 --> 00:26:13,038
The actual work this device is doing is mechanical in nature.

352
00:26:13,772 --> 00:26:16,908
It's using an electric motor inside this enclosure

353
00:26:16,975 --> 00:26:20,845
to spin a mechanical compressor which compresses a gas.

354
00:26:21,313 --> 00:26:22,781
And that's all it's doing.

355
00:26:23,548 --> 00:26:30,322
The whole "refrigerant turns into a liquid and back" part 
happens naturally as a result of heat transfer.

356
00:26:31,156 --> 00:26:35,694
It's absorbing and releasing its latent heat energy all on its own.

357
00:26:36,261 --> 00:26:39,898
The machine is simply creating the conditions for that to happen.

358
00:26:40,000 --> 00:26:43,568
And it uses heat exchangers and fans to speed it up.

359
00:26:44,569 --> 00:26:50,642
Because the refrigerant condenses and vaporizes separately to the act of compressing it,

360
00:26:50,642 --> 00:26:58,583
the refrigeration circuit is actually capable of moving more heat energy than is required to run the compressor.

361
00:26:59,684 --> 00:27:02,253
We call this the coefficient of performance.

362
00:27:02,587 --> 00:27:08,693
And when you get, say, three times as much 
heat moving capacity as you do input power,

363
00:27:09,094 --> 00:27:11,694
that's a COP of 3.

364
00:27:12,030 --> 00:27:13,999
Now, in an air conditioner like this,

365
00:27:14,332 --> 00:27:20,205
that would mean that for every watt of input power, 
you get three watts of cooling power.

366
00:27:21,006 --> 00:27:23,341
That's precisely how this little window unit,

367
00:27:23,341 --> 00:27:29,014
which is rated for 5000 BTUs per hour, 
(equivalent to roughly 1.5kW)

368
00:27:29,014 --> 00:27:31,850
only draws about 500W from the wall.

369
00:27:32,684 --> 00:27:37,155
The motors in the compressor and fan assembly consume that much power,

370
00:27:37,155 --> 00:27:42,193
but the refrigeration circuit is producing 
three times as much cooling power.

371
00:27:43,061 --> 00:27:49,434
And that is precisely why the dehumidifier 
has all the same parts as this air conditioner.

372
00:27:50,001 --> 00:27:55,106
You're getting extra heat moving capacity because the refrigeration cycle is awesome.

373
00:27:55,769 --> 00:27:57,275
Except....

374
00:27:57,909 --> 00:27:59,110
well, wait a minute.

375
00:27:59,411 --> 00:28:05,417
Yes, this machine has all the parts of a heat pump, 
but it isn't pumping heat anywhere at all.

376
00:28:06,051 --> 00:28:13,158
The condenser, which in an air conditioner has to go outside so it can actually get heat energy out of the building to cool it down...

377
00:28:14,059 --> 00:28:16,494
is, uh, here.

378
00:28:17,295 --> 00:28:22,834
It's sitting literally right behind the evaporator and in the same airstream.

379
00:28:23,468 --> 00:28:31,309
Which means that immediately after air is drawn through the evaporator and chilled by the refrigerant, absorbing latent heat energy,

380
00:28:32,711 --> 00:28:38,083
the air gets heated right back up on its way out by the refrigerant releasing latent heat energy.

381
00:28:39,050 --> 00:28:40,251
What's the deal?

382
00:28:41,386 --> 00:28:46,591
Well, we don't actually care at all about moving heat in this case,

383
00:28:46,858 --> 00:28:51,463
we just want to make a cold surface for water in the air to condense on.

384
00:28:52,163 --> 00:28:55,066
That's one way we can get water vapor out of the air.

385
00:28:55,366 --> 00:28:58,570
And the reason that works goes back to relative humidity.

386
00:28:59,337 --> 00:29:03,208
Remember that air can only hold on to so much water vapor,

387
00:29:03,575 --> 00:29:08,046
and the cooler the air is, the less water vapor it can absorb.

388
00:29:09,047 --> 00:29:17,922
This means that if you're able to cool it below the temperature at which air would become fully saturated and at 100% humidity

389
00:29:17,922 --> 00:29:21,282
(which, by the way, is a temperature we call the dew point),

390
00:29:21,726 --> 00:29:30,000
well, then suddenly the air's gonna have too much water in it, 
and the excess moisture will precipitate out of the air and onto cold surfaces.

391
00:29:30,401 --> 00:29:34,873
That temperature is called the dew point because that's why dew happens.

392
00:29:35,206 --> 00:29:39,043
You could say it's the, uh, dew process.

393
00:29:39,844 --> 00:29:42,447
Hey, side note, that was an awful pun,

394
00:29:42,447 --> 00:29:46,706
but did you know that due process 
(d. u. e. due process)

395
00:29:46,706 --> 00:29:52,624
is really just a fancy way of saying everyone is innocent until proven guilty?

396
00:29:53,558 --> 00:29:57,395
Last I checked, that's a core belief that all Americans share.

397
00:29:58,029 --> 00:30:05,069
If for some reason you no longer feel that everyone deserves 
the presumption of innocence until they are proven guilty,

398
00:30:06,104 --> 00:30:09,340
I think you might be having some 
un-American thoughts at the moment.

399
00:30:09,808 --> 00:30:11,209
Might want to get that checked out.

400
00:30:11,890 --> 00:30:15,046
Anyway, that's enough reinforcement of societal norms for today.

401
00:30:15,814 --> 00:30:20,285
You've experienced water condensing on cold things many times before.

402
00:30:20,885 --> 00:30:23,555
Cold drinks sweat in the summer months

403
00:30:23,755 --> 00:30:29,861
because the air right next to the cold surface of a can or glass becomes cooled below the dew point,

404
00:30:29,861 --> 00:30:31,863
so dew forms.

405
00:30:32,463 --> 00:30:35,733
That water used to be water vapor in the air,

406
00:30:36,100 --> 00:30:39,370
but the cold surface of the can caused it to condense.

407
00:30:40,205 --> 00:30:47,645
A dehumidifier is simply a machine with a very large, 
cold surface that we force air through

408
00:30:47,645 --> 00:30:51,583
so that we can cause the same effect at a much larger scale.

409
00:30:51,783 --> 00:30:57,922
So large that we can decrease the humidity in an enclosed space, or even an entire house.

410
00:30:58,857 --> 00:31:03,127
Now, as we know, the dehumidifier doesn't cool the air in a room,

411
00:31:03,361 --> 00:31:07,031
but it is still using a refrigeration circuit to do its job.

412
00:31:08,066 --> 00:31:12,003
I don't know precisely what coefficient of performance this machine runs at,

413
00:31:12,337 --> 00:31:17,008
but for the sake of the video, 
I'm going to assume it operates with a COP of 4.

414
00:31:17,976 --> 00:31:22,259
That means since this machine draws about 300W when it's running,

415
00:31:22,259 --> 00:31:27,118
it produces 1200 watts of cooling power in the evaporator right here.

416
00:31:28,286 --> 00:31:35,526
But of course, that also means it's producing 1200 watts of heating power in the condenser right in front of it.

417
00:31:35,994 --> 00:31:38,496
Those numbers are always going to match.

418
00:31:39,364 --> 00:31:44,802
Which would imply that since the condenser and evaporator are in the same airstream,

419
00:31:45,103 --> 00:31:49,340
their combined heating and cooling power will always cancel each other out.

420
00:31:50,541 --> 00:31:52,677
BUT THAT'S NOT WHAT HAPPENS.

421
00:31:53,278 --> 00:31:57,615
See, refrigerants aren't the only substances with a latent heat of vaporization.

422
00:31:58,316 --> 00:32:02,320
All substances have that, including water.

423
00:32:03,321 --> 00:32:07,959
Just as liquid water needs to absorb latent heat energy in order to vaporize,

424
00:32:08,559 --> 00:32:13,698
water vapor needs to release that latent heat energy to condense into a liquid.

425
00:32:14,699 --> 00:32:17,535
This always happens whenever water condenses,

426
00:32:17,769 --> 00:32:23,574
but it can be incredibly difficult for us to notice 
because it's latent heat and we can't feel it.

427
00:32:24,342 --> 00:32:29,614
For instance, when you grab a cold beverage from the fridge 
and condensation starts to form on its sides,

428
00:32:30,114 --> 00:32:33,985
that condensation doesn't feel hot because it isn't.

429
00:32:34,319 --> 00:32:39,824
Those water droplets will have a sensible temperature pretty close to the dew point temperature.

430
00:32:40,191 --> 00:32:45,530
But the water will impart its latent heat into the can as it condenses,

431
00:32:45,797 --> 00:32:52,370
causing the contents inside to warm up much more quickly than if the air was perfectly dry.

432
00:32:53,304 --> 00:33:00,945
And that heating effect won't stop until the surface of the can is above the air's dew point temperature.

433
00:33:01,245 --> 00:33:04,515
All right, and where does the dehumidifier fit into all this?

434
00:33:05,350 --> 00:33:09,387
Well, its whole job is to get water vapor out of the air,

435
00:33:09,554 --> 00:33:14,125
which it does by forcing it to condense onto the cold surface of the evaporator.

436
00:33:14,525 --> 00:33:19,063
And that means it's going to have to deal with the latent heat of water vapor.

437
00:33:20,098 --> 00:33:21,866
And how exactly does it deal with it?

438
00:33:22,700 --> 00:33:27,505
By converting it into sensible heat which we can feel.

439
00:33:28,339 --> 00:33:32,577
That's why the exhaust got so hot after I switched on the humidifiers.

440
00:33:33,945 --> 00:33:38,416
Now, I don't think the reason that happens is very easy to intuit,

441
00:33:38,616 --> 00:33:44,122
but it's pretty dang fascinating and is the key to this whole video, so I'm going to do my best to explain it.

442
00:33:45,289 --> 00:33:48,459
If the air in a room has no moisture in it at all,

443
00:33:48,760 --> 00:33:52,497
then when it goes through this dehumidifier,
nothing would really happen.

444
00:33:53,197 --> 00:33:59,675
The air would be chilled by the 1,200 watts of... cold the evaporator is sucking out of it,

445
00:33:59,675 --> 00:34:05,476
but then it would be heated right back up by the 1,200 watts of heat being released by the condenser.

446
00:34:06,277 --> 00:34:08,774
Since the two coils are right next to each other,

447
00:34:08,774 --> 00:34:14,519
the air coming out of the machine should be essentially the same temperature it was when it entered,

448
00:34:14,786 --> 00:34:17,855
plus 300W of heat from the motor windings.

449
00:34:18,823 --> 00:34:22,460
When humid air is drawn through the cold evaporator, though,

450
00:34:23,127 --> 00:34:24,729
weird stuff happens.

451
00:34:25,463 --> 00:34:30,101
Its cold surfaces will cause the air passing through it to fall below the dew point,

452
00:34:30,468 --> 00:34:36,674
and that forces water vapor in the air to begin condensing into water on the surfaces of the evaporator.

453
00:34:37,642 --> 00:34:43,614
And when that happens, as it always does, the water releases its latent heat energy

454
00:34:43,881 --> 00:34:46,017
which the refrigerant absorbs.

455
00:34:46,751 --> 00:34:49,120
But it's latent heat.

456
00:34:49,654 --> 00:34:53,691
It's heat we cannot feel and thermometers cannot register,

457
00:34:54,025 --> 00:34:56,394
which causes a very strange effect.

458
00:34:57,428 --> 00:35:03,234
No matter what's going on, 
the evaporator can only absorb 1200 watts of heat total.

459
00:35:03,868 --> 00:35:08,673
So if it's absorbing water's latent heat as it condenses,

460
00:35:09,474 --> 00:35:14,745
then it's actually losing the ability to cool the air that passes through.

461
00:35:15,780 --> 00:35:21,853
For example, if it's absorbing, say, 
800W of latent heat from water condensing on it,

462
00:35:22,520 --> 00:35:31,329
then two thirds of the evaporator's cooling capacity is going towards a process which does not lower the air temperature.

463
00:35:32,263 --> 00:35:34,999
However, there's a fact we cannot get around.

464
00:35:35,566 --> 00:35:39,370
The evaporator still absorbed 1,200 watts of heat.

465
00:35:40,171 --> 00:35:47,712
We couldn't feel 800W of it because it was latent heat, 
but it was still heat that was absorbed by the refrigerant.

466
00:35:48,679 --> 00:35:55,653
With 1,200 watts going into the evaporator, 
1,200 watts has to come out of the condenser.

467
00:35:56,053 --> 00:36:00,691
And it does - the condenser releases 
all the heat the evaporator absorbs.

468
00:36:00,892 --> 00:36:05,830
Latent or not, it doesn't care, 
and the total is always 1,200 watts.

469
00:36:06,597 --> 00:36:11,435
But with the 800W of cooling not happening because of condensing water,

470
00:36:11,936 --> 00:36:17,141
we experience a surplus 800W of 
sensible heat coming out of the condenser.

471
00:36:17,875 --> 00:36:24,315
All of the latent heat the evaporator absorbed becomes sensible heat when the condenser rejects it.

472
00:36:24,949 --> 00:36:28,152
Add that to the 300W of heat coming from the motor windings,

473
00:36:28,486 --> 00:36:33,024
and now there's 1,100 watts of 
sensible heat coming from this little machine.

474
00:36:33,858 --> 00:36:37,228
That's why the air leaving the dehumidifier is hot.

475
00:36:37,762 --> 00:36:44,702
This machine is converting the latent heat from condensing water vapor into sensible heat we can actually feel.

476
00:36:45,770 --> 00:36:48,372
And it just plops that heat right into the room.

477
00:36:49,240 --> 00:36:52,783
I find this incredibly fascinating because I'm a heat pump nerd,

478
00:36:52,783 --> 00:36:58,849
and this is one of the most visceral ways I've found to experience a machine generating much more heat

479
00:36:58,849 --> 00:37:00,318
than it apparently should.

480
00:37:01,219 --> 00:37:08,593
It seems impossible for a device which only draws 300W from the wall to produce air as hot as this does.

481
00:37:09,360 --> 00:37:12,964
But that's precisely what happens thanks to the power of a heat pump.

482
00:37:14,298 --> 00:37:17,468
But this isn't just trivia that's fun to play around with.

483
00:37:17,702 --> 00:37:24,375
It's actually a very important concept to understand because of how it relates to comfort and cooling.

484
00:37:25,376 --> 00:37:30,081
Most people agree that when the weather is warm, 
drier air is more comfortable.

485
00:37:30,681 --> 00:37:34,619
But while these machines can and will certainly dry out the air,

486
00:37:35,186 --> 00:37:40,791
the basic reality here is 
they're going to release a lot of heat to do that.

487
00:37:41,425 --> 00:37:44,195
Less when the air is already fairly dry.

488
00:37:44,428 --> 00:37:49,867
But even at 50% relative humidity, these things can produce a surprising amount of heat.

489
00:37:50,935 --> 00:37:55,706
Since they're usually controlled by a humidistat it won't produce that heat constantly,

490
00:37:55,706 --> 00:37:58,042
just when it needs to run to lower humidity.

491
00:37:58,876 --> 00:38:01,379
But it might as well be a space heater when it's running,

492
00:38:01,846 --> 00:38:05,616
so don't expect them to make you comfortable because they don't.

493
00:38:05,783 --> 00:38:07,151
That's not their job.

494
00:38:07,585 --> 00:38:13,724
They make otherwise humid environments safe for things 
which can be affected by moisture damage,

495
00:38:14,058 --> 00:38:15,760
and that's the extent of their role.

496
00:38:16,694 --> 00:38:19,879
If you're wondering how I can say that with such confidence,

497
00:38:19,879 --> 00:38:26,437
well, now it's time to imagine what would happen if you use a dehumidifier when you also have air conditioning.

498
00:38:27,471 --> 00:38:31,876
An air conditioner also has 
a cold evaporator absorbing energy from the air,

499
00:38:32,076 --> 00:38:37,882
so it also has to deal with the latent heat load 
from water vapor in the air condensing on it.

500
00:38:38,983 --> 00:38:40,951
But unlike the dehumidifier,

501
00:38:41,085 --> 00:38:48,726
an air conditioner can move that heat outside as it deals with it, 
which means for our intents and purposes it's gone.

502
00:38:49,794 --> 00:38:56,500
But the air conditioner still faces the same problem 
in that it can only move so much heat.

503
00:38:56,934 --> 00:39:02,840
And for every watt of its cooling capacity 
it spends condensing water out of the air,

504
00:39:02,840 --> 00:39:06,344
a watt of sensible cooling power is lost.

505
00:39:07,211 --> 00:39:10,147
This means when the air is extremely humid,

506
00:39:10,147 --> 00:39:16,854
an air conditioner is mainly just producing a lot of water and seems to struggle to cool the air temperature.

507
00:39:17,788 --> 00:39:20,180
When that's happening, you might think

508
00:39:20,180 --> 00:39:22,159
"well, then add a dehumidifier!

509
00:39:22,526 --> 00:39:27,531
Give it the job of dealing with that water vapor so the air conditioner doesn't have to."

510
00:39:28,766 --> 00:39:30,234
But have you spotted the problem?

511
00:39:31,168 --> 00:39:37,241
While the dehumidifier will absolutely reduce 
the latent heat load that the air conditioner must deal with,

512
00:39:37,775 --> 00:39:40,845
it won't actually reduce the total heat load.

513
00:39:41,679 --> 00:39:48,686
It simply turns the water's latent heat into sensible heat, 
which the air conditioner will still have to deal with.

514
00:39:49,754 --> 00:39:55,059
What I'm saying here is that using a dehumidifier in a space that's already air conditioned

515
00:39:55,493 --> 00:39:56,961
generally doesn't help.

516
00:39:57,661 --> 00:40:05,002
If you are cooling the air anyway, the air conditioner will generally remove enough moisture to keep everything safely dry.

517
00:40:05,903 --> 00:40:11,041
There are situations where 
adding a dehumidifier to your HVAC strategy can make sense.

518
00:40:11,442 --> 00:40:15,413
For instance, in the shoulder seasons
it might be getting too damp inside

519
00:40:15,413 --> 00:40:18,015
when it's not warm enough to run the air conditioner.

520
00:40:18,749 --> 00:40:22,119
And sometimes it can be legitimately necessary.

521
00:40:22,887 --> 00:40:28,692
If your air conditioner wasn't sized correctly, 
it might not be handling the moisture on its own.

522
00:40:29,493 --> 00:40:33,022
This whole can of worms
(the latent heat load of water vapor)

523
00:40:33,022 --> 00:40:37,835
is precisely why sizing an air conditioner correctly is so important.

524
00:40:38,636 --> 00:40:44,141
It needs to run fairly long cycles 
for it to actually extract water from the air,

525
00:40:44,542 --> 00:40:49,980
and an oversized air conditioner can produce 
too much sensible cooling too quickly,

526
00:40:50,247 --> 00:40:54,652
which causes it to run short cycles 
which don't effectively dehumidify.

527
00:40:55,486 --> 00:41:02,026
Although modern variable-capacity systems are much more flexible and they are improving the situation greatly.

528
00:41:02,960 --> 00:41:05,529
Still, even with an optimal air conditioner,

529
00:41:05,830 --> 00:41:10,968
if you have bad enough moisture ingress issues 
from poor air sealing or seepage,

530
00:41:11,535 --> 00:41:13,537
a dehumidifier can still be necessary.

531
00:41:14,405 --> 00:41:19,637
But in an ideal world, assuming you have 
air conditioning and you regularly use it,

532
00:41:19,637 --> 00:41:26,183
you shouldn't really need a dehumidifier at all except in unconditioned or poorly conditioned spaces

533
00:41:26,350 --> 00:41:29,119
like basements, crawl spaces, garages, etc.

534
00:41:30,154 --> 00:41:32,323
But there is one last wrinkle:

535
00:41:33,123 --> 00:41:36,694
an air conditioner can only get the air so dry.

536
00:41:37,495 --> 00:41:41,866
Because air's dew point temperature falls as humidity does,

537
00:41:41,866 --> 00:41:45,736
before long, an air conditioner reaches humidity equilibrium.

538
00:41:46,437 --> 00:41:53,177
At 72°F and 50% relative humidity, the dew point is about 52°F.

539
00:41:53,844 --> 00:42:00,351
And the evaporator coil in a properly functioning air conditioning system doesn't get much colder than that.

540
00:42:00,885 --> 00:42:03,220
So at ordinary room temperatures,

541
00:42:03,220 --> 00:42:07,625
an ordinary air conditioner can't drop humidity much below 50%.

542
00:42:08,759 --> 00:42:11,595
If you truly need or want it lower than that,

543
00:42:12,029 --> 00:42:17,501
a dehumidifier can get you a little bit lower and most allow you to run them nonstop if you wish.

544
00:42:18,369 --> 00:42:23,140
Just keep in mind it'll be working hard 
to do that consuming energy of its own,

545
00:42:23,541 --> 00:42:26,644
and it will produce more heat for your air conditioner to deal with.

546
00:42:27,327 --> 00:42:28,746
But can they save money?

547
00:42:29,780 --> 00:42:33,384
Well, that's a big, fat, "it depends."

548
00:42:33,984 --> 00:42:39,757
I mean, it's a concrete Yes if you have damp problems
and a dehumidifier saves your stuff from damage.

549
00:42:40,391 --> 00:42:42,426
But when it comes to energy costs,

550
00:42:43,114 --> 00:42:45,462
ehhhhh.... that's not easy to determine.

551
00:42:46,363 --> 00:42:51,735
Assuming a dehumidifier can remove more moisture 
per kilowatt-hour than your air conditioner can,

552
00:42:52,403 --> 00:42:56,740
then so long as your air conditioner 
can keep up with the extra heat it's producing,

553
00:42:56,941 --> 00:43:00,744
that might lower your energy costs a bit.

554
00:43:01,712 --> 00:43:03,614
But to be honest, I wouldn't expect it to.

555
00:43:04,415 --> 00:43:08,986
These things are great at what they do, 
but they aren't exactly energy misers

556
00:43:09,286 --> 00:43:14,825
and full blown air conditioning systems (at least recent ones) are really energy efficient.

557
00:43:15,526 --> 00:43:18,696
High-end systems with variable speed blowers and compressors

558
00:43:18,696 --> 00:43:25,235
can even alter the ratio between latent and sensible heat loading by tinkering with airflow and refrigerant pressures.

559
00:43:25,903 --> 00:43:31,342
Slowing air down can get the evaporator colder which will remove more moisture.

560
00:43:31,675 --> 00:43:34,845
And with the right sensors, you can make sure the coil doesn't ice up.

561
00:43:35,746 --> 00:43:38,115
But even with basic air conditioning,

562
00:43:38,382 --> 00:43:44,221
if it's keeping your home dry on its own, 
there's really not much a dehumidifier is going to do for you.

563
00:43:44,488 --> 00:43:47,224
It's just gonna make noise for no good reason.

564
00:43:48,025 --> 00:43:54,000
The only situation where I personally think 
of a dehumidifier as a potential cost saving thing

565
00:43:54,000 --> 00:43:58,435
is when you're away from home and not using air conditioning at all,

566
00:43:58,602 --> 00:44:02,206
but you still want to ensure indoor humidity doesn't get too high.

567
00:44:03,173 --> 00:44:09,246
If you don't care about the temperature, well then you should be happy to let a dehumidifier run its little heart away.

568
00:44:09,380 --> 00:44:13,550
That's definitely going to be more cost effective
than cooling the place when nobody's home,

569
00:44:13,751 --> 00:44:18,989
and a warmer indoor temperature compared to 
outside air tends to reduce humidity issues anyway.

570
00:44:20,157 --> 00:44:25,429
But unless you travel a lot 
or like you've got a vacation home somewhere,

571
00:44:25,663 --> 00:44:31,502
I would be very surprised if you'd actually get your money's 
worth out of the purchase of a dehumidifier.

572
00:44:32,503 --> 00:44:37,007
Also, to make a single dehumidifier effective for an entire house,

573
00:44:37,007 --> 00:44:42,146
you'd probably need to use your HVAC system's fan setting to move air around,

574
00:44:42,146 --> 00:44:45,416
and you'd be surprised how much power those blower motors use.

575
00:44:45,849 --> 00:44:48,018
It's usually a couple hundred watts at least.

576
00:44:48,819 --> 00:44:55,092
Alright, so now it's time to close this video out, 
which I'll do by acknowledging the flaw of dehumidifiers like this.

577
00:44:56,126 --> 00:44:59,363
These don't work very well in colder temperatures.

578
00:44:59,830 --> 00:45:04,935
And the temperature doesn't even need to be that cold 
for them to stop working so well, or indeed at all.

579
00:45:06,003 --> 00:45:10,574
These things are built to a cost 
and use very simple refrigeration circuits.

580
00:45:10,941 --> 00:45:12,676
They're either running or they're not.

581
00:45:13,377 --> 00:45:21,218
And this means that the operating pressures in the evaporator and condenser are going to depend mostly on the ambient air temperature.

582
00:45:22,086 --> 00:45:28,625
And when the air temperature gets 
somewhere around 55°F or colder, that's about 13 Celsius,

583
00:45:28,625 --> 00:45:34,029
the refrigerant pressure in the evaporator might be low enough for the refrigerant boiling point

584
00:45:34,029 --> 00:45:36,734
to be below the freezing point of water.

585
00:45:37,468 --> 00:45:42,372
And when that happens, 
the evaporator will freeze the water that condenses on it.

586
00:45:43,273 --> 00:45:49,580
And that will eventually plug up the evaporator with ice and then air can't travel through it anymore.

587
00:45:50,481 --> 00:45:55,185
Now any decent dehumidifier 
is going to be able to detect that this is happening

588
00:45:55,352 --> 00:45:59,590
and will shut off the compressor for a long enough period of time for the ice to melt.

589
00:45:59,990 --> 00:46:03,527
And that will happen pretty quickly
since it keeps the blower fan running.

590
00:46:04,428 --> 00:46:10,334
But those periodic defrosts limit how much it can actually run and thus limit its effectiveness.

591
00:46:11,235 --> 00:46:16,006
However, this downside 
may not matter at all depending on your local climate.

592
00:46:16,707 --> 00:46:21,044
Where I live, you don't have to use 
a dehumidifier when the weather's cold.

593
00:46:21,478 --> 00:46:27,017
These things usually only get fired up in April or May 
and then get turned off around October.

594
00:46:27,851 --> 00:46:30,988
Cold but damp just isn't much of a thing here.

595
00:46:31,188 --> 00:46:36,493
We only encounter that in the shoulder seasons, 
and never for long enough to require intervention.

596
00:46:37,361 --> 00:46:40,864
And remember, simply heating the air lowers humidity.

597
00:46:41,431 --> 00:46:44,902
And you don't have to heat it very much to have a dramatic effect.

598
00:46:45,769 --> 00:46:54,211
When it's 55 degrees outside (13 Celsius), even if it's raining 
and the outdoor air is fully saturated with water,

599
00:46:54,211 --> 00:47:01,752
maintaining an indoor temperature of 68 degrees (20 Celsius) will lead to indoor humidity of 63%.

600
00:47:02,853 --> 00:47:05,122
That's probably a little higher than ideal,

601
00:47:05,322 --> 00:47:08,592
but it's nowhere near as humid as raining.

602
00:47:09,693 --> 00:47:13,096
That's why humidity usually isn't a problem in the heating season.

603
00:47:13,597 --> 00:47:16,033
And here, where it gets real cold in the winter,

604
00:47:16,400 --> 00:47:22,372
indoor air is so dry that we often 
want to add moisture, hence the humidifiers.

605
00:47:22,873 --> 00:47:24,842
The best part of Midwestern weather

606
00:47:24,875 --> 00:47:27,477
is that humidity is always wrong!

607
00:47:27,978 --> 00:47:34,918
Anyway, because the icing doesn't really happen when virtually anyone in the US actually needs a dehumidifier,

608
00:47:35,519 --> 00:47:38,121
this is the only kind that's sold here.

609
00:47:38,989 --> 00:47:41,658
The refrigeration cycle is just too efficient,

610
00:47:41,758 --> 00:47:47,564
and our weather patterns mean the icing issue 
is only a problem for a week or two, if that.

611
00:47:48,599 --> 00:47:52,736
But as the old saying goes, 
there's more than one way to dry a flat.

612
00:47:53,770 --> 00:47:56,406
In a future video, we'll take a look at this:

613
00:47:56,840 --> 00:47:59,343
a rotary desiccant dehumidifier.

614
00:48:00,177 --> 00:48:01,979
This is a fascinating little machine

615
00:48:01,979 --> 00:48:07,451
which doesn't have the cold ambient performance problems a vapor-compression dehumidifier does.

616
00:48:08,485 --> 00:48:15,659
But it does have several drawbacks, which is probably why I had to wade through tons of Amazon sludge

617
00:48:15,659 --> 00:48:18,195
just to find this one model for sale.

618
00:48:19,229 --> 00:48:20,330
That's for later, though.

619
00:48:20,330 --> 00:48:23,200
And speaking of Amazon sludge, remember this thing?

620
00:48:23,901 --> 00:48:28,672
Well, this piece of garbage 
does technically remove moisture from the air,

621
00:48:28,939 --> 00:48:36,013
and it uses the same "create a cold surface and blow air past it" principle that the real boy dehumidifier does,

622
00:48:36,713 --> 00:48:39,049
but it's missing a refrigeration circuit

623
00:48:39,182 --> 00:48:42,920
and uses a Peltier element instead.

624
00:48:43,787 --> 00:48:45,034
Yeah. Remember those?

625
00:48:45,034 --> 00:48:49,373
Those things that get put into novelty beverage coolers that don't work?

626
00:48:49,373 --> 00:48:52,763
Well, they also get put into dehumidifiers which don't work.

627
00:48:53,730 --> 00:48:57,834
In that same bathroom with ambient humidity over 80%.

628
00:48:58,402 --> 00:49:04,308
This so-called "dehumidifier" produced 
this much water in two hours.

629
00:49:04,775 --> 00:49:06,243
That's 22g.

630
00:49:07,277 --> 00:49:08,645
Maybe this would be useful

631
00:49:08,645 --> 00:49:11,748
for like a terrarium or perhaps a small closet,

632
00:49:11,949 --> 00:49:13,884
but otherwise these things are just silly.

633
00:49:14,318 --> 00:49:19,820
There is a reason the catch buckets of a proper dehumidifier are so big.

634
00:49:19,853 --> 00:49:26,363
In the same two hours, this guy removed 1.2 liters 
of water from the air - 55 times as much!

635
00:49:26,763 --> 00:49:31,068
And yet it only consumed ten times as much energy as this thing did.

636
00:49:32,035 --> 00:49:33,737
That's the power of a heat pump.

637
00:49:33,737 --> 00:49:35,305
Effective and efficient!

638
00:49:36,139 --> 00:49:42,379
if you noticed in the temperature logger chart I showed earlier that my testing happened back in August of 2024...

639
00:49:43,113 --> 00:49:49,720
Well, that's because this video had an entirely different scope and concept back then, which I abandoned.

640
00:49:49,953 --> 00:49:52,556
in no small part because I would have finished it

641
00:49:52,723 --> 00:49:56,026
right when people would be 
putting their dehumidifiers away for the winter.

642
00:49:57,127 --> 00:50:00,597
I wanted to pit these three dehumidifiers against each other

643
00:50:00,597 --> 00:50:04,735
and was mostly interested in water extracted per kilowatt hour,

644
00:50:05,268 --> 00:50:08,651
but ultimately that was fluff against the bigger message of

645
00:50:08,651 --> 00:50:13,110
"latent heat is very confusing and dehumidifiers 
do not help you stay comfortable."

646
00:50:14,311 --> 00:50:17,180
But when we look at the rotary desiccant machine,

647
00:50:17,381 --> 00:50:19,516
we'll definitely bring that topic back up.

648
00:50:20,450 --> 00:50:21,718
Because, well,

649
00:50:22,290 --> 00:50:25,589
it's not very efficient, but it is very interesting.

650
00:50:26,189 --> 00:50:27,609
So stay tuned.

651
00:50:28,669 --> 00:50:31,182
♫ condensedly smooth jazz ♫

652
00:50:33,930 --> 00:50:35,532
Anyway, that's enough reinforcement of societaul

653
00:50:36,366 --> 00:50:37,567
Wow, that's a mouthful.

654
00:50:38,568 --> 00:50:41,538
Anyway, that's enough reinforcement of societal norms for today.

655
00:50:41,838 --> 00:50:43,807
when we look at the rotary desiccant machine,

656
00:50:43,974 --> 00:50:45,742
we'll definitely bring that top it back up.

657
00:50:46,510 --> 00:50:48,011
Well, what happened there?

658
00:50:48,512 --> 00:50:50,080
so it can ruin your belongings.

659
00:50:50,547 --> 00:50:52,816
And if that's not enough, yeah, I'm going to restart that.

660
00:50:53,083 --> 00:50:57,856
relative humidity is 50% saturated and thus has abdorb.

661
00:50:58,815 --> 00:50:59,450
Blerp.

662
00:51:00,023 --> 00:51:01,224
It has example.

663
00:51:01,291 --> 00:51:03,193
Okay, so we got to read this one faster.

664
00:51:05,195 --> 00:51:07,130
So I screwed up for several reasons.

665
00:51:07,631 --> 00:51:09,533
worked diligently to undo that

666
00:51:09,766 --> 00:51:11,968
which you can see as this fairly stready,

667
00:51:12,369 --> 00:51:13,637
stready dip of water.

668
00:51:15,939 --> 00:51:16,767
Oh boy.

669
00:51:20,000 --> 00:51:23,452
OK, so I did the captions in an entirely different way this time and it didn't work as well as I'd hoped.

670
00:51:23,452 --> 00:51:26,669
But that doesn't mean I'm going to forget the end of video captions gag!

671
00:51:26,669 --> 00:51:30,463
This is it. It's not a very good one.

672
00:51:30,943 --> 00:51:33,890
dew process