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Using a humidifier with AC in summer


SwampNut
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I've been told several times that this is bad, according to "common knowledge."  But I can't find any such thing when I google it.  The most negative thing I can find is to be careful not to have the humidity go too high.  We have an automatic humidifier, and my thought would be to set it around 45, maybe 40.  Comments?

 

 

Humidifiers in the Summer

The issue is mostly present in the winter, but if you live in a dry climate such as here in San Diego, it’s possible to experience these symptoms all year. Even if you live in a very wet place, if it’s hot you’re probably running your air conditioner. That’s a sure way to dry out your home. Running a humidifier will help fight dry, itchy skin, even in the summer. Plus, did you know it can save you money? Think about it. Running a humidifier in tandem with your air conditioner means that your AC is cooling wet air. You know those ridiculously overpriced fan/spray bottles sold at amusement parks? It’s the same principle. Cooler air inside your home means you can raise the temperature on your AC. This in turns cuts your electric bill. Stop allergies and save money. It’s a win-win.

 

When Should I Start Using Humidifier with Air Conditioner?

Usually, in summer, we use air conditioners almost all the time. As I mentioned earlier, the air conditioner removes both moisture and heat while cooling our home. Due to dry air, you can have skin-related problems such as dryness, itchiness, etc. Besides, when the humidity becomes low, it can cause respiratory problems as well. If you have someone in your home who has asthma problems, you should be more concerned about the humidity of your home.

So, if you’re currently facing these problems, you must need a vaporizer with your AC unit.

  • Dryness
  • itchiness
  • Headaches
  • Chapped Lips
  • Nose Irritation, etc.

 

 

 

 

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Relevant physics...

 

Evaporating water consumes energy, cooling the house.  So running the humidifier with heating is actually a fight.  You have to heat the water to change its state.  The type of humidifier doesn't change this; we have an ultrasonic but it doesn't change state.  It aerosolizes the still-liquid water, which then can more easily absorb energy and change state.  It's always about five degrees cooler near the humidifier.  Simple rule of physics.

 

The AC removes SOME water from the air, not all.  And it reduces temp.  RH is a ratio of temp and absolute humidity.  The AC reduces AH, but *might* not lower RH because it's also cooling.

 

From an AC tech:

If you live where the air is extremely dry, perhaps with a RH less than 20%, it could be reasonable to use both at the same time. If you don’t let the RH increase to more than about 40%, the condenser on your AC will not become wet and the AC will not remove any moisture, i.e., there will be no latent heat load on your AC. But if the RH becomes too high because of the humidifier, the AC will remove part of it thereby increasing the latent heat load on your AC and running up your power bill unnecessarily.

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That's why it's so hard to get decent info.  There are few places where these conditions exist.  Even in Southern CA, the hot areas also have more humidity, commonly.  I have set the humidifier to 40.  

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I saw a few references to that, the question is what is "enough?"  Everyone seems to talk about Southern humidity, not AZ humidity.  The difference between bringing the air down from 80% outside versus bringing it up from 10% outside.

 

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Yeah, I really do understand. 

 

The air in my house when the winter at 80F inside with outside temps in the -10F range can really dry us out.

 

 No. 3 got us this for Christmas. It keeps us from getting electroshock treatments every time we shut the lights on.

 

The vapor is cold.

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11 hours ago, XXitanium said:

How does your AC usage Vs outdoor humidity vary during peak heat outdoors?

 

I'm not sure I understand.  The peak cooling happens during the lowest (relative) humidity of course.  The AH doesn't seem to vary much, so as temps change, RH does.  It's typical for peak cooling to be at the same time as 10% or less outside.  In a short part of the year we may have a few 50% days due to monsoons.

 

I've never heard it called an economizer, but I've considered doing a whole-house fan for the MANY days when it's cold for part of the day, and hot for part.  Also a big part of our cooling is from solar radiation, so it can be under 80 air temp and still need cooling.  Any outside air would remove the humidity, and introduce dust and shit potentially.

 

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The names are not unrelated.

 

A whole-house swamp cooler is unheard of around here, except in old/shitty/small houses.  I'm not sure why.  Moving enough air for this space is probably one huge reason.  I suspect there are other issues since I haven't seen one in any neighborhood I'd want to live in.

 

 

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1 hour ago, SwampNut said:

The names are not unrelated.

 

A whole-house swamp cooler is unheard of around here, except in old/shitty/small houses.  I'm not sure why.  Moving enough air for this space is probably one huge reason.  I suspect there are other issues since I haven't seen one in any neighborhood I'd want to live in.

 

 

 

Mine works phenomenally well - especially as an afterthought with the house not being designed around it - but the climate is different enough between Phoenix and Prescott to matter. 

 

There has never been a high-temp/low humidity day that this $400 window unit didn't keep temps under 75 inside, and I've seen 103 outside here.  It's in an otherwise unused room on the lower level (north side) of the house, so it's rarely seen or heard.  Now, when monsoon season comes along and outside humidity gets above 30%, efficiency is essentially nil - it just makes it clammy inside.  Having a respectable AC unit is still a requirement for a brief part of the year here.

 

I wish I could design a house with evaporative cooling in mind, there are lots of little things that would make it more efficient.  Plumb it into the central air system and install up-ducts that vent into the attic - send the relatively cool, moist house air into the attic and flush some of that heat load as well.  Put several solar panels on the south side of the house or on the roof to shade surfaces while generating the power to run the cooler. 

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22 minutes ago, IcePrick said:

Mine works phenomenally well - especially as an afterthought with the house not being designed around it - but the climate is different enough between Phoenix and Prescott to matter. 

 

That whole 20 degrees cooler thing.  They were popular and worked well in Tucson also.  In fact I lived in at least one house that had both, so you could refrigerate for those awful 6-ish weeks and swamp the rest of the time.  It was a lot like what you describe, with auto vents into the attic.  Pressure would open them, same as a whole-house fan vent.

 

An attic fan could help too.  And I really need to renew the attic insulation, but finding someone without a referral is one of those things I hate.

 

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On 3/28/2022 at 7:02 PM, XXitanium said:

Air conditioning basically doesn't work till enough humidity is removed from the space being conditioned. 

 

@JoWhee right?

EDIT: I wrote this before reading all the comments and OP. As someone who lives in the north I'm no stranger to dry and chapped skin itchy as fuck also. A good moisturizer is the easy solution. I'm not a fan of humidifying because of all the possible issues. mold, scale buildup in the unit, but if it's causing medical or for that matter computer issues, then obviously, humidify, just buy a good automatic unit. 

 

 

Air conditioning is just a heat pump it's pumping heat from one place to another, as it's impossible to pump "cold" . The dehumidification is a byproduct of the cooler air being able to hold less water, causing the relative humidity to drop. Air temperature and humidity are related, google psychrometric chart if you're into that kind of detail (I'm NOT). It's probably why the same size A/C in Arizona might work better than the same one in mississippi, because the one in AZ isn't dealing with as much humidity and therefore less total heat assuming the temperature is the same and not 140 degrees. It's also the reason some idiot will say it's not the heat it's the humidity, because you feel it more when it's a damp heat.

 

 1234.jpeg.7f1100d0804607637f4d6703154e8ac1.jpeg

Edited by JoWhee
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3 hours ago, JoWhee said:

just buy a good automatic unit. 

 

There's a thread on the details, but...  Good ultrasonic with auto control, easy descale, connected to an RO unit so it never really scales at all.  A separate sensor confirms it doesn't go too high.  I've got it at 40% now.  The weather suddenly took a turn with some rain, so the AC only ran for a day or so.  High of only 78 today.

 

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