Dehumidifier - add to HVAC or stand alone

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My house is not extremely moldy or humid, but my wife has developed a bad mold allergy and we have to get the house less humid before the weather gets warmer in May. I have talked to several HVAC people about adding a dehumidifier to the main system. This will be expensive but I will do it if I have to.
One guy told me that one stand alone unit often does the trick. I can buy one of these at Home Depot for about $160. They are noisy and you have to empty them frequently though and I don't really want one running in the house. Then he told me something I am questioning, and this is my real question for you. My house has a crawl space, just about 3 feet high. I put plastic down years ago. This fellow told me I could put a stand alone dehumidifier in the crawl space under the house and it had a good chance of solving my problems and lowering the humidity in the whole house. Does this make sense?
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tom carr wrote:

You put plastic down years ago?
York makes an air conditioning unit with dehumidification as a benefit and reheat. I don't remember the model numbers, but it was presented several years ago at a York Dealers meeting. Give them a look up.
--
Zyp



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Wife spends a lot of time in the crawlspace ?
--




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Any AC system will remove humidity from the air. It's one of the things they do naturally. Please tell us about your heating system. Gas, oil? Radiators? Forced air?
As to the portable dehum, most of them have a knock out, so you can drain the bin through a garden hose, into a sink or other drain. Since dehum dump the heat into the room, they are a heat gain, as well as using a bunch of electric.
Plastic in the crawl space. Just to mention the obvious. If the plastic is on the ground, then put the dehum on top of the plastic may help. If the plastic is stapled to the bottom of the floor, that's different.
The last time I had some serious allergy problems, I had to take apart the AC, clean it out and sanitize it. Amazing, what grows in wet areas. If you have central AC, may be long past time to have the indoor coil taken out, and cleaned. Not a job for a home owner. Please also look under your refrigerator. Open the doors, and snap off the "kick plate". Often they have a tray for the condensate. This tray lifts and pulls out. Scrub it, and sanitize with a blast of clorox bleach.
Best wishes, and let us know what happens.
--
Christopher A. Young
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It is a forced air system. I had it installed about 7 years ago. It is in the attic. Central heat and air. The house is a one story wood house built in 1950 here in Atlanta Ga. Atlanta is pretty humid in the summer, but not in the winter.

I have had lots of warning about the electricity. Just how bad is it? Is it worse than a window unit AC for example? If I do add a denum to my central heat and air, will it increase my electric bill in the summer by 50% or 100% or what?

The plastic is on the ground. I put it out myself several years ago. At the time someone told me you are supposed to leave 10% of the ground uncovered. I didn't understand why but I did it that way. I think I will go back and put down more plastic and make sure 100% of the ground is covered unless someone here tells me you are not supposed to.

I am going to have someone who knows what they are doing do that. Also, I was told I need to replace the plenums with metal plenums. The ones there now feel like some kind of heavy cardboard and I was told that is not good.

The system is 7 years old. How often should that be done?

Will do.
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It is a forced air system. I had it installed about 7 years ago. It is in the attic. Central heat and air. The house is a one story wood house built in 1950 here in Atlanta Ga. Atlanta is pretty humid in the summer, but not in the winter.
CY: yes, I'd have to guess, GA can be humid.

I have had lots of warning about the electricity. Just how bad is it? Is it worse than a window unit AC for example?
CY: Typically dehum run 1/5 to 1/4 HP compressor. I'm not sure what the running amps is, probably 4 to 5 amps. So, 600 to 700 watts while it's running. About the same as a window AC. So, for that matter, might make more sense to run a window AC if you need the cooling.
If I do add a denum to my central heat and air, will it increase my electric bill in the summer by 50% or 100% or what?
CY: No way for us to be sure. Figure about 600 watts while it's running.

The plastic is on the ground. I put it out myself several years ago. At the time someone told me you are supposed to leave 10% of the ground uncovered. I didn't understand why but I did it that way. I think I will go back and put down more plastic and make sure 100% of the ground is covered unless someone here tells me you are not supposed to.
CY: I havn't heard either way or the other. I'd want to cover all the ground.

I am going to have someone who knows what they are doing do that. Also, I was told I need to replace the plenums with metal plenums. The ones there now feel like some kind of heavy cardboard and I was told that is not good.
CY: Metal, with insulation is good. Foam board, for example. Don't want to absorb a bunch of heat from the attic. You do have attic venting, I hope? Maybe electric vent, set to a temperature switch?

The system is 7 years old. How often should that be done?
CY: Totally depends on the situation. Dust level, run time, etc. Might easily be time.

Will do.
CY: If your fridge is "frost free" it will have a pan some where. Some are behind the kick plate, and others are on the back, welded to the top of the compressor. Any case, they do grow algae and crud.
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...

...
What exactly is laying plastic on the ground supposed to gain you? When it rains, does the water collect on the plastic sheet?
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wrote:

If it's raining in your crawlspace you've got a problem with humidity.
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I wish to nominate "kool" for the understatement of the year award.
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On Thu, 3 Apr 2008 23:10:40 -0400, "Stormin Mormon"
..........and as usual Stormy, you win the Wittless dumb-fuque of the year" award.
Bubba
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I just looked. Mine doesn't have a tray. There is about an inch of dust under there though, so I need to move the fridge, vacuum, and then I guess I might as well clean it all with bleach.
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Forgot to mention. Only on frost free refrig.
Vacuum out the dust is a good idea. Both for energy saving, and also for allergies. Clean with bleach also sounds good. If there are a bunch of tubes and wires under your fridge, that's where the unit tries to release the heat energy from inside the fridge. Cleaning it will save you money. Compressor won't have to work as hard.
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Thanks for the info. That all makes perfect sense. So much of this is just applying a basic understanding of physics, heat, moisture, mechanics and so on.

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So, so true..... it's all pretty basic.
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I have been reading about the humidex system at this site: http://www.humidexhome.com/index.cfm
What they are saying seems logical. They say moisture sinks, and that by sucking air from a vent in the floor, down into the crawl space and thus also forcing the air in the crawl space out of the house, you reduce moisture in the house without running a dehumidifier.
It seems to me you could do the same thing with a fan blowing air out of the crawl space and a vent in the house floor, without spending $1200 on their unit.
This raises one new question though. If moist air sinks, why are bathroom fans in the ceiling?
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Would you want your exhaust fan in the floor? It can be done for a price! Heat rises, moist sinks,cold falls and shit stinks!
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Will the outside air (coming in) be less or more humid?
It's possible that a vent fan drawing humid air out of the crawl space may reduce the humidity in the home. Easy enough to try it, I guess. Let us know what works out.
Does moist air sink? Well, fog travels along the valley. Not sure that applies.
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Here's an interesting paper on this topic:
http://www.buildingscienceconsulting.com/resources/mechanical/hvac/conditioning_air.pdf
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On Mar 27, 9:16 pm, snipped-for-privacy@hatespam.com (Hot-Humid) wrote:

Thats great. Thanks so much. I will read it in detail later today.
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Tom do you self a fever get portable unit at Home Depot and put it any room that is convenience to you. Forget about integrating into AC system unless you are looking for problems with AC, it does not need to be in any specific place your central air will move the air through out of your home. If you can put it close to return air of AC Tony

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