Dehumidifier - Not your typical question

[Brikp]

OK - I am not going to ask what brand or if I can connect up to my floor drain or whatever.

I am asking about central air. It seems to me that the biggest reason, for my personal comfort, to run AC in summer is to remove humidity. If I have a relatively warm house but no humidity I would be quite comfortable.

Is there such a device to add to a central HVAC? I have seen add-on humidifiers but never add-on de-humidifiers. If such a thing existed would it be just as expensive to run as just running the AC?

I am thinking about this from a cost savings perspective mainly.

I did do a google search and found one built into a air/air exchanger/ filter device as well.

So, this got me thinking about indoor air quality as well.

The Thermastor device parts only will be $3-4K. I can probably install myself but I'm sure I wouldn't get any payback on my energy bill at that price.

So, I guess I would need to figure may days of cooling reduction of I used a central dehumidifier, figure the cost of a such a set-up, plug in my kwh operating cost and figure out if it would pay back ever.

I am in SE PA, pretty humid at times. I had a somewhat hard time justifying upgrading from a 10SEER to the 12 I am having put in. The cost difference was $400. Payback for me I figure will be 7 years!

OK, so to boil it all down. Is there a way to save on AC costs via dehumidification that doesn't have high upfront costs that would negate any ROI?

[m Ransley]

A portable dehumidifier is what I use since my AC is oversized. Yours may be oversized if humidity is a problem.

[m Ransley]

a 10 vs 12 seer saves apx 20 % , im guesing, at a 400 difference you must not run the AC much. Many people see a 1 yr payback. I wouldnt even consider a 12. You say you are getting a new unit, well I hope you had a proper load calc done, your AC will remove the humidity if sized and instaled right, to big and it will just cool to fast.

[m Ransley]

a 10 vs 12 seer saves apx 20 % , im guesing, at a 400 difference you must not run the AC much. Many people see a 1 yr payback. I wouldnt even consider a 12. You say you are getting a new unit, well I hope you had a proper load calc done, your AC will remove the humidity if sized and instaled right, to big and it will just cool to fast.

[Doug Miller]

Such a device does exist, and you already have one: it's called an air condtioner.

Think of central A/C as a giant dehumidifier, or, if you prefer, think of a dehumidifier as a miniature air conditioner.. Both air conditioners and dehumidifiers operate in the same manner. The only functional difference is that a dehumidifier has the compressor and the evaporator in a single package, and thus exhausts its waste heat into the same room, whereas an air conditioner has the evaporator indoors and the compressor outdoors so that the waste heat is removed from the building. In a nutshell, dehumidifiers remove moisture while making the indoor environment warmer, and air conditioners remove moisture while making the indoor environment cooler. Your choice.

Generally speaking, one large unit is more efficient than several smaller ones; thus, the cost to operate central air conditioning may be less than the cost to operate several portable dehumidifiers, if you're thinking of going that route.

[John Hines]

A de-humidifier is basically an air conditioner, with the hot coil in the air flow as well, for little temp change.

Put the hot coil outside, and you have an air conditioner, on the same electricity.

Just set it so that the AC doesn't run very frequently, so it just dries some air out.

[dadiOH]

Move to Arizona, hang up a wet sheet and point a fan at it.

-- dadiOH _____________________________

dadiOH's dandies v3.0... ...a help file of info about MP3s, recording from LP/cassette and tips & tricks on this and that. Get it at

[Art]

Carrier used to have a commercial about how every place they checked on the "weather map" it was 72 degrees if a carrier central air was installed. I got tired of that commercial and emailed them because talking to technicians, there is no way you can guarantee a reasonable humidity at 72 degrees. Anyway they actually emailed me back and said the following:

"Thank you for contacting Carrier. Equipment can be installed to achieve the

72 degree temperature as stated on our commercial. However, the dealer must know that these circumstances are wanted, so that the load can be adjusted accordingly. With this type of adjustment, other factors may be sacrificed such as humidity at lower temperatures. Typically systems are designed with the 20 degree differential taken into consideration".

The 20 degree drop refers to a statement in my original email as to what the temp should be expected versus outside according to one tech.

I had the HVAC replaced in my parents condo and had to have 6 guys come before I found one who would actually do a load calculation (old system was too small). Any way to sum up the one key thing I learned from all my reading that I thought was important is that for any system working correctly, the air is going to be exiting out at an ideal temperature. If it is coming out warmer it is not working correctly. That also means that since there is only one right temperature, putting in a bigger outdoor unit is not going to help a system not big enuf. You also need more air and if the air handler is too small there is not much you can do to cool your house down other than to replace it too. Bottom line there is only one right temperature for the air to be exiting at and since there is only one right temperature, if your house doesn't get cold enuf then you need more air handling capacity (in addition to cooling capacity).

[Stormin Mormon]

The only difference between a dehum and an AC is that the AC dumps the waste heat outdoors.

Well, also the AC turns on and off based on temp. The dehum turns on and off based on relative humidity.

As for installing AC yourself, better get some information. If it means connecting line set and charging with freon, that's the AC techie's job.

AC guys talk about "latent heat" which is heat removed that doesn't change the temperature. The short of this is that latent heat equals humidity. "sensible heat" is that heat that lowers the temp when removed. This is dry heat.

When I was a kid, the folks next door got a central AC put in. They were very pleased they got a dehumidifier built in. Surprise!

[SQLit]

I looked into an ac change 10 to 14 seer, new vfd air handler and condenser, Trane 14xli. I found a site that said in my neighbor hood (Phoenix) I would save ~ $360.00 a year a tad more than the 20%. Cost for the change was $5800.00 identical sized units. I do not plan to be in the house for 10 years so I passed.

There are several sites that have calculators that allow comparisons http://198.147.238.24/ac_calc/default.asp I used this one. It allows for comparisons between 2 units. Results were startling to me. I figured it would be more than that.

I spent the $360.00 in extra insulation in the attic. Since this is my first summer we shall see.

[Brikp]

I don't think humidity will be a problem. house is not finished yet. It will have a proper sized AC system. I was just thinking that a house with lower humidity wouldn't need as much AC.

Thanks for your reply.

[Brikp]

New construction. Unit will be sized properly and is being installed by a reputable sub.

[Brikp]

No, I was not thinking of portable units. Thanks for your reply.

[Brikp]

I am not planning to install the AC or furnace myself. It is new construction and will be installed by a reputable contractor. I thought if there was an add-on device, similar to the humidifiers that add-on, I could handle that.

Thanks to everyone for the replies. Seems that there will be no cost benifit to a whole house dehumidifier if I could find one. AC is a dehumidifier in a sense.