Why does high humidity cause air conditioners to work harder and is
there any sort of dehydration device that can be strapped onto the A/C
to economize energy usage of the system?

Howdy hondocrouch-ga,

The cool coils of an air conditioner causes moisture to condense on the coils.
If there is too much moisture in the air, in the form of high humidity, then
the air conditioner has to work harder in order to try to remove the moisture
from the air.

The New Jersey Board of Public Utilities produced a web site on the New Jersey
ENERGY STAR Homes program, titled "Right-Sized Air Conditioners" that speaks
to this point, and how the problem might not be high humidity, but rather it
might be an oversized unit.
http://www.njenergystarhomes.com/html/builder/tutorial/RightSizedAC.html

"Better humidity control. In order for air conditioners to dehumidify or dry
the air, they have to cycle long enough for moisture to condense on the coils
and drain away. With oversized units, short-cycling reduces the amount of
condensation that drains off the coils and even allows some moisture to
evaporate back into the air. Air that is not properly dehumidified can be
uncomfortable and promotes the growth of mold and mildew indoors."

The above referenced page has all sorts of good tips on air conditioner
efficiency, including that the solution to the problem you describe might
be getting a "right sized" unit.  You should read it in detail for other
tips, etc.

There are "add ons" which will provide a dehumidification process to an air
conditioner.  One such device is Environmental Pool Systems' Veri-Dry device.
http://www.dry-air.com/veriDry.htm

"VERI-DRY is a Moisture Removal - Mold Inhibiting device that can be
installed on any conventional air conditioning system, air source or water
source heat pump. This device converts those systems into a dedicated highly
efficient moisture-removing device, (dehumidifier)."

Rather than go the "add on" route, one could just get a dedicated device to
remove moisture from the air, a dehumidifier.  Therma-Stor makes a unit named
the Santa Fe Rx Dehumidifier.
http://www.thermastor.com/prod_santaferx.htm

"The Santa Fe Rx operates much more quietly than the Santa Fe, making it an
ideal choice for ... residences ..."

R.E. Williams Contractor, Inc. carries a mulitple use unit.
http://www.rewci.com/90btupoairco.html

"9000 BTU Portable Air Conditioner Dehumidifier Heater"

Want to remove moisture from the air and eliminate buying bottled water at
the same time?  This company, appropriately named Air2Water, produces the
Dolphin/dragonfly? T16, which does just that.
http://www.air2water.net/residential_products_aquosus.html

"The T16 uses the Aquovate technology that works to convert ambient
atmospheric water vapour into potable water, treated by Air2Water?s advanced
membrane and purification technologies."

Google's Froogle produces all sorts of traditional room dehumidifiers priced
from $109.95 on up.
http://froogle.google.com/froogle?price1=100&price2=&btnP=Go&scoring=p&q=dehumidifier&price=between

If you need any clarification, please feel free to ask.


Search strategy:

Google search on: humidity "air conditioner" reduce efficiency
://www.google.com/search?q=humidity+%22air+conditioner%22+reduce+efficiency

Google search on: "air conditioner" dehumidifier "add on"
://www.google.com/search?q=%22air+conditioner%22+dehumidifier+%22add+on%22

Looking Forward, denco-ga - Google Answers Researcher

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Request for Answer Clarification by hondocrouch-ga on 27 Aug 2005 11:23 PDT

Dear Denco-ga:

Thanks for the answer.  In your answer you state that [with high
humidity]"...the air conditioner has to work harder in order to try to
remove the moisture from the air".  This is the crux of my question
and I'm still a little confused - what's happening there that makes
the A/C have to work harder?  I've seen the coils with moisure beads
and drainoff, but why specifically does this cause the AC to work
harder vs. a dry environment?

Many thanks

Hondo

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Clarification of Answer by denco-ga on 27 Aug 2005 20:56 PDT

Howdy Hondo,

The New Jersey Board of Public Utilities entry part of my answer pretty
much states the reason.
http://www.njenergystarhomes.com/html/builder/tutorial/RightSizedAC.html

"In order for air conditioners to dehumidify or dry the air, they have to
cycle long enough for moisture to condense on the coils and drain away."

So, the more moisture (the higher the humidity) there is, the longer the
air conditioner has to run in order to rid the air of the moisture.  As
long as moisture is condensing on the coils of the air conditioner, the
air conditioner will continue running, as the air conditioner is now
trying to cool the condensed water and not the air passing through it.

As the coils in a high humidity situation are continually coated with
water, the coils now have a reduced effiency when it comes to drawing
(well, actually transferring) the heat from the air, as we now have
coil-water-air contact instead of coil-air.  The air conditioner can
only be set to a certain "low" temperature, otherwise the water freezes
on the coils, which then in turn blocks the flow of air, etc.

Hope this clarifies things a bit for you.

Looking Forward, denco-ga - Google Answers Researcher

Quick and thorough!

Thanks for the 5 star rating, Hondo.

Looking Forward, denco-ga - Google Answers Researcher