Combination ac/dehumidifier unit

I'm looking for a window or wall air conditioner that can also be used as stand alone dehumidifier when I don't need cooling. I presently own a portable floor standing dehumidifier that works fine but it dumps hot air into the family room while it's dehumidifying & it's bucket has to be manually dumped when full. (It's in a basement family room so running a drain hose would look terrible) I realize that all ac units will dehumidify but they only cycle on/off based on temperature...not humidity level.
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What you are asking for..they are really the same. A dehumidifier IS a small AC, only the heat that is removed is put back into the air.
Now, Mitsubishi Mr Slim units offer a dehumidifiy mode. They also use electric strips to temper the air temp.
There are thermostats that double as humidistats...what do you really want to do?
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What I want to do (I thought I was clear) is dehumidify my basement family room (It's a split entry ranch so it has normal windows in the basemement) without adding more heat down there & without having to empty buckets. It seems to me someone used to sell a window air conditioner with a humidifying setting for when you really didn't need cooling. (Most ac units I have seen wont even cycle on (regardless of the humidity level) much below 65 degrees)
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It is not dumping any heat into the room that was not alaready there. It cools the air, extracts the moisture, then re-heats it to where it was before. Only added heat is from the motor driving the unit, very minimal.
(It's in a basement family room so running a

You can buy a small pumpt that goes into the su mp and a smal line r ns out a drain, window, whatever. Easy to do yourself and does not look all that bad if done in a corner or painted to match the wall.

I've never seen what you are looking for. You'd have to divert the air back to the room, just like your dehumidifier. If not, you'd be cooling the room and then paying to heat it. I've seen setups in industrial situations where the AC and the heat are run at the same time to control humidity in critical operations.
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Edwin Pawlowski wrote:

But the motor heat is not minimal, and the dehumidifier also adds 1000 Btu of heat to the room for every pint of water extracted.

Setting the temperature low and blocking some airflow might help. You might add a humidistat.
Or automatically ventilate the basement when outdoor air is drier than indoor air. This can warm or cool the basement as needed, and dehumidify with 100X less energy than a compressor.
Finding the moisture source (eg air leakage or an unpainted slab) and reducing it would also help.
Nick
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The only way to dehumidify and not cool and not heat is to add reheat to a standard ac unit. works good but very expensive to operate. Normal ac does 80 percent cooling, 20 percent moisture removal. Thermastor makes high efficiency dehumidifiers, but they are not cheap and still add some heat back into room. Some models include a pump to get rid of condensate. What you want would have to be custom made, very expensive. Thermastor is 1-800-533-7533. Great product, they make ducted models also. The only thing I have ever seen like what you want is an indoor swimming pool dehumidifier. has built in condensor for hot gas reheat plus outside condensor coil. It can switch between dehumidifier and ac modes. Commercial units. Try Dectron. Wait till you see the price on THAT!
Stretch
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Obviously Nick doesnt own a house or have a basement because here he goes again with his 100x more energy to run a compressor crap. FYI Nicko My 700 sq ft basement is dehumidified to 45- 50% all summer for 3.50 a month verified with a Kill- A- Watt. Running a 200 watt vent fan just does not do it, I tried, but you never have tried nick. Running a 200 w fan just 12hrs a day would cost me 9$ a month so my dehumidifier is more than half the cost of trying to pull in fresh air. You forgot one little fact nicko in summer outside air is humid. Go live in a house and try your theories for once nick.
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Is it an old dehumidifier new Energy Star labeled units are 2 times more efficient and produce much less heat . I enjoy the extra heat as my basenent is completely underground and cool. I only notice 2-3 degree increase. You could use a condensate pump or raise the unit up higher for auto draining. If you have forced air adding a closeable basement return and supply would give you flexibility in moving conditioned air in and hot air out. Or both window AC and dehumidifier. Changing to flourescent lights will help as a 100 watt incandesant really puts out 90 watts or so, of heat.
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And the compressor which draws 600 watts or so. I'd call that dumping heat.
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Never seen such a doodad. But, it sure makes sense.
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m Ransley wrote:

Wrong again. I've owned several.

With basements. You are a _presumptive_ little ignorant worm :-)

Simple physics. You might try it sometime :-)

Congrats. That isn't much dehumidification, but if you didn't live next to a lake, you might do it for 3.5 cents a month with a 90 W 2470 cfm fan that automatically turns on when outdoor air is drier.
Nick
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m Ransley wrote:

It's time to ignore you again :-)
Nick
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Nickavecmerde you just pull irrelevant BS numbers out your ass with your calculator , you have no hands on , no real experience , nothing to back you up but fantasies of an idiot , you just make up BS theories that don`t reflect actual situations for most. Your "humidification wastes energy' " Flood your basement floor for free humidity" " I put a humidistat on my steam radiator for humidity" posts prove you are an idiot that continues to post irrelevant, misleading , wrong info. You are like a bad computer program Garbage in-Garbage out.
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bob smith wrote:

night, will that indoor humidity stay low during the day or will it rise back up by noon?
That depends on how fast the moisture enters the house and what the house is made of, ie how well it can store moisture. A house made entirely with indoor tile walls can't store much. A more typical house filled with wood and cloth and paper can store more. IIRC, the equilibrium moisture content by weight of some woods is about 30% of the RH of the surrounding air. Exposed or aerated concrete is also good. See Kurt Kielsgard Hanson's 142 page catalog of sorption isotherms as LBM technical report 162/86 under http://www.byg.dtu.dk/publications/reports.htm

"Drier," as in less absolute vs relative humidity, ie a lower humidity ratio w, in pounds of water per pound of dry air, which requires a calculation, starting from RHs and temps. And the fan needn't run only at night, or every night. The outdoor humidity ratio (vs RH) doesn't vary much over a day. NREL says w = 0.005 on an average April day in Phila with a 52.4 and 62.6 F daily min and max. If the house requires heat, we might better ventilate during the day... 70 F air at 60% RH has wi = 0.0095, so a 2470 cfm fan that moves 60x2470x0.075 = 11,115 pounds of air per hour can remove 11,115(wi-w) = 49.7 pints of water per hour of operation, with an energy cost of 90/49.7 = 1.8 watt-hours per pint, 330 times less than the 600 watt-hour/pint cost of a typical dehumidifier.
Nick
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Not to jump into the middle of a ripping flame war, but I have a question.
Assuming the nighttime humidity is low and the daytime humidity is high. If you use ventilation to bring in the lower humidity air only at night, will that indoor humidity stay low during the day or will it rise back up by noon?

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I thought humidity generaly increased at night, either way during summer I never realy get low humidity out doors, it is usualy 55 - 75 % and for many a month 75%+ not enough of a variable in percentage to dry anything especialy my basement. But many are not completly underground and have windows all around, for those sure it may work. Ive done both and end up leaving the dehumidifier on. I realy only get low humidity and warmth in fall as does alot of central US
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Thats very unlikely to be seen much in practice.

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m Ransley wrote:

Relative humidity increases at night as the air temp drops, but absolute humidity (as measured by dew point or pounds of water per pound of dry air) doesn't change much.

anything especialy my basement...
Then again, you live next to a lake, and 55% air at 50 F has the same moisture as 55exp(-9621(1/(50+460)-1/(70+460)) = 27% at 70 F. The calc below says outdoor air is dry enough to keep a house below 60% at 70 F for all but 360 hours in a Typical Meteorological Year in Philadelphia, with at most 75 "wet hours" in a row near the end of July.
If moisture enters the house at say, 8 pints per day, it has to store about 24 pints over 3 days to use ventilation for dehumidification in Phila. Concrete stores about 1% moisture by weight as the RH of the surrounding air increases from 40 to 60%, and it weighs about 150 lb/ft^3, so we might store 24 pounds of water in 2400 pounds (16 ft^3) of concrete. Mold takes about 2 weeks to form, above 60% RH...
A serious ventilation controller would compare the energy needed for dehumidification by ventilation with the energy needed by a dehumidifier in winter and an air conditioner in summer, including the energy needed to warm outdoor air in winter and cool it in summer, and adapt to weather conditions to minimize energy usage.
20 PH=.6*EXP(17.863-9621/(70+460))'house vapor pressure ("Hg) 30 WH=.62198/(29.921/PH-1)'house humidity ratio 40 DAYSTART0'display start time (days) 50 DSYSTART*24'display start time (hours) 60 RANGE000'dISPLAY RANGE (HOURS) 70 LINE (0,0)-(639,349),,B:XDFd0/RANGE:YDF=3.88 80 FOR TR` TO 80 STEP 10'temp ref lines 90 LINE (0,349-YDF*(TR-10))-(639,349-YDF*(TR-10)):NEXT 100 CFM$70'whole house window fan cfm (Lasko 2155A) 110 OPEN "ecayear" FOR INPUT AS #1:LINE INPUT#1,H$ 120 FOR H=1 TO 8760'hours of typical (TMY2) year 130 INPUT#1,MONTH,DAY,HOUR,TDB,WIND,TDP,IGLOH,SS,WS,NS,ES 140 PA=.6*EXP(17.863-9621/(TDP+460))'ambient vapor pressure ("Hg) 150 WA=.62198/(29.921/PA-1)'ambient humidity ratio 160 PSET(XDF*(H-DS),349-YDF*(TDB-10)) 170 'PSET(XDF*(H-DS),349-YDF*(TDP-10)) 180 IF WA<WH THEN WETSTRING=0:GOTO 230'dry hour 190 WETHOURS=WETHOURS+1'accumulate wet hours 200 WETSTRING=WETSTRING+1'accumulate wet string length 210 IF WETSTRING>WETMAX THEN WETMAX=WETSTRING'measure max wet string length 220 LINE (XDF*(H-DS),290)-(XDF*(H-DS),300)'mark wet hours 230 IF DAY=1 AND HOUR=.5 THEN LINE (XDF*(H-DS),349)-(XDF*(H-DS),345)'tick months 240 NEXT H 250 PRINT WETHOURS,WETMAX
wet hours per year: 360 longest wet string: 75
Nick
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