Windows A/Cs with automatic (not manual) dehumidification?

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Old 07-06-16, 02:03 PM
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Windows A/Cs with automatic (not manual) dehumidification?

Does there exist a window or portable A/C that will go into dehumidify while in cooling mode if the compressor is not running? The units I have seen have a separate dehumidify mode which then precludes cooling and vice versa. I want one that will dry the air if the a/c is slightly oversized, which causes the compressor to not run enough to dry the air.
 
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Old 07-06-16, 02:58 PM
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Welcome to the forums.

An air conditioner and a dehumidifier are the same exact units.
An air conditioner discharges the warm air outside and a dehumidifier discharges the warm air back into the room.

The portable A/C's are a not an energy efficient way to cool the air. They were designed primarily to be used where the installation of a window unit was not possible or allowed. If you have no choice but to use a portable A/C.... at least purchase the two duct unit.

Humility can be controlled by the setting of the fan speed and the thermostat.
 
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Old 07-06-16, 05:42 PM
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Thanks for your reply. Maybe we got our wires crossed. Can you help with the question I asked?
 
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Old 07-06-16, 06:05 PM
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As Pete said, an air conditioner and a dehumidifier have the same basic components and construction and operating principle. Air is cooled to below the dew point, where it releases water, and the cool dry air is blown into the room. As he said, the difference is what happens to the warm air from the condensing coil.

For a window unit to switch to dehumidify only, meaning remove moisture but don't cool the room, it would have to be able to somehow channel the warm air from the condensing coil (which is at the back of the unit (farthest outside) back into the house, where it would mix with the cooled (and dehumidified air) from the cooling coil.

This capability is available in portable air conditioners (floor standing) because all you have to do is disconnect the exhaust duct so the warm air flows into the room where it mixes with the cool air. AFAIK, there are no window air conditioners with this capability.
 
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Old 07-06-16, 06:50 PM
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1. I have used an LG portable floor standing a/c with two modes, cool and dehumidify, which can be selected from the front panel. If I can switch modes manually myself, why can't they design an option that would switch the mode to dehumidify automatically when in cooling mode and the compressor shuts off? I was asking if anyone has seen such an option.

2. I am interested in buying a large window or thru-wall 220V unit for cooling 900sf, probably 18000 BTU. I am worried about the air not being dehumidified enough (I am sensitive to dewpoints above ~55) if the compressor does not run often enough. What would you do to ensure this doesn't happen?
 
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Old 07-06-16, 07:23 PM
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1. In dehumidify mode the compressor is still running. That mode runs the fan slower so the air spends more time in contact with the cooling coils and gives up more of it's moisture. It's mostly marketing hype. I'm not aware of any unit that does this automatically.

2. The best thing you can do is buy a lower capacity unit (btus) so it has to run more often and for longer periods. And use the low fan speed. If you buy a big unit and it cools off the room in 10 minutes and only runs for a couple of minutes every 15 minutes to keep it cool, it won't be effective at removing moisture.

And don't run it during the day and then open windows to let in cool but damp air at night; you'll have to start all over removing moisture the next day.
 
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Old 07-06-16, 07:26 PM
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Have you considered a split unit ?
That has one part mounted inside on the wall with the condensor unit outside.

The unit cannot dehumidify without the compressor running. The air must be chilled for the moisture to condense and be drawn out of the air. In dehumidify mode the compressor would need to be cycled briefly and the fan would be run on slow speed.

I was looking around online and I did locate a few models that have dry or dehumidify modes but nothing that claims to be automatic.
 
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Old 07-06-16, 07:47 PM
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PJmax, yes AAMOF a split system was my first choice. I have moved on from that because of budget. My quote for a 2-head was $5400 installed. I am hoping to get a large wall/window unit for under $1k. I can run the 220 myself.
 
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Old 07-07-16, 05:43 AM
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You should do a load Calc before selecting the size of your window air conditioner. Here is a free LoadCalc and sizing software HVAC Load Calculation - Maunualj - Whole House Loadcalc

If you need to better control humidity it is better to undersize the window unit little so that you get more run time when load conditions are not as heavy.

I have a little half-ton 6,000-Btuh window unit with the wind machine 20" fan that circulates air through the entire first floor and it will cool down the 650-sf area to 72F and 50% relative humidity even on heavy load days.

You should not need a large wall air-conditioner; you should cool that area with one ton or less of cooling; be sure and do the load Calc. Again, what is the square footage?
 
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Old 07-07-16, 06:48 AM
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Wow, that is quite the calculator. I will work on the numbers it needs.

I own a 2-family home and live in the top flat. It is 900sf, but there are many corners involved. The front half of the flat is an open kitchen-dining-living room area. The back half consists of 2 bedrooms and a bathroom, all discreet rooms with doorways. My plan is to put the window unit in the back window of the bedroom that has a direct path to the front half of the flat, and a ceiling fan in the kitchen running in reverse.

BTW, thanks to everyone for the help.
 
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