Dehumidifier or Window AC for Basement

D107

I have a similar problem--but basement does get hot in summer and is not served by central ac. So i'm figuring keep ac on low fan (but high 'cool' to minimize heat buildup, and let it gradually dehumidify AND cool? day of your post i saw a 5000kbtu unit at best buy.

thanks as always,

David

Steve Garson_2

Dehumidifier or Window AC for Basement

Living in Boston, I use a dehumidifer all summer to prevent mold and mildew in my basement. This works fine, but as you know, a dehumidifier generates heat. Since my house has central AC, this has a cost.

I have a 6000 BTU window AC that I can put in a basement window. Do you think this might be more cost effective to keep humidity levels down, or will the normally cooler nature of a basement prevent this from being effective?

What do you suggest?

ed wallace

dehumidifier vs a/c

Hi Steve i believe you would be better off with a portable a/c that way you have an a/c that sits on the floor and vents out a window the condensate can either be collected in the internal bucket or piped to a condensate pump and pump to a sink

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ed wallace

dehumidifier vs a/c

Hi Steve i believe you would be better off with a portable a/c that way you have an a/c that sits on the floor and vents out a window the condensate can either be collected in the internal bucket or piped to a condensate pump and pump to a sink

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ed wallace

dehumidifier vs a/c

Hi Steve i believe you would be better off with a portable a/c that way you have an a/c that sits on the floor and vents out a window the condensate can either be collected in the internal bucket or piped to a condensate pump and pump to a sink

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Brad White_78

The way a dehumidifier works....

Steve, a refrigerant-based dehumidifier is nothing more than an air condiditioner with both the evaporator (cooling coil) and condenser (heat rejection coil) in the same room essentially.

Your classic console type DH has a tubing type coil usually (mine does anyway) with sparse fins.

Your average window AC unit has a three or more row finned coil which is better at removing moisture. (The more rows the better moisture removal and the slower the air flow the better moisture removal...)

If you were to use the window AC unit (installed as an AC unit, rejecting heat to the outside), a couple of things will happen. Firstly, there is little heat gain load in most basements. The AC system relies on temperature so will be satisfied quickly relative to an upstairs room with more exposure. Secondly, the unit would tend to cycle on and off, cooling the room but not giving the humidity a chance to condense and be removed. Cooling without removing humidity RAISES the RH and rapidly so.

So what I suggest is, place the window AC unit on a large trash barrel or other drain pan and pump to collect and discharge the condensate. Install this entirely indoors and buy as small a unit as is commercially available. The 6000 BTUH unit that you have may well be it.

When such a unit runs it will reject heat above and beyond the sensible cooling capacity of the AC unit. For the roughly 4,500 BTUH of sensible heat your 6,000 BTUH unit can remove (about 1,440 Watts equivalent) it will remove about 1.5 pints of water from the air per hour. It will also reject about 7-8,000 BTUH of sensible heat back into the space. This in turn will impose a load for the AC unit to work against. Yes, the air temperature will eventually climb but this also depresses the RH. It is all about balance point.

You have the means to try this and see how well it works for you, only for the cost of electricity for the trial period. Catch the condensate and see how much you actually get.

I have to presume that your central AC does not serve your basement. Is this correct? In which case any load imposed from having a warm basement will be minimal. The ground temperature will help offset this temperature rise too.

Hope this helps.

Brad

Steve Garson_2

Brad:

Very interesting. I guess I can also measure the wattage used versus water condensed as well. Thanks for explaining the reason why the AC alone wouldn't do the trick.

Steve

Brad White_79

Steve

Good point on using a Watt Meter (Kill-A-Watt is what I have) to monitor the draw.

Let me know how you make out.

Brad

Brad White_9

Yes, David

But in your case you want to run it as a conventional AC unit, rejecting the condenser heat (heat of rejection) outdoors. Otherwise you will positively heat the space.

But you rightly grasped the concept of low speed = longer retention time over the coil. Remember though, if it gets too humid down their and the airflow is too low you may frost over the coil. That will not help!