A coworker is looking for an inexpensive dehumidifier for his basement. I told him to use an old “window unit” air conditioner and drain the water into a bucket or floor drain.
But now I’m having second thoughts… would an air conditioner work just as well as a “real” dehumidifier? Is a dehumidifier and an air conditioner basically the same thing? I’ve always thought they were, but I must admit I’m not 100% sure.
(One obvious difference is that a dehumidifier is controlled by RH level, while an air conditioner is controlled by temperature. But if that’s the only difference, I don’t consider it a big deal. He can just manually turn the air conditioner on & off.)
They are the same thing but a dehumidifier is optimized for removing water.
you could run the a/c in a window (as it was designed - and if you have a window) and still remove the humidity (and get cooling) but it will most likely get too cold before it dried out.
Also some a/c use the water to cool the outside (hot) coils for better efficency which if you run it entirely inside then you would be adding humidity. the a/c have a pool of water that has to fill before any water runs out. The water in that pool is distrubuted by a ring attached to the fan motor and sprayed against the coils.
Something I am considering is taking hot dry air from the top of the house and venting it into the cooler damper 1st level (which is 1/2 u/g).
Air conditioning was initially a result of an attempt to dehumidify air. IIRC a printing plant was having problems with humidity causing ink to run or not set right. The company hired someone to figure out a way to dehumidify the air. The result was essentially an air conditioner (albeit a primitive one…I think it amounted to a swamp cooler). The odd thing about the method chosen was to actually blow air across water (which is what a swamp cooler does). At first blush one would suppose that blowing air across water is a silly way to dehumidify air. But, as anyone who gets out of water in a wind knows, evaporating water cools off. Cold air does not have as much capacity to hold water with the upshot being drier air.
I think there are several ways dehumidifiers go about their work these days but about the only real difference I saw was that a dehumidifier will re-warm the cold air to avoid the air conditioning effect. This sounds energy inefficient but some models will blow the cold air back across the condensor coil which heats up (if you ever stand by the exhaust vent of an air conditioner you’ll notice that the air is hot).
In short, an air conditioner or a dehumidifier will do the trick of lowering humidity. What you choose depends on initial cost, operating cost and what your real purpose for the thing is in the first place.
I should have also stated that my advice was to not install the A/C in a window. (In fact, his basement doesn’t even have windows.) I told him to just set the A/C window unit on a table and drain the water into a bucket (which could be periodically dumped). Of course, the A/C unit would have the effect of heating the basement, but so would a dehumidifier. So my question is: Would this work O.K.?
In New Mexico a swamp cooler adds humidity to the air. It works to cool your house because the air looses heat evaporating the water in the pads of the cooler This cool now moister air is pumped into your house. So what ever the guy did for the printers it was not a swamp cooler.
You’re probably right and it is a dim memory. I’ve tried looking for a cite but to no avail. William Carrier invented what we now know today as an air conditioner and the same basic principles invented back in the late 1800s are still used today.
I thought the guy who did the work for the printing company did something else but looking into it a swamp cooler seems highly unlikely. Swamp coolers only work in dry air. The more humid the air the worse they work. On days in Chicago when we have 95% humidity a swamp cooler would be nearly worthless. So, if a printing company was having humidity problems it would certainly seem that a swamp cooler would be far from the ideal solution.
Still, I swear I remember something about a printing company needing to lower humidity and the ‘side-effect’ of the solution for lowering humidity was cooler air which everyone appreciated as well.
A dehumidifier (at least the one I have) consist of one fan blowing across both the heating and cooling coils. The way it works is a dehumidifier sucks in the relatively high RH ambient air, which drops in temperature on the “cold coils”. Since cold air cannot hold as much water vapor as warm air, the coils are low enough in temperature to cause the water vapor condenses on the coils (and the H20 drops into a dispenser). You are free to assume that the dew point of the air is roughly equal to the temperature of the coils and the RH has dropped from ambient. At this point, the now colder, drier air is blown over the “hot coils” and while the dew point remains the same, the RH drops even lower. (Same thing happens in the winter when your outside low RH air is drawn into the house-- which would explain the presence of “humidifiers” in homes during the cold season.)
An air conditioner is different in the “hot” and “cold” coils are divided into separate areas each with a fan.
A heat pump is the same thing as an AC, but one has the ability to switch the coils from “hot” to “cold” and visa versa.
When I lived in Phoenix as a kid, we had a portable swamp cooler which you would fill with H2O and turn on the fan; in this case, the RH would increase while the temperature dropped (due to the latent heat of vaporization; i.e., it took “heat” to convert the water from a liquid to a gas). I remember with glee the days when the RH hit 5% how cool the air was when it was 110°F
A dehumidifier (at least the one I have) consist of one fan blowing across both the heating and cooling coils. The way it works is a dehumidifier sucks in the relatively high RH ambient air, which drops in temperature on the “cold coils”. Since cold air cannot hold as much water vapor as warm air, the coils are low enough in temperature to cause the water vapor condenses on the coils (and the H20 drops into a dispenser). You are free to assume that the dew point of the air is roughly equal to the temperature of the coils and the RH has dropped from ambient. At this point, the now colder, drier air is blown over the “hot coils” and while the dew point remains the same, the RH drops even lower. (Same thing happens in the winter when your outside low RH air is drawn into the house-- which would explain the presence of “humidifiers” in homes during the cold season.)
An air conditioner is different in the “hot” and “cold” coils are divided into separate areas each with a fan. It can still reduce humidity, but not as efficiently.
A heat pump is the same thing as an AC, but one has the ability to switch the coils from “hot” to “cold” and visa versa.
When I lived in Phoenix as a kid, we had a portable swamp cooler which you would fill with H2O and turn on the fan; in this case, the RH would increase while the temperature dropped (due to the latent heat of vaporization; i.e., it took “heat” to convert the water from a liquid to a gas). I remember with glee the days when the RH hit 5% how cool the air was when it was 110°F
Turns out it was William Carrier who was the guy working for the printing company. The company assumed heat was wreaking havoc with their paper and asked Carrier to solve the problem. Carrier realized that it was humidity that was affecting the paper…not heat. So, Carrier set out to find a way to dehumidify air and the happy side effect to that was that it cooled the air as well and there you go…air conditioning was born.
It turns out that Carrier’s invention was basically a typical air conditioner that we are familiar with today and not a swamp cooler as I had initially supposed. I just thought it was interesting that cool air was a side-effect and not the initial purpose of an air conditioner.
Here’s a link and a quick quote from that page (the linked article is quite short).
However, a pet peeve of mine is when people use air conditioning in lieu of having a dehumidifier. It’ll be raining and I’ll get on the city bus and the damn bus driver has the A/C on, so it is dry and 46° and I’m wet and already cold from being rained on and the water is evaporating off my saturated clothes to make me colder, just wonderful.
Ill just add that running an AC 24 hours a day would cost you a significant amount more than running a DH. Much larger power consumption. The AC would never shut off because the temp in the room would never really drop because the hot ari from the back of the AC is being pumped into the room with the cool air.