Dehumidifier as Aircon

May 14, 2007 9 Replies

Hi all



Following on from "It's A/C Time Again", I noticed when we were running a dehumidifier some years back to dry our house out, that the removal of moisture also dropped the temperature significantly. Is it safe, cheaper, sufficiently effective to use a dehumidifier in place of aircon? From memory, it wasn't frighteningly noisy.



Phil


The compressor type will increase the temperature and probably won't be any good from the human comfort point of view as aircon (you'd need to lose the extra heat without losing the dried air). I don't have experience of the absorbtion disk type.

Standard refrigeration types produce lukewarm air, not cold. To use it as a/c you'd need to split the 2 airstreams and add a 2nd fan. Probably doable, but I wouldnt bother.

One would greatly lower RH, making things more comfortable, but not reduce ambient temp.

NT

If you have damp problems, then yes. Otherwise you're going to produce warmed-up, drier air, which isn't usually what we need when we need aircon. Generally not a good idea.

With apower rating of 200w running 1/10th the time, thats 20w mean power. Ambient temp rise would be unmeasurable. But reduced RH does improve comfort on hot days.

NT

You're forgetting C.O.P

Cheers

Richard

That would be against the laws of physics. A dehumidifier takes in electric power and extracts heat from the air to cause the water to condense. The heat is put back into the air + the heat from the electricity used. So you get heat from a dehumidifier not cold.

Maybe you felt cooler because the air was drier and your sweat then cooled you?

A 200W dehumidifier is about 10l/day at 80% RH, or 0.4l/hour. Running at 10% duty cycle, it's 0.04l/hr, which is just 30% of the moisture given off by one sedentary human*. So no, you won't notice this at all. A 1kW air conditioner will be removing around 50 times this amount, and that becomes noticable.

  • I've also ignored contribution by ventilation and the reduction in performance of the dehumidifier as the humidity drops (5l/day at 60% RH), and taking these into account the effectiveness become very much worse.

Where does COP come into it

NT

Our dehumidifier removes moisture and in the process puts the latent heat back into the room, incresing temperature.

Our aircon also reduces the humidity, and slightly reduces the temperature. The combined drop is a lot more comfort.

The dehumidifier is fine in winter, but the temperature rise in summer is not offset by a big enough drop in humidity.

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