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Is my dehumidifier working correctly?

 
steward
Posts: 6477
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We have a year old dehumidifier that we use to attempt to make our house more comfortable on muggy hot summer stretches.  I don't know if it's always done this but now I notice that it is pumping out warm air when it's running the condenser and cold air when it takes a break from dehumidifying.  Is it normal for it to put out warm air (90+ degrees) when running?

I thought I understood dehumidification to be similar to an air conditioner where it takes a refrigerant and cools it to run the room air past.  That condenses water out of the air.  Shouldn't it also leave the air colder in the process?  Or is it then using that colder room air to dump the refrigerant's newly acquired heat to?

It just seems silly to be drying out the air but also heating it up.
 
pollinator
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Refrigerant dehumidifiers run the air over both the evaporator (cold, the side that condenses the moisture from the air) and the condenser (hot, the side that is shedding the heat that came from the energy released by the condensing water). You'll always have a positive heat difference as long as there is there's water vapour present, so it's actually a pretty effective heater for small spaces. This makes them less than ideal in the summertime.

If you don't want to heat your room/house with this, what you need is a split heat pump or AC unit. This puts the condenser outside and moves the heat to the great outdoors.
 
pollinator
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Also is it a refrigerant one? The one I have isn't (It can't be I need it to work at lower temps) Silica gel dehumidifiers kick out quite a bit of heat.
 
Mike Haasl
steward
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Thanks Phil, that makes sense.  So now I have to balance if the added heat is worth the reduced moisture  

I'm pretty sure it's a refrigerant one Skandi, based on the noises it makes as it turns on and off.

Time to invent a permie dehumidifier....
 
pollinator
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Actually, if you're condensing humidity out of the air, the energy needs to go somewhere after it's left the water vapour. So the condensate, sans heat energy, sits on whatever it's condensed out on, and the heat goes into the air.

Literally the only way air conditioning works is to relegate the heat energy of the exchange outside the building envelope. Otherwise, it's like trying to cool your house with an open refrigerator. The fridge will pump heat out to the coils in the back, but if the coils aren't outside the building envelope, the heat stays.

As to a permie dehumidifier, I would take an old rad and a drip tray and run well water or river water through it, or water from the mains. Once the rad heats up to the point that it needs a refresh, the water gets dumped into the grey water system, and the rad water refreshed. If a slow fan blows air over the exchanger, it becomes a cooler as well.

-CK
 
Mike Haasl
steward
Posts: 6477
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Thanks Chris, that got my noodle cranking.  I think I'll start a new thread to explore this more...
 
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