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Air Conditioning and a Separate Dehumidifier

Anyone done any sort of calculations or theories to see if running a separate dehumidifier in a basement cuts down any central air conditioner run time on the rest of the house?

Reply to
Hench
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Increases, as the dehum puts out heat. . Christopher A. Young Learn more about Jesus

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. . "Hench" wrote in message news:knh6kb$na5$ snipped-for-privacy@dont-email.me... Anyone done any sort of calculations or theories to see if running a separate dehumidifier in a basement cuts down any central air conditioner run time on the rest of the house?

Reply to
Stormin Mormon

but how much heat? If I have a 10 seer 1.5 ton a/c that's 18 000 btu removed per hour, if my memory is correct.

But if the air is drier, then the human body can handle a higher temperature, thus the a/c would be run less?

Or so the theory goes...

Reply to
Hench

This heat can be good if air conditioner is over sized, and get proper dehumidification.

Greg

Reply to
gregz

You'd have to check the watts of the dehum. IIRC, 1500 watts an hour is

but how much heat? If I have a 10 seer 1.5 ton a/c that's 18 000 btu removed per hour, if my memory is correct.

But if the air is drier, then the human body can handle a higher temperature, thus the a/c would be run less?

Or so the theory goes...

Reply to
Stormin Mormon

Since the basement is cooler, you'd be better off putting the dehumidifier in the warmest, most humid place in the house - usually upstairs. Remember, warm air can carry more water vs cool air.

But the efficiency of small portable dehumidifiers is crap, so the heat they put out is more of a load on your A/C vs the good they do at removing a quart or so of water an hour.

Clean your A/C evap and condenser coils - that'll do way more good vs putzing with the dehumidifier.

Reply to
Home Guy

Another way to get a bit more humidity out of your indoor air is to run the melt water drain line on the back of your frost free fridge into a drain.

When a frost free fridge goes into it's defrost cycle, it has an electric heater that melts the frost off the evaporator coils. That melt water then flows down a tube into a receiving pan which is typically around or above the warm compressor. Thus, that melt water just gets re-evaporated into the ambient air in your kitchen. Directing that melt water into a drain helps dehumidify your house a bit by preventing the melt water from being re-evaporated into your ambient air.

The melt water drain tube will typically be a black rubber tube running under the condensor tubing on the back of the fridge from the back of the freezer compartment to the bottom of the fridge where the compressor is. You can just drill a hole through the floor and add an additional length of tubing to run the melt water into a floor drain in your basement or whatever. We're not talking about much water, but we're not talking about much expense for 20 feet of vinyl tubing either.

Reply to
nestork

That's for sure. If you use the AC to take out the humidity, it's dumping the heat generated by the compressor outside and also taking heat from the house and moving it outside too. With a dehumidifier, it's only removing humidity, while adding heat.

Only reason I can see for using the dehumidifier would be if the system is so oversized that the house gets cooled off without taking out enough humidity.

Reply to
trader4

I would agree, though it's not that simple. If all of the water that was taken out in the basement were to end up in the upper floors (doubtful) much of that energy would have to be used by the AC. The AC, being larger, will likely be more efficient but it's not just adding the two together.

Reply to
krw

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Reply to
Harry Sen

Does it really add heat?

Well, sure, a little from the operation of the motor and compressor.

But in the sense of an AC unit, not really. An AC unit has a small amount of heat generated by the operation of the compressor, and a huge amount of heat MOVED from inside the house to outside the house. (A heat pump does t he reverse in cold weather).

A dehumidifier doesn't do that. It operates the same way an AC does, but i t only moves the heat from the front of the unit to the back of the unit. So that heat movement is a wash.

I would think a whole house AC with reheat would be more efficient than a n ormal AC plus a separate dehumidifier though.

Reply to
TimR

Note that this is an old thread, which has just been revived. But yes, that's the heat I was referring to. How much is a little depends on your perspective. It's not unusual for dehumidifiers to cost $30 a month to run. Some folks probably have small electric heaters that they use that use a similar amount. And that $30 produces the same amount of heat via the dehumidifier. Is it going to significantly raise the temp of a house? No, but it's still added heat.

t of heat generated by the operation of the compressor, and a huge amount o f heat MOVED from inside the house to outside the house. (A heat pump does the reverse in cold weather).

it only moves the heat from the front of the unit to the back of the unit. So that heat movement is a wash.

Yes, that portion is. But you still have $30 worth, or whatever the monthly bill is, of electric energy being dumped inside the house. With the central AC, only the blower portion is contributing heat. The much larger compressor load is losing it's heat outside.

normal AC plus a separate dehumidifier though.

IDK, but I say it's a moot point, because whenever I've had a humidity issue in the house, putting on the AC, dropping the temperature 2F, took care of it. In other words, the humidity only becomes a problem when some AC is also desirable, or at least not objectionable.

Reply to
trader_4

Okay, I see your point, and agree. Note that I was in error saying a dehum idifier moves heat from the front to the back of the unit. It does, but it also dumps heat down the drain in the form of condensed water. Some of th at water may absorb heat from the dehumidifier as it warms up after it come s off the coil, so it's probably not $30. Might be $29.50.

a normal AC plus a separate dehumidifier though.

An AC reduces humidity but doesn't control it. Whether that reduction is e nough depends mostly on luck, a little bit on getting the size of the unit correct. You can control it with a humidistat and reheat, that's going to take more electricity use though.

Reply to
TimR

error saying a dehumidifier moves heat from the front to the back of the unit. It does, but it also dumps heat down the drain in the form of condensed water. Some of that water may absorb heat from the dehumidifier as it warms up after it comes off the coil, so it's probably not $30. Might be $29.50.

CY: The dehum moves heaat from the back (cold) to the front (blows out warm). Water releases heat as it condenses, so as the water turns from vapor to liquid, it released more heat into the room. Which heat is blown out the front of the dehum.

that reduction is enough depends mostly on luck, a little bit on getting the size of the unit correct. You can control it with a humidistat and reheat, that's going to take more electricity use though.

CY: That makes sense.

- . Christopher A. Young learn more about Jesus .

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Reply to
Stormin Mormon

Much as I hate to admit it, you're right. I had brain cramp, obviously.

The heat transfer to cool the air down to dewpoint is a wash, just moves from back to front. The heat transfer to make the water change state from gas to liquid is a net gain to the room.

Reply to
TimR

Dehum adds both the heat from the motor, and also the heat which is called "latent heat of vaporization" which comes into play when a liquid changes to a vapor. Or, in this case a vapor to a liquid. When water vapor condenses, it releases a LOT of heat.

Free standing dehum release a lot of heat.

- . Christopher A. Young learn more about Jesus .

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Reply to
Stormin Mormon

I had brain cramp, obviously.

is a wash, just moves from back to front. The heat transfer to make the water change state from gas to liquid is a net gain to the room.

Just to be OCD, here. Please include the electric motor in the compressor, which releases heat.

Brain cramp. No big deal, some times I forget the

- . Christopher A. Young learn more about Jesus .

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Reply to
Stormin Mormon

Nope. Not gonna do that. If I did that, I'd have to include the heat the motor in the ceiling fan adds, and that means ceiling fans are a bad idea, and nobody wants to hear that.

Reply to
TimR

You already did include it. We were talking about a dehumidifier that uses say $30 worth of electricity a month. That $30 includes the heat that's generated by the compressor motor. Essentially all that $30 winds up as heat in the room.

Reply to
trader_4

I'm sure you know but it may not be obvious to all that the $30 for operation of the equipment does not include the heat generated by phase change of the water being condensed.

Air conditioners use a given amount of electricity to produce a given amount of work.

But they move about 5 times as much heat as the work that is input. Some of that heat is latent heat.

Reply to
TimR

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