DIYbanter - View Single Post - OT Which direction is your ceiling fan SUPPOSED to run?

rickman

On 7/4/2014 2:37 PM, wrote:
On Fri, 04 Jul 2014 12:55:56 -0400, rickman wrote:

On 7/4/2014 10:31 AM, wrote:
On Fri, 04 Jul 2014 04:06:11 -0400, rickman wrote:

On 7/4/2014 12:57 AM, Tim Wescott wrote:
On Thu, 03 Jul 2014 22:28:23 -0400, krw wrote:

On Thu, 3 Jul 2014 17:00:16 -0700, "Pico Rico"
wrote:

"RobertMacy" wrote in message
newsp.xif3so2o2cx0wh@ajm...
On Thu, 03 Jul 2014 16:29:47 -0700, Pico Rico
wrote:

"RobertMacy" wrote in message
newsp.xif3f3zo2cx0wh@ajm...
...snip...
So my question is WHICH way is this !@#$#@ system designed for? UP
or DOWN air in the summer?

it depends if you have air conditioning.

again which way? for what reason? elaborate?

heat rises. If you have ac, you want to push the warm air down so it
can become ac'd. If you don't have ac, you might as well leave the warm
air up there were it will be less noticed.

But you can cool to a higher temperature if you help the convection off
your skin. Add in evaporative cooling and a breeze is a big win, at
least in small rooms, like a home.

We have air conditioning which keeps the house at 78, and a way
undersized room dehumidifier which we set up in the master shower, turn
on the circulating fan in the furnace, and basically slowly and
inefficiently dry out the whole house.

It makes a huge huge difference how hot it feels -- and we're in Oregon,
where everyone is a humidity wimp.

Do you realize the dehumidifier is just an AC unit where the heat is
exhausted back into the room? You could do the same thing by running a
small space heater which would make the AC run more often which does a
much better job of taking the humidity out of the air. Actually, I've
never seen a house with AC that still had high humidity, but then I'm
not in the Pacific northwest.
If the AC is oversized it is not efficient at removing humidity
because it doesn't run long enough. ANd if it isn't warm enough to
require running the AC, you still have the humidity.

Running the heater and the A/C at the same time MIGHT help, by forcing
the AC to run more, but it most certainly is NOT efficient. At the
price of electricity in Ontario, particularly during peak periods, it
doesn't make any sense at all. We run the AC off-peak to drop the
temperature and keep the house closed up on-peak to keep the heat out.
As soon as it cools down outside the wife wants to open the windows -
even when the humidity is 81%+ outside and only 40% inside.

Slowly getting her trained, after 33 years.

But that is exactly what you *are* doing, running that dehumidifier is
the same as running the big AC unit. I guess it might be more expensive
to run the heat outside rather than keep it in.... but no, the heat is
always run outside by the big unit because of the thermostat.

Clearly the small unit is less efficient, small things usually are. So
why not run the big unit that does a great job of removing the moisture?
It is larger so will need to run much less to lower the humidity. It
is also equipped to remove the water while most room dehumidifiers have
a bucket you need to empty unless you have it tied into a drain.
You are not getting my point. The AC, if oversized, moves a lot of
air over the cold colil for a short amount of time while drawing large
amount of current and removing a small amount of humidity.

I do "get" your point, I just don't agree with it.

A smaller A/C moves less air over the cold coil for a longer period of
time, and moves more air to reduce the temperature by the same amount,
using less power to do so.

I don't think that follows. Most of the power in an AC unit is in the
compressor which creates the cooling. Reducing the temperature of the
air is going to take the same total amount of cooling, so there is no
power saving in a smaller unit. They size units to keep the initial
costs down and to provide enough cooling for the warmest days.

so it removes more moisture for the same
amount of current drawn. The BTU/watt efficiency may very well be the
same - or the big one may even be more efficient - but the efficiency
as a dehumidifier is significantly better on the smaller A/C unit.

Your conclusions simply don't follow your premise. Unless there is
something less effective about the condensation of water in the large
unit it will end up collecting the same amount of moisture from the air.
But in reality there is an effect that makes the larger unit work
better. If the airflow over the coils does not cool the air below the
dew point, no water condenses at all. A sufficiently small unit with an
adequate air flow may well not lower the air temperature enough to
extract enough water during the process.

If it is not cool enough to require air conditioning, but is too humid
for comfort, running a small de-humidifier is a LOT more efficient
than running the big-assed air conditioner AND the furnace!!!!

Again, no substantiation, just a claim. Running the small dehumidifier
removes small amounts of water AND warms the room requiring the AC to
run. Running the large AC unit will remove the water more quickly. If
it does not remove enough water heat must be added as it runs to remove
enough humidity (becoming a dehumidfier). The question is which unit is
more efficient as a dehumidifier and talking about "big-assed" ACs does
not answer the question. You are coming up with an answer based on an
emotional analysis of inadequate data.

The one fact I know is that my AC unit produces enough water to require
a pump to remove it and runs repeatedly all day. A dehumidifier I have
used will fill the two gallon bucket in a day or so in the worst humid
days of summer in the DC area. Still not sufficient data to prove one
or the other since I have never measured the output. But the AC only
cycles on and off while the dehumidifier runs continuously 24/7 until
the bucket is full.

Only a total idiot would run the AC and heat at the same time to
reduce the humidity in the house.

You still fail to understand that is *exactly* what you are doing with
the dehumidifier. It had a hot coil and a cold coil. The hot coil
produces all the heat entering the cold coil plus the electrical energy
coming from the outlet. So you actually warm the room with that unit
requiring the AC to turn on even if it is otherwise not needed.

As for the de-humidifier producing heat - it only produced a fraction
of it's total power consumption as heat output. The heat coming off
the back of the unit is just heat removed from the air (and moisture)
entering the front of the unit. The latent heat of
vaporization/condensation of the water removed is the only appreciable
"heat" produced. (971 BTU/lb) So for every US gallon of water removed,
aproxemately 8000 BTU.

If it takes 12 hours to remove a gallon, that is 672 btu/hr or less
than 200 watts.

I'm not sure what you mean by the fraction comment. ALL electrical
energy consumed by this unit ends up as heat, mostly at the hot coil.

The condensed water has had its heat removed and then put back into the
air on the hot side of the unit. The question is where does that heat
go? Only part of the heat at the hot coil was from cooling the air,
most of it was from condensing the water. With a dehumidifier the
entire latent heat of evaporation is returned to the room along with the
heat from the electrical power required to make it all work. This will
heat up the room. With an AC unit that heat is exhausted outside
reducing your cooling costs. Don't think the latent heat of evaporation
needs to be returned to the room to maintain a temperature. When water
evaporates it cools. When it condenses it releases that heat and will
warm the room.

I guess one difference is that we have few days when we need
dehumidification but not cooling. If you actually need your space
warmed with dehumidification rather than cooled, then the dehumidifier
might be more efficient. But if you don't need the extra heat the AC
unit will have to run to maintain a temperature.

--

Rick