i see in the other thread that there is talk of
running the AC to get rid of humidity, so i thought
i'd bust this topic out into it's own thread...

is there any significant difference in cost between
running a dehumidifier and the AC?

my guess is that in our case that the cost would
be different, but the tradeoff against having another
machine to maintain or purchase might make it not
worth the bother for as little as we use it.

the cost would be different because when we run the
AC two motors are running whereas if we had a separate
dehumidifier only one would be running (and it might
be a lot more efficient).


songbird

On Friday, July 17, 2015 at 9:34:58 AM UTC-4, songbird wrote:
i see in the other thread that there is talk of
running the AC to get rid of humidity, so i thought
i'd bust this topic out into it's own thread...

is there any significant difference in cost between
running a dehumidifier and the AC?

my guess is that in our case that the cost would
be different, but the tradeoff against having another
machine to maintain or purchase might make it not
worth the bother for as little as we use it.

the cost would be different because when we run the
AC two motors are running whereas if we had a separate
dehumidifier only one would be running (and it might
be a lot more efficient).


songbird

It comes down to this. If you want heat removed from the space
too, then AC is the way to go. If you want to maintain the temp
then a dehumidifier is the solution. Actually, the dehumidifier
will be adding some heat to the space from the electricity used to
run it. If it's central AC, it will also be able to handle a
large area, it's capacity is going to be many times that of a
dehumidifier. The dehumidifier is most useful in my experience in
places like a basement, where you don't want to lower the temperature
but want to take out the humidity.

I think your motor count is off too. Central AC would have
3 motors: air handler, compressor, condenser fan. Dehumidifier
would have two: compressor and blower. Wall AC unit, not sure
if it's 2 or 3. But the number of motors really doesn't tell
you anything of much use anyway.

songbird wrote:
i see in the other thread that there is talk of
running the AC to get rid of humidity, so i thought
i'd bust this topic out into it's own thread...

is there any significant difference in cost between
running a dehumidifier and the AC?

my guess is that in our case that the cost would
be different, but the tradeoff against having another
machine to maintain or purchase might make it not
worth the bother for as little as we use it.

the cost would be different because when we run the
AC two motors are running whereas if we had a separate
dehumidifier only one would be running (and it might
be a lot more efficient).


Same # or motors either way. One compressor motor, and one fan motor for
"portable units". AC built into the house heating system would have an extra fan
motor outside. The AC generally would draw significantly more power when running
than a portable dehumidifier because they generally involve larger compressors.
A dehumidifier will heat up the area it dehumidifies, whereas an AC will cool it
because the AC releases the heat it produces outside. If hot humid weather is
the issue, the AC will likely get you more comfort for the energy used but will
use more energy if used much.

trader_4 wrote:
....
It comes down to this. If you want heat removed from the space
too, then AC is the way to go. If you want to maintain the temp
then a dehumidifier is the solution. Actually, the dehumidifier
will be adding some heat to the space from the electricity used to
run it. If it's central AC, it will also be able to handle a
large area, it's capacity is going to be many times that of a
dehumidifier. The dehumidifier is most useful in my experience in
places like a basement, where you don't want to lower the temperature
but want to take out the humidity.

I think your motor count is off too. Central AC would have
3 motors: air handler, compressor, condenser fan. Dehumidifier
would have two: compressor and blower. Wall AC unit, not sure
if it's 2 or 3. But the number of motors really doesn't tell
you anything of much use anyway.

our AC is part of the heating system so it has
the outside unit and the inside blower motor. not
sure where the compressor is and if that is a
separate motor.

this house is fairly small and one level so it's
pretty efficient to heat and cool, i just hate running
the AC. in the future i hope to be able to get by
with a small dehumidifier and a small fan instead of
running the AC.


songbird

On 7/17/2015 9:58 AM, trader_4 wrote:
It comes down to this. If you want heat removed from the space
too, then AC is the way to go. If you want to maintain the temp
then a dehumidifier is the solution. Actually, the dehumidifier
will be adding some heat to the space from the electricity used to
run it. If it's central AC, it will also be able to handle a
large area, it's capacity is going to be many times that of a
dehumidifier. The dehumidifier is most useful in my experience in
places like a basement, where you don't want to lower the temperature
but want to take out the humidity.

I think your motor count is off too. Central AC would have
3 motors: air handler, compressor, condenser fan. Dehumidifier
would have two: compressor and blower. Wall AC unit, not sure
if it's 2 or 3. But the number of motors really doesn't tell
you anything of much use anyway.


First, that's pretty much what I would have
said. Dehum is used in naturally cool spaces
like cellars.

Wall or window AC typically have one fan motor,
which has a blade on each end of the shaft.

In terms of energy efficiency, the big factors
are type of compressor, and how clean are the
coils.

--
..
Christopher A. Young
learn more about Jesus
.. www.lds.org
..
..

On Friday, July 17, 2015 at 10:10:40 AM UTC-4, Bob F wrote:
songbird wrote:
i see in the other thread that there is talk of
running the AC to get rid of humidity, so i thought
i'd bust this topic out into it's own thread...

is there any significant difference in cost between
running a dehumidifier and the AC?

my guess is that in our case that the cost would
be different, but the tradeoff against having another
machine to maintain or purchase might make it not
worth the bother for as little as we use it.

the cost would be different because when we run the
AC two motors are running whereas if we had a separate
dehumidifier only one would be running (and it might
be a lot more efficient).


Same # or motors either way. One compressor motor, and one fan motor for
"portable units". AC built into the house heating system would have an extra fan
motor outside. The AC generally would draw significantly more power when running
than a portable dehumidifier because they generally involve larger compressors.
A dehumidifier will heat up the area it dehumidifies, whereas an AC will cool it
because the AC releases the heat it produces outside. If hot humid weather is
the issue, the AC will likely get you more comfort for the energy used but will
use more energy if used much.

I'm not so sure about the energy used part. A central AC that
runs an hour can remove as much humidity as a dehumidifier running
maybe 12 or 24 hours. The dehumidifier uses less watts, but it
has to run a lot longer. Also, if you get a new, two stage central AC,
ECM variable speed blower, etc, it's going to be more efficient
than a 20 year old 10 SEER unit and it will be very good at removing
humidity.

On Friday, July 17, 2015 at 10:46:22 AM UTC-4, songbird wrote:
trader_4 wrote:
...
It comes down to this. If you want heat removed from the space
too, then AC is the way to go. If you want to maintain the temp
then a dehumidifier is the solution. Actually, the dehumidifier
will be adding some heat to the space from the electricity used to
run it. If it's central AC, it will also be able to handle a
large area, it's capacity is going to be many times that of a
dehumidifier. The dehumidifier is most useful in my experience in
places like a basement, where you don't want to lower the temperature
but want to take out the humidity.

I think your motor count is off too. Central AC would have
3 motors: air handler, compressor, condenser fan. Dehumidifier
would have two: compressor and blower. Wall AC unit, not sure
if it's 2 or 3. But the number of motors really doesn't tell
you anything of much use anyway.

our AC is part of the heating system so it has
the outside unit and the inside blower motor. not
sure where the compressor is and if that is a
separate motor.


the outside unit has two motors, the compressor and the fan.

trader_4 wrote:
....
the outside unit has two motors, the compressor and the fan.

ah, ok, thanks!

a small unit that runs longer might be ok (say if you have
solar panels that only put out a few kw/hr).


songbird

On Friday, July 17, 2015 at 8:58:32 AM UTC-5, trader_4 wrote:
On Friday, July 17, 2015 at 9:34:58 AM UTC-4, songbird wrote:
i see in the other thread that there is talk of
running the AC to get rid of humidity, so i thought
i'd bust this topic out into it's own thread...

is there any significant difference in cost between
running a dehumidifier and the AC?

my guess is that in our case that the cost would
be different, but the tradeoff against having another
machine to maintain or purchase might make it not
worth the bother for as little as we use it.

the cost would be different because when we run the
AC two motors are running whereas if we had a separate
dehumidifier only one would be running (and it might
be a lot more efficient).


songbird

It comes down to this. If you want heat removed from the space
too, then AC is the way to go. If you want to maintain the temp
then a dehumidifier is the solution. Actually, the dehumidifier
will be adding some heat to the space from the electricity used to
run it. If it's central AC, it will also be able to handle a
large area, it's capacity is going to be many times that of a
dehumidifier. The dehumidifier is most useful in my experience in
places like a basement, where you don't want to lower the temperature
but want to take out the humidity.

I think your motor count is off too. Central AC would have
3 motors: air handler, compressor, condenser fan. Dehumidifier
would have two: compressor and blower. Wall AC unit, not sure
if it's 2 or 3. But the number of motors really doesn't tell
you anything of much use anyway.

At the house we have a 4 ton central AC unit and a 5000 btu window unit in the living room used as a dehumidifier. I'd leave the house after setting the hall thermostat to 80F and the little window unit running. Returning to the house later in the day, the temperature will be 80F but the humidity low. Setting the hall thermostat to 72F quickly cools the house down. ^_^

[8~{} Uncle AC Monster

On Friday, July 17, 2015 at 9:10:40 AM UTC-5, Bob F wrote:
songbird wrote:
i see in the other thread that there is talk of
running the AC to get rid of humidity, so i thought
i'd bust this topic out into it's own thread...

is there any significant difference in cost between
running a dehumidifier and the AC?

my guess is that in our case that the cost would
be different, but the tradeoff against having another
machine to maintain or purchase might make it not
worth the bother for as little as we use it.

the cost would be different because when we run the
AC two motors are running whereas if we had a separate
dehumidifier only one would be running (and it might
be a lot more efficient).


Same # or motors either way. One compressor motor, and one fan motor for
"portable units". AC built into the house heating system would have an extra fan
motor outside. The AC generally would draw significantly more power when running
than a portable dehumidifier because they generally involve larger compressors.
A dehumidifier will heat up the area it dehumidifies, whereas an AC will cool it
because the AC releases the heat it produces outside. If hot humid weather is
the issue, the AC will likely get you more comfort for the energy used but will
use more energy if used much.

An AC unit doesn't produce heat, it moves it. Any heat produced by the motors is small compared to the amount of heat transferred from the inside to the outside. A heat pump moves heat in either direction thus the name heat pump. 8-)

[8~{} Uncle Hot Monster

On 7/17/2015 11:48 AM, Uncle Monster wrote:

At the house we have a 4 ton central AC unit and
a 5000 btu window unit in the living room used as a
dehumidifier. I'd leave the house after setting the
hall thermostat to 80F and the little window unit
running. Returning to the house later in the day,
the temperature will be 80F but the humidity low.
Setting the hall thermostat to 72F quickly cools
the house down. ^_^

[8~{} Uncle AC Monster


Sounds like the central AC is over sized?

--
..
Christopher A. Young
learn more about Jesus
.. www.lds.org
..
..

Uncle Monster wrote:
On Friday, July 17, 2015 at 9:10:40 AM UTC-5, Bob F wrote:
songbird wrote:
i see in the other thread that there is talk of
running the AC to get rid of humidity, so i thought
i'd bust this topic out into it's own thread...

is there any significant difference in cost between
running a dehumidifier and the AC?

my guess is that in our case that the cost would
be different, but the tradeoff against having another
machine to maintain or purchase might make it not
worth the bother for as little as we use it.

the cost would be different because when we run the
AC two motors are running whereas if we had a separate
dehumidifier only one would be running (and it might
be a lot more efficient).


Same # or motors either way. One compressor motor, and one fan motor
for "portable units". AC built into the house heating system would
have an extra fan motor outside. The AC generally would draw
significantly more power when running than a portable dehumidifier
because they generally involve larger compressors. A dehumidifier
will heat up the area it dehumidifies, whereas an AC will cool it
because the AC releases the heat it produces outside. If hot humid
weather is the issue, the AC will likely get you more comfort for
the energy used but will use more energy if used much.

An AC unit doesn't produce heat, it moves it. Any heat produced by
the motors is small compared to the amount of heat transferred from
the inside to the outside. A heat pump moves heat in either direction
thus the name heat pump. 8-)

Try running a dehumidifier continuously in an enclosed area. You'll quickly
notice how much warmer that area becomes. There is a lot of waste heat produced
by the motors in AC or dehumidifier. The AC just hides it by exhausting it
outside.

songbird wrote:
trader_4 wrote:
...
the outside unit has two motors, the compressor and the fan.

ah, ok, thanks!

a small unit that runs longer might be ok (say if you have
solar panels that only put out a few kw/hr).


The problem with using central AC to dehumidify is that it will do that job very
quickly, then will continue expensively to cool down the house. It is way
oversize to just dehumidify. If you coule cycle it on/off for a short period
every hour (half hour?) you might get the desired dehumidification, but
certainly there would be inefficiencies.

Using a small window AC might be a better choice than a dehumidifier, as it
would exhaust the waste heat and more from the house as it dehumidifies, not
heat the house up like a dehumidifier does.

On Friday, July 17, 2015 at 12:02:42 PM UTC-5, Stormin Mormon wrote:
On 7/17/2015 11:48 AM, Uncle Monster wrote:

At the house we have a 4 ton central AC unit and
a 5000 btu window unit in the living room used as a
dehumidifier. I'd leave the house after setting the
hall thermostat to 80F and the little window unit
running. Returning to the house later in the day,
the temperature will be 80F but the humidity low.
Setting the hall thermostat to 72F quickly cools
the house down. ^_^

[8~{} Uncle AC Monster


Sounds like the central AC is over sized?

--
.


The central unit was installed before I moved in because the owner had anticipated the need due to his plans to remodel and add on to the house. The problem is that the expansion never happened but the insulation isn't all that great in the older house so it works out OK. The little window unit could never cool the house but it works well to dehumidify the air in the house.. ^_^

[8~{} Uncle House Monster

On Friday, July 17, 2015 at 1:31:51 PM UTC-4, Bob F wrote:
songbird wrote:
trader_4 wrote:
...
the outside unit has two motors, the compressor and the fan.

ah, ok, thanks!

a small unit that runs longer might be ok (say if you have
solar panels that only put out a few kw/hr).


The problem with using central AC to dehumidify is that it will do that job very
quickly, then will continue expensively to cool down the house.

Only if you set it to a low temp and leave it on. When I want to
remove humidity, I lower one or two degrees.


It is way
oversize to just dehumidify.

Funny that all the manufacturers of AC eqpt include dehumidification,
offer thermostats that turn the units on based on humidity, etc.
as features and that it works so well.


If you coule cycle it on/off for a short period
every hour (half hour?) you might get the desired dehumidification, but
certainly there would be inefficiencies.


When it's not that hot, I can turn mine on for 20 mins and it
brings the humidity down in the *whole house* so that it's
comfortable again. It's a dramatic difference and you can
feel it. Yes, I might have to do it again in a few
hours because I don't have a thermostat with humidity control
in it. But it sure works better than having one little
dehumidifier in one room. Plus, I don't have to empty water
buckets.


Using a small window AC might be a better choice than a dehumidifier, as it
would exhaust the waste heat and more from the house as it dehumidifies, not
heat the house up like a dehumidifier does.

Or just turn the central AC on. Good grief.

On Fri, 17 Jul 2015 09:31:59 -0400, songbird
wrote:

i see in the other thread that there is talk of
running the AC to get rid of humidity, so i thought
i'd bust this topic out into it's own thread...

is there any significant difference in cost between
running a dehumidifier and the AC?

my guess is that in our case that the cost would
be different, but the tradeoff against having another
machine to maintain or purchase might make it not
worth the bother for as little as we use it.

the cost would be different because when we run the
AC two motors are running whereas if we had a separate
dehumidifier only one would be running (and it might
be a lot more efficient).


songbird
The typical stand-alone dehumidifier also has 2 motors, but they are
smaller. The units are also less effective, but are handy when you do
not want to significantly cool the space while removing excess
humidity.

It is humid enough here today to want to run the AC or dehumidifier,
but cool enough that to get any dehumidification effect from the AC
the house would become uncomfortably cold - so the portable
dehumidifier is removong about 45 liters of water per day from the air
in the house, maintaining about 40% RH without unduly cooling the
house.

On 07/17/2015 3:40 PM, wrote:
....

The typical stand-alone dehumidifier also has 2 motors, but they are
smaller. The units are also less effective, but are handy when you do
not want to significantly cool the space while removing excess
humidity.

It is humid enough here today to want to run the AC or dehumidifier,
but cool enough that to get any dehumidification effect from the AC
the house would become uncomfortably cold - so the portable
dehumidifier is removong about 45 liters of water per day from the air
in the house, maintaining about 40% RH without unduly cooling the
house.

And actually, they _warm_ the house slightly as both the waste heat from
the compressor and the motors is exhausted into the living space...

--

On 7/17/2015 2:36 PM, Uncle Monster wrote:

The central unit was installed before I moved in because the owner had anticipated the need due to his plans to remodel and add on to the house. The problem is that the expansion never happened but the insulation isn't all that great in the older house so it works out OK. The little window unit could never cool the house but it works well to dehumidify the air in the house. ^_^

[8~{} Uncle House Monster


One of my window units, I ran the condensate drain out
the bottom, rather than leaving the water in the tray
to grow mold and irritate my allergies. Works nicely.
Cools and dehumidifiers. No slinger ring efficiency,
but I can handle that.

--
..
Christopher A. Young
learn more about Jesus
.. www.lds.org
..
..

On 7/17/2015 2:36 PM, Uncle Monster wrote:


The central unit was installed before I moved in
because the owner had anticipated the need due to
his plans to remodel and add on to the house. The
problem is that the expansion never happened but the
insulation isn't all that great in the older house
so it works out OK.


The little window unit could never cool the house
but it works well to dehumidify the air in the
house. ^_^

[8~{} Uncle House Monster


I thought you were going to write that with better
insulation, you would not need the central AC.

-
..
Christopher A. Young
learn more about Jesus
.. www.lds.org
..
..

Stormin Mormon wrote:
On 7/17/2015 11:48 AM, Uncle Monster wrote:

At the house we have a 4 ton central AC unit and
a 5000 btu window unit in the living room used as a
dehumidifier. I'd leave the house after setting the
hall thermostat to 80F and the little window unit
running. Returning to the house later in the day,
the temperature will be 80F but the humidity low.
Setting the hall thermostat to 72F quickly cools
the house down. ^_^

[8~{} Uncle AC Monster


Sounds like the central AC is over sized?

If oversized it'll short cycle causing inefficiency and
impacting comfort level.