Basics:

Have an oversized AC unit causing a humidity problem. I have been
given many suggestions for fixing, but would like feedback on the
different options.


Solutions:

After talking with different HVAC contractors about the problem, I have
been given three suggestions. Before throwing good money after bad, I
would like input on the validity of the suggested fixes. In addition,
if there are any other fixes that could work, please let me know.

Suggestion 1: Replace unit with proper sized unit

This solution is "the proper way" to fix the problem, and was how
it should have been handled in the first place. However, I am being
told that everything needs to be replaced, including ductwork to
account for differences in blower motor output of the smaller unit. I
have been told that the duct work pressures will be different and that
everything needs to be sized according to the system as a whole. Is
this true?

Since all our new drywall will need to be ripped up to install new duct
work, I would hate to have to go down this path.

Suggestion 2: Change size of compressor

Is this really an option??? One contractor said I could just put in a
lower rated compressor, but I am skeptical of this solution. I have
been reading other posts on the news group, and it sounds to me like
the blower will still be moving air at the same rate over the coils,
and that this may still leave my house humid since the moving air will
have less contact with the coils. Is this true?

Suggestion 3: Install central dehumidification

This seems logical; with the only issues being the unit will run less
efficiently since it would still short cycle, causing stress to
controls, motor, etc. Additionally, I will be paying electricity for a
dehumidifier to run on top of my AC. On the plus side, we will get
humidity control year round, even when too cool for AC. Are there any
other caveats to this approach?

"bucholtz-gmail-com" wrote in message
oups.com...
Basics:

Have an oversized AC unit causing a humidity problem. I have been
given many suggestions for fixing, but would like feedback on the
different options.


Solutions:

After talking with different HVAC contractors about the problem, I have
been given three suggestions. Before throwing good money after bad, I
would like input on the validity of the suggested fixes. In addition,
if there are any other fixes that could work, please let me know.

Suggestion 1: Replace unit with proper sized unit

This solution is "the proper way" to fix the problem, and was how
it should have been handled in the first place. However, I am being
told that everything needs to be replaced, including ductwork to
account for differences in blower motor output of the smaller unit. I
have been told that the duct work pressures will be different and that
everything needs to be sized according to the system as a whole. Is
this true?

Yes


Since all our new drywall will need to be ripped up to install new duct
work, I would hate to have to go down this path.

Suggestion 2: Change size of compressor

Is this really an option??? One contractor said I could just put in a
lower rated compressor, but I am skeptical of this solution. I have
been reading other posts on the news group, and it sounds to me like
the blower will still be moving air at the same rate over the coils,
and that this may still leave my house humid since the moving air will
have less contact with the coils. Is this true?

Not the approach I would take. Turtle says just the opposite bigger
condenser smaller air handler.
It is ok that I say that right mate?


Suggestion 3: Install central dehumidification

This seems logical; with the only issues being the unit will run less
efficiently since it would still short cycle, causing stress to
controls, motor, etc. Additionally, I will be paying electricity for a
dehumidifier to run on top of my AC. On the plus side, we will get
humidity control year round, even when too cool for AC. Are there any
other caveats to this approach?

First how was it determined that the unit is to big?
What is the temp differential? return and supply air temps
My unit is running between 20-25 degrees.
What is the set temperature?


WAG for the home owner. Change the fan speed to one setting lower. See if
that lengthens the run times. Which should increase the dehumidification

Your right about the issue being addressed in the beginning.

bucholtz-gmail-com wrote:
/snip/
Since all our new drywall will need to be ripped up to install new
duct work, I would hate to have to go down this path.

Since you are going smaller in condenser and coil size (and therefore
lower in velocity) there is need for new duct work....and this is the
right solution to the problem. .

"bucholtz-gmail-com" wrote in message
oups.com...
Basics:

Have an oversized AC unit causing a humidity problem. I have been
given many suggestions for fixing, but would like feedback on the
different options.


Solutions:

After talking with different HVAC contractors about the problem, I have
been given three suggestions. Before throwing good money after bad, I
would like input on the validity of the suggested fixes. In addition,
if there are any other fixes that could work, please let me know.

Suggestion 1: Replace unit with proper sized unit

This solution is "the proper way" to fix the problem, and was how
it should have been handled in the first place. However, I am being
told that everything needs to be replaced, including ductwork to
account for differences in blower motor output of the smaller unit. I
have been told that the duct work pressures will be different and that
everything needs to be sized according to the system as a whole. Is
this true?

Since all our new drywall will need to be ripped up to install new duct
work, I would hate to have to go down this path.

Suggestion 2: Change size of compressor

Is this really an option??? One contractor said I could just put in a
lower rated compressor, but I am skeptical of this solution. I have
been reading other posts on the news group, and it sounds to me like
the blower will still be moving air at the same rate over the coils,
and that this may still leave my house humid since the moving air will
have less contact with the coils. Is this true?

Suggestion 3: Install central dehumidification

This seems logical; with the only issues being the unit will run less
efficiently since it would still short cycle, causing stress to
controls, motor, etc. Additionally, I will be paying electricity for a
dehumidifier to run on top of my AC. On the plus side, we will get
humidity control year round, even when too cool for AC. Are there any
other caveats to this approach?


Increase the size of the area being cooled to better match the system,
install a duct to the garage. The amount of energy you waste cooling the
garage may be less than the cost to correct the problem. Not ideal but
perhaps you have another uncooled space that is not a garage like an
enclosed porch. You can close off this area during heating season.

Opening a window would have a similar effect of enlarging the cooling load
but that is an obvious waste and least preferred but it may relieve some of
your humidity problems short term. Not all the way, just a crack.

Increase the cooling load in other ways: Cut down a shade tree, open some
curtains, install less efficient windows (not). have the kids leave the
door open too often. etc.

PipeDown wrote:

"bucholtz-gmail-com" wrote in message
roups.com...


Basics:

Have an oversized AC unit causing a humidity problem. I have been
given many suggestions for fixing, but would like feedback on the
different options.


Solutions:

After talking with different HVAC contractors about the problem, I have
been given three suggestions. Before throwing good money after bad, I
would like input on the validity of the suggested fixes. In addition,
if there are any other fixes that could work, please let me know.

Suggestion 1: Replace unit with proper sized unit

This solution is "the proper way" to fix the problem, and was how
it should have been handled in the first place. However, I am being
told that everything needs to be replaced, including ductwork to
account for differences in blower motor output of the smaller unit. I
have been told that the duct work pressures will be different and that
everything needs to be sized according to the system as a whole. Is
this true?

Since all our new drywall will need to be ripped up to install new duct
work, I would hate to have to go down this path.

Suggestion 2: Change size of compressor

Is this really an option??? One contractor said I could just put in a
lower rated compressor, but I am skeptical of this solution. I have
been reading other posts on the news group, and it sounds to me like
the blower will still be moving air at the same rate over the coils,
and that this may still leave my house humid since the moving air will
have less contact with the coils. Is this true?

Suggestion 3: Install central dehumidification

This seems logical; with the only issues being the unit will run less
efficiently since it would still short cycle, causing stress to
controls, motor, etc. Additionally, I will be paying electricity for a
dehumidifier to run on top of my AC. On the plus side, we will get
humidity control year round, even when too cool for AC. Are there any
other caveats to this approach?



Increase the size of the area being cooled to better match the system,
install a duct to the garage. The amount of energy you waste cooling the
garage may be less than the cost to correct the problem.

There is a room TH that has a "wide variable differential temp 'manual'
setting." Kick-on at say 78 kick-off at say, 74-F.
Also, slow the fan CFM to close to 350-cfm per ton of cooling.
Use a large 20" fan to circulate the air to keep within the "Human
Comfort Zone."

What is that the Brand and Model number of that RM TH?

http://www.udarrell.com/air-conditio...tent-heat.html

Install a dehumidistat wired in parallel to the RM TH; might get a bit
cold if you set the dehumidistat too low.
- Darrell - udarrell

--
Crank Your Air-Conditioner Up To Specs
http://www.udarrell.com/air-conditio...city-seer.html

Since you are doing this for you self
I think this would be you simplest solution
to you problem of humidity?
get you self some type of thin sheet metal
and pair of sheer so you can cut sheet metal to size you
may need, and start blocking air flow through the cooling
coil, start from the bottom end, and make sure that you are
putting this metal on the side where the air inter in to coil
do it couple inches at time this will reduce temperature
on the coil and increase moisture, (do not freeze coil)
removal. start the unit and see the results if you have
instrument that you can check Humidity before and after
that would definitely help you but first check it
before you make change log it down and check
after the change so you can see the results immediately
if you do not have instrument to make immediate check
then you will had to gave some time to see the results
This will work but I can't say how good and
how much of air block you may need to do?
I would like to hear from you if you follow suggestions
Good luck from Dido!

"bucholtz-gmail-com" wrote in message
oups.com...
Basics:

Have an oversized AC unit causing a humidity problem. I have been
given many suggestions for fixing, but would like feedback on the
different options.


Solutions:

After talking with different HVAC contractors about the problem, I have
been given three suggestions. Before throwing good money after bad, I
would like input on the validity of the suggested fixes. In addition,
if there are any other fixes that could work, please let me know.

Suggestion 1: Replace unit with proper sized unit

This solution is "the proper way" to fix the problem, and was how
it should have been handled in the first place. However, I am being
told that everything needs to be replaced, including ductwork to
account for differences in blower motor output of the smaller unit. I
have been told that the duct work pressures will be different and that
everything needs to be sized according to the system as a whole. Is
this true?

Since all our new drywall will need to be ripped up to install new duct
work, I would hate to have to go down this path.

Suggestion 2: Change size of compressor

Is this really an option??? One contractor said I could just put in a
lower rated compressor, but I am skeptical of this solution. I have
been reading other posts on the news group, and it sounds to me like
the blower will still be moving air at the same rate over the coils,
and that this may still leave my house humid since the moving air will
have less contact with the coils. Is this true?

Suggestion 3: Install central dehumidification

This seems logical; with the only issues being the unit will run less
efficiently since it would still short cycle, causing stress to
controls, motor, etc. Additionally, I will be paying electricity for a
dehumidifier to run on top of my AC. On the plus side, we will get
humidity control year round, even when too cool for AC. Are there any
other caveats to this approach?

several suggestions:

1) Install a ducted dehumidifier, like Therma-Stor or AprilAire. Tie
it into your existing supply duct system and install a separate return
for it.

2) Install the proper size system. No, you don't need new ducts for
the lower air flow. Most duct systems are undersized anyway! Install
dampers on all the branch ducts, do a room by room load calculation and
do a proper air balance using a flow hood, This requires a competent
contractor, with the proper tools and training; only about 1 in 10 can
actually do this!

3) Measure the air flow with a flow hood or another accurate air
measuring instrument. In high humidity environment, you should have
around 350 CFM per ton. This does not mean measuring with the
contractor's hand, that IS NOT accurate.

4) If the system is recent vintage, you may be able to replace just
the outdoor unit if you can get a manufacturer's certified match. The
outdoor and indoor units should be the same brand unless the
manufacturer says otherwise. Then adjust the overall air flow to 350
CFM per ton. Also do an air balance!

5) Do not block parts of the coil, that will cause all kinds of
problems. Adjust overall air flow with the blower speed and dampers.
Blocking parts of the coil with metal can cause uneven evaporation of
refrigerant and may cause liquid refrigerant to slug the compressor.
BIG DAMAGE!!!

6) Seal the ducts, close the windows, provide return paths for all
supply grilles. Opening windows will just allow more moisture to come
in from outside. Installing exhaust fans will do the same thing by
pulling the house into a negative pressure and sucking in outside air!

Get someone to measure the airflow and humidity and quit guessing. And
get rid of contractors who guess!!!!!!

Stretch

On Tue, 23 Aug 2005 20:14:18 GMT, "PipeDown"
wrote Re Correcting Oversized AC:

Increase the cooling load in other ways: Cut down a shade tree, open some
curtains, install less efficient windows (not). have the kids leave the
door open too often. etc.

Also, you can try keeping doors & windows closed, but leave a couple
of 100w lights on in several rooms or run a small electric heater near
the air intake.
--
To email me directly, remove CLUTTER.

"bucholtz-gmail-com" wrote in message
oups.com...
Basics:

Have an oversized AC unit causing a humidity problem. I have been
given many suggestions for fixing, but would like feedback on the
different options.


Solutions:

After talking with different HVAC contractors about the problem, I have
been given three suggestions. Before throwing good money after bad, I
would like input on the validity of the suggested fixes. In addition,
if there are any other fixes that could work, please let me know.

Suggestion 1: Replace unit with proper sized unit

This solution is "the proper way" to fix the problem, and was how
it should have been handled in the first place. However, I am being
told that everything needs to be replaced, including ductwork to
account for differences in blower motor output of the smaller unit. I
have been told that the duct work pressures will be different and that
everything needs to be sized according to the system as a whole. Is
this true?

Yes. The ductwork is not a seperate system, its PART of the existing.


Since all our new drywall will need to be ripped up to install new duct
work, I would hate to have to go down this path.

Suggestion 2: Change size of compressor

Is this really an option??? One contractor said I could just put in a
lower rated compressor, but I am skeptical of this solution. I have
been reading other posts on the news group, and it sounds to me like
the blower will still be moving air at the same rate over the coils,
and that this may still leave my house humid since the moving air will
have less contact with the coils. Is this true?

You mean a lower rated condensor?
Some of the smaller, high SEER units use larger blowers and evap coils than
the rated capacity of the condensor.
The metering will have to be changed, and it possibly could be done....if
you have done some reading about higher SEERS, you may also continue to have
a humidity problem.
I dont get your comment about less contact with the coils...you mean less
contact time?


Suggestion 3: Install central dehumidification

This seems logical; with the only issues being the unit will run less
efficiently since it would still short cycle, causing stress to
controls, motor, etc. Additionally, I will be paying electricity for a
dehumidifier to run on top of my AC. On the plus side, we will get
humidity control year round, even when too cool for AC. Are there any
other caveats to this approach?


Sounds nice, but you will about crap when you see how much say..an AprilAire
central dehumidifier costs.

"bucholtz-gmail-com" wrote in message
oups.com...
Basics:

Have an oversized AC unit causing a humidity problem. I have been
given many suggestions for fixing, but would like feedback on the
different options.


Solutions:

After talking with different HVAC contractors about the problem, I have
been given three suggestions. Before throwing good money after bad, I
would like input on the validity of the suggested fixes. In addition,
if there are any other fixes that could work, please let me know.

Suggestion 1: Replace unit with proper sized unit

This solution is "the proper way" to fix the problem, and was how
it should have been handled in the first place. However, I am being
told that everything needs to be replaced, including ductwork to
account for differences in blower motor output of the smaller unit. I
have been told that the duct work pressures will be different and that
everything needs to be sized according to the system as a whole. Is
this true?

Since all our new drywall will need to be ripped up to install new duct
work, I would hate to have to go down this path.

Why would you need to rip out all the ducts? If you have loose ducts in the
crawlspace above the ceiling, why not just replace those with smaller ducts,
leaving everything that's encased in walls and such alone? Or, put some
kind of flow restrictors behind the registers.

Suggestion 2: Change size of compressor

Is this really an option??? One contractor said I could just put in a
lower rated compressor, but I am skeptical of this solution. I have
been reading other posts on the news group, and it sounds to me like
the blower will still be moving air at the same rate over the coils,
and that this may still leave my house humid since the moving air will
have less contact with the coils. Is this true?

I wouldn't monkey with the actual design of the unit. What if, 10 years
down the line, you need to have work done on it, and the contractor doesn't
know about the modifications?

Suggestion 3: Install central dehumidification

This seems logical; with the only issues being the unit will run less
efficiently since it would still short cycle, causing stress to
controls, motor, etc. Additionally, I will be paying electricity for a
dehumidifier to run on top of my AC. On the plus side, we will get
humidity control year round, even when too cool for AC. Are there any
other caveats to this approach?

If you have humidity problems year round, this is probably a smart move
regardless.

Pagan

Just get a dehumidifier and leave the fan blower on all the time.
Place the dehumidifer near one of the registers. Cheap and easy. When
unit needs to be replaced next, then get the proper size. I would not
change ducts, you should be able to do what you want by changing the
fan motor speed.

wrote in message
oups.com...
Just get a dehumidifier and leave the fan blower on all the time.
Place the dehumidifer near one of the registers. Cheap and easy. When
unit needs to be replaced next, then get the proper size. I would not
change ducts, you should be able to do what you want by changing the
fan motor speed.


Reducing a duct in place is easy, all you need to do is put solid foam
insulation in the duct to reduce the cross sectional area. This may require
disassembly of certain sections to gain access.

Increasing the duct size would require replacement

Just try the slower fan first and see if it works berore you get too worried
about air velocity vs volume. Another posters suggestion about reducing the
airflow at the condensor also sounds reasonable (inexpensive and reversable
if it dosen't work)

Reducing the size of the registers or closing some dampers would have some
effect as well.