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Posted by Kenneth Bodine on June 26, 2008, 6:49 pm
I have a 2000 sf home with a 4 ton Goodman installed. The unit is about 5
years old, straight AC, strip heat. This unit has never been what I
hoped. The front of the house is considerably warmer than the interior
and rear of the home. I cycles on every 10 minutes (or less) and runs for
8 minutes, then shuts off. I have had several AC men look at it, and have
been told various reasons for the problem. I have heard the unit is too
big, the unit is too small, the plenum is too small, the ducts are too
small, there is not enough insulation in the attic, the thermostat is in
the wrong place, the ducts are in the wrong place, you aren't making
enough static pressure, etc...
I am no AC man, but it seems to me that these are all possiblilties - or
guesses. I can't imagine that everything listed is wrong. What are some
ways to limit the issues? How much insulation should the attic have?
What is the rule of thumb for duct sizes, unit sizes, cycle times? I
would just like to have a unit that works right and doesn't wear me out
with worry...any suggestions?
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Posted by PeterD on June 26, 2008, 11:31 pm
On 26 Jun 2008 22:49:36 GMT,
kennethbodine_at_sbcglobal_dot_net@foo.com (Kenneth Bodine) wrote:
>I have a 2000 sf home with a 4 ton Goodman installed.
Where? Nevada, Florida or Maine?
> The unit is about 5
>years old, straight AC, strip heat. This unit has never been what I
>hoped.
WHat had you hoped?
>The front of the house is considerably warmer than the interior
>and rear of the home.
That's nice. Now, which *direction* is the front of the house? The
sunny side by chance (south?)
>I cycles on every 10 minutes (or less) and runs for
>8 minutes, then shuts off.
So it runs for eight minutes, then is off for two, then comes back on?
OK, seems fair to me.
>I have had several AC men look at it, and have
>been told various reasons for the problem. I have heard the unit is too
>big, the unit is too small, the plenum is too small, the ducts are too
>small, there is not enough insulation in the attic, the thermostat is in
>the wrong place,
Of all those comments, that one is the one that may be correct.
>the ducts are in the wrong place,
WHere are the ducts?
>you aren't making
>enough static pressure, etc...
Is this a packaged system, or a added to existing heat system?
>
>I am no AC man, but it seems to me that these are all possiblilties - or
>guesses. I can't imagine that everything listed is wrong. What are some
>ways to limit the issues? How much insulation should the attic have?
In Maine, for AC, not that much... Goes to location, location,
location.
>What is the rule of thumb for duct sizes, unit sizes, cycle times? I
>would just like to have a unit that works right and doesn't wear me out
>with worry...any suggestions?
WOrry? WHat are you worried about?
Next time put some facts in:
Where you are.
Outside temperature?
Temp in the cooler areas/rooms?
Temp in the warmer areas/rooms?
How much insulation you have?
What type (even brand and model) of unit you have?
If duct location is suspect, where are the ducts?
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Posted by Kenneth Bodine on July 1, 2008, 10:31 pm
Kenneth Bodine had written this in response to
http://www.thestuccocompany.com/construction/Re-Causes-for-Short-Cycling-AC-14520-.htm
:
-------------------------------------
PeterD wrote:
> On 26 Jun 2008 22:49:36 GMT,
> kennethbodine_at_sbcglobal_dot_net@foo.com (Kenneth Bodine) wrote:
>>I have a 2000 sf home with a 4 ton Goodman installed.
> Where? Nevada, Florida or Maine?
>> The unit is about 5
>>years old, straight AC, strip heat. This unit has never been what
>> I
>>hoped.
> WHat had you hoped?
>>The front of the house is considerably warmer than the interior
>>and rear of the home.
> That's nice. Now, which *direction* is the front of the house? The
> sunny side by chance (south?)
>>I cycles on every 10 minutes (or less) and runs for
>>8 minutes, then shuts off.
> So it runs for eight minutes, then is off for two, then comes back on?
> OK, seems fair to me.
>>I have had several AC men look at it, and have
>>been told various reasons for the problem. I have heard the unit
>> is too
>>big, the unit is too small, the plenum is too small, the ducts are
>> too
>>small, there is not enough insulation in the attic, the thermostat
>> is in
>>the wrong place,
> Of all those comments, that one is the one that may be correct.
>>the ducts are in the wrong place,
> WHere are the ducts?
>>you aren't making
>>enough static pressure, etc...
> Is this a packaged system, or a added to existing heat system?
>>
>>I am no AC man, but it seems to me that these are all possiblilties
>> - or
>>guesses. I can't imagine that everything listed is wrong. What
>> are some
>>ways to limit the issues? How much insulation should the attic
>> have?
> In Maine, for AC, not that much... Goes to location, location,
> location.
>>What is the rule of thumb for duct sizes, unit sizes, cycle times?
>> I
>>would just like to have a unit that works right and doesn't wear me
>> out
>>with worry...any suggestions?
> WOrry? WHat are you worried about?
> Next time put some facts in:
> Where you are.
> Outside temperature?
> Temp in the cooler areas/rooms?
> Temp in the warmer areas/rooms?
> How much insulation you have?
> What type (even brand and model) of unit you have?
> If duct location is suspect, where are the ducts?
OK, based on some of the feedback, it sounds like I short-changed you on
information. I live in North Central Texas. The temp outside is in the
low 80's at night, and high 90's to low 100's during the day. The unit I
have is a split system Goodman single stage 4 ton straight AC (NOT a heat
pump), with strip heat. The house is a single story ranch home with mostly
8 ft ceilings. The house faces southeast, in the shape of a T, with the
lower part of the T facing north. 5 years ago, the garage was converted
to a living area, and there was a 480 sq ft addition put on, hence the
change to the 4 ton Goodman. The AC man used the existing ducts, added
new 2 10" supply lines for the addition - broken into 8's for the bdr, and
a 6 for the restroom and utility area - this is the part facing north, and
it is very comfortable - about 75 degrees. The converted garage, which
faces south, has 2 8's for a 20 x 17 area, and feels a little more humid,
but still around 76 degrees. The center part of the home is the coolest,
generally at about 74 degrees. The temp in the eastern portion of the
house is the part that stays the warmest. It is generally 78 or 79
degrees, and very stuffy. Both of the bdr's have two 5'0 x 5'0 windows,
one facing south, one facing north, and two facing east (1 per bedroom).
The ducts for all the old house are located right in the center of the
room, 7 inch round ducts. They were initially only used for heat - no AC.
When the house was switched to AC, there was only about 1200 sq ft, and a
2.5 ton heat pump was attached. The home was very comfortable then, even
cold. When I added the space and went to a new unit, I had hoped the house
would stay as comfortable with the new system, but this is not the case.
As far as insulation is concerned, there is about 6 inches of cellulose
insulation in the attic, and r-11 in the walls. The windows are single
hung, but have an additional storm window mounted, with about 3 inches
space between the two panes.
You asked what I am worried about. The short cycling worries me. I am
afraid that I will blow the compressor - as the unit is getting more
noticably loud as the years have passed - very quiet when I first
installed, and now loud enough to wake me at night or have someone ask me
what that noise is when it first comes on. After it runs for a few
minutes, it gets pretty quiet again.
Based on this data, is it still the consensus that the ducts need to be
relocated? I hope this is a little more informative!! Thanks for the
info.
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Posted by Dioclese on June 28, 2008, 8:42 am
Similar warm in front, cooler in rear of the house. Most noticably in heat
of the day. House faces the south.
AC stagnant (end cycle to beginning of cycle) time varies with the exterior
temperature. And, the length of time AC is actually on varies with external
temps and entry/exit traffic into the home. Not consistent figures like
yours.
Thermostat location is typical hallway adjacent to bedrooms.
--
Dave
We have a right to choose.
Choices have consequences,
for both self, and others.
You probably considered yourself.
>I have a 2000 sf home with a 4 ton Goodman installed. The unit is about 5
> years old, straight AC, strip heat. This unit has never been what I
> hoped. The front of the house is considerably warmer than the interior
> and rear of the home. I cycles on every 10 minutes (or less) and runs for
> 8 minutes, then shuts off. I have had several AC men look at it, and have
> been told various reasons for the problem. I have heard the unit is too
> big, the unit is too small, the plenum is too small, the ducts are too
> small, there is not enough insulation in the attic, the thermostat is in
> the wrong place, the ducts are in the wrong place, you aren't making
> enough static pressure, etc...
>
> I am no AC man, but it seems to me that these are all possiblilties - or
> guesses. I can't imagine that everything listed is wrong. What are some
> ways to limit the issues? How much insulation should the attic have?
> What is the rule of thumb for duct sizes, unit sizes, cycle times? I
> would just like to have a unit that works right and doesn't wear me out
> with worry...any suggestions?
>
> -------------------------------------
>
>
>
>
> ##-----------------------------------------------##
> Delivered via http://www.thestuccocompany.com/
> Building Construction and Maintenance Forum
> Web and RSS access to your favorite newsgroup -
> alt.building.construction - 13834 messages and counting!
> ##-----------------------------------------------##
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Posted by ransley on July 1, 2008, 7:44 pm
On Jun 26, 5:49=A0pm, kennethbodine_at_sbcglobal_dot_...@foo.com
(Kenneth Bodine) wrote:
> I have a 2000 sf home with a 4 ton Goodman installed. =A0The unit is about=
5
> years old, straight AC, strip heat. =A0This unit has never been what I
> hoped. =A0The front of the house is considerably warmer than the interior
> and rear of the home. =A0I cycles on every 10 minutes (or less) and runs f=
or
> 8 minutes, then shuts off. =A0I have had several AC men look at it, and ha=
ve
> been told various reasons for the problem. =A0I have heard the unit is too=
> big, the unit is too small, the plenum is too small, the ducts are too
> small, there is not enough insulation in the attic, the thermostat is in
> the wrong place, the ducts are in the wrong place, you aren't making
> enough static pressure, etc...
>
> I am no AC man, but it seems to me that these are all possiblilties - or
> guesses. =A0I can't imagine that everything listed is wrong. =A0What are s=
ome
> ways to limit the issues? =A0How much insulation should the attic have?
> What is the rule of thumb for duct sizes, unit sizes, cycle times? =A0I
> would just like to have a unit that works right and doesn't wear me out
> with worry...any suggestions?
>
> -------------------------------------
>
> ##-----------------------------------------------##
> Delivered via =A0http://www.thestuccocompany.com/
> Building Construction and Maintenance Forum
> Web and RSS access to your favorite newsgroup -
> alt.building.construction - 13834 messages and counting!
> ##-----------------------------------------------##
To simplly get it to cycle less adjust the anticipator for a larger
swing, or get a thermostat that you can adjust. For a hot room you
likely need more supply, but I think you need an inteligent tech, as
they all should have sold you a thermostat.
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