Hi jessica, hope you are having a nice day

On 14-Jun-05 At About 02:15:32, jessica wrote to All
Subject: AC size?

j From: "jessica"

j Our house is 2700 square feet, and insulated well for a 20 year
j house. Our ducts are R6. What other information would be useful?


There are just too many variables and way too much info needed to do a manual
J over the net. the only way is to have someone on site who can see the room
layouts and get measurments etc..

-= HvacTech2 =-


... "I can levitate birds but nobody cares..." - s.w.

___ TagDude 0.92á+[DM]
++++++++++++++++++++++++++++++++++++++++++++++++++ +++++++++++
spam protection measure, Please remove the 33 to send e-mail

We have decided to go with a 14 seer heat pump with back up propane.
Now the question is what size? Different contractors have said
anywhere from 3 ton to 4 ton. Only one contractor actually did a
Manual J. He determinded we need 41,000 BTU for cooling and 75,000 BTU
for heating. He recommends we go wtih a 4 ton unit. There are actual
BTU's and sensible BTU's, and given our area, we should size to 4 ton
to match the "sensible BTU's" Does this make sense? This contractor
has come with very good reviews. We just want to oversize the unit.

I live in southern maryland about 35 miles south of D.C. We have very
hot and humid summers.

Thank you!

Jessica

Since only one did any calculations, the others are just guessing. And
what do you expect from the newgroup? We have no way of knowing
anything about your house, how big it is, how well it's insulated, etc.

Our house is 2700 square feet, and insulated well for a 20 year house.
Our ducts are R6. What other information would be useful?

"jessica" wrote in message
ups.com...
Our house is 2700 square feet, and insulated well for a 20 year house.
Our ducts are R6. What other information would be useful?

Windows - size, type, how many, which way they are facing (north, south,
east, west)
Construction- wood, stucco, vinyl, brick. 2 by 4, 2 x6. how high are the
ceilings, what kind/color are the shingles, how much insulationg in the
walls/ceiling/attic, on a slab? Crawlspace? basement?
Rooms - how many, how big, how many people/appliances in each
Location- which direction does it face, do you have a lot of trees.

There are a lot of other things to consider, too.

Did you call my company? We do all of St. Mary's, Charles, Calvert, and
parts of PG........

"jessica" wrote in message
oups.com...
We have decided to go with a 14 seer heat pump with back up propane.
Now the question is what size? Different contractors have said
anywhere from 3 ton to 4 ton. Only one contractor actually did a
Manual J. He determinded we need 41,000 BTU for cooling and 75,000 BTU
for heating. He recommends we go wtih a 4 ton unit. There are actual
BTU's and sensible BTU's, and given our area, we should size to 4 ton
to match the "sensible BTU's" Does this make sense? This contractor
has come with very good reviews. We just want to oversize the unit.

I live in southern maryland about 35 miles south of D.C. We have very
hot and humid summers.

Thank you!

Jessica

"We just want to oversize the unit." Is this really what you want to say?
Over sizing a unit is just spending more money than you need. Just making
the compressor bigger is the mark of the unexpended. Bigger compressors
usually come with bigger fans. Can your duct work handle the added CFM's?

I do not have a clue what a "sensible BTU" is nor how to measure it.

Is humidity an issue for your environment? If so contact the guy that did
the manual J and ask him specifically about a VFD air handler, and removal
of humidity.
I installed on my last home a 12 seer 5 ton American Standard with the VFD
air handler. It worked excellent for humidity control.

The installer is more important than the equipment. Have you considered
having the ducts cleaned before the change out? I would also recommend that
the air filter be sized larger than necessary (1.5x) That way you can use
higher efficiency filters and not have the static drop of the filter bother
the air handlers performance. Dirt and dust is a big deal in the desert of
Arizona, and I have a dog.

On 14 Jun 2005 14:15:32 -0700, "jessica"
wrote:

Our house is 2700 square feet, and insulated well for a 20 year house.
Our ducts are R6. What other information would be useful?

Read the other posts about some homeowners liking their homes kept at
65 degrees when it is 95 outside.

Are you one of those? If so, you may want to oversize
substantially. Personally, I am NOT one of those and want my system
to struggle to keep the temperatur at 77 on a 95 degree day. That
means I want it to run for about 4 hours without shutting off on every
hot afternoon of summer and if someone leaves the door open or cooks a
roast or ... , then I expect the temperature to creep up to 80 with
the ac running constantly.

Which one are you?

I ment 'We just do NOT want to oversize the unit.'

Humity is an issue here. What is VFD? We are getting a propane furnace
with a variable speed blower so we can get the higher SEER out of the
heat pump. Does this have anything to do with VFD?

He will be enlarging the cold air intake and putting the filter there.

jessica wrote:
We have decided to go with a 14 seer heat pump with back up propane.
Now the question is what size? Different contractors have said
anywhere from 3 ton to 4 ton. Only one contractor actually did a
Manual J. He determinded we need 41,000 BTU for cooling and 75,000
BTU for heating. He recommends we go wtih a 4 ton unit. There are
actual BTU's and sensible BTU's, and given our area, we should size
to 4 ton to match the "sensible BTU's" Does this make sense? This
contractor has come with very good reviews. We just want to oversize
the unit.

I live in southern maryland about 35 miles south of D.C. We have very
hot and humid summers.

Thank you!

Jessica

Only one meets the requirements. He did the numbers and comes
recommended. Frankly the most important part of the whole thing is the
installer. It appears (and I have no way of knowing for sure) you have a
good one. A good one will consider local conditions (like your humidity)
when designing a installation.

--
Joseph Meehan

Dia duit

Jessica -

here is the problem with getting a unit that is larger than you need

when the A/C kicks on, because it is oversized for you house, it cools it so
fast that it just runs for a brief spurt.

the problem is that the OTHER forgotten function of A/C in the summer is
dehumidification, if you want to be comfortable

the oversized A/C unit runs such a brief time to get the house cooled down,
that there is not enough time to adequately dehumidity.

so folks who buy an "oversize" unit, while their intention is to be more
comfortable, end up LESS comfortable in a cool, but clammy home.

get the correct size, and no more

"jessica" wrote in message
ups.com...
I ment 'We just do NOT want to oversize the unit.'

Humity is an issue here. What is VFD? We are getting a propane furnace
with a variable speed blower so we can get the higher SEER out of the
heat pump. Does this have anything to do with VFD?

He will be enlarging the cold air intake and putting the filter there.

VFD= variable frequency drive same as your words "blower"


Since he is enlarging the return, ask about making the filter area at least
1.5 times the area normally used. Example, if the normal filter assembly is
a 20x25 use a 20x30 filter cost is the same. but there is more surface area
for the fan to draw from. My new York a/c has some serious issues with
static air pressure. Basically give it a dirty filter and it will not cool
my home. The unit loses most cooling at 0.70 inches of static. Not great
when the filters I use CLEAN start out at 0.28.

Also ask about a tube return grill instead of the stamped grill. Again less
static air pressure.
Just suggestions for better performance.

Size doesn't matter.


"jessica" wrote in message
oups.com...
We have decided to go with a 14 seer heat pump with back up propane.
Now the question is what size? Different contractors have said
anywhere from 3 ton to 4 ton. Only one contractor actually did a
Manual J. He determinded we need 41,000 BTU for cooling and 75,000 BTU
for heating. He recommends we go wtih a 4 ton unit. There are actual
BTU's and sensible BTU's, and given our area, we should size to 4 ton
to match the "sensible BTU's" Does this make sense? This contractor
has come with very good reviews. We just want to oversize the unit.

I live in southern maryland about 35 miles south of D.C. We have very
hot and humid summers.

Thank you!

Jessica

We'd like to know the heat input, in the form of appliances, and windows,
and other environmental sources. Also the daily operation, if the doors are
opened frequently (I had this happen, a house that never quite got cool. The
two elderly residents were smokers, and the door was open all the time, as
they went out to smoke).

I doubt you can get all the relevant details over the net. cause we won't
know to ask, and you won't know to say.

--

Christopher A. Young
Learn more about Jesus
www.lds.org
www.mormons.com


"jessica" wrote in message
ups.com...
Our house is 2700 square feet, and insulated well for a 20 year house.
Our ducts are R6. What other information would be useful?

Oscar_Lives posted for all of us...
I don't top post - see either inline or at bottom.

Size doesn't matter.

I guess we will have to ask Jessica!
--

Tekkie

"SQLit" wrote in message

I do not have a clue what a "sensible BTU" is nor how to measure it.


Sensible heat is the heat energy contained in the contents of the house.
Stored heat, I guess is a good term for it. A chair at 80 degrees contains
more heat than the chair at 70 degrees. I don't know how you go about
measuring it. Once you reduce the sensible heat in a building, it will not
gain as long as the AC continues to run and remove any additional heat
coming into the house.
--
Ed
http://pages.cthome.net/edhome/

cowboy wrote:

Jessica -

here is the problem with getting a unit that is larger than you need

when the A/C kicks on, because it is oversized for you house, it cools it so
fast that it just runs for a brief spurt.

the problem is that the OTHER forgotten function of A/C in the summer is
dehumidification, if you want to be comfortable

the oversized A/C unit runs such a brief time to get the house cooled down,
that there is not enough time to adequately dehumidity.

so folks who buy an "oversize" unit, while their intention is to be more
comfortable, end up LESS comfortable in a cool, but clammy home.

get the correct size, and no more


In a humid climate, I would rather undersize a little than oversize.
It needs the runtime to ring out the humidity and achieve the Human
Comfort Zone.
- udarrell

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

Stormin Mormon wrote:


cause we won't
know to ask, and you won't know to say.


Perfect example of a typical dead, dumb and blind mormon asking another
typical deaf, dumb and blind mormon for truth concerning the cult he's a
slave to.

--
Learn The Truth About Mormonism
http://mormonssuck.com/links.html

SQLit wrote:

I do not have a clue what a "sensible BTU" is nor how to measure it.

Really? A sensible Btu can cool a pound of water 1 F.
A latent Btu can condense 1/1000 of a pound of water vapor.

Nick

wrote in message
...
SQLit wrote:

I do not have a clue what a "sensible BTU" is nor how to measure it.

Really? A sensible Btu can cool a pound of water 1 F.
A latent Btu can condense 1/1000 of a pound of water vapor.

Nick

True but that does not tell how to measure it. How can I tell how many
sensible Btu are in a given mass?

Edwin Pawlowski wrote:

...How can I tell how many sensible Btu are in a given mass?

Toss it into a bucket of water.

Nick

From when I took some AC courses, "sensible heat" is when you add or remove
BTU, and it makes a temperature difference. For example, you heat or cool
dry air. The temp goes up or down.

Latent heat is adding or removing BTU, which doesn't make a temperature
change -- in other words, humidity. An example is running an AC which
condenses out a lot of water, but doesn't change the temp. We'd call that
"reducing latent heat".

Or, so it was explained to me.

--

Christopher A. Young
Learn more about Jesus
www.lds.org
www.mormons.com


"Edwin Pawlowski" wrote in message
. ..

"SQLit" wrote in message

I do not have a clue what a "sensible BTU" is nor how to measure it.


Sensible heat is the heat energy contained in the contents of the house.
Stored heat, I guess is a good term for it. A chair at 80 degrees contains
more heat than the chair at 70 degrees. I don't know how you go about
measuring it. Once you reduce the sensible heat in a building, it will not
gain as long as the AC continues to run and remove any additional heat
coming into the house.
--
Ed
http://pages.cthome.net/edhome/

Stormin Mormon wrote:

From when I took some AC courses, "sensible heat" is when you add or remove
BTU, and it makes a temperature difference. For example, you heat or cool
dry air. The temp goes up or down.

Latent heat is adding or removing BTU, which doesn't make a temperature
change -- in other words, humidity. An example is running an AC which
condenses out a lot of water, but doesn't change the temp. We'd call that
"reducing latent heat".

Or, so it was explained to me.


Well stated.
Design makes a considerable difference in the ratio of latent to
sensible as does airflow and run time.
Also, as the humidity level of the air increases so does the ratio of
latent condensate change of state heat absorbed increase.
Studying the graphed charts illustrated in the link below, clearly
reveals this relationship ratio equation.
As the humidity level goes up the condenser discharged heat which
includes the latent heat goes up as the sensible temperature drop goes down.

--

What is the most Affordable Path to the "Human Comfort Zone" Goal?
http://www.udarrell.com/air-conditio...tent-heat.html

"jessica" wrote in message
oups.com...
We have decided to go with a 14 seer heat pump with back up propane.
Now the question is what size? Different contractors have said
anywhere from 3 ton to 4 ton. Only one contractor actually did a
Manual J. He determinded we need 41,000 BTU for cooling and 75,000 BTU
for heating. He recommends we go wtih a 4 ton unit. There are actual
BTU's and sensible BTU's, and given our area, we should size to 4 ton
to match the "sensible BTU's" Does this make sense? This contractor
has come with very good reviews. We just want to oversize the unit.

I live in southern maryland about 35 miles south of D.C. We have very
hot and humid summers.

Thank you!

Jessica


This is Turtle.

Go with the contractor that did the Manual J and go along with the 4 ton 14 seer
/ propane back up because some contractor have dought about the Manual J reading
and will up a 1/2 ton in there recommendations to remove errors.

i just can't picture Southern Maryland being a hot area of the country but could
see a humid area.

TURTLE

TURTLE wrote:

"jessica" wrote in message
roups.com...


We have decided to go with a 14 seer heat pump with back up propane.
Now the question is what size? Different contractors have said
anywhere from 3 ton to 4 ton. Only one contractor actually did a
Manual J. He determinded we need 41,000 BTU for cooling and 75,000 BTU
for heating. He recommends we go wtih a 4 ton unit. There are actual
BTU's and sensible BTU's, and given our area, we should size to 4 ton
to match the "sensible BTU's" Does this make sense? This contractor
has come with very good reviews. We just want to oversize the unit.

I live in southern maryland about 35 miles south of D.C. We have very
hot and humid summers.

Thank you!

Jessica



This is Turtle.

Go with the contractor that did the Manual J and go along with the 4 ton 14 seer
/ propane back up because some contractor have dought about the Manual J reading
and will up a 1/2 ton in there recommendations to remove errors.

i just can't picture Southern Maryland being a hot area of the country but could
see a humid area.

TURTLE


Turtle, we know that they should size for the latent humidity load as
well as the sensible load.
That is especially true in a high humidity area like he lives in.
The latent load is a major critical factor toward efficiently achieving
the human comfort zone.

When the humidity is high the latent load will take a lot of BTUs away
from the sensible capacity of the evaporator; which will also provide
more needed run-time.
However, they should be careful not to oversize, --because it takes
adequate run-time to get the humidity percentage down.

If they have the blower speeds to do it,-- they could use a relay
operated by a dehumidistat to go to 350-cfm per ton airflow for a colder
coil, when needed until the dehumidistat is satisfied.
- udarrell

--

What is the most Affordable Path to the "Human Comfort Zone" Goal?
http://www.udarrell.com/air-conditio...tent-heat.html

udarrell wrote:
TURTLE wrote:

"jessica" wrote in message
oups.com...


We have decided to go with a 14 seer heat pump with back up propane.
Now the question is what size? Different contractors have said
anywhere from 3 ton to 4 ton. Only one contractor actually did a
Manual J. He determinded we need 41,000 BTU for cooling and 75,000 BTU
for heating. He recommends we go wtih a 4 ton unit. There are actual
BTU's and sensible BTU's, and given our area, we should size to 4 ton
to match the "sensible BTU's" Does this make sense? This contractor
has come with very good reviews. We just want to oversize the unit.

I live in southern maryland about 35 miles south of D.C. We have very
hot and humid summers.

Thank you!

Jessica



This is Turtle.

Go with the contractor that did the Manual J and go along with the 4
ton 14 seer / propane back up because some contractor have dought
about the Manual J reading and will up a 1/2 ton in there
recommendations to remove errors.

i just can't picture Southern Maryland being a hot area of the country
but could see a humid area.

TURTLE

Turtle, we know that they should size for the latent humidity load as
well as the sensible load.
That is especially true in a high humidity area like he lives in.
The latent load is a major critical factor toward efficiently achieving
the human comfort zone.

When the humidity is high the latent load will take a lot of BTUs away
from the sensible capacity of the evaporator; which will also provide
more needed run-time.
However, they should be careful not to oversize, --because it takes
adequate run-time to get the humidity percentage down.

If they have the blower speeds to do it,-- they could use a relay
operated by a dehumidistat to go to 350-cfm per ton airflow for a colder
coil, when needed until the dehumidistat is satisfied.
- udarrell

If it's a piston metered coil, then how are you going to charge the
system? In low or high speed?
What happens to superheat when the blower speed changes?

hvacrmedic

RP wrote:



udarrell wrote:

TURTLE wrote:

"jessica" wrote in message
oups.com...


We have decided to go with a 14 seer heat pump with back up propane.
Now the question is what size? Different contractors have said
anywhere from 3 ton to 4 ton. Only one contractor actually did a
Manual J. He determinded we need 41,000 BTU for cooling and 75,000
BTU
for heating. He recommends we go wtih a 4 ton unit. There are actual
BTU's and sensible BTU's, and given our area, we should size to 4 ton
to match the "sensible BTU's" Does this make sense? This contractor
has come with very good reviews. We just want to oversize the unit.

I live in southern maryland about 35 miles south of D.C. We have very
hot and humid summers.

Thank you!

Jessica




This is Turtle.

Go with the contractor that did the Manual J and go along with the 4
ton 14 seer / propane back up because some contractor have dought
about the Manual J reading and will up a 1/2 ton in there
recommendations to remove errors.

i just can't picture Southern Maryland being a hot area of the
country but could see a humid area.

TURTLE

Turtle, we know that they should size for the latent humidity load as
well as the sensible load.
That is especially true in a high humidity area like he lives in.
The latent load is a major critical factor toward efficiently
achieving the human comfort zone.

When the humidity is high the latent load will take a lot of BTUs
away from the sensible capacity of the evaporator; which will also
provide more needed run-time.
However, they should be careful not to oversize, --because it takes
adequate run-time to get the humidity percentage down.

If they have the blower speeds to do it,-- they could use a relay
operated by a dehumidistat to go to 350-cfm per ton airflow for a
colder coil, when needed until the dehumidistat is satisfied.
- udarrell

If it's a piston metered coil, then how are you going to charge the
system? In low or high speed?
What happens to superheat when the blower speed changes?
hvacrmedic

That is what the rule makers' should have eliminated instead of the 10-seer.
For those high humidity conditions we ought to pump the system down and
tear out the flow-rator-****er crappers and replace them with TXVs.

Well, we know what can happen with low temperature heatloads combined
with low CFM; freeze-ups and slugged compressors.
Some hot blooded babes that get all sweaty in bed doing it, run the
RM-TH at 68 or lower at night when it's real cool outside.

Of course, that provides us with more work. I always told her or him to
buy a big floor fan and run it on high if they were going to be doing it
most of the night. Some laughed and some got ****ed off but then usually
started laughing. One fine lady just rolled her big blue eyes blushed
then looked away. (That's all I'm saying here.)
- udarrell

--

What is the most Affordable Path to the "Human Comfort Zone" Goal?
http://www.udarrell.com/air-conditio...tent-heat.html

udarrell wrote:

RP wrote:



udarrell wrote:

TURTLE wrote:

"jessica" wrote in message
oups.com...


We have decided to go with a 14 seer heat pump with back up propane.
Now the question is what size? Different contractors have said
anywhere from 3 ton to 4 ton. Only one contractor actually did a
Manual J. He determinded we need 41,000 BTU for cooling and 75,000
BTU
for heating. He recommends we go wtih a 4 ton unit. There are actual
BTU's and sensible BTU's, and given our area, we should size to 4 ton
to match the "sensible BTU's" Does this make sense? This contractor
has come with very good reviews. We just want to oversize the unit.

I live in southern maryland about 35 miles south of D.C. We have very
hot and humid summers.

Thank you!

Jessica





This is Turtle.

Go with the contractor that did the Manual J and go along with the 4
ton 14 seer / propane back up because some contractor have dought
about the Manual J reading and will up a 1/2 ton in there
recommendations to remove errors.

i just can't picture Southern Maryland being a hot area of the
country but could see a humid area.

TURTLE


Turtle, we know that they should size for the latent humidity load as
well as the sensible load.
That is especially true in a high humidity area like he lives in.
The latent load is a major critical factor toward efficiently
achieving the human comfort zone.

When the humidity is high the latent load will take a lot of BTUs
away from the sensible capacity of the evaporator; which will also
provide more needed run-time.
However, they should be careful not to oversize, --because it takes
adequate run-time to get the humidity percentage down.

If they have the blower speeds to do it,-- they could use a relay
operated by a dehumidistat to go to 350-cfm per ton airflow for a
colder coil, when needed until the dehumidistat is satisfied.
- udarrell


If it's a piston metered coil, then how are you going to charge the
system? In low or high speed?
What happens to superheat when the blower speed changes?
hvacrmedic

That is what the rule makers' should have eliminated instead of the
10-seer.
For those high humidity conditions we ought to pump the system down and
tear out the flow-rator-****er crappers and replace them with TXVs.

Well, we know what can happen with low temperature heatloads combined
with low CFM; freeze-ups and slugged compressors.
Some hot blooded babes that get all sweaty in bed doing it, run the
RM-TH at 68 or lower at night when it's real cool outside.

Of course, that provides us with more work. I always told her or him to
buy a big floor fan and run it on high if they were going to be doing it
most of the night. Some laughed and some got ****ed off but then usually
started laughing. One fine lady just rolled her big blue eyes blushed
then looked away. (That's all I'm saying here.)
- udarrell

I'm not touching that

hvacrmedic