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Grille Size vs Duct Size StarkShark 10-29-2007
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Posted by StarkShark on October 29, 2007, 11:09 pm

> kjpro @ usenet.com wrote:
>
>>
>>
>>>The heating and cooling in my house is functioning well. One room
>>>
>>>
>>upstairs
>>
>>
>>>is a little cool when the heat is on, a little warm when the AC is
>>>on, but that's about it. It's a forced air system that was installed
>>>to replace a gravity feed coal furnace.
>>>
>>>The system has two air returns. One in the living room, about 12
>>>inches square, and a
>>>
>>>
>>
>>"giant one in the kitchen"
>>
>>Against Code
>>
>>
> Returns are never supposed to be put in kitchens or bathrooms.
> No Returns in basements, unless gas (oil) furnaces, water heaters &
> gas dryers are tightly sealed off separate from the Return area.
>
> Why wasn't a big Return Run put upstairs for cooling?
> Do you live in a hot climate? - udarrell
>
Sorry to have left out a lot of information. I know HVAC is complex; I just
thought
the question might be simple.

The house was built about 1903 with a coal furnace. In the last hundred years
it has
had an upstairs, two additions and a bathroom added, and at some point (perhaps
after
the additions) the furnace was changed to forced air. The present unit is only
about
10 years old.
The filter is 20 by 30 inches and is inserted in a slot at the furnace, just
before
the air enters the fan chamber.

The room that is now the kitchen may not have been the kitchen a 100 years ago,
so it
may not have been built with the return in the kitchen. I have no way of
knowing why
the builders did not include a cold air return upstairs, but it may have been
motivated by the desire to avoid disturbing the lathe and plaster walls.

I also do not know why a "*LOCAL*, competent, licensed, insured, professionally
trained, HVAC technician" did not move the air return to ensure the system was
up to
code. I was not here when the furnace was installed. I know that it was
installed by
a "*LOCAL*, competent, licensed, insured, professionally trained, HVAC
technician"
because the company's faded sticker is on the side of the furnace.

I'm in northern KY. Midwest climate with mild winters and hot summers.
The unit's ability to keep the house comfortable is not in question. I did
mention
that only one room runs slightly warm in summer and slightly cool in winter, but
that
was technically not relevant to my question.

I think I failed to ask my question correctly. If I were to ask if the opening
to the
duct could be made larger, I suspect the answer would be "Sure, make it as large
as
you want it. Just don't change the length or size of the duct itself." So if I
ask
it the other way, "If all things remain exactly the same, can the opening to the
duct
be reduced?"

I thought the answer would be easy, like, "Sure. Just don't make the total
surface
area of the opening smaller than the surface area of the pipe." Or perhaps
there
would be a rule of thumb like, "The surface are of the opening to the duct must
be the
same as the surface area of the duct multiplied by 1.25" or something like that.

I have read a huge amount of HVAC information over the past week, and can't seem
to
find the answer. So what am I missing?

I'm not trying to re-size the duct or make it longer or shorter. I am aware of
friction coefficients and angles and turbulence and the limiting effect of air
grilles.

I also know that surface area isn't really appropriate for talking about pipes,
but
I'm working with the size of the opening. If the size of the opening is larger
than
the size of the duct, then that looks like a funnel to me.

Am I so far out in left field that I don't even know I'm playing hockey, or am I
at
least in the ball park?

Udarrell, thank you for your response. If someone asked me how polymorphism can
be
used in his or her C++ program, and I responded, "call a college educated
programmer
with a PHD to write the code for you," I should think that I would be considered
rude.

Stark



Posted by on October 30, 2007, 1:08 am

>
> > kjpro @ usenet.com wrote:
> >
> >>
> >>
> >>>The heating and cooling in my house is functioning well. One room
> >>>
> >>>
> >>upstairs
> >>
> >>
> >>>is a little cool when the heat is on, a little warm when the AC is
> >>>on, but that's about it. It's a forced air system that was installed
> >>>to replace a gravity feed coal furnace.
> >>>
> >>>The system has two air returns. One in the living room, about 12
> >>>inches square, and a
> >>>
> >>>
> >>
> >>"giant one in the kitchen"
> >>
> >>Against Code
> >>
> >>
> > Returns are never supposed to be put in kitchens or bathrooms.
> > No Returns in basements, unless gas (oil) furnaces, water heaters &
> > gas dryers are tightly sealed off separate from the Return area.
> >
> > Why wasn't a big Return Run put upstairs for cooling?
> > Do you live in a hot climate? - udarrell
> >
> Sorry to have left out a lot of information. I know HVAC is complex; I
just thought
> the question might be simple.
>
> The house was built about 1903 with a coal furnace. In the last hundred
years it has
> had an upstairs, two additions and a bathroom added, and at some point
(perhaps after
> the additions) the furnace was changed to forced air. The present unit is
only about
> 10 years old.
> The filter is 20 by 30 inches and is inserted in a slot at the furnace,
just before
> the air enters the fan chamber.
>
> The room that is now the kitchen may not have been the kitchen a 100 years
ago, so it
> may not have been built with the return in the kitchen.


But it is now and its against code.


> I have no way of knowing why
> the builders did not include a cold air return upstairs, but it may have
been
> motivated by the desire to avoid disturbing the lathe and plaster walls.
>
> I also do not know why a "*LOCAL*, competent, licensed, insured,
professionally
> trained, HVAC technician" did not move the air return to ensure the system
was up to
> code.


Because the Homeowner was to cheap to do it right.


> I was not here when the furnace was installed. I know that it was
installed by
> a "*LOCAL*, competent, licensed, insured, professionally trained, HVAC
technician"
> because the company's faded sticker is on the side of the furnace.


Has a faded sticker, so they have to be competent... LOL


> I'm in northern KY. Midwest climate with mild winters and hot summers.
> The unit's ability to keep the house comfortable is not in question. I
did mention
> that only one room runs slightly warm in summer and slightly cool in
winter, but that
> was technically not relevant to my question.
>
> I think I failed to ask my question correctly. If I were to ask if the
opening to the
> duct could be made larger, I suspect the answer would be "Sure, make it as
large as
> you want it. Just don't change the length or size of the duct itself."
So if I ask
> it the other way, "If all things remain exactly the same, can the opening
to the duct
> be reduced?"
>
> I thought the answer would be easy, like, "Sure. Just don't make the
total surface
> area of the opening smaller than the surface area of the pipe." Or
perhaps there
> would be a rule of thumb like, "The surface are of the opening to the duct
must be the
> same as the surface area of the duct multiplied by 1.25" or something like
that.


You didn't like our answers, TOUGH SHIT.


> I have read a huge amount of HVAC information over the past week, and
can't seem to
> find the answer. So what am I missing?


The right book.


> I'm not trying to re-size the duct or make it longer or shorter. I am
aware of
> friction coefficients and angles and turbulence and the limiting effect of
air
> grilles.
>
> I also know that surface area isn't really appropriate for talking about
pipes, but
> I'm working with the size of the opening. If the size of the opening is
larger than
> the size of the duct, then that looks like a funnel to me.


Point?


> Am I so far out in left field that I don't even know I'm playing hockey,
or am I at
> least in the ball park?


Most ball parks are fairly large.


> Udarrell, thank you for your response. If someone asked me how
polymorphism can be
> used in his or her C++ program, and I responded, "call a college educated
programmer
> with a PHD to write the code for you," I should think that I would be
considered rude.


Too bad for them.



Posted by StarkShark on October 30, 2007, 9:17 am

>
>>
>> > kjpro @ usenet.com wrote:
> <snip>
> Because the Homeowner was to cheap to do it right.
Point well made. I'm sure you are right.

>
>> I was not here when the furnace was installed. I know that
it was
> installed by
>> a "*LOCAL*, competent, licensed, insured, professionally
trained,
>> HVAC
> technician"
>> because the company's faded sticker is on the side of the
furnace.
>
>
> Has a faded sticker, so they have to be competent... LOL
I see that you have the ability to read, but your comprehension
isn't very strong. You'll need to work on that. Find the right
book about reading. I was describing the condition of the
sticker, not the ability
of the technician. It was the name printed on the sticker that
brought me to the belief that a "competent" installer did the
work...a long time ago, as suggested by the faded condition of
the sticker.

>
> You didn't like our answers, TOUGH SHIT.
LOL. Once again, I refer you to a book about reading
comprehension.

>> I'm working with the size of the opening. If the size of the
opening
>> is
> larger than
>> the size of the duct, then that looks like a funnel to me.
>
>
> Point?
That you have poor reading comprehension.


>
>
>> Am I so far out in left field that I don't even know I'm
playing
>> hockey,
> or am I at
>> least in the ball park?
>
>
> Most ball parks are fairly large.
A very good point. You're saying I am in the park, but nowhere
near the ball. Okay.

>
>> Udarrell, thank you for your response. If someone asked me
how
> polymorphism can be
>> used in his or her C++ program, and I responded, "call a
college
>> educated
> programmer
>> with a PHD to write the code for you," I should think that I
would be
> considered rude.
>
>
> Too bad for them.
A surprisingly troll-like attitude. Eat your vitamins and get
some sleep. You obviously make some good points, but they don't
need to be couched in scorn.

You're beginning to make me suspect I stepped in troll feces.

Posted by Noon-Air on October 30, 2007, 11:30 am


>> Too bad for them.
> A surprisingly troll-like attitude. Eat your vitamins and get
> some sleep. You obviously make some good points, but they don't
> need to be couched in scorn.
>
> You're beginning to make me suspect I stepped in troll feces.

Your close.... but its homeowner feces. Homeowners belong in
alt.home.repair, not here. this is a forum for professionals *IN THE HVAC
TRADE*.

Most homeowners/slumlords come in here expecting us to tell them how to fix
their broken 30 year old, Jurassic, furnace for free, or are not happy with
their heating and cooling system that was either self installed, or
installed by the lowest bidder. They get pissy when they get told that its
going to cost them money to get it done right. They expect their system is
supposed to last forever, but they trade in their $50,000 SUV every other
year. FWIW, the chance of some 'moaner coming on here being one of *MY*
customers, or being in my service area, is about 1 in 4 BILLION.

Its kind of like the idiot that thinks they can price shop over the phone
and call asking "How much is an air conditioner??" when they don't have a
clue what they have or size or efficiency or....
Try calling a car dealership and ask them "How much is a car??". you get
the idea.

Its not our problem when they get told what they don't want to hear.
I have to deal with my own customer base and tell them when its time to
replace their system....its not what they want to hear, but they know its
what they *need* to hear. They know its going to cost them $$$$$$$$ to
replace their system when its time. My customers also know they will get
their moneys worth.....they don't care about low price, they just want it
done right.

Until you can actually show somebody the difference, and the results, they
won't know whats right and whats not. You can get it done by a *COMPETENT*,
licensed, insured, professionally trained, Master HVAC Technician, or you
can get it done cheap. Its your choice.

In the mean time, please go troll alt.home repair......not here.

Thanx



Posted by StarkShark on October 30, 2007, 10:10 pm

>
>
>>> Too bad for them.
>> A surprisingly troll-like attitude. Eat your vitamins and get
>> some sleep. You obviously make some good points, but they don't
>> need to be couched in scorn.
>>
>> You're beginning to make me suspect I stepped in troll feces.
>
> Your close.... but its homeowner feces. Homeowners belong in
> alt.home.repair, not here. this is a forum for professionals *IN THE
> HVAC TRADE*.
My mistake. Thanks for the pointer to home repair.


>
> Most homeowners/slumlords come in here expecting us to tell them how
> to fix their broken 30 year old, Jurassic, furnace for free, or are
> not happy with their heating and cooling system that was either self
> installed, or installed by the lowest bidder. They get pissy when they
> get told that its going to cost them money to get it done right. They
> expect their system is supposed to last forever, but they trade in
> their $50,000 SUV every other year. FWIW, the chance of some 'moaner
> coming on here being one of *MY* customers, or being in my service
> area, is about 1 in 4 BILLION.
I can understand your frustration. That's like my clients that want to
keep adding features to a program, but don't want to pay for the work.

> Its kind of like the idiot that thinks they can price shop over the
> phone and call asking "How much is an air conditioner??" when they
> don't have a clue what they have or size or efficiency or....
> Try calling a car dealership and ask them "How much is a car??". you
> get the idea.
Yes, I do.

>
> Its not our problem when they get told what they don't want to hear.
> I have to deal with my own customer base and tell them when its time
> to replace their system....its not what they want to hear, but they
> know its what they *need* to hear. They know its going to cost them
> $$$$$$$$ to replace their system when its time. My customers also know
> they will get their moneys worth.....they don't care about low price,
> they just want it done right.
>
> Until you can actually show somebody the difference, and the results,
> they won't know whats right and whats not. You can get it done by a
> *COMPETENT*, licensed, insured, professionally trained, Master HVAC
> Technician, or you can get it done cheap. Its your choice.
>
> In the mean time, please go troll alt.home repair......not here.
I'm not a troll here or anywhere. I was attacked. If the first response
I received was "A better place to ask this would be alt.home.repair" I
would have said thank you and moved on.

> Thanx
You're welxome.

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