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AC Sizing and compatability John 10-03-2008
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Posted by John on October 3, 2008, 8:20 pm


My son and I bought a foreclosure for he and his wife to live in. We
are having Gas heat and electric AC put in. My son is in construction
and was given the name of an HVAC company who gave us a great price.
They are recommending a carrier 120k BTU Gas furance and a 5 ton
carrier AC (where the evaporator mounts on top of furnace). The house
is about 1750 SF but we plan to expand ti to about 2300. Some folks
are telling us these units are too big. and particularly with the AC
too big is not good. (they say it will cool too quick and not remove
the moisture)

By the way - the installer has already installed the 5 ton evaporator
over the furnace. he claims he can still add a 4 ton compressor and
"slow down the fan". Is this viable?

1) What would be the right size AC for this house?
2) can I have an evaporator and compressor taht are different sizes?

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Posted by on October 3, 2008, 8:24 pm



>My son and I bought a foreclosure for he and his wife to live in. We
>are having Gas heat and electric AC put in. My son is in construction
>and was given the name of an HVAC company who gave us a great price.
>They are recommending a carrier 120k BTU Gas furance and a 5 ton
>carrier AC (where the evaporator mounts on top of furnace). The house
>is about 1750 SF but we plan to expand ti to about 2300. Some folks
>are telling us these units are too big. and particularly with the AC
>too big is not good. (they say it will cool too quick and not remove
>the moisture)
>
>By the way - the installer has already installed the 5 ton evaporator
>over the furnace. he claims he can still add a 4 ton compressor and
>"slow down the fan". Is this viable?
>
>1) What would be the right size AC for this house?

        I need a vehicle to do stuff for work. What kind should I
get ?


>2) can I have an evaporator and compressor taht are different sizes?

        You can have whatever you please.


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Posted by Bubba on October 3, 2008, 8:59 pm



>My son and I bought a foreclosure for he and his wife to live in. We
>are having Gas heat and electric AC put in. My son is in construction

Construction? What does he do? Hold a wooden handle and dig holes?

>and was given the name of an HVAC company who gave us a great price.

Good. A great price and a shitty install. What more could you ask for?

>They are recommending a carrier 120k BTU Gas furance and a 5 ton
>carrier AC (where the evaporator mounts on top of furnace). The house
>is about 1750 SF but we plan to expand ti to about 2300. Some folks
>are telling us these units are too big. and particularly with the AC
>too big is not good. (they say it will cool too quick and not remove
>the moisture)
>
>By the way - the installer has already installed the 5 ton evaporator
>over the furnace. he claims he can still add a 4 ton compressor and
>"slow down the fan". Is this viable?

Sounds like you have the cart before the horse?

>1) What would be the right size AC for this house?

That would depend on what the load calculation says. What does it say?

>2) can I have an evaporator and compressor taht are different sizes?

You can have whatever you want.
First I would look for a clue.
Bubba

Posted by Noon-Air on October 3, 2008, 9:25 pm



> My son and I bought a foreclosure for he and his wife to live in. We
> are having Gas heat and electric AC put in. My son is in construction
> and was given the name of an HVAC company who gave us a great price.

Shopping for a comfort system by price only is about the most idiotic thing
you can do.

> They are recommending a carrier 120k BTU Gas furance and a 5 ton
> carrier AC (where the evaporator mounts on top of furnace). The house
> is about 1750 SF but we plan to expand ti to about 2300.

Even at 2300 sqft, I can't feature that any home would need more than about
3 tons, unless it has 12ft high ceilings throughout the house and half the
windows are busted out. Size the system for the *existing* structure. The
only time to upsize the equipment is if the walls for the addition are
already blacked in... otherwise its only a pipedream.

> Some folks
> are telling us these units are too big. and particularly with the AC
> too big is not good. (they say it will cool too quick and not remove
> the moisture)

Listen to them, they are correct.

> By the way - the installer has already installed the 5 ton evaporator
> over the furnace. he claims he can still add a 4 ton compressor and
> "slow down the fan". Is this viable?

Make him take it all out, do Manual J, and Manual D calculations to
correctly size the equipment and ductwork for the home.


> 1) What would be the right size AC for this house?

Can't say without doing the calculations.

> 2) can I have an evaporator and compressor taht are different sizes?

Do you want it to work as it was designed to??

Personally, it sounds like suspiciously like there is no licensed contractor
and that you bought the equipment over the internet, now you have the wrong
size, and don't have a clue how to install it, or what to do with it. Quit
throwing good money after bad, and get it done right.

BTW... did anybody bother to tell you that equipment bought over the
internet voids the warranty???


Posted by John on October 6, 2008, 10:47 am


>
>
> > My son and I bought a foreclosure for he and his wife to live in. We
> > are having Gas heat and electric AC put in. My son is in construction
> > and was given the name of an HVAC company who gave us a great price.
>
> Shopping for a comfort system by price only is about the most idiotic thi=
ng
> you can do.
>
> > They are recommending a carrier 120k BTU Gas furance and a 5 ton
> > carrier AC (where the evaporator mounts on top of furnace). The house
> > is about 1750 SF but we plan to expand ti to about 2300.
>
> Even at 2300 sqft, I can't feature that any home would need more than abo=
ut
> 3 tons, unless it has 12ft high ceilings throughout the house and half th=
e
> windows are busted out. Size the system for the *existing* structure. The
> only time to upsize the equipment is if the walls for the addition are
> already blacked in... otherwise its only a pipedream.
>
> > Some folks
> > are telling us these units are too big. and particularly with the AC
> > too big is not good. (they say it will cool too quick and not remove
> > the moisture)
>
> Listen to them, they are correct.
>
> > By the way - the installer has already installed the 5 ton evaporator
> > over the furnace. he claims he can still add a 4 ton compressor and
> > "slow down the fan". Is this viable?
>
> Make him take it all out, do Manual J, and Manual D calculations to
> correctly size the equipment and ductwork for the home.
>
> > 1) What would be the right size AC for this house?
>
> Can't say without doing the calculations.
>
> > 2) can I have an evaporator and compressor taht are different sizes?
>
> Do you want it to work as it was designed to??
>
> Personally, it sounds like suspiciously like there is no licensed contrac=
tor
> and that you bought the equipment over the internet, now you have the wro=
ng
> size, and don't have a clue how to install it, or what to do with it. Qui=
t
> throwing good money after bad, and get it done right.
>
> BTW... did anybody bother to tell you that equipment bought over the
> internet voids the warranty???

Thanks to all who tried to help me. And to those who felt they need to
reap abuse on me - I have no idea what warranted it

To be clear - this is NOT an internet deal - I would never try to do
something as complex as this a homeowner- I went out to 4 licensed
contractors - all they were told is we want to convert to gas heat (it
was oil hot air but unit was and ADD AC in a 1750 SF house we planned
to grow to 2400 SF. All sizings and costs were left to them. The house
is in Connecticut, was built in 1942 and in the woods - fair amount of
shade. The selected contractor is licensed in the State of NY and has
done many installations - his price was the best but there was no
indication whatsoever there was any issue. Were it not for a person
making a casual comment about the size of the units - I wouldn't even
have been asking these questions. I made every effort to be legit and
this is what I get - an oversized system and abuse from some of you?
Thanks to those who tried to help. I will get with the contractor and
try to get it downsized.



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