Home Repair forum - A/C system advice for 2 story residential

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A/C system advice for 2 story residential

Bill

2007-05-28, 9:25 pm

We have a 40 year old Florida home 2450 sq. ft. with large windows;
also 1 acre lot with lots of big/tall oak shade trees. We currently
have an outside older 3 ton Trane A/C unit (rated 10 seer) which is
underpowered but with the help of a couple of upstairs window units we
do ok. I think its time to upgrade/replace the Trane; what I am
thinking is a 4 ton higher efficient (maybe 14 or 16) unit. My wife
thinks that if we replace with another 3 ton higher efficient AND
install a smaller unit for upstairs - programmable so that the bottom
primarily runs during the day and the top primarily at night (upstairs
is all bedrooms) we would possibly be more efficient and cooler.
Obviously big up front install costs for upstairs unit but if we are
willing to absorb those - is this usually the more efficient way to
go? Thanks in advance - Bill

Bill Stock

2007-05-29, 3:25 am

"Bill" <bspratt@yahoo.com> wrote in message
news:1180404252.237281.203420@p47g2000hsd.googlegroups.com...
> We have a 40 year old Florida home 2450 sq. ft. with large windows;
> also 1 acre lot with lots of big/tall oak shade trees. We currently
> have an outside older 3 ton Trane A/C unit (rated 10 seer) which is
> underpowered but with the help of a couple of upstairs window units we
> do ok. I think its time to upgrade/replace the Trane; what I am
> thinking is a 4 ton higher efficient (maybe 14 or 16) unit. My wife
> thinks that if we replace with another 3 ton higher efficient AND
> install a smaller unit for upstairs - programmable so that the bottom
> primarily runs during the day and the top primarily at night (upstairs
> is all bedrooms) we would possibly be more efficient and cooler.
> Obviously big up front install costs for upstairs unit but if we are
> willing to absorb those - is this usually the more efficient way to
> go? Thanks in advance - Bill

I'm in a similar boat, 3 ton unit with one window unit upstairs, but in a
cooler climate and about 3500 sq. ft. South facing upstairs rooms can reach
85+ with the AC running. The best solution would be a multi unit mini-split,
but it comes in around 12K. A 4 ton unit might help some, but our ductwork
sucks, so a mini split would be a better option. I bought a portable last
year, but the aluminum wiring couldn't handle the load over the long haul.
Plus it's a PITA to use with the casement windows.

Depending on your situation a separate unit for upstairs is probably the way
to go. I might buy a single mini for the one room in the short term.

udarrell

2007-05-29, 3:25 am

Bill Stock wrote:

>"Bill" <bspratt@yahoo.com> wrote in message
>news:1180404252.237281.203420@p47g2000hsd.googlegroups.com...
>
>
YES.
[color=darkred]
>I'm in a similar boat, 3 ton unit with one window unit upstairs, but in a
>cooler climate and about 3500 sq. ft. South facing upstairs rooms can reach
>85+ with the AC running. The best solution would be a multi unit mini-split,
>but it comes in around 12K. A 4 ton unit might help some, but our ductwork
>sucks, so a mini split would be a better option. I bought a portable last
>year, but the aluminum wiring couldn't handle the load over the long haul.
>Plus it's a PITA to use with the casement windows.
>
>Depending on your situation a separate unit for upstairs is probably the way
>to go. I might buy a single mini for the one room in the short term.
>
>
Window units cost a lot less than mini-splits, plus smaller BTUH
ratings, and a small bedroom does not need a lot of BTUH to cool at night.
Do a manual J on each room to get a number on heat-gain.
http://www.udarrell.com/airconditio...h_charting.html

Half-Ton Room A/C - Cools over 900 sq.ft. @ 104 HT Index - Daytime,
entire first floor in older 1930's house
- udarrell

--
WISDOM PRINCIPLE DIRECTED EMPOWERMENT COMMUNICATIONS -
THE REAL POLITICAL ISSUES and WISDOM BASED PEOPLE EMPOWERMENT
http://www.udarrell.com/
http://www.udarrell.com/my_pages2.htm ***
http://www.udarrell.com/recognizing_real_enemies.html
http://jesuschristsavior.net/Beatitudes.html
Reality Is Not An Easy Thing To Be Confronted With, or to Accept!

Bill

2007-05-29, 1:25 pm

On May 28, 11:10 pm, udarrell <anonymo...@anonymous.com> wrote:
> Bill Stock wrote:
>
>
> YES.
>
>
>
> Window units cost a lot less than mini-splits, plus smaller BTUH
> ratings, and a small bedroom does not need a lot of BTUH to cool at night.
> Do a manual J on each room to get a number on heat-gain.http://www.udarrell.com/airconditio...e_btuh_chart...
>
> Half-Ton Room A/C - Cools over 900 sq.ft. @ 104 HT Index - Daytime,
> entire first floor in older 1930's house
> - udarrell
>
> --
> WISDOM PRINCIPLE DIRECTED EMPOWERMENT COMMUNICATIONS -
> THE REAL POLITICAL ISSUES and WISDOM BASED PEOPLE EMPOWERMENThttp://www.udarrell.com/http://www.udarrell.com/my_pages2.htm***http://www.udarrell.com/recognizing...Beatitudes.html
> Reality Is Not An Easy Thing To Be Confronted With, or to Accept!- Hide quoted text -
>
> - Show quoted text -

Thanks for the response - I guess what I'm really asking is if we are
willing to "eat" the installation costs, would our power bill go up or
down with 2nd unit upstairs? We have 4 bedrooms that each will have a
window unit vs the central unit.

Stormin Mormon

2007-06-02, 9:25 am

Just cause your system has a 3 ton name plate, doesn't guarantee
you're getting three tons of cooling. I'm remembering a call I
had last year. the fellow had a 3.5 ton AC, and it wasn't cooling
the house. He was thinking maybe needed 5 tons. I asked his
permission to service the unit, and when I finished, it was
cooling just fine.

You may replace the system if you like, but it's possible that a
good servicing would get you by for several more years.

--

Christopher A. Young
You can't shout down a troll.
You have to starve them.
..

"Bill" <bspratt@yahoo.com> wrote in message
news:1180404252.237281.203420@p47g2000hsd.googlegroups.com...
: We have a 40 year old Florida home 2450 sq. ft. with large
windows;
: also 1 acre lot with lots of big/tall oak shade trees. We
currently
: have an outside older 3 ton Trane A/C unit (rated 10 seer)
which is
: underpowered but with the help of a couple of upstairs window
units we
: do ok. I think its time to upgrade/replace the Trane; what I am
: thinking is a 4 ton higher efficient (maybe 14 or 16) unit. My
wife
: thinks that if we replace with another 3 ton higher efficient
AND
: install a smaller unit for upstairs - programmable so that the
bottom
: primarily runs during the day and the top primarily at night
(upstairs
: is all bedrooms) we would possibly be more efficient and
cooler.
: Obviously big up front install costs for upstairs unit but if
we are
: willing to absorb those - is this usually the more efficient
way to
: go? Thanks in advance - Bill
:

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