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Posted by on July 28, 2006, 8:53 pm
We recently had central AC installed (oh god, it's heaven after 23
years of Southern Ontario summers...), and I'm wondering if the AC unit
is correctly sized for the house. The unit the company installed is a
3 ton Amana 14 SEER model, which is actually slightly oversized by the
system they use. They recommend 1 ton per 1000 square feet, and the
house is about 2500 square feet, not including the basement (and garage
of course). The house is a bit weird. It's what they call a "great
house" style nowadays, I think. Basically, almost the whole thing is
one big room, and just the bedrooms and laundry room are actually
distinct rooms with doors. I'm told this screws with air flow to the
upstairs quite a bit because of the weird way they have to install
ducts. I'm not sure if it would affect the choice of AC unit size.
Anyhow, it obviously works, and the lack of humidity is great. I keep
it set at 24C (75F) for the most part, which is a comfortable
temperature, and it is able to maintain that even when it gets above
35C (95F) outside. However, if I set it below that, it struggles to
maintain the temperature. For instance, today I tried setting it at
22C (72F) in the morning, and it was able to maintain that until late
afternoon, when it went up to 24 even with the AC running full time.
Outside temperature was 27.5C (82F). Another time, it was not running
in the morning (tripped the breaker in an unrelated incident), and by
the time we noticed, the temperature had gone up to around 27C. We
reset the breaker and set it to 24, and even with it running full time,
the temperature did not go down until the evening. On that day it was
very hot outside, around 36C (97F). I called and asked the company
that installed it about this stuff, and they claim it's normal and not
to worry.
Now, 24 is okay, and I am happy to leave it at that for the most part,
but I'm getting the feeling the unit they installed is undersized for
this house. I have friends who set their AC to 20C (68F) or 21C (70F),
and it doesn't have any trouble maintaining that temperature on hot
days. I know it's not good to have an oversized unit installed, but
it's also not good to have an undersized unit running all the time to
maintain the temperature.
I'd love to hear your thoughts on the subject. I'm not sure whether to
just live with it or try to have the company install a larger unit (or
even if it's actually required).
Chris
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Posted by udarrell on July 28, 2006, 9:07 pm
chrisbirkett@hotmail.com wrote:
>We recently had central AC installed (oh god, it's heaven after 23
>years of Southern Ontario summers...), and I'm wondering if the AC unit
>is correctly sized for the house. The unit the company installed is a
>3 ton Amana 14 SEER model, which is actually slightly oversized by the
>system they use. They recommend 1 ton per 1000 square feet, and the
>house is about 2500 square feet, not including the basement (and garage
>of course). The house is a bit weird. It's what they call a "great
>house" style nowadays, I think. Basically, almost the whole thing is
>one big room, and just the bedrooms and laundry room are actually
>distinct rooms with doors. I'm told this screws with air flow to the
>upstairs quite a bit because of the weird way they have to install
>ducts. I'm not sure if it would affect the choice of AC unit size.
>
>Anyhow, it obviously works, and the lack of humidity is great. I keep
>it set at 24C (75F) for the most part, which is a comfortable
>temperature, and it is able to maintain that even when it gets above
>35C (95F) outside. However, if I set it below that, it struggles to
>maintain the temperature. For instance, today I tried setting it at
>22C (72F) in the morning, and it was able to maintain that until late
>afternoon, when it went up to 24 even with the AC running full time.
>Outside temperature was 27.5C (82F). Another time, it was not running
>in the morning (tripped the breaker in an unrelated incident), and by
>the time we noticed, the temperature had gone up to around 27C. We
>reset the breaker and set it to 24, and even with it running full time,
>the temperature did not go down until the evening. On that day it was
>very hot outside, around 36C (97F). I called and asked the company
>that installed it about this stuff, and they claim it's normal and not
>to worry.
>
>Now, 24 is okay, and I am happy to leave it at that for the most part,
>but I'm getting the feeling the unit they installed is undersized for
>this house. I have friends who set their AC to 20C (68F) or 21C (70F),
>and it doesn't have any trouble maintaining that temperature on hot
>days. I know it's not good to have an oversized unit installed, but
>it's also not good to have an undersized unit running all the time to
>maintain the temperature.
>
>I'd love to hear your thoughts on the subject. I'm not sure whether to
>just live with it or try to have the company install a larger unit (or
>even if it's actually required). Chris
>
>
On hot and/or very humid days if it is sized correctly, it should run a
lot, even most of the time.
It needs long run-time cycles to remove moisture. to achieve the "Human
Comfort Zone."
http://www.udarrell.com/air-conditioning-latent-heat.html
An oversized unit will get it very cold but humid and clammy!
I would keep what you have as it should keep you comfortable.
- udarrell
--
Air Conditioning's Affordable Path to the "Human Comfort Zone Goal"
http://www.udarrell.com/air-conditioning-total-heat-enthalpy-latent-heat.html
Techs:
http://www.udarrell.com/ac-trouble-shooting-superheat-subcooling.html
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Posted by daytona on July 28, 2006, 9:09 pm
Thermostat - set it and forget it
Running all the time....as long as it is running, it is removing humidity
(remember that)
In different parts of North America...systems are sized totally different
than other parts.
I didn't know the glacier receded that far to give Ontario temps higher than
75° (F)
But you don't see temps that high that often...
So my $.02 says it is fine
> We recently had central AC installed (oh god, it's heaven after 23
> years of Southern Ontario summers...), and I'm wondering if the AC unit
> is correctly sized for the house. The unit the company installed is a
> 3 ton Amana 14 SEER model, which is actually slightly oversized by the
> system they use. They recommend 1 ton per 1000 square feet, and the
> house is about 2500 square feet, not including the basement (and garage
> of course). The house is a bit weird. It's what they call a "great
> house" style nowadays, I think. Basically, almost the whole thing is
> one big room, and just the bedrooms and laundry room are actually
> distinct rooms with doors. I'm told this screws with air flow to the
> upstairs quite a bit because of the weird way they have to install
> ducts. I'm not sure if it would affect the choice of AC unit size.
>
> Anyhow, it obviously works, and the lack of humidity is great. I keep
> it set at 24C (75F) for the most part, which is a comfortable
> temperature, and it is able to maintain that even when it gets above
> 35C (95F) outside. However, if I set it below that, it struggles to
> maintain the temperature. For instance, today I tried setting it at
> 22C (72F) in the morning, and it was able to maintain that until late
> afternoon, when it went up to 24 even with the AC running full time.
> Outside temperature was 27.5C (82F). Another time, it was not running
> in the morning (tripped the breaker in an unrelated incident), and by
> the time we noticed, the temperature had gone up to around 27C. We
> reset the breaker and set it to 24, and even with it running full time,
> the temperature did not go down until the evening. On that day it was
> very hot outside, around 36C (97F). I called and asked the company
> that installed it about this stuff, and they claim it's normal and not
> to worry.
>
> Now, 24 is okay, and I am happy to leave it at that for the most part,
> but I'm getting the feeling the unit they installed is undersized for
> this house. I have friends who set their AC to 20C (68F) or 21C (70F),
> and it doesn't have any trouble maintaining that temperature on hot
> days. I know it's not good to have an oversized unit installed, but
> it's also not good to have an undersized unit running all the time to
> maintain the temperature.
>
> I'd love to hear your thoughts on the subject. I'm not sure whether to
> just live with it or try to have the company install a larger unit (or
> even if it's actually required).
>
> Chris
>
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Posted by Chris Birkett on July 28, 2006, 9:15 pm
daytona wrote:
> Thermostat - set it and forget it
> Running all the time....as long as it is running, it is removing humidity
> (remember that)
> In different parts of North America...systems are sized totally different
> than other parts.
>
> I didn't know the glacier receded that far to give Ontario temps higher t=
han
> 75=B0 (F)
> But you don't see temps that high that often...
> So my $.02 says it is fine
Well, for most of July and August the temperature is usually around
30C, higher (38C) or lower (20C) some days, so it's not exactly cool.
Chris
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Posted by udarrell on July 28, 2006, 9:26 pm
chrisbirkett@hotmail.com wrote:
>We recently had central AC installed (oh god, it's heaven after 23
>years of Southern Ontario summers...), and I'm wondering if the AC unit
>is correctly sized for the house. The unit the company installed is a
>3 ton Amana 14 SEER model, which is actually slightly oversized by the
>system they use. They recommend 1 ton per 1000 square feet, and the
>house is about 2500 square feet, not including the basement (and garage
>of course). The house is a bit weird. It's what they call a "great
>house" style nowadays, I think. Basically, almost the whole thing is
>one big room, and just the bedrooms and laundry room are actually
>distinct rooms with doors. I'm told this screws with air flow to the
>upstairs quite a bit because of the weird way they have to install
>ducts. I'm not sure if it would affect the choice of AC unit size.
>
>Anyhow, it obviously works, and the lack of humidity is great. I keep
>it set at 24C (75F) for the most part, which is a comfortable
>temperature, and it is able to maintain that even when it gets above
>35C (95F) outside. However, if I set it below that, it struggles to
>maintain the temperature. For instance, today I tried setting it at
>22C (72F) in the morning, and it was able to maintain that until late
>afternoon, when it went up to 24 even with the AC running full time.
>Outside temperature was 27.5C (82F). Another time, it was not running
>in the morning (tripped the breaker in an unrelated incident), and by
>the time we noticed, the temperature had gone up to around 27C. We
>reset the breaker and set it to 24, and even with it running full time,
>the temperature did not go down until the evening. On that day it was
>very hot outside, around 36C (97F). I called and asked the company
>that installed it about this stuff, and they claim it's normal and not
>to worry.
>
>Now, 24 is okay, and I am happy to leave it at that for the most part,
>but I'm getting the feeling the unit they installed is undersized for
>this house. I have friends who set their AC to 20C (68F) or 21C (70F),
>and it doesn't have any trouble maintaining that temperature on hot
>days. I know it's not good to have an oversized unit installed, but
>it's also not good to have an undersized unit running all the time to
>maintain the temperature.
>
>I'd love to hear your thoughts on the subject. I'm not sure whether to
>just live with it or try to have the company install a larger unit (or
>even if it's actually required). Chris
>
>
On hot and/or very humid days if it is sized correctly, it should run a
lot, even most of the time.
I have a 6,000-Btuh half ton window unit that in SW WI cools over 900
sq. ft., that is 1800 sq. ft. per ton. We have many days with quite high
humidity making it feel like +95-F to over 100-F. Yet it cools the first
floor three rooms and a hallway in an older home to perfect comfort
levels. Well, this first link won't work, it's too long & on two lines.
<A
HREF="http://www.udarrell.com/airconditioner_current_temperature_btuh_charting.html">
It needs long run-time cycles to remove moisture. to achieve the "Human
Comfort Zone."
http://www.udarrell.com/air-conditioning-latent-heat.html
An oversized unit will get it very cold but humid and clammy!
I would keep what you have as it should keep you comfortable.
- udarrell
--
Air Conditioning's Affordable Path to the "Human Comfort Zone Goal"
http://www.udarrell.com/air-conditioning-total-heat-enthalpy-latent-heat.html
Techs:
http://www.udarrell.com/ac-trouble-shooting-superheat-subcooling.html
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