I have never lived in a house with an AC that was "too big" but have
been in many with an AC that was too small. Some of them have to run
nearly continuously to struggle to maintain a decent temp. Whatever a
sensible design program comes up with I would round up another half
ton unless I was really really sure it's answer was good enough.
On Thu, 8 Feb 2007 19:21:30 -0800, "Martino"
wrote:
This is where my knowledge was (way) off, I guess. The software's Seattle
default summer dry and web b. values were 82 and 66 respectively and I
overwrote the higher one. With 80 and 64 (per your comments) the output is
as follows:
4.14 tons (based on latent + sensible)
5.15 tons (based on 75% sensible capacity)
My house is fairly large (5,700 sq. ft) and has large window areas and a
number of cathedral ceilings. Knowing that many units are 5 tons max (as
one of you also mentioned) I wonder if a 5 tone unit will be adequate.
Thanks for pointing the error
"udarrell" wrote in message
t...
Martino wrote:
Many local HVAC companies just guess the size of the AC unit and therefore
I
decided to run my new house data through a Manual J compliant software.
Depending on design summer temperature I obtain the following AC size (in
tons) recommendations
Summer Temp Size 1 Size 2
90F 4.76 6.02
95F 5.04 6.46
100F 5.32 6.89
105F 5.61 7.33
The house is being build near Seattle where the max summer temp rarely
exceeds 105F but gets to 100F for a week or so during summer. 90F can
stay
with us for few weeks per summer.
I am a bit confused about two sizing recommendations:
Size 1 is based on sensible and latent heat gain
Size 2 is based on 75% Sensible Capacity
I do not want to oversize my A/C unit but I do not want to significantly
undersize it either. What do you think? Thanks.
First off, you have to use the summer design conditions for your area!
Washington, Seattle-Tacoma airport, Official listed Summer Design is 80
dry bulb & 64 wet bulb, or around a low 41% relative humidity.
Therefore, you are using Summer Design temperatures that are way too high!
Run the above 80-F dry bulb & 64-F wet bulb temps through your manual J
software, then tell us what you get.
How many square footage is your home? Did you figure the heat-gain
correctly?
The ductwork & airflow is critical to efficient operation!
http://www.udarrell.com/proper_cfm_b...syste ms.html
- udarrell
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WISDOM PRINCIPLED EMPOWERMENT COMMUNICATIONS - THE REAL POLITICAL ISSUES
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