Originally Posted By: phughes
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Does anyone have a good rule of thumb for sizing an A/C unit?
Does anyone have a good rule of thumb for sizing an A/C unit?
Originally Posted By: jmyers
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Peter,
The best rule of thumb I could possibly give you when it comes to sizing heating/cooling units is, "leave it to the professional".
It can be frustrating but there are just too many variables when it comes to sizing these units and you are asking for trouble if you comment on the unit size.
Joe Myers
Originally Posted By: phughes
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Thanks
Originally Posted By: jmyers
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Peter,
You are certainly welcome.
Maybe someone here can help you out with a sizing chart or something along that line but if you do come across one us it for your own information and don't share it with the client. Meaning that if you find one you think is undersized call for an evaluation by the professional.
Joe Myers
Originally Posted By: dbush
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Peter, I thought the “rule” was 600 sf per ton. Maybe I’m nuts though. Well, I guess the two aren’t necessarily related.
–
Dave Bush
MAB Member
"LIFE'S TOUGH, WEAR A HELMET"
Originally Posted By: gbeaumont
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Hi Dave & Peter,
Much as I hate being in agreement with Joe..  he's right on this one.
Although the rule of thumb is something to have at the back of your mind there are to many influences on size of AC unit.
1) local climate
2) orientation of house
3) windows of the house
4) thermal efficiency of the house
and those are just the quick ones, up here in New England the ton per 600sq ft would be great in most homes but in the south I think it would be undersized in most properties.
--
Gerry Beaumont
NACHI Education Committee
e-mail : education@nachi.org
NACHI phone 484-429-5466
Inspection Depot Education
gbeaumont@inspectiondepot.com
"Education is a journey, not a destination"
Originally Posted By: Aldo Marcozzi
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| Gerry Beaumont wrote: |
| Hi Dave & Peter,
Much as I hate being in agreement with Joe..  he's right on this one. Although the rule of thumb is something to have at the back of your mind there are to many influences on size of AC unit. 1) local climate 2) orientation of house 3) windows of the house 4) thermal efficiency of the house and those are just the quick ones, up here in New England the ton per 600sq ft would be great in most homes but in the south I think it would be undersized in most properties. |
Peter
Gerry and Joe are both correct: He left on the keyboard the following items:
5) High ceilings
6) Cathedral ceiling (temperature differential in the second floor)
7) Number of Skylites.
Types of construction materials, wall thickness,air infiltration, floor material is also part of size calculation (if you want to be more accurate) and hundred more things. Gerry is right. Just take Joe advise. Inspect only if the system "at the time of inspection" is working or not.
Here is the appropriate rule of thumb( it depends how big is your thumb!!!)
In Florida or similar clime: each ton. of air conditioning cover 450 to 700 sq/f. In Michigan because is colder you need one ton. for every 700 to 1000 sq/f. (info took from NJ study book)
aldo
Originally Posted By: gbeaumont
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Hey Joe,
help it looks like we have some competition in the smartass department
–
Gerry Beaumont
NACHI Education Committee
e-mail : education@nachi.org
NACHI phone 484-429-5466
Inspection Depot Education
gbeaumont@inspectiondepot.com
"Education is a journey, not a destination"
Originally Posted By: jmyers
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Gerry,
I don't think we need any more competition in the smarta$$ department but that Aldo guy is ok, I have spoken with him on occasion. We'll give him a break this time...but the next time we have to go tie up his thumbs! 
Joe Myers
Originally Posted By: Aldo Marcozzi
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| Gerry Beaumont wrote: |
| Hey Joe,
help it looks like we have some competition in the smartass department    |
Gerry
Sorry if I offended you, by all means is the last thing I will do to my friends. Honestly, I thought was funny when I mentioned you left more items in the keyboard.
I also want you to know, that I am not trying to be smart, only informative. I am new in these posts and people don't knows me, Joe do, he knows how much I respect people.
aldo
Originally Posted By: gbeaumont
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Hi Aldo,
no sweat, I was only teasing you no offence heck if I can deal with Joe I can deal with anybody, you to will get used to my sense of humor
–
Gerry Beaumont
NACHI Education Committee
e-mail : education@nachi.org
NACHI phone 484-429-5466
Inspection Depot Education
gbeaumont@inspectiondepot.com
"Education is a journey, not a destination"
Originally Posted By: matthew berman
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Peter and others,here in michigan the rule of thumb is 600 ft. per ton,but i dont recommend you use any rule of thumb and / or mention size being to small or to big.This is not part of a home inspection as you all know.You could be very very wrong by using rule of thumb.It either works or it dont at the time of inspection.Let the pro,s do the sizing, they have all the manuals and formulas-------matt
Originally Posted By: jmyers
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Peter,
I take a thermometer in with me. You could take the temperature of the air coming out the supply duct. Anything above or below 5 degrees depending on the heating or cooling, I consider good. Typically you will find them around 10 degrees and higher. Lower indicates a problem that should be evaluted by a professional. I hope I did not confuse you too badly on that! 
Joe Myers
Originally Posted By: chorne
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Hey guys,
The formula that I use is CFM x temp. difference x1.08=btuh
Although I generally do not report it. Use it for your own
info. and sort of have a base to start from for capacity.
Carla
ps. Joe I havn't heard from you for a while, did you get your
flowers? 
Originally Posted By: jmyers
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Carla,
Thanks for the information. I try to use the simple approach especially when explaining it to the client.
I missed the flowers but I did get a weekend at the shore, peanut butter fudge included (next best thing to some good smelling flowers). 
Joe Myers
Originally Posted By: jhagarty
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–
Joseph Hagarty
HouseMaster / Main Line, PA
joseph.hagarty@housemaster.com
www.householdinspector.com
Phone: 610-399-9864
Fax : 610-399-9865
HouseMaster. Home inspections. Done right.
Originally Posted By: chorne
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hey Joe,
Did you eat the peanut butter fudge!! 
Carla
Originally Posted By: jmyers
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Carla,
OF COURSE!! I don't buy stuff to look at it! 
Joe Myers
Originally Posted By: chorne
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Hey Joe,
Obviously you are of clean mind! Get it yet?
Carla 