Pull back to 2.5 Ton and be OK?

[RomulanSpy]

Since our house was constructed in '93. We've added large shade trees on west side, tinted all windows and added screening and WILL add more insulation to attic (perhaps bring up to R-49)

Presently, we have a builder-grade 3T Armstrong 10 SEER. With improvements made/will be made-could we go down to a 2 1/2 T unit and still keep the house as nice as our present 3T does? The only time the Armstrong has struggled to cool was during the month of hell in August of 2000.

One caveat that may interfere with this best laid plan is that we're seriously looking at an Amana 18 SEER ASZ18 and AEPF Air Handler for upgrade next spring. Thoughts or suggestions would be appreciated over these next 9-10 months as we move forward in the costly but needed endeavor
thanx yet again.
Rom

[dash]

You probably could ,buthave a load calc done!

[dj3901783]

I see all new homes in Arizona having a 400 sq. ft. per ton set up. Older homes are closer to 450-500 so I'm sure it would be fine. One thing to look at is the fact that the 3 ton unit might actually have a higher seer rating than the smaller unit. Just because a unit says 19 seer it might not be... With a two stage unit you'll be running on the low speed a lot anyway if you're house is well insulated. I would stick with the 3 ton unless I only had 1000 sq. ft., but you'll have to look into those details about the exact seer rating of the units in question.

[ARPA]

I see all new homes in Arizona having a 400 sq. ft. per ton set up. Older homes are closer to 450-500 so I'm sure it would be fine. One thing to look at is the fact that the 3 ton unit might actually have a higher seer rating than the smaller unit. Just because a unit says 19 seer it might not be... With a two stage unit you'll be running on the low speed a lot anyway if you're house is well insulated. I would stick with the 3 ton unless I only had 1000 sq. ft., but you'll have to look into those details about the exact seer rating of the units in question.

How in the "he" double hockey sticks can you even make a statement like that? Are you in this industry? Do you KNOW what calculations you must do to properly......figure the size of equipment needed, the kind of equipment needed, or the proper duct size needed, or even why they are important?
I have one for you. I just bid a home, in Key Largo Florida. 1500 square feet. It comes to 2 tons.
Another home in West Palm Beach, 1200 square feet, needed 3 tons....
Now, how is your "rule of thumb" work here??

Jees............

To the original question. Dash is right. Find someone that does a proper load calculation for you. It's the ONLY way to tell for sure.

[dj3901783]

LOL, I was trying to see where he lived, I'm guessing he doesnt have a custom home with concrete walls or something crazy like hay insulation. Just giving him an example. Also with a 3 ton having let's say 1200 cfm can't be thrown all out of whack by reducing to 1000 cfm can it? Maybe I'm crazy or I just havent had the experience yet...

[hvaclover]

How in the "he" double hockey sticks can you even make a statement like that? Are you in this industry? Do you KNOW what calculations you must do to properly......figure the size of equipment needed, the kind of equipment needed, or the proper duct size needed, or even why they are important?
I have one for you. I just bid a home, in Key Largo Florida. 1500 square feet. It comes to 2 tons.
Another home in West Palm Beach, 1200 square feet, needed 3 tons....
Now, how is your "rule of thumb" work here??

Jees............

To the original question. Dash is right. Find someone that does a proper load calculation for you. It's the ONLY way to tell for sure.

He must have a Telescoping thumb

HEY APRA: What were the main architectural dieeferences between the two homes you just mentioned?

[ARPA]

He must have a Telescoping thumb

HEY APRA: What were the main architectural dieeferences between the two homes you just mentioned?

The home in Key Largo was a special built class 5 hurricane house. 2' thick poured concrete with block glass windows, etc.
The other home, absolutely none what so ever insulation...
I could not belive the calcs. But , after numerous times running them, I installed the systems and they are cooling....perfectly.

[dj3901783]

most new homes have R-30 or R-38 which is slightly more than the older homes, but at 500 sq ft. per ton they keep up just fine... so they're "new" calcs if they are even doing them , are 400 sq. ft. per ton so obviously they are leaving some to spare... unless they are planning on everyone adding on to their house LOL... the solid concrete basement homes I've seen were always 700-1000 sq. ft. per ton...

[RomulanSpy]

The home in Key Largo was a special built class 5 hurricane house. 2' thick poured concrete with block glass windows, etc.
The other home, absolutely none what so ever insulation...
I could not belive the calcs. But , after numerous times running them, I installed the systems and they are cooling....perfectly.

Simply amazing.

Wonder if it'd withstand our annual F-3 tornadoes?

[hvaclover]

The home in Key Largo was a special built class 5 hurricane house. 2' thick poured concrete with block glass windows, etc.
The other home, absolutely none what so ever insulation...
I could not belive the calcs. But , after numerous times running them, I installed the systems and they are cooling....perfectly.

Kinda funny to me because cause in Modern Refrigeration (Class text book)

they gave an example on doing a cooling calc on a 900 sq ft home with no insulation.

Can't remember the design temp but it was a hotter part of the use.

After 6 pages of data the class figured five tons of cooling.

I always thought there was something wrong with the numbers but the instructor hand book showed five tons too.

I'm just glad I know my territory and the building practices that are used.

Makes sizing a lot easier.

[beenthere]

So the new homes hey're building in Arizona have less insulation then the older homes?

[beenthere]

Ask a Vulcan. His logical will tell you to get a load calc done.

Live long and prosper.

[hvaclover]

Man, you have got to change your screen name or you're gonna get hammered.

Pick something sexy like VulcanNymph or something.

Bring back "Enterprise".