2.5 Ton vs 3.0 Ton

[Mary9921]

approximately 86 degrees

[Tech Blue]

how cold is the air coming out?

[meoberry]

Sorry, 3 tons is crazy for 1100 sq ft.

If you really require that much cooling, fix the house and ductwork. Throwing larger equipment at the problem won't make it go away.

Chances are that the ductwork isn't sufficient for the 1000 cfm a 2.5 ton unit needs to move, let alone 1200 cfm for 3 tons.

I live and work down here. And I have seen 3 ton units on 1000 sq. foot that would not cool. Depends on how old the house is. How much outside air infiltration there is. And yes y'all made good points about insulation and all. But most of the older homes down here have no insulation under the floors much less any in the exterior walls. As for duct work sizing, Good luck with that in older homes. Most of them don't have enough space in the attic to crawl in much less fitting the right size duct work in. Roofs down here where never meant to shed snow. Just water. Odds are the original duct work was designed for heat only, The payscale is so low down here most people can barely afford the system muchless new duct work. Another question you should ask is do they ever intend to close in the garage. More than likely they will find that the ductwork is to blame for the lack of cooling plus poorly insulated.

[MM#7]

I live and work down here. And I have seen 3 ton units on 1000 sq. foot that would not cool. Depends on how old the house is. How much outside air infiltration there is. And yes y'all made good points about insulation and all. But most of the older homes down here have no insulation under the floors much less any in the exterior walls. As for duct work sizing, Good luck with that in older homes. Most of them don't have enough space in the attic to crawl in much less fitting the right size duct work in. Roofs down here where never meant to shed snow. Just water. Odds are the original duct work was designed for heat only, The payscale is so low down here most people can barely afford the system muchless new duct work. Another question you should ask is do they ever intend to close in the garage. More than likely they will find that the ductwork is to blame for the lack of cooling plus poorly insulated.

good post.

[udarrell]

The preceding posts illustrate why it is very important.to have a Home Energy Efficiency Audit with blower door numbers; later with a Manual J heatgain Calc

In FL.; is there any help available from Power Companies or other sources for the preceding work listed above?
Are there any loans that can be paid back with the utility cost savings?

It would important to use vapor barriers & also get the high humidity infiltration down to the minimum 0.35-Air Changes per Hour (ACH).

If you size for long runtimes with the lowest airflow per tonnage for a colder evap-coil for better humidity control higher temps will work okay; they also said they are comfortable at 80-F.

My advice; use large floor type fans to circulate the air & dress to keep cool; that is a much better cost-effective & comfort option than over-sizing an A/C on undersized heating duct systems that won't cool worth a hoot...

Also, try making the Return Air filter area larger.
http://www.udarrell.com/filters_type...lect_from.html

[Mary9921]

it's pretty cold coming out of the air vents

[Mary9921]

We have pretty good insulation in the ceiling...hubby put it in after hurricane Andrew. And the house was built in 1984. No insulation in the floor or exterior walls

[Mary9921]

Also, was wondering about a variable speed motor...is it worth the extra $$$?
Should I get the unit with the vsm?, as opposed to the one w/out it?

[udarrell]

it's pretty cold coming out of the air vents

Why don't U buy a digital thermometer & a low cost humidity gauge, at a local hardware store, so U & the rest of us know what indoor temp-drop the system is producing at what humidity level.

Also check the temp-rise of the air off the outdoor condenser; all of these easy checks provide important clues to what the system is doing.

It is also critically important that the CFM of the duct system be checked.

[amd]

I live and work down here. And I have seen 3 ton units on 1000 sq. foot that would not cool.

Do those 3 ton units actually provide 3 tons of cooling? 1200 cfm in a small house must be very drafty.

For houses with really bad ductwork which isn't practical to fix, perhaps installing mini-splits is a good option.