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-   -   HVAC Snafu in my house (http://www.diychatroom.com/f17/hvac-snafu-my-house-69023/)

Cracker Red 04-14-2010 09:43 AM

HVAC Snafu in my house
 
Hello everyone. I appreciate your time and info in this matter.

House is 2700sq ft 2 story home over a basement with 3 walls in the ground.
No trees, largest portion of the house is facing south, neighbors house to the west does provide some shade. Nothing on the east.

Lennox equipment, 3 ton upstairs, 1.5 ton downstairs (outside unit is 1.5 ton, coil/air handler is 2).

Problem: In the summer in GA (Atlanta), the temps can climb to 105, and stay there for weeks. The upstars has no problem cooling to any temp we want, the lower floor will struggle and run all day to keep it at 82deg. Obviously, the power bill is high as well.

I don't mind paying 350 a month for electricity in the summer, given that the house will stay at 70. But doing it to come home to a 82 degree house isn't pleasant.

Thanks guys for your input. I just want to make sure I'm doing the appropriate thing, and don't want to have to pay to have it done twice. I know it's a long read, I was trying to provide as much info as I could to help someone suggest an answer.

Possible reason for the problem:

The 1st floor unit has a 10" return, made of flex duct. The chase that it is in seems like it would be good enough for a 12, and maybe a 14" return.

The registers are few and far between. As best I can tell, there are 2 6" ducts and a single 8" duct coming out of the 1st floor unit. The 8" y's into 2 6", and the other 2 6" go straight through the walls upstairs, down into a torpedo duct on the first floor and then into their own registers.

6 registers in total downstairs.

I'm HOPEFUL that increasing the return to 12 or 14 will solve all the problems I'm having, but I'm thinking it's going to need additional ductwork to get more air downstairs as well. I've found a single spot upstairs where I could place a 8 or 10" duct, which would blow out in the kitchen.

Thoughts, ideas, help!

please :)

-Theo

beenthere 04-14-2010 04:04 PM

What size is the first floor unit?

10" flex duct doesn't move much air. So yes a 12 or 14" will be an improvement. How much is hard to say.

Cracker Red 04-14-2010 04:30 PM

1.5 ton outside compressor, 2.0 ton coil and furnace. 3 years old, 13 seer lennox unit.

Marty S. 04-14-2010 05:03 PM

You need more return and more supplies on first floor. Add two more supplies along with increasing the return size. That still might not be enough,1.5 tons is mighty small for that sized area and 105 degree temps.

beenthere 04-14-2010 06:07 PM

Go with at least a 14" return duct if that chaise has room for it. Without crushing the duct.

A 10" ran the way you say to the kitchen. May end up with enough bends in it. That you don't get much more then another 200 CFM through it. But it would help your system to keep the first floor cooler.
How much can't say from here. It might also make your kitchen a bit too cool.

sweaty 04-14-2010 09:09 PM

You'll get better bang for the buck if you thoroughly seal and insulate your basement and attic first. Do the job once, it saves you money forever. With the tax credit, your neighbors help you pay for it.

Cracker Red 04-15-2010 12:33 AM

Quote:

Originally Posted by beenthere (Post 428742)
Go with at least a 14" return duct if that chaise has room for it. Without crushing the duct.

A 10" ran the way you say to the kitchen. May end up with enough bends in it. That you don't get much more then another 200 CFM through it. But it would help your system to keep the first floor cooler.
How much can't say from here. It might also make your kitchen a bit too cool.

I can deal with a bit too cool if need be. Kitchen/living room (where the thermo is) is all one big room really. It's where we spend 90% of our awake time, and where the house is the most uncomfortable when it's bad (hot) out.

I should have a larger return in the house by Wed, but won't know if it's worked until the summer rolls around. I might just go ahead an upgrade the compressor to a 2ton since R22 units are going to be hard to get soon.

Cracker Red 04-15-2010 12:34 AM

Quote:

Originally Posted by sweaty (Post 428846)
You'll get better bang for the buck if you thoroughly seal and insulate your basement and attic first. Do the job once, it saves you money forever. With the tax credit, your neighbors help you pay for it.


Sweaty, I'm listening. Where do I look for more info?

beenthere 04-15-2010 06:19 AM

Quote:

Originally Posted by Cracker Red (Post 428926)
I might just go ahead an upgrade the compressor to a 2ton since R22 units are going to be hard to get soon.

If you get a new outside unit. You'll probably also need a new inside unit. Since its doubtful your indoor unit is a match to a 13 SEER condenser.

Getting a new 2 ton condenser installed and reusing your current indoor coil. Could reduce the new condensers capacity that its only a 1.7 ton unit.


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