Outdated/ Inefficient Design

[Lodesert_Dan]

Hello,

I have a question about the design of an HVAC "system" in our home. What concerns me is that there is no return air ducting.

The air handler and compressor unit are brand new 14 SEER Lennox eguipment, 2.5 ton capacity. It is 104 degrees outside, and the system runs continuously- AND will only cool the house to about 79 degrees.

The evaporative cooler works better than this- BETTER than a refrigerant system??

The structure being cooled is an 1100 sq ft block house with a rectangular footprint (approximately 43' x 25')- having the typical living room/dining area/kitchen on one half of the home, with the bedrooms/bathrooms in the other half.

A long hallway separates the bedrooms in the middle of the house, and this is where nearly all of the air circulation takes place:
The air handler is in a closet at the west end of the home (at the end of said hallway), and the largest air delivery duct is at the east end of the hallway in the living room.

Is there any way to increase airflow through the air handler or improve air circulation?
I'm baffled by this- as the air handler sits on a "shelf" (with a hole in it, of course), and the door to the closet is currently open. We tolerated the old system last year: running constantly, barely cooling the house- thinking that it was just "Old". Now, with new equipment, it appears that the design of the system is simply too inefficient, and that there's really no way to add return air ducting.

Thanks so much for your input.

Dan

[Joe Harper]

104 outside, 79 inside...your doing excellent. Your system is probably a little oversized. You should only expect a 20 degree difference from outside to inside temp.

[Shophound]

No return? So how is this air handler getting any air?

Post some pics if you want to see a lot of discussion here on your post.

[beenthere]

Might have some duct leakage.
call your contractor back to check it.

[Shophound]

104 outside, 79 inside...your doing excellent. Your system is probably a little oversized. You should only expect a 20 degree difference from outside to inside temp.

This is not always the case. My own house is 1,800 square feet. Last summer we reached 105 on two days over a weekend. My a/c system is 3 tons. It not only held my setpoint of 75 degrees, it cycled. Indoor humidity levels also stayed below 50% (which is not astounding, being that outdoor dewpoints tend to drop at 105 degrees dry bulb, even in Texas). In short, with a well tuned a/c and a building envelope that is insulated better and is more airtight than average, stick frame or block construction can be kept 30 degrees below 105 without undue heartburn.

OP's a/c sounds hacked in, and who knows how well his structure is insulated?

[Lodesert_Dan]

No return? So how is this air handler getting any air?

Post some pics if you want to see a lot of discussion here on your post.


It's getting air through the bottom. It sits on a shelf about about 19" off the ground, but there is no ducting, just a hole.
It's my understanding that this may limit the air circulation (?)


I'll post a photo shortly.

Thanks

[Lodesert_Dan]

104 outside, 79 inside...your doing excellent. Your system is probably a little oversized. You should only expect a 20 degree difference from outside to inside temp.


The thermostat is really close to the air handler-- it's another 3-4 degrees warmer in the east end of the house.
People here are used to living/shopping/working in about a 74-76°. Even when it hits 112°--No kidding.

[Lodesert_Dan]

OP's a/c sounds hacked in, and who knows how well his structure is insulated?


We also own a 1200 sq ft, TWO story condominium here, it uses a very similar split system except that the returns are ducted through the ceilings in a couple of spots. It cools extremely well, and does cycle, even when it gets REALLY hot.

[Lodesert_Dan]

Might have some duct leakage.
call your contractor back to check it.

Yeah, I wouldn't be surprised. We had someone in the attic to install some can lights recently, too-- it's a real tight fit.

[Joe Harper]

This is not always the case. My own house is 1,800 square feet. Last summer we reached 105 on two days over a weekend. My a/c system is 3 tons. It not only held my setpoint of 75 degrees, it cycled. Indoor humidity levels also stayed below 50% (which is not astounding, being that outdoor dewpoints tend to drop at 105 degrees dry bulb, even in Texas). In short, with a well tuned a/c and a building envelope that is insulated better and is more airtight than average, stick frame or block construction can be kept 30 degrees below 105 without undue heartburn.

OP's a/c sounds hacked in, and who knows how well his structure is insulated?

I guess my point being if I do a heat load calc im using the 95/75 values. I wouldnt expect to get much more than a 20 split. Im sure that the larger coil on a high eff unit helps with the max condensing temp on those hot days.

[Lodesert_Dan]

Post some pics if you want to see a lot of discussion here on your post.

here's one

[beenthere]

That belongs posted on the wall of SHAME.

[Lodesert_Dan]

That belongs posted on the wall of SHAME.


Huh!? :eek:

[motoguy128]

Huh!? :eek:

That's not a proper retrun or supply plenum. It's pretty much hacked in. I'd guess you're not getting adequate ariflow and.or have lots of duct leakage as mentioned before.

In dry desert climates, you need lots of airflow for maximum sensible capacity, since humidity is not an issue.

[Lodesert_Dan]

That's not a proper retrun or supply plenum. It's pretty much hacked in. I'd guess you're not getting adequate ariflow and.or have lots of duct leakage as mentioned before.

In dry desert climates, you need lots of airflow for maximum sensible capacity, since humidity is not an issue.


Ok- so the design of the plenum can make that much difference?
The duct that runs the length of the house is only about 18" above the top of the air handler.

I plan on getting up in the attic to check over the ducting.