Does this sound right, 24 degree temp drop?

[HotEnuf]

Thanks in advance

Location Austin,TX
1660 sf house
50yr old construction (original r-values, minimal attic insul., original windows)

2nd year in house.
Last summer 10+year old AC unit ran mostly non-stop and couldn't get below 80 degrees when it was 100+ outside (which is typical for most of July and August)

Technician (from a reputable company) diagnosed compressor was old and failing= couldn't keep up. Recommended solution: replace air conditioner (and furnace), and ducts, and insulate ducts, and insulate attic. Couldn't afford all of that so just replaced Air conditioner and furnace in the early spring (inside and outside unit Lennox XC14 and Lennox CB30B34 X7001). Now our Avg. outside temp for June was 100 degrees (not looking forward to record breaking July and August) and inside temp still can't get below 79~80 degrees.
The company is reporting a 24 degree temp drop across the system which is what they supposedly design to. Is this what I am stuck with unless I spend more money to insulate the ducts, put in a radient barrier, ventilate and insulate my attic? I could have spent the money on doing all that instead of on the new unit if the inside temp is the same right? And when it gets to 110~112 degrees, is my best hope 90 degrees inside? The technician knew I wasn't getting any work done on the ducts/ insulation- Is there reasonable cause to think the unit may be undersized?
FYI, I have a very pregnant wife and toddler at home and we would like it to be 75 degrees.

[beenthere]

Sounds like you have low air flow issues.

Probably was the problem with your old unit.

Ask them if they can speed up the fan.

Your duct work is probably undersized.

[BaldLoonie]

They should have looked at everything when they sold you the new system. That means run a load calc to see what size the house needs, check size of duct system to be sure it could support the size unit the house needs. The 24° drop says low airflow. So chances are the ducts are undersized for the 2.5 ton so even if you really needed a 3 ton, you don't have the ducts for it. Demand that they do a heat gain calc first thing. If it agrees with the size they installed, then have them check duct sizing and integrity. If undersized, price fairly bring up to snuff. If the A/C is undersized, they should upgrade in size and increase the ductwork at a fair price. They did say you needed more than just a unit & blower so they may have already done this but by not being able to afford it, you may have to put up with what you have til you can.

[davegreenlee]

How do you expect Tech,s to solve the problems without actually being there to evaluate what the problem might be?
It could be a bunch of different thing,s. I find the customers who complain the most are the one,s that tried to cheap out in the first place, going for the cheapest price is not always the best avenue to drive down when all you,ve got is a beginners License.
Not trying to be rude, but you should to do a little research on your installers, after all, you get what you pay for.
A Good Tech will identify your problem, give you a price, if you can afford the alterations, then have them done, and by all means get other quotes.
But asking for online solutions is telling me something already.
Best of Luck

[Phasewolf]

I am a bit confused on this one. What does temp drop on the coil have to do with the outside temp? If it is 100* outside and the ac runs until it is say 80* inside the air from the return is going to be near 80* correct? would it not still drop it 24* from that point or am I missing something here.

[bobRitchie]

I know the pros on this board all are in the business of central A/C.

I have central A/C now, but have lived in a number of homes that
were made quite habitable by a couple of window units.
( Admitedly in Northeastern climates, not TX) If I stay
unemployed my next house might feature window units.

If cash is truly short they can provide a pretty good quick fix.

You can buy the small BTU ones at home depot for $100.
You probably have hot spots where the central isn't doing as
well anyway.

Of course you need to be sure you don't overload your wiring.

[allan38]

Have a radiant barrier installed on the underside of the roof deck and blow in some insulation in the attic. Install some solar screens over the windows that the sun shines directly on. Make sure your ductwork isn't leaking.


Austin Energy has a weatherization program to do much of that.