New system can't get below 75 on hot day -- accept the work as done?

So I just had a local company install a new, upstairs unit in my home.

Some details on the upstairs: - roughly 1,200 sq feet - 12 foot ceilings - insulated attic above - vents exist from both the upstairs and downstairs unit (downstairs unit helps out)

So, after the installation of the new system (2.5 ton Bryant), the unit could not keep up on a hot day. 84 degrees outside, unit set to 72 and cannot get below 76.

I informed the company, who came back out and installed a second intake return (there was only 1 previously). I was assured this would allow the system to keep up.

Well, it hasn't. 88 degrees outside, unit set to 72 and can't get it below 75.

So I am desperate for advice. I haven't yet received the invoice.

Is it unreasonable to expect this new system to keep up under fairly standard conditions? (it will get hotter this summer!)

If so, what should I be requesting from the company (I can already hear the owner's voice telling me they've done all they can do)?

If I request further work, is it standard to hold payment until the work is complete?

Thanks in advance for any insight!

submitted by /u/DavidDunne
[link] [comments]