1137 sq feet on it's own a two ton unit should work ok and in some cases 1137 sq feet with a 2 ton would be oversized.

However, load calculations figure things via windows, air volume (height of ceilings, size of doors against a load --- your insulating features of the house etc.)

So if your structure has a number of windows among other load raising issues putting in a 2 ton unit may not keep up under all scenarios especially if you are hitting 105 on a regular basis.

As far as the indoor air handler goes the manufacturer's make tight fit units, but with the pandemic and supply problems effecting things they probably aren't available right now.

On top of all that R410a the refrigerant that the new unit will use is on the cusp of being banned in California by 2025. Unless someone sues or something else your new unit runs low on R410a refrigerant those in Ca may be forced to replace again.

So if you can it *might* be better for you to wait a bit. It is expected that the new refrigerant systems should start showing up later this year / early next year.

Click to enlarge.

I service the Katy, Texas area.

Hi, Oscar,

In California you have Title 24 requirements which need to be met. These affect everything from HVAC equipment sizing to inspections and performance testing. Check with local HVAC experts and find out about the various requirements and how your replacement contractor will meet them.

Two walls are common walls and one is shaded most of the day. the one wall that gets sun is facing east. so only direct sun, until a little past 12:00 pm. I usually keep the thermostat at 78 during the day and 80 after 11:00 pm. it goes down to 76 from 7pm to 11pm to cool the rooms upstairs. and it's been working fine. the machine doesn't seem to either run to oftern or for too long.

Yes, if a permit is requested. And third party leak testing and certain remediation after the work is done is required. The pros in HVAC, in my experience, consider a reasonable effort to do a load calc a starting point for every job. Hacks don’t bother or will fudge the inputs for the result they want.

Title 24 spells out the requirements Elmer notes above.

Duct leakage testing is required for both new construction and replacements of HVAC equipment--even without ductwork modifications (there are different performance standards for each.) Reducing duct leakage can reduce both the initial size and cost of replacement equipment as well as the ongoing operating expense.

As with most things, the OP will be well served to hire a licensed professional and doing things according to code requirements.

As I recall, the leakage testing is to detect 1) leakage problems from old ductwork and its connections, and 2) sloppy work by the HVAC contractor in connecting the new equipment to the existing ductwork and plenums. Which is why it's conducted by a third party.

Also as I recall, when the leakage target is exceeded, leak detection and repair are required only for accessible air pathways. Meaning those ducts and plenums in an attic, a crawlspace or basement (which are rare here), or in a closet. It's not necessary to open up walls or ceilings.

For me, the testing was reassuring but non-events because both locations passed easily. At one, a visual inspection in the walk-in crawlspace (side of a hill) indicated leakage at most metal to metal junctions (dark spots on insulation) so extensive sealing work was done in advance. At the second, the contractor's visual inspection suggested all was well and so it was.