Brand new mini-splits not working/contractor seems lost but also made a huge error...

Good morning,

I did my homework, interviewed 5 highly rated companies, and went with the best company and system and day 1 the system is not working correctly. I am in Albuquerque, NM so high dessert with huge daily temp flux and I have a 2 story home 1,435 sq ft with a great deal of solar gain. I switched last week from evaporative cooling to mini-splits. I kept my gas furnace in place. The brand installed is Carrier and below are the details about the units and the compressor.

Since it is July, I have been very stressed about this issue and hot while the contractor is making assurances but the tech who installed and came out to trouble shoot just does not seem to know much in depth. What I have found is that they sold me a compressor that is not large enough for the 4 indoor units they sold me so that is probably problem #1. 4 units need 36,000 BTUs and compressor is for 30,000 BTUs. Now I am loosing heart. This company was vetted by the credit union I used for the loan as well as me. Not feeling like they are competent now but also, not sure what to do. Yes everything is under warranty but if they messed up the basic math on the compressor and they are lost on why the system isn't working. . . . can I really trust them to fix this? Also, is there possible damage now to my indoor units even if they replace the condenser? The 18,000 BTU unit does not cool at all even with all other units off and a reset. Please advise.

Model: 40MAHBQ18XA3 (18K BTU’s Heating/Cooling) Kitchen/Living

Model: 40MAHBQ06XA3 (06K BTU’s Heating/Cooling) BR-1 Model: 40MAHBQ06XA3 (06K BTU’s Heating/Cooling) BR-2 Model: 40MAHBQ06XA3 (06K BTU’s Heating/Cooling) BR-3

Variable Speed with a Digital Inverter Compressor
Outdoor Unit:
MULTI-ZONE CONDENSER
Model: 38MGHBQ30DA3

Issues:

The mini-splits are not working. The large unit is downstairs and does not cool at all. The small units are in the bedrooms upstairs and the one directly above the large unit downstairs over cools by 20+ degrees unless the downstairs unit is off and then it doesn't cool at all. All units are set to cool mode. The other unit in the back with the two problem units does much better and is about 20 feet closer to the compressor but it does lose ability to regulate the temperature when the other units on that side are on though so far only a few degrees. The 4th small unit upstairs on the front of the house is not having problems. All are tied into the 30,000 BTU compressor.

Thank you very much!
Gari