Lennox Gas/Electric Pak won't cool below 83F

[mayahere]

Last November we replaced a 20+ year old hvac system with a 3.5 ton Lennox 13GCSXA-42083X gas/electric packaged unit. The heating element on the old system had gone out and our home warranty company arranged to have the Lennox unit installed. The house is a one-story that is approximately 1,400sf. The house is in Las Vegas, NV and we have tenants in it. A few weeks ago, late-June, the tenants reported they could not get the house to cool below 84-85F. We called the home warranty company who sent out techs from two different companies. Both found the unit was working properly ie air leaving the vents was 61F. The last one indicated these units had not been tested in heat above 95F by the manufacturer and really struggle to keep up in the summer. He said the new EPA freon was also a reason. Are these units appropriate for Las Vegas summers of 105 -115F? Our 20yr plus unit keep the house comfortable so we do not think it is in insulation or duct issue. Is there anything we can do? Not being able to cool the house below 83-84F during the summer is really a problem especially because this is a rental. We put in a new thermostat, my husband retaped ducts and added additional insulation. I am assuming hot air in the house is not getting pulled out sufficiently but I don't know. Please help with ideas. The home warranty company is shockingly not being particularly helpful. There are ceiling fans throughout the house that run constantly and the tenants change the indoor filter monthly. Thanks so much.

[Freon]

Do you remember the size (tons) of the old system? If it was 3.5 tons or less then the cooling should be the same as before. Since this system is less than 1 year old I would also have the installing company come and check. I assume their warranty is for 1 year. As a stop-gap, consider letting the tenants use window AC units. Home repair warranties are not worth the paper they're printed on.