I have a 5-yr old 1,600 s.f. (single story) townhome in Houston, built in 07. The builder-grade LENNOX A/C is a 3-ton unit that until recently had been working fine (conventional box/A-Coil w/TXV, not a slab). (R410A) A couple weeks ago we noticed it not cooling well & unable to achieve 75-degree set point (wife going through 'the change' so greenies pls don't lecture me). Before doing anything I checked the return air (80 deg) and register temp (72 deg) nearest the plenum. Outside temp 95. Obviously something wrong. Amprobe showing 9A which seemed about normal, perhaps a little low, data plate shows RLA is 14A.
We called the same co. we've used & trusted for years tho they's recently changed ownership. (they also come every spring and fall for seasonal inspection, media filter changes, etc). The tech says low refrigerant, performs leak check but initially finds nothing, later discovers small leak at needle valve where manifold gauges attach. He evacuates the system & replaces an o-ring seal, pumps it down & recharges, adding 2 lbs of coolant. However, only minimal improvement. 80 deg return, 68 at register. Tech says should be at least 15 deg w/18~20 optimum. (Amprobe now showing 12A). System pressure showing 400 psi high side and 140 low side (indoor temp 76). Tech trying to talk me into replacing the TXV with a piston. I think I'm ready for a second opinion. Thanks.