No response to my first question so will ask again; maybe HVAC is just too damn complicated for anyone to know the answer.
Will a 410a system work properly without a TXV at the coil?
After half a dozen visits over three years, the latest service tech tells me the installers put the wrong type valve in my Carrier 410a system (38TXA / CD5A) and the system will almost always freeze up to some degree unless it has a TXV. Says he's 100 percent sure that a TXV kit to replace the piston valve near the coil will make the system work right. Says he's never seen a piston valve in a Puron system. None of the other techs ever noticed this; they claimed the problem was line-related, airflow-related or just a poor install. Carrier booklet says the 38TXA is equipped with piston valve but may be upgraded with a 410a TXV. System was installed by a company with a good reputation; service contract is with a company with an excellent reputation. But EVERY service tech has a different explanation; do any of these guys know what the heck they're talking about?