I have installed four new 355CAV042060 furnaces. Intermittent "heat cycle will not shut off", either manually or when satisfied. I have installed well over fifty Evolution systems with Evolution controls, Venstar, Totaline, ect...never a problem. When I called Carrier tech they refused to support Totaline thermostats even though their supply house sold it to me. I called Venstar, and they were actually very helpful. I was told they had recently heard from someone else with the same problem. After calling Carrier tech numerous times with no help, I was finally told by tech support that Carrier has removed resisters in their new circuit boards. I was told by Venstar resisters were needed in the furnace circuit board in order to stop amperage from flowing through Triac circuits. The solutions is simple, use a thermostat which utilizes relays or add a relay between w1 and thermostat. Here is "OUR" problem, until this week, I was not aware of Triac circuits. I am assuming my fellow contractors and their clients are in the dark as well. The danger to life and property will occur when someone installs a Triac based thermostat, such as a Venstar (the most popular thermostat on the market), on a Carrier/Bryant system that does not have resisters in the circuit board. Also, when existing systems have their circuit boards replaced with new style circuit boards, but still utilize Totaline/Venstar thermostats, which the system was originally installed with. I have been fortunate so far, I just have to replace a set of melted horizontal blinds in a classroom. Yes, it got that hot. If this was a residential setting, I could have dead pets or worse. I am very disappointed with the response I have received from Carrier, as I am a advertising factory authorized dealer, and have been for years. I'm sure there are a lot of people on this forum that are better techs than myself. I really hope there was a legitimate reason for the change in the boards other than market share.