Looking for some help with a High Efficeincy Unit and how Econet works

I upgraded my Central Unit recently. It has a Seer rating of 17 and it is a variable speed unit. Problem I am having is the Thermostat’s very slow response time. For instance, I raised the thermostat from 68 to 69 because if felt damp inside the house. I went to pay bills on the computer and forgot about the heater. All of a sudden it dawned on me how hot the room was and that the heater was still running. So I went to the Econet thermostat to turn the unit off. While it was running it was showing 68 room temperature and 69 setting. After the unit was shut off, the temperature started climbing and within 2-3 mins it was reading 72 degrees. Any ideas? It does not appear to happen when it is cooling. How is that possible? This is the second issue I had with the Rheem in a month in which it was installed . First issue was the control valve to hold head pressure on compressor was not working causing a low freon pressure shut down. Please tell me I did not buy a piece of junk!