These comments originated in my Thread "Thermostat Issues".
I now have validation from two others in addition to myself
that recent digital thermostats have been programmed to
delibrately lie to us!
I just wanted to make this a little more obvious since
its getting buried pretty deep in my original thread.
The stat lies!
I have a TC803, and have found that it does not tell the truth in an apparent (programmed) attempt to make me happy with its accuracy and performance.
The behavior I have observed is that whenever the ambient temperature is within about two degrees of the setpoint then the stat will tell me that the ambient temperature is at the setpoint.
I can catch it at this "little white lie" by making a large ( five degrees or so) change to the setpoint, and the stat will then display the correct ambient temperature. To see this, you need to catch the stat when the ambient temperature has either overshot the setpoint by a degree or two, or when the ambient is approaching the setpoint with only a degree or two left to go. In both situations the stat will display the setpoint as being the ambient temperature until you make the big change to the setpoint and then the stat will display the true ambient.
Had me fooled (dumb and happy) for a while just after the new system was installed. Then I checked the accuracy of the stat with a digital thermometer that displayed tenths of a degree and learned that the stat seems to have been programmed to report sucess with reaching the setpoint a little optimistically.
Most of them. Just raise the temp 2 degrees, and it will report a different temp then it was reading before you changed it.
A couple minutes later, they will revert back.
How many times must one fix something before it is fixed?