Top critical review
"It don't mean a thing, if it ain't got that swing!"
September 5, 2018
This is an attractive and capable thermostat with a well-designed user interface, but it has one defect that is serious and, for us, fatal. I had read other reviews that mentioned the absence of an adjustable "swing" -- the gap between the "on" and "off" temperatures. That didn't concern me much; but what I didn't realize is that it lacks an effective swing altogether.
Here is what I mean, and why it's a problem. We installed it to control a simple one-zone air conditioning system. (Our heat is on a different thermostat.) During the day there is no obvious problem. It is a different story at night, when there is not much going on inside the house, and the sun is not heating the exterior. The thermostat runs the A/C until the house cools to its target temperature, and then turns off. A little later, it turns on, but just for 30 seconds or so, and then shuts down again. After a few minutes it cycles on and off again. And again. And again.
I think the design is defective. It bases the on/off function on the reading of the digital display. The programmers may have felt that "off" at 77 and "on" at 78 would provide a 1-degree swing, but that is not true. The real temperature may only be oscillating between 77.49 and 77.51 degrees. The result is that the system is, in engineering terminology, is "flailing" between the on and off states that are spaced too close together.
When this happens the system is never "on" long enough to do any actual cooling. What happens is that the fan causes air currents in the room that contains the thermostat, and the moving air causes tiny oscillations above and below the target temperature, which the thermostat reacts to. This is why a thermostat that is using a digital thermometer should always be programmed to have at least a 2-degree "swing," so that the actual swing is at least one degree.
Anyway, my family can all sleep with the A/C on or off, but none of us can sleep with the constant oscillation. For the rest of the family, it's just the noise that keeps them awake. For me, it's the realization of how expensive it is going to be to repair the capacitor and/or the compressor, when they are worn out from constant cycling. So I'm back in the market for a different thermostat.