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URL:  http://boards.fool.com/the-best-answer-i-can-come-up-with-is-to-have-30424417.aspx

Subject:  Re: Thermostat w/ Remote Sensor Date:  12/10/2012  6:14 PM
Author:  Radish Number:  123322 of 129264

The best answer I can come up with is to have some kind of wall mounted unit which will have the features of the current thermostat, but also a mobile temp sensor which can be moved from room to room.

Honeywell has had thermostats with remote temperature sensors for decades. However, all of them I've looked at average the temperatures, which is completely wrong. To give an extreme example: if the temperature at the main thermostat is 100 degrees and you have one remote temperature sensor which is at 40 degrees, then 100+40/2=70 degrees. If the system is set, say, to heat up to 68 degrees and cool to below 85 degrees, then with one room at 100 and another at 40 it would do nothing since the 70 degree average is between the 68 and 85 degree set points. It should at least turn the fan on whenever the temperatures differ by more than a few degrees, in hopes that the air circulation would even the temperatures out... but it doesn't. In real life the temperatures aren't usually so extreme, but the example illustrates how if the temperature is several degrees too high at one sensor and several degrees too low at another, the system will do nothing to correct that (and this happens in houses, especially when you have a lot of glass and some rooms face south and others north).

It's been a few years since I looked at them. Honeywell pioneered innovations like running the system a certain number of times per hour and varying the run duration (rather than starting the system at one setpoint and continuing to run until the temperature goes a certain number of degrees above/below the setpoint) which greatly reduces swings in temperature in the rooms. Since humans are really good at feeling changes in temperature, minimizing the temperature fluctuations significantly improves comfort. It's hard to believe these people would persist in something as obviously idiotic as simply averaging all the temperatures.

Phil
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