3 ms·
I was under the impression that one of the major challenges faced by Nest was running off only the power available by safely drawing from the existing wires. W
by zellyn 13y ago
I was under the impression that one of the major challenges faced by Nest was running off only the power available by safely drawing from the existing wires.
Without that constraint, it's a much easier problem.
- Florin_Andrei 13y agoWait, there's power there? Where from?
- twoodfin 13y agoThermostats turn your heat/AC/fan on and off by connecting and disconnecting an electric circuit. Older analog thermostats did this mechanically; newer ones do it with electronic switches. That circuit has some small amount of current running through it to signal to the heating unit whether it's connected or not. The control circuitry in the heating unit is sensitive to a range of voltage values. It has to be, because V=IR, and there's no way to know exactly how much wire (and thus R) will be strung through your house. The Nest can thus pull some current off the wire to charge its battery but keep the signal strong enough to flip the heater on and off. My house has a new electronic "zone box", which, because it's all semiconductors, only needs to run a very small amount of current through the wires. That's not enough for the Nest to charge. Fortunately, the standard home heating wiring includes a "common" wire, with a low amount of constant voltage suitable for devices like the Nest.
- smackfu 13y agoHere's a description of some of the issues involved: http://www.marco.org/2011/12/17/nest-incompatibility-without-c-wire http://www.marco.org/2011/12/17/nest-incompatibility-without...