_-Unbeliever-_

_-Unbeliever-_ t1_iy9mg5r wrote

Without a common wire the nest (and other smart stats) use ugly hacks to drop the voltage between R and one of the other control pins. The side effect is that a lower voltage means more current to maintain the same wattage. This can cause damage to both old school transformers and new digital control systems. The nest will also short cycle your system occasionally to charge the battery if there is no C wire and the system isnt running enough.

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