Nest power connector that installs in furnace that supplies addition
current to thermostat for charging, also fully charged by micro usb on
back 24 hrs before putting back on sub base has worked great for last
three months.
If you have a two wire install nest makes a device that sits in furnace
you still have two wire install so not running new Tatar wires but
device hooks into common , R,W then you attach Tstat R and W to device.
Not sure how this works but increase ch...