Question 1

does nest need a c wire

Accepted Answer

Only if you want it to work for more than a year. The instructions and folks here will tell you the c wire isn't required,  but I have found that that is not really true.  Sure, it will work for 6 to 12 months, but then the battery will die. You can then try charging it with a USB cable but the first time you do that you will get a couple days more use from it. After that, it won't last long enough to work. And, if you try to replace the battery there's a good chance that won't work, either and, if you are lucky enough to still be under warranty,  it voids your warranty.  My 2nd nest has just failed and rather than buy a 3rd, or pay an electrician to add a c wire, I am going to replace it with a much less expensive honeywell.

Question 2

does this work with 220v

Accepted Answer

NO, a not. Google Nest is not designed for 220v electrical-baseboard heating systems, and attempting to connect it to such a system will destroy the unit.

However, if your baseboard system is boiler/steam-heated, it WILL work with those, since those are still a low-voltage system that simply opens & closes a valve to regulate temperature.

On a side note, it is utterly dreadful just how poor the quality other answers here are. Do people honestly not know what 220v is in relation to heating? Folks, simply enough, if you don't know the answer, then DON'T respond.

Question 3

How does it detect when you're home? If we're gone and kids are home with a babysitter, will it know someone's home? Or is it based on cell location?

Accepted Answer

If you add Nest Protect smoke/CO detectors, the system will also use their motion detectors to sense if you're home.  This can be useful if the thermostat is located somewhere that doesn't get much foot traffic or if you spend long hours in another room.

Question 4

Can the Nest replace my current Nexia thermostat ?

Accepted Answer

You will have to get a wiring diagram to see if nest is compatible.

ASIN	B01MXC366M
Additional Features	Programmable
Backlight	Yes
Best Sellers Rank	#17,866 in Tools & Home Improvement ( See Top 100 in Tools & Home Improvement ) #75 in Home Thermostats & Accessories
Brand Name	Google
Color	White
Connectivity Protocol	Wi-Fi
Connectivity Technology	Wi-Fi
Control Method	App
Control Type	Remote Control
Controller Type	WiFi
Customer Reviews	4.4 4.4 out of 5 stars (10,300)
Display Type	LCD
Finish Types	Unfinished
Global Trade Identification Number	00813917020203, 08907758011116
Included Components	Display, Base, Nest Pro installation card, Installation And Welcome Guide, Mounting screws and labels, Nest screwdriver, Optional Trim Plate
Item Dimensions D x W x H	8.4D x 8.4W x 2.8H centimeters
Item Type Name	Thermostat
Item Weight	1 Pounds
Manufacturer	Nest
Manufacturer Part Number	T3017US
Material Type	Metal
Model Name	T3017US
Model Number	T3017US
Mounting Type	दीवार माउट
Number of Batteries	1 Lithium Ion batteries required. (included)
Power Source	Corded Electric
Product Style	Minimalist
Screen Size	2.1 Inches
Shape	Square
Specific Uses For Product	Air conditioning, Heating, Ventilation systems, Heat pumps
Specification Met	Energy
Temperature Control Type	Automatic
UPC	642892801039 813917020203
Voltage	24 Volts

Nest 3rd Generation learning programmable Thermostat White T3017US

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