Google Nest Power Connector - C Wire Adapter for Smart Thermostats - 3.98in Accessory

Of the 3 thermostats I replaced with google Nest units in my house, the 2nd floor one I could not pull out and replace the old 2-wire R/W cable. (Two 1st floor thermostat locations I replaced with 3-wire cable). This Power Connector cleverly solves the problem. Attached near boiler controller in basement, it converst the W function of a 2 wire to a C (common) function. That ensures 24V continuous power to keep thermostat continuously up and running. The W function is done by superimposing a signal whereby the Power Connnector implements the R/W relay closure and opening.Be sure that your controller for your heating system has a "C" Terminal- many older (pre 2000) systems don't. If it does not, likely its transformer may be under powered for operting smart thermostats. There are electronics solutions available to augement older controllers to support smart thermostats. (I bought one made by Argo).

See what I did there?…Having bought a Nest thermostat (which installed easily and worked great), I found the installed battery failed after about a year. Replacing the battery in the Nest Learning Thermostat is *not* easy and requires dismantling the thermostat body. When the battery failed, it lost the WiFi connection on account of no power. My A/C guy noted that the circuit doesn’t have a C wire. This wire provides power to the thermostat and without it the thermostat has to rely entirely on the batteries. He offered to run a C wire from the furnace control panel, but that would require a lot of work and a substantial amount of money.This power connector is a much better way. It easily installs at the furnace control panel and basically allows the other wires to provide what musicians call in a microphone “phantom power” to the thermostat.Problem solved. For way less than running a cable through the walls.

Installed a Nest thermostat on my daughter’s condo and found out she only had two wires, red and white with no possibility of running a real C wire due to plaster walls. Confirmed that the furnace had a C wire (critical) and then ordered this dongle. My application was a heat only furnace so the wiring was fairly simple.I strongly recommend that you get three of the wagu type snap-on UL approved wiring connectors unless you have screw terminations to attach to. There are two of the snap on connectors in the box but you will need three more for the furnace side . Trust me - have the connectors handy and installing this device is easy, I tried to use twist on wire nuts but the nuts would no stay on.You need to “tell” the nest thermostat that this adapter was installed during the programming phase on your phone or tablet. Do that slowly because if you miss the check box that says this device was installed the thermostat will not work and the only way to fix it is to delete the thermostat and install it as a new device.Note - This device is specifically designed for the nest thermostat. It will not work as a workaround to add a missing C wire to other thermostat brands.

I recently installed a nest learning thermostat. I did not have a C wire but the nest nevertheless worked fine. I read online that it's a matter of time until getting the battery low error so I thought I'd be proactive and add a charging path for the thermostat.Installation was very simple, opened the HVAC panel, connected the R and Y thermostat wires to this power connector and the R and Y from the connector back to the HVAC board. Additionally, I connected the C wire coming from the connector to the C slot on the board. I used a multimeter to make sure that indeed is a C wire which was pretty obvious as it was coming from secondary of the 110/24 transformer.The annoying part is the nest learning will not give you any indication if the power connector is detected and working or not. This should be added considering this is from Google and not a third-party and the thermostat can get updates. So I had to check the power in the thermostat's settings. I was getting Iin=40 mA with AC OFF and Iin=20 mA when AC ON which is basically the same as having no C connection. To triple check, I then removed the connector and repurposed my G (fan) wire to C slot on the thermostat and the same C slot I used before with the connector at HVAC. Checked my thermostat settings then and I was getting Iin=200 mA which showed the C connection was actually working. Unfortunately, this isn't a feasible solution for me since my AC doesn't automatically turn the fan ON without G connection.I could not find anywhere how this connector is supposed to work but my assumption is it internally switches between R-Y path to R-C path when R-Y is not needed so the thermostat doesn't have to draw so little current from R-Y without making the AC ON or malfunctioning. However this is supposed to work, it obviously didn't for me.I see some people had luck with this item but I am still giving it one star since not only it didn't work for me, the device has no status indicator to tell if it is defective or simply not working with a certain system. They could add some small LEDs or at least they could show on the thermostat or in the app that this is detected and if it is working/not working.