Review on Black 24 Volt Transformer & C Wire Adapter for Ecobee, Nest, Honeywell Smart WiFi Thermostats, Ring, Blink Video, Nest Hello, Skybell, August Doorbell: Power Supply Compatibility by Tommie Lawson

My Nest E thermostat worked for a couple of weeks but when it got really cold I got cold air instead of heat. I investigated the problem and adding a common 24V power supply helped solve the problem for others. The hotop transformer seemed like the perfect solution and it came with a long cable. I ran two wires from the transformer to the nest, connected one to C (common) and added the other to the red wire connection. It didn't work at first so I switched the wires from the transformer and then it worked fine showing 24V input on terminal C. The outlet is now working fine. My only concern is that the transformer wires are not solid copper like the wiring for the jack should be. I'm not sure if this could become an issue later, but Nest is fine for now.