VIIVRIA 24V Transformer with C Wire Adapter

I was so glad I came across this item.
I purchased my Ring doorbell and Chime about two years ago and sit in a bag because I didn’t understand how to install a jumper with my existing doorbell. (I’m sure it was probably simple, but I am not good with wiring.) So now I had moved into an apartment with no pre-existing doorbell. This made it so much simpler. Easy instructions and works perfectly.
My next house this product is going with me.

I initially installed this with the base model Nest Thermostat. There’s another review with pictures showing how to set it up. However, it did not work in my case. The Nest freaked out- it was showing the temperature as being way higher than it actually was (+15 F!!!), and I even got an email from Google saying I should immediately unplug the c-wire adaptor to avoid damage to my thermostat. So no, this adaptor is not always compatible with the devices that it claims. A lot is subject to your particular HVAC setup and its peculiarities.

I ended up returning my Nest and getting an Ecobee 3 lite instead. The c-wire adaptor seems to be working perfectly with it without any issues (so far).

I’ll give some advice, including repeating what the other reviews have mentioned so that you can have an easier installation process.

First, other than the lack of a c-wire, make sure your wiring and heating system is compatible with the smart thermostat you’re using. Your thermostat company of choice should have a compatibility checker.

Second, once you plug this in, the wire is LIVE. It should go without saying that you should INSTALL FIRST, PLUG IN SECOND.

Third, if you own your home, i.e. you have the ability to mess with your HVAC wiring, just do that and forget about this product. You’ll likely lose independent fan control but I don’t see why that matters unless your fan is also a de-humidifier (in which case the situation might arise where you might want to run your fan without also running heat/cool). I live in an apartment and my fan is also a dehumidifier, so I’m a good case for this product.

Lastly, This adaptor has two wires. One has a black stripe on it and the other one is plain white. I read in another review that these do different things, though I haven’t tested the voltage/polarity myself. the white wire, without the black stripe, goes in C. My system has 4 wires: G, Y, R, W. When installing an Ecobee (probably also works with the fancier Nest thermostats, and some may have success with the base model Nest), the black-stripe wire gets bunched in with the R wire in the Rc slot, and the white-only wire goes in C. The wires in this adaptor are pretty thin but it can still be tough to fit it in with your R-wire. Other than that, follow all instructions in the instruction manual of your thermostat.

Hope this is helpful!

It’s fine with the Wyze thermostat. I didn’t have a C wire so this was the cheapest and easiest route. Ran the plug from the attic down behind the wall where the existing thermostat wires came out. Connected the white/black striped wire to the R input along with the red wire, and the solid white wire to the C input. Kicked on right away. No issues.

I took a star off because while the instruction may not be wrong but did not work for me. Here is how I get my Amazon Thermostat to work. Here are some facts first-

1. The HVAC does have a C wire but could not power the Amazon Thermostat, it appears that my HVAC C wire has 24 volts but not enough current (amps) to power the Thermostat. Hence need to add the transformer.
2. I live in Florida, so the heating and the AC are in one unit, that means the R(H) and RC are jumped together with only 1 Red wire.
3. I can’t say for other areas but in South Florida this way will work.
4. When I followed the transformer instruction and mirror to the Amazon Thermostat, push the right button to connect one transformer wire to RH and the other wire to C and the Red wire from HVAC to R. I only get heat and not AC.
5. To correct the issue and viewed at least DIY videos and learn to fix it. You need to merge the Red wire and one of the transformer power wire to a new leg that can insert into the R with the bottom right blue clip pushed up to allow the R and RC jumper to connect internally.

Once that was done, everything work correctly. I have have heat and AC. The reason that I had only heat but not AC, because the R in the Amazon Thermostat is for “HEAT” and since you push the right blue clipper down, it disconnect the R and RC. There for there is no power sent to the AC unit.
Since the the Amazon Thermostat cannot easily jump the connectors, then you must introduce a 3rd wire for the R connection with transformer power wire, Red from HVAC, bundle all three wire together.

Hope this help you to install without a C wire or low amperage C wire. I have to say the Thermostat works great. Good luck.