Hotop 1 Pack 24 Volt Transformer, 40 VA AC Transformer Plug in with PTC Fuse Competible with All Versions of Ring Doorbell and Thermostat, Compatible with Nest, Ecobee, Sensi, Honeywell, 24V Adapter

You'll find many doorbell/thermostat transformers on Amazon... many are underpowered. This one is not. It is hefty, and appears well-built. It can handle multiple smart thermostats (to provide the C-wire power). I recommend it, and will use it for all future C-wire/thermostat installs.

I purchased the Hotop 24VAC 40VA plug in transformer to replace the 25.5VAC 25VA plug in power supply that came with my Rainbird ESP-Me irrigation controller. The original power supplies are notorious for breaking, and used ones in good condition go for $70 on EBay. The Hotop plug in transformer is a little over-rated for what the Rainbird system needed, but the Hotop was one of the very few 3 prong grounded 120VAC inputs with a 3 wire 24VAC grounded output that I was able to find to match the original Rainbird power supply. I used the 3 wire cord from the original supply and connected it to the 24VAC screw terminals on the back of the transformer case. The measured voltage output from the Hotop read 27VAC with 124VAC input from my house outlet. The original power supply (25.5VAC output) supplied 29VAC, so I'm not worried as the 27VAC is within the range of the 24VAC control valves in my system. Excellent product for an excellent price.

I installed a Nest Thermostat (the basic non-Learning one) in my home, but was unable to use the transformer on my zone controller - it was way too old and not outputting nearly enough power to keep the thermostat on. This solves the problem! If you have the same problem (2-wire heat only, no Common wire) here's how to power your thermostat. Doing it this way, you'll plug in the transformer near your furnace and won't have to have the wire or transformer visible from your living space. You will need:1. A transformer (this item)2. A Nest Power Connector3. Nest Thermostat already installed and firmware updated4. Pages 10-11 of the Nest Power Connector Pro Installation Guide - The "Pro" guide has the necessary info for installing with an external transformer, the basic version does not.5. Some 18/2 thermostat wire to connect the transformer to the Nest Power Connector.Good luck!

Plenty of current for most needs. Easy to install although its larger and heavier than necessary for a single thermostat. Only complaint is the fact that it gets somewhat warm. Yes, this is normal, but given the load on my application its excessive.

Excellent Product.

I went out of my way to write a review for this transformer after searching endlessly for a compatible AC adaptor for my Google Nest Doorbell Battery version. Google has lots of documentation for the transformer for the wired next doorbell with chime, but nothing for the battery version.This transformer works perfectly with the Google Nest Doorbell, battery version. There were also no instructions so I followed another reviewer here who used it for their Ring camera doorbell and the Google Nest works the same way. Connect the two wires to the two outside posts (0V and 24V), and leave the Ground post blank. After connecting the system up this way and adding the connector provided with my Next Doorbell battery version, the app now shows that it is hardwired for power. The Nest Doorbell battery version will not record 24/7 video, even with a hardwired power connection. You need to buy the non-battery version to get that feature. However, I bought this adaptor specifically so I would no longer need to take the doorbell off to charge so it accomplished that goal.

Used with isolation relay to power Ecobee Smart thermostat.

It comes without wiring info, had to rely on photos on AMZ page.I had a new Ring, so I temporarily wired it with a short piece of new wire just to test everything.First thing I noticed is when I bent a “J” onto the wires to connect , the terminal screws are so close to the indent its all but impossible to get the wire around the screws.Plugged in and pilot light on so all good, except Ring said it didn’t have powerThe thing is very heavy ( which means it probably gets warmer after awhile ) yet the housing has no ventilation. Doesn’t seem like a long term solution.Lastly, the cover came half off when I unplugged it - gently . Didn’t bother wasting more time getting multimeter to test output. Returned it.