Reddit reviews Fyve 24 Volt Transformer, C Wire Adapter, Compatible with Nest Honeywell Ecobee Sensi Thermostats, Doorbell Transformer for All Versions of Ring Nest Hello Skybell, Extra Long 25' Cable

Hey there! Sorry that this is happening to you. While I agree with others, it makes no sense that that using your fan wire as a common fixed your issue - But it did! So that's great news for now.

For the record, I have had clients before tell me your same exact story - Their Nest suddenly needed a common after years of it working perfectly. Whether it's due to a surprise update, power outage, or strange anomaly - don't worry, others have been in your shoes. Just another quirk that comes with having the Nest.

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• Here is an adapter of sorts that you were looking for (Plug in outlet common maker): https://www.amazon.com/Adapter-Transformer-Honeywell-Thermostat-Fyve/dp/B075PN6NCV/
  
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• Here is another option (add -a-wire at the air handler): https://www.amazon.com/FAST-STAT-Common-Thermostat-Extender-Connection/dp/B01N6ERM04/
  
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  The "plug in" common wire is by far the easiest method, however you'll have to be creative on how you'll hide the wiring. Hope this helps!

If you don't mind an external transformer near the thermostat, you can just buy this:

https://www.amazon.com/Transformer-Honeywell-Thermostat-Fyve-Global/dp/B075PN6NCV

The wires from the transformer go into Rc and C. Your current wires go into Rh and W. I did this for my parents. Works amazing.

Note that if you dont have an existing C wire and dont wanna run new wire you can also buy a plug-in adapter that fakes it.

24 Volt C-Wire Power Adapter/Transformer for Ecobee Nest Honeywell Emerson Smart WiFi Thermostat by Fyve Global | 25 ft Cable https://www.amazon.com/dp/B075PN6NCV/ref=cm_sw_r_cp_apa_i_bKCwCbMYZWJN9

24 Volt C-Wire Power Adapter/Transformer for Ecobee Nest Honeywell Smart Wifi Thermostat By Fyve Global | 25 Foot Cable https://www.amazon.com/dp/B075PN6NCV/ref=cm_sw_r_cp_api_8kOMBbDXX81VD

If you don’t have an extra wire, you can buy a 24v wall wort to power the nest. It isn’t pretty but it works.

https://www.amazon.com/dp/B075PN6NCV/ref=cm_sw_r_sms_awdb_t1_G6eSAbRZ5368R

Ok just making sure. Call the maintenance guy for the apartement complex and see if he can help you get it sorted. My guess is that you have a standard R and W wire (no idea which is which without seeing the boiler). If you need a C wire, you're going to need to have a plug in transformer.

Am I seeing correctly that this is a wood-burning furnace with electric backup? That's fun- I don't often see those around here (western PA, USA)!


Personally, I get a little nervous about splicing in wires to control boards without photos. It *looks* like you should be ok in this case, but it might be better to just use a plug-in 24V transformer (~$15 USD) https://www.amazon.com/Transformer-Honeywell-Thermostat-Fyve-Global/dp/B075PN6NCV

99% chance you need a C wire. Myself and many others with 2 wire boiler systems were in this boat (even down to getting the same error e195). The good news is that it sounds like you already have a third wire in your walls, even if it isn't hooked up. You could just try and connect the wire to your boiler transformer but I wouldn't recommend this. Those transformers weren't meant to power both the boiler and an additional device (the Nest) and you'll likely see more power problems. Instead, you could purchase a plug-in external transformer, plug it in near your boiler, and send power over the C wire (there's lots of articles on how to do this - it's dead easy). I've been running mine in this configuration for a year with zero e195 errors. I actually had to take the extra step of installing a FastStat CommonMaker to "fake" a third wire as I didn't have one in my walls but luckily you don't have to do that.

**EDIT: You do not require a Nest Pro installer for this... if you were able to install your Nest then you will be able to do the above very easily.

I think your problem is the C wire... per your comment you have RC/W/Y/G... you need a C.

If your unit has a C terminal but unused, you can use the adapter ecobee's include to make a 4 wire system work. If not, then you might need something like this:
https://www.amazon.com/Transformer-Honeywell-Thermostat-Fyve-Global/dp/B075PN6NCV/ref=sr_1_3?ie=UTF8&qid=1511237224&sr=8-3&keywords=c++wire+adapter

in addition to the adapter ecobee includes to give you power. Then treat that as your C... I haven't personally done this, maybe someone here can give you more feedback.

This is the only thermostat on my system....it’s a small house, so just one zone. I found a 24v transformer without the relay that’s included in the venstar, has high reviews. Is the relay aspect in the venstar really needed?

https://www.amazon.com/gp/aw/d/B075PN6NCV/ref=ya_aw_od_pi?ie=UTF8&psc=1

I never tried disconnecting it completely. I bought a power supply from Amazon for it and have it on, but not actually controlling anything.

https://www.amazon.com/gp/product/B075PN6NCV/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1

https://www.amazon.com/Adapter-Transformer-Honeywell-Thermostat-Fyve/dp/B075PN6NCV

This is basically what I need, because there is no options to put one in for my Air Handler/Furnace.

I don't have a c-wire in my steam heat system either. Got a Nest Gen 3 thermostat coz National Grid was selling it for $109 as part of Earth Week. I ordered a plug-in transformer to act as a c-wire. The reviews sound promising. Will report back once I have it installed.

Looks like you have everything you need..should be able to use pek


Or you get one of these

24 Volt Transformer, C-Wire Power Adapter for Nest Honeywell Emerson Sensi, Nest Hello Skybell Smart WiFi Thermostat and Doorbell Power, 25 ft Cable by Fyve Global https://www.amazon.com/dp/B075PN6NCV/ref=cm_sw_r_cp_apa_i_mshRDb7B8FXEX

/u/DrkMith Your post is super clear, and incredibly helpful. Yes, I do run the fan on occasion for circulation. That add-a-wire device seems like magic; very cool and handy and seems like my best option. I watched the video, it's within my capabilities I believe. If you've installed them before, any advice or watchouts?

One other note, if all I need is the C wire to the nest to get the setup to work, could I instead use a 24vac transformer connected to a normal outlet? Something like this: https://www.amazon.com/dp/B075PN6NCV/ref=cm_sw_r_sms_apa_i_Im6QDbHZ0Y450

Thank you for your expertise on this.

I didn't have a c wire at my thermostat, so I bought an adapter on Amazon for around $16. It simply plugs into a nearby outlet.

The one I used is https://www.amazon.com/Adapter-Transformer-Honeywell-Thermostat-Fyve/dp/B075PN6NCV

It comes with installation instructions which are available on the Amazon page. There's also YouTube videos.

You can purchase plug in transformers that provide the voltage for the c-wire depending on your system and thermostat. Here is an example on Amazon: https://www.amazon.com/dp/B075PN6NCV/

The c-wire is suppose to be for providing power to the thermostat. Some thermostats have built in batteries and so the c-wire provides voltage to keep battery charged. Not sure about Ecobee thermostat.

I wonder if adding this to my thermostat would work?

https://www.amazon.com/dp/B075PN6NCV/ref=cm_sw_r_cp_api_8kOMBbDXX81VD

Thank you for the response, @dapala1

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Yes, the two black wires are from the 24V transformer C wire adapter: https://www.amazon.com/Adapter-Transformer-Honeywell-Thermostat-Fyve/dp/B075PN6NCV

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If I tape up the other black wire, the ecobee will not turn on. Should I try something different?

I've seen a few of those and honestly was wondering if they'd work on any thermostat. I've found ones like this https://www.amazon.com/Adapter-Transformer-Honeywell-Thermostat-Fyve/dp/B075PN6NCV/ref=sr_1_3?ie=UTF8&qid=1549852751&sr=8-3&keywords=c+wire+adapter and wondered if I could possibly use it on, say, a Nest thermostat like this one https://www.amazon.com/Nest-T3007ES-Thermostat-Temperature-Generation/dp/B0131RG6VK/ref=sr_1_3?ie=UTF8&qid=1549842584&sr=8-3&keywords=smart+thermostat&vas=%7B%27vw%27%3A%27B01E4FWXY2%27%7D or any other thermostat that required the use of a C wire to operate.

That one looks good. Here is one I found that is rated for the nest but only outputs 300mA.

https://www.amazon.com/Transformer-Honeywell-Thermostat-Fyve-Global/dp/B075PN6NCV

If it only requires 300mA, then either one will work.

Did a little research real quick so I could give you the correct spots to hook it up. here is a link to what you buy and you will hook one to your C port and one to your RC port. It does not matter which one. Also make sure you move that small red jumper cable that’s connecting your RH to your RC.

So basically you will have four wires. (Important to remove the tiny red wire!)
A red and black cable from your wall. Red will go RH and black will go to W.
2 wires from your new transformer. One will go to C and one will go to RC. (Doesn’t matter which one because they can interchange. Plug it into your outlet and you’re all set. Literally takes 5 minutes!

Thanks for all y'all's input! I've got an ecobee3 lite and I'm going to try the 'repurpose G wire as C wire' tactic this evening (we never use the fan independently of the furnace -- pretty sure my wife is unaware that's even an option).

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In the event that doesn't work, my plan is to supply 24V to the thermostat with one of these (which quite conveniently includes a wiring diagram in the product images).

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mad props to this blog post that linked the 24V power supply and goes into a little greater detail.

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quick disclaimer: I am not the author of that blog, nor am I qualified to be offering wiring advice.

I’ve installed many Nests in two wire only heating systems. Unless you have multiple zones, you have a very low chance of needing a common wire installed.

However, if installing a new bundle of wires is something you don’t want to do or don’t have the money for, here is another solution:
24 Volt C-Wire Power Adapter/Transformer for Ecobee Nest Honeywell Emerson Smart WiFi Thermostat by Fyve Global | 25 ft Cable https://www.amazon.com/dp/B075PN6NCV/

Here is an album I took of the control board. I have tried running my own C-wire from an outlet separate from the control board and that did not work for the Ecobee3 lite

this is what I used for that: https://www.amazon.com/Transformer-Honeywell-Thermostat-Fyve-Global/dp/B075PN6NCV

sorry for bothering you again. i found this thermostat voltage adapter on amazon (https://www.amazon.com/Transformer-Honeywell-Thermostat-Fyve-Global/dp/B075PN6NCV). would this work for my system if i use it to power Nest (as there is no C wire). thank you

Maybe? 24 Volt C-Wire Power Adapter/Transformer for Ecobee Nest Honeywell Smart Wifi Thermostat By Fyve Global | 25 Foot Cable https://www.amazon.com/dp/B075PN6NCV/ref=cm_sw_r_cp_apa_i_nl20BbXE66AP7

Here are the wires. The green one comes out at the heater and just hangs (not connected to anything). The wall heater in the bedroom does not have a green wire.


If I purchase an adapter, can I just use it as the C wire?

I got this:

24 Volt Transformer, C-Wire Power Adapter for Ecobee Nest Honeywell Emerson Sensi, Ring Doorbell Pro, Nest Hello, Skybell, Smart WiFi Thermostat and Doorbell Power, 25 ft Cable by Fyve Global https://www.amazon.com/dp/B075PN6NCV/ref=cm_sw_r_cp_apa_i_HTKiDbK0DNCZ1

Unfortunately I can’t run a wire from the unit because I’m in an apartment. Should I keep the jumper and remove the wire going from transformer to RC? (So the transformer would only power the C)

I know these are probably basic questions so I appreciate the help man.

Btw I’m using this type of transformer.
https://www.amazon.com/dp/B075PN6NCV/ref=cm_sw_r_cp_api_i_MXqzDbKY8SWCF