How are you all doing?

I tried to connect the digital thermostat (Ecobee3) instead of my old honeywell thermostat. The original wiring is below (figure 1) Figure 1

HVAC is located on the ceiling of bathroom and looks like these. FYI, there is no board or control center for it. The blue wire in this picture is the free wire I would like to use for C wire (figure 2). It is not connected to any wire or transformer. The end of wire is just free. Figure 2

It might seem like there are separate transformers for AC and heater. The Y wire is from one wire bundle (Figure 3). Figure 3

R wire which was hooked up at Rc in my old thermostat, G wire and W wire all are connected to a part which seems like a transformer (figure 4 and 5) enter image description here enter image description here

I did 2 different connections.

a. I connected free blue wire to the blue wire which is stretched out from transformer (in figure 5 at the bottom). The thermostat was not turned on and just blinking.

b. I connected free blue wire to the black (or brown) wire at the same point depicted in figure 2. Thermostat was successfully turned on but when I tried to turn the AC on, there was a burning (because I smelled something burning) and I shut the power off. I don't know where the burning was.

I have no idea how I can connect free blue colored wire to which part of transformer to supply 24V to thermostat.

I am absolutely new to this electrical thing so please kindly suggest or recommend me a good solution. If you need more detailed pictures I will provide them ASAP.

oh, the ecobee wires connection is below (figure 6) enter image description here

  • Trial and error connecting things up is not a good thing to do. You could have damaged your new thermostat, the heater control system, the cooler control system or even the connection wiring. Such damage could cost you many 100's of USD if not 1000's. It would make a lot more sense for you to bring in a professional heating/cooling contractor to install this thing instead of posting a huge string of mostly not useful photos here on the internet.
    – Michael Karas
    Mar 14 '18 at 3:57

If we read your manual correctly it states to install the PEK.


You can also look here: https://www.stevejenkins.com/blog/2014/09/how-to-install-an-ecobee3-smart-thermostat/

And a guide to the wire color codes is found here:

Why are the white and orange wires both connected to my thermostat's W terminal?

That said if you are looking to get around the PEK - of course I can understand that you see 'No Control Board' or Terminal Connections but simply a bunch of things wire nutted together, that maybe this is why you skipped that item.

In order to do this - you need 24VAC for that common wire and it should follow the color code for the common wire [BLACK] at least black tape both ends of your blue wire if you can't pull a black wire.. (as this tells people what circuit in the HVAC it is supposed to be) , of course that is only if you are interested in doing it right.

In Picture number 2 You have a Green , White, Red and Black wire coming down from top left. Now since there is not a real drawing of what is where and how it is hooked up and your pictures are a bit difficult to trace the wires ..

I am guessing that the Black wire is the 24VAC common that you will need to connect to - it appears to be wire nutted in the back to a brown or purple wire - I am guessing that goes to the condenser unit. First check it for voltage with a volt meter on AC setting and measure between that wire and the frame screws of the unit. Do not hold the meter by the metal leads - hold the plastic of the leads and measure - do not touch any metal with your hands! You can get electrocuted or shocked.

After measuring and making sure it is 24 Volts AC - you can hookup your blue wire as long as you taped a black band around the end with black tape - to identify it as really being a black wire. Now you have the proper voltage and wire.

EXCEPT you already hooked up stuff previously and let the smoke out of something, so depending on how much smoke was let out.. your unit should be able to run.

All of this said : Your system should work if you did not burn up anything previously.

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