is my A/C system wifi-compatible


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Old 05-21-13, 11:21 AM
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is my A/C system wifi-compatible

Just bought the Honeywell WiFi Thermostat RTH6580WF and before opening the package learned that I needed a "C" wire in my existing wiring.

Well, when I opened the existing White-Rodgers theromstat panel (which by the way only controls my A/C system and not my heating system), I only saw three wires:

Blue wire was connected to "G" (not "C")
Red wire was connected to "Rc"
White wire was connected to "Y" (not "W")

Is my system capable of being controlled via WiFi?

See pic below of my existing wiring...

 
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Old 05-21-13, 03:59 PM
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See this link: Honeywell Wi-Fi Programmable Thermostats and then click on installation video for instructional videos on how to use that thermostat with your existing wiring.
 
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Old 05-21-13, 04:11 PM
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Did that already but its still not obvious b/c I only have three wires.
 
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Old 05-21-13, 04:18 PM
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This video... simply ignore the extra W wire and do everything else. Don't overthink it.

http://www.youtube.com/embed/AUfV30ttxgc
 
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Old 05-22-13, 04:57 AM
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Disregard the colors, get them completely out of your mind as the have absolutely no bearing on what terminal they are connected to.

 
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Old 05-22-13, 05:48 AM
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EDIT....the below was posted prior to seeing the wiring diagram that was just posted. I think it all makes sense to me now. I will report back on my progress.

---------------------------------------------------------------

Yes, that's the video I watched. Not trying to overthink it, just want to make sure I don't damage any circuitry in the process.

What confuses me is why a BLUE wire is connected to my G terminal, and why a WHITE wire is connected to my Y terminal. Shouldn't GREEN and YELLOW wires have been used, respectively?

I guess I'm going to venture into the attic later this week and see the connections up there. In the panel near the air handler, the BLUE wire should be connected to the G terminal and the WHITE wire should be connected to the Y terminal to make sense of the wiring in the thermostat, right?

If that is the case, then what I need to do is move the BLUE wire from G terminal to the C terminal (in both the panel and new thermostat). Then I need to jumper the Y terminal in the panel (the one with the WHITE wire) and the now-empty G terminal. In the new thermostat I need to connect the WHITE wire (which is now technically connected to the Y terminal and G terminal in the panel) to the Y terminal.

Am I making any sense here?
 

Last edited by opeets; 05-22-13 at 06:30 AM.
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Old 05-22-13, 07:46 AM
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Someone just ran what ever wire they had laying around for your thermostat. That's not a problem for the person doing the original install but it messes everyone up afterwards.

And you seem to have the proper wire placement correct.
 
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Old 05-22-13, 10:43 AM
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So I took a peek at my AHU (Freedom Air AHX4800A1) in the attic a short while ago. It was not easy to get to and pulled a quad trying to step over a large flex duct so right now I'm in quite a bit of pain.

Once I got to the unit I traced the wire coming from the thermostat to an entry point behind a panel. There were two other sets of wires entering the unit as well. What were these for? I didn't have time to trace them.

In any case, I took a look at the panel and noticed that it had hex screws, which of course you can't open with a flat head or phillips screwdriver. Since I didn't feel like going back to the garage and coming back to start a job I'm still skeptical about starting I decided to take some pics, close the attic hatch, and get some feedback.

My concern is that by removing the ~10 screws the panel might offer some resistance in coming off and with the use of force I might end up doing something that I wouldn't know how to undo. The panel is also a lot larger than I thought it would be.

See pics below for right side of AHU panel, left side of AHU panel, and AHU label.
On the right side of the AHU you can see (at the bottom of the pic) the thermostat's wire coming into the corner.

Another thing that I was concerned with was the proximity of the AC power line coming in and the four screws in the middle of the panel right above the Energy Guide label. I don't know if anything is attached to that panel from inside the unit.

Yes, I know, this is something I should have thought to do last month, not now as the warm weather approaches.



 
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Old 05-22-13, 05:22 PM
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You need to remove the door on the right. Do not remove the 4 screws holding the plate on by the energy guide label.... it is a removable door for breakers if your system had electric strip heaters.
 
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Old 05-23-13, 06:16 AM
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I emailed Honeywell tech support prior to the posting in this forum, and I just received a reply last night. Their direction below sounds a lot different than what video instructs you to do...

To assist you better, do you by chance have any extra wires? For your system of cool only your wiring is correct. Rc is power to the cooling system, y is the call for cooling, and g is the call for your fan; wire color is just a tracing tool from thermostat to furnace and so just keep the same color going to the same terminal as the old thermostat. If you have an extra wire connect it to c on the thermostat and then go to the unit and connect that extra wire into c there as well. Otherwise get a 24 vac transformer and remove the jumper between r and rc and connect one end of the transformer to r and the other to c. Make sure the jumper is out though when doing that.

Are they saying that in order to provide the necessary power to the WiFi-enabled embedded system I should run another wire (with at least two leads) behind my wall to a place in my attic, connect it to a transformer, and tap that transformer in to my electrical system? I would assume that I would not need to change anything in the air handler in this case. Are there 24vac transformers that plug into standard electrical outlets? That would be easier because I have at least one open outlet in the attic. Otherwise I would have to tap into the box that my light bulb is mounted to.

Why would one end of the transformer go into R (which would have been unjumpered from Rc)? Is that acting as a ground or something?
 
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Old 05-23-13, 06:31 AM
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If you follow Kevin's diagram in post 5 you are supplying the thermostat with power. When the thermostat calls for AC it connects power to the Y and G terminal. In the diagram that is what you are doing.... just with one wire instead of two.

The only reason to consider additional wiring is if you want to turn the fan on without the AC on.
 
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Old 05-23-13, 06:46 AM
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Understood, but I'd rather not open the AHU to move the Blue wire to C and Jumper the Y/G terminals. Its just something I don't feel comfortable doing, especially when the attic is hot, dark, cramped, and I'm on planks of plywood. If my AHU were in the basement in a cool environment I would definitely not hesitate. I really should have started thinking about this in April, not late May.

I think that the non-invasive approach of adding a transformer is a better idea in my situation.
 
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Old 05-23-13, 06:52 AM
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Its not a great idea at all. You are better off doing as I said.
 
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Old 05-23-13, 07:12 AM
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Okay I hear you. Would you mind telling me why you feel that way? Is there a technical reason or is it just a preference? I just saw a YT video where a guy added a walwart-type transformer to power his thermostat. And why would Honeywell recommend this to me?
 
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Old 05-23-13, 08:46 AM
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The reason why... other than I do this for a living and you should simply listen to me .... is because you will essentially be combining two 24v circuits. This can cause system damage if done wrong. Doing it my way is safe as long as you kill all power to the ahu when you do it.
 
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Old 05-23-13, 08:52 AM
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Those are two very good reasons. Thanks for the extra bit of info, I will heed your advice. Will report back when I make progress.
 
 

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