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Discussion Starter · #1 ·
Hello! New to the forum.

I am a DIY'er with very limited knowledge when it comes to HVAC systems. I would like to replace my thermostat with an Ecobee and the instructions don't seem too bad but I'm cautious as not to screw up a fairly expensive appliance in my home.

I have a Trane system with an air handler and heat unit outside (apologies if I call things by the wrong name). This is an eclectic system, not gas.

There are 2 paths within the Ecobee install guide. One with a "C" wire and one without a "C" wire. When there is no "C" wire for the thermostat, they have you install a PKE off the controller board of the air handler (at least I think they are talking about the air handler). A few wires are removed from the control board and connected to the PKE and then some wires from the PKE go to the control board. Any additional wires for other accessories that are on the control board remain as/is.

Question 1: Is the control board where the thermostat wires connect in the air handler? How do I "correctly" get into this to see the controller board?
Question 2: How can I best determine the bundle of wires that are for the thermostat vs. other bundles that may be there for other accessories (apparently there is a humidifier as part of this system)
Question 3: Does my thermostat have a C wire? Maybe I need to get some better pictures, but I don't even see the letter C anywhere on it.

The instructions only talk about a 3 or 4 wire setup and I am assuming they are specifically referring to the thermostat and mine is 4 wire, best I can tell. There are just a lot of other wires and letters not mentioned and unfortunately, lacking a "C" so I am looking for a bit of advice before I proceed.

I was totally happy to have my local HVAC folks come out and do the install and I was even completely fine with an hour labor at $200, but unfortunately they told me it would cost $750 to install, which for 20 minutes of work by a pro, seems a bit excessive.

So, looking for an assist here to ensure I do things correctly.

Thanks!
Bob

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See this thread:


The 'C wire' on old thermostat is likely on the 'B' terminal for this type of setup.
 

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It looks like you already have a common.

It looks like you have a heatpump and the thermostat is using a outdoor temperature sensor.

The install/setup is more complex.

Ecobee can do it but won't use sensor, uses internet instead which is not as good.

The outdoor temp is used to lock out the heatpump when it gets too cold to justify running it and lock out the auxiliary heat when it's warm enough to never need it.

Heatpumps are best left at a constant temperature in heating mode anyway, so best to skip the gimmicky ecobee wifi stat and keep what you have.
 

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What is the model number of the existing thermostat. Kinda looks like an RTH8000 ish series, but there's a lot of models in that series.

What's the model number of the trane air handler (indoor unit) . The model number is the outside unit. Post a picture of the wiring at the control board inside the air handler.

Heatpumps are best left at a constant temperature in heating mode anyway, so best to skip the gimmicky ecobee wifi stat and keep what you have.
It has great tracking which can be very useful at distinguishing between losing ground on an exceptionally hot day verse a slight mechanical problem on a more mild day. Especially if the problem is intermittent. The aux heat can be locked out based on outdoor temp and will try to not use it anyways during recovery. It adjusts the recovery rate based on outdoor temp and house history. It isn't perfect but if you leave for weekends or similar, it can save some energy over time. I do agree that setting back at night doesn't make a whole lot of sense for heat pumps, if it's not simply for comfort.

Cheers!
 

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I know ecobee is quite a good stat.
Wonder if they'll ever include a real outdoor temperature sensor.

The picture shows existing has S1, S2 terminals and they're wired. rth8500 doesn't support that
Based on the terminal labeling, I suspect it's a trane labelled honeywell vision pro.
 
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