I am trying to install a new ecobee Tstat (EB-STATE6-01) on a 1980's hot water heating system. It has an old White-Rogers type 125-202 Tstat. The Tstat has three wires (a forth is not connected).



I have traced the wires back to the zone valve which is a White Rogers Type 1311. The wires are connected as follows:


I spent some time on the phone with ecobee support and they said the system was in compatible with ecobee. I am not confident that the person I was working with was competent. I have searched this forum and have seen implementations with a two wire system like this, Installing Ecobee T-Stats with White Rodgers Zone Valves , but my system has three wires.

I have read other forums that suggest a relay is needed.

Does anyone have a wiring diagram for this type of a setup.

Thanks, FJ

 

Apparently Ecobee has changed the connection method.
It used to be it would acknowledge either connection to R.
Now when using C you need to connect to Rc.

Good job and you're welcome.

 

Welcome to the forums.

I'm a little disappointed in Ecobee. The thermostat companies are so busy trying to better the other companies just offering a new product. They neglect to provide proper technical support. When I see that.... the thermostat goes on my do-not recommend list. Very unfortunate for a company like Ecobee.

Proper wiring diagrams should be.... no must be.... offered. A customer should not have to watch a video or download an app to install a product.

Does that thermostat come with an electronic control module that goes at the furnace ?
I need you to point me to the online info to that thermostat.
You will probably need a 24v relay too.

 

PJmax, Thank you for your prompt reply.

Here is a link to the Ecobee Tstat that I purchased. https://www.ecobee.com/en-us/smart-t...ostat-premium/

Ecobee did spend about an hour on the phone with me but basically said to call a technician. Here is a call summary they sent back to me. "Based on the pictures you sent me you are likely not immediately compatible with ecobee.

This is because you have 2 wires that open and close the valve, whereas ecobee is only compatible with systems that only require 1 wire for opening and closing.

If you would still like to try to install the ecobee, you can try to use an isolation relay as a workaround for this issue.

I recommend doing this with a technician."

These are some links that suggested:


Helpful Resources:

ecobee thermostat installation with an isolation relay

My heat-only system only has two or three wires connected to the thermostat. Am I compatible with ecobee?

What types of HVAC systems are ecobee thermostats compatible with?

I wish I knew how the ecobee worked when it gets a heat call. From what I can tell from the old mercury WR Tstat it simply connected the Red (hot wire) from one terminal to the other, moving power from the #6 zone terminal to the #4 terminal when the Tstat called for heat. I don't know what kind of a signal the ecobee puts out on the Rc or Rh terminal. But could it be used to switch a relay that basically did that job?

Thanks, FJ

 

Ecobee support is usually really helpful. But I think because your situation extends beyond a simple isolation relay they limit their advice. Anyways, I believe one half of a DPDT relay should suffice here (including pin #s on a standard 90340 relay):

W and C would go across the coil.
R would be common (pin #4)
6 NC (pin #5)
4 NO (pin #6)

 

You can use any 24vac SPDT or DPDT relay. I use 90-293Q. One of several choices available.
Emerson relay

 

Hi Pete, Thank you, I have ordered the 90-293Q relay.

Below is a drawing of my complete system (I think). I have read different posts on the Rc vs Rh, one would think I should connect to the Rh terminal, but I have read that only Rc works? My diagram shows it connected to Rc, if that doesn't work I will try the Rh.



Please let me know if you see something that does not look right.

Thank you, FJJ

 

Your transformer diagram says "neutral leg."
Technically it's called common.
Other than that non-issue.... you're all set.

You should be able to use either R terminal. Ecobee checks both locations.

 

Just to close this thread. I installed the Relay and the Ecobee is working as it should. The only odd thing is that I did try it with the Rh terminal and it did not work, using the Rc does.

A shout out to this Forum and Pjmax in particular. Thank you for the help that Ecobee was not able to provide.

FJJ