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Ecobee 3 Installation 2-wire Honeywell thermostat.

lcghostlcghost Newton, NJMember

I have two Ecobees that are replacing two Honeywell thermostats. Each thermostat currently has two wires only (there is no third stuffed inside the wall). There is a red and a white. The white is connected to "W" and the red is connected to "R" and jumped to "Rc".

The furnace is an oil boiler for hot-water baseboard. The controller on the furnace has only two wires for the thermostats, labeled "T T". There are also two flow-control valves that have wires connected to both the thermostats, and the 24v transformer; which is on the wall near the furnace and seems to power the thermostats.

I realize that this is not very descriptive as I'm not terribly knowledgable about heating systems. I can provide pictures, or would even be agreeable to someone wanting to FaceTime to get an actual look at what I'm talking about.

Very desperate for help. What is my best option here?

Answers

  • denwooddenwood Ontario, CanadaMember
    edited January 2016 Answer ✓

    You need a C wire (return path for 24V) to power the stat. Call Ecobee and they will send you an install doc to cover your setup. You can use a Fast Stat..or ideally run new wire. The support crew are great...just call them. This is the extra information link on 2 wire installs: https://ecobee.zendesk.com/entries/96808048-ecobee3-Heat-only-2-wire-boiler-furnace-installations

    I just installed nine stats, four of them radiant like yours. I used the C terminal on the zone valve 24V transformer, and had extra wires in the wall to run the C to each stat. I had to also reverse the RH and W wire connections from the old stat to Ecobee3 before the stats would power up.

  • lcghostlcghost Newton, NJMember
    edited January 2016

    Thank you so much for the response. A lot more things make sense to me. I am going to run new wires, I started with the basement as the stat is on the wall right opposite the boiler room. I did reverse the wires like you suggested and it powered right up. It just won't seem to call for heat and I keep getting emails from Ecobee warning me so. Any thoughts on where I wee wrong? Could I maybe send you pictures or something? Maybe I'm missing something simple?

  • lcghostlcghost Newton, NJMember

    Also, I know the furnace will fire as the old stat upstairs which is still installed does kick the furnace on, as did the old basement one.

  • denwooddenwood Ontario, CanadaMember
    edited January 2016 Answer ✓

    Unfortunately I'm not an HVAC specialist, otherwise I would be better at advice. TT contacts are "dry" contacts, so are simply closed to signal heat to your boiler. So they don't see 24V. Your 24V transformer likely powers the zone valves, which also likely signal "open" by closing a switch. Are there four wires coming from each zone valve? Two wires likely power your zone valve via the 24V transformer (circuit completed at your stat when it calls for heat), and two connect to the zone valve's switch. That zone valve switch may be connected to the TT terminals on your furnace controller. If you have access to a multimeter to read 24v AC, you should be able to sort out what is needed.

    On my setup, similar to yours, RH goes to the "hot" side of the transformer, C and W1 go to the neutral "common" side, with the zone valve in series with W1. RH to C should show 24V AC with a multimeter. Connecting RH to W should call for heat. My zone valves integrate a switch, so the boiler simply sees a closed circuit to call for heat.

  • lcghostlcghost Newton, NJMember

    Ok cool, that's very helpful. There are actually only 3 terminals in the zone valves. How might that change things?

  • denwooddenwood Ontario, CanadaMember
    edited January 2016 Answer ✓

    Like this?

    If so, your C wire should connect to the transformer neutral side. RH and W would be connected as they were to your old stat. Just make sure RH actually connects to the "hot" side of the transformer. If connected correctly, checking at the stat, RH to C will show 24V AC, and C to W will show 0V AC.

  • lcghostlcghost Newton, NJMember

    Awesome! Thank you. That's perfect. The old man and I are going to knock this out this weekend for sure. Thank you.

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