# U1 wire and Honeywell smart thermostat



## Not A Plumber (Mar 11, 2013)

We recently built a new house and in preparation I bought a RTH9585WF thermostat a few months ago (well before the house was done). I'm finally getting around to installing it and have noticed that it does not have a place to connect a U1 wire as my current tstat (Honeywell Vision 8000). I've done some research and know that the U1 wire is a relay that's used for humidification systems or 2 stage cooling system (among other things). So, I went up in the attic to see what it's connected to. I found it's connected to a Honeywell damper actuator. I'm not sure what exactly it does other than opening and closing a damper, meaning I don't know the benefits or if it could be disabled. But, what are my options? Can use this thermostat? I'm hoping so because it's too late to return it. I bought this one in particular because it works with Smartthings and I got a great deal on it. Please help


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## roughneck (Nov 28, 2014)

The duct that the damper is connected to, does it run outside?


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## Not A Plumber (Mar 11, 2013)

Yes, I believe so. My understanding is that new houses are so tightly sealed/insulated that this duct is needed to bring fresh air into the house. So, I guess I do understand the benefit of the damper and don't want to compromise that functionality. So, the only question that remains is whether there's a place to connect that wire on this tstat.


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## user_12345a (Nov 23, 2014)

The retail honeywell stats can't control ventilation, keep the vision pro 8000.

Ecobee 3/4 is about the only good stat available to the consumer that can control humidifier, ventilation, etc.

https://www.ecobee.com/2014/11/ventilators-humidifiers-dehumidifiers-accessories-ecobee3/


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## Not A Plumber (Mar 11, 2013)

That's kind of the conclusion I was coming to. I was hoping there would some sort of relay or something that I could hook up. Fortunately, the Ecobee works with Smartthings to. So, hopefully they'll let me exchange the Honeywell, despite being well past the return date. I work there, so maybe I can pull some strings 🙂 Thank you for your help.


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## user_12345a (Nov 23, 2014)

learn how your ventilation works and was set up before purchasing another thermostat.


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## Not A Plumber (Mar 11, 2013)

So, I was able to exchange the Honeywell for the Ecobee 4 (after finding out that the new Ecobee 3 Lite doesn't support ventilation). My only question now is whether the orange wire that's currently connected to the U1 spot would connect to the acc + or acc - on the Eco. Currently the orange wire is attached to the white wire from the damper actuator. The red wire from the DA is connected to the the C terminal on the main unit. So, would the orange wire go in the acc- spot.


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## user_12345a (Nov 23, 2014)

It goes straight to a damper actuator, there isn't a control for ventilation?

You have to check the ecobee instructions.

Should be able to get it to apply power from R (which is power - C is the return path) so you don't need two wires for ventilation.

You have to decide how you want it to ventilate and what the options are.

May be able to to x minutes per hour (where it opens the damper and turns on the furnace fan), do it based on indoor humidity to stop it from getting too high in winter, or something else.

It may be helpful to go into the settings menu of the existing stat and see how it was set up for ventilation.


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## Not A Plumber (Mar 11, 2013)

There are two wires coming off the DA (red and white)
https://photos.app.goo.gl/oiYPNpthqdQKmHwX2

The white wire is attached to the orange wire and the red goes to the "C" terminal on the furnace. 
https://photos.app.goo.gl/xuwLA82ZMxF3HPhM2

Hopefully these pics work. I'll definitely poke around in the settings to see how the ventilation is configured now. Thanks again for your help.


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## Not A Plumber (Mar 11, 2013)

Here are the pics. The coiled wire is coming from the DA.

20180407_081043 by loudfocus2, on Flickr

20180407_080920 by loudfocus2, on Flickr


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## user_12345a (Nov 23, 2014)

So the wire going to C in the furnace stays and the wire going to the stat needs to be connected to the right terminal.

You have to see if the damper is normally open or closed and see what ventilation options the ecobee has.

Have to get it to send power from R rather than treat it as a separate contact that has two wires.

For single wire accessory it says wire to acc+.

I can't find the manual with the settings menu so can't advise on setup for ventilation.


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