Need help with ST supported thermostat with no C wire

(Ron S) #1

I need serious help finding couple of thermostats that ST can support without running a Common wire. I have two thermostats (White Rodgers) in two zones for Weil McLain (baseboard heating). These existing thermostats have just a red and a white wire and of course a battery.

I am not too handy or a DIY expert but need to replace these with something that I can control via ST. Any suggestions?

I am totally frustrated with the existing ones.

(Convinced ST will never be unbroken…) #2

Two suggestions:

If your heaters have traditional HVAC terminals, but only two wires are run to the thermostat, try one of these.

If not, consider building your own thermostat using a temp sensor, and an LFM-20 to control power to your heater(s) (provided that they draw less than 20A).

(Ron S) #3

Adding the “add a wire” requires messing with HVAC system. Right? Wish I was that handy! :frowning: those Weil McLain’s are one complex system as far as I think. It’s some CGA gold 25 or something like that. Came with the house from the previous owner).

(Convinced ST will never be unbroken…) #4

Are yours hydronic? If so, I think the add a wire is the way to go. Get a HVAC guy out there to see if it can be hooked up. If it can, you’ll have your choice of any thermostat you want down the road.

(Jody) #5

My house did not have a c-wire so I just added a simple 12v power brick. There are numerous youtube videos on how to power the t-stat with a powerbrick.

(Ron S) #6

I think so. Be a little patient with me. This being the first home and first year of home ownership. :slight_smile: I think so. I have baseboard heat (which I guess is hydronic) all over the house and the furnace/boiler/heater in the basement (Weil McLain) and a water heater (A.O.Smith). Two zones - One thermostat in the Living Room (1st floor) and the second one on the second floor (bedroom).

Will take your suggestion and get the HVAC guy to check it out. As such they are expected next week for maintenance.

(Ron S) #7

K. Will take a look too once in home today. Thanks.

(Yves Racine) #8


You can also buy z-wave thermostats like the CT30 or the CT100 models that work with AA batteries. I have the CT30 and it can be integrated with ST without C wire. I use it to control my fireplace in the
master bedroom. These types of thermostats don’t work with baseboard heating (in-line electric heaters) though.

See the following links:


(Ron S) #9

Thanks. But will have to check if it works with hydronic baseboard heating.

(Yves Racine) #10


If your usage is with baseboard heating only (120/240V), the only thermostat out-there that can be remotely controlled for that usage is the following:

This is a new device in pre-order now. They are supposed to publish their APIs in 2015. As soon as their APIs are published, I can work on integrating it to ST just like I did with the ecobee thermostat.

See the following links about the work I’ve done for the ecobee thermostat.


Lowering thermostat when leaving - energy efficient?
Urgent help regarding thermostat
(Ron S) #11

The current white Rodgers looks like this with a red and white only.