My first post so I’m not sure about posting a link or uploading images.
I frequently install floor warming wire under tile floors. Typically the heating wire leads are brought to an electrical box. Depending on the thermostat the the load wires are connected to terminals or wires on the thermostat. At least one temp sensor is under the tile (I always install a spare) The sensor leads are connected to the marked terminals. The power feed may be 120 VAC or 220 VAC depending on the heat wires. This one will do both. In the past I always placed a GFI in the feed but lately the GFCI is integrated into the thernost like this one.
There are typically several terminals for sensors and/or controlling relays for larger systems. This install does not need an extra relay. What is different with this thermostat is that it has one terminal labeled Home Automation and one labeled COM. According to the literature, including the installation manual, if the home automation terminal and the COM terminal have a short or 24 VAC applied it will switch the thermostat between the ‘Away’ temperature and regular operation.
It is a SunTouch thermostat, specifically it is a SunSet Comand Touch thermostat #500850. It is advertised that his thermostat has the ability to be controlled by home automation. They also have a programanal thermostat that has WiFi. The price for the WiFi thermostat ranges around $225 to $260 vs this one cost me $145.
I knew that I might need additional room to install whatever device would be required. To that end I installed another electric box. That box has 120 VAC and 2 pair of 18ga, wire from that box to the thermostat box. My preference is to install a Z wave or Zigbee device that will allow me to start the floor heat remotely several hours before guests are expected.
The installation instructions are online http://media.wattswater.com/IOM-ST-Command.pdf I will quote the section on home automation:
Home Automation System Rough-in Wiring
A short or 24 VAC applied between the Away and Com terminal will switch the thermostat between the ‘Away’ temperature and regular operation.
Pull 18 AWG to 24 AWG 2-conductor shielded wire from the home automation control to this control location.
Strip the wire ends to 1/8" long.
Sensor, relay and home automation connections are made to the terminal block by inserting the wires into the square openings and tightening the screws on the side.
Connect the sensor wires to the SENSOR terminals on the thermostat. These connections are not polarity sensitive.
For a SunStat Relay C3, connect 2 wires from the relay to the Com and Relay terminals on the thermostat. Ensure the com wire at the relay is the same conductor connected to the Com terminal on the thermostat.
Connect the Away and Com terminals to the appropriate conductors from a home automation system.
Refer to the instructions for the home automation control before making these connections.
My request is twofold, one is for suggestions on what device would work in this application. The other is to clarify my confusion about the shorting of the 2 terminals. Is it a momentary contact, or is it left on for one condition and off for the other?
I would be most happy with a battery powered device or I can tap into the 120 VAC in the box. This bathroom is as far from the hub as it can be without going outside. There are several Z-wave plus devices closeby. I will probably place a Z-wave repeater in the area. I prewired the house for cat 6 to avoid using WiFi, so while I could put an access point in the next room over, I would prefer to not use WiFi
What suggestions come to mind? I have seen other posts where people are looking for a thermostat for electric floor heating. Maybe this could be that solution. Under the right circumstances it might be able to control base heating. Most of these types of thermostats can use remote sensors like the ones under the tile, or use air temperature by changing the settings…