Replacing/modifying 240v dual pole thermostat for Smartthings control


(Kevin) #1

Hello, just bought a brand new house, but didn’t get in on the process early enough to choose “smart things” as options throughout the house, so I’m starting the upgrade process. I’m also fairly new to the community so I apologize for potentially stupid questions. I promise I have searched for answers first without complete success.

So I am trying to upgrade the thermostat for the heated floors in my bathroom. Currently installed is the Aube TH115:

From what I have gather here on the forums and the rest of the interwebs, I have two main options:

  1. Replace the thermostat with a Smartthings compatible one. Unless I am mistaken there is no dual pole 240v smartthings compatible thermostat in existence to act as a direct replacement. That leaves me with rewiring it for a single pole and hooking up a compatible thermostat, of which the selection is pretty slim. The only one I’ve found that seems viable is the Stelpro KI (STZW402WB+) Z-Wave Electric Baseboard Thermostat. I’m not entirely uncomfortable doing the rewiring, and have easy access to professional electrician help if need be.

  2. Modify the wiring for the current thermostat to include an adequately rated in wall switch, to power the heat on and off while having the existing thermostat always on and set at whatever we elect as the “warm” temp.

For our usage, the heat will only be on for an hour or two in the morning, and possibly the same in the evening. And, although both thermostats work based on regulating ambient temp, the only real concern is my wife’s cold feet on warm tiles. Our morning schedule is never consistent, so in an ideal world, I’ll eventually figure out how to trigger this whole thing based on whoever’s alarm is set earlier or something along those lines, but that is a post for another day.

The advantages I see for the replacement thermostat are that everything is being used as it was designed and there will be control over all of the settings of the thermostat via smartthings as opposed to simple on/off. On the downside, I have to convert dual pole to single pole, it does not monitor the floor temperature (and turn off if it gets too hot), and it will cost more.

The advantages of the in wall switch are cost, the monitoring of the floor temp, and keeping the dual pole setup. Downside, the only control I have is on/off, but in reality maybe it’s not a huge deal since all I’m looking for is warm tiles twice a day. The other downside is that, as you can see in the picture, the electrical box is already pretty jam packed. I don’t have any idea how I would fit a switch in there too.

So, my questions are:

  1. Are there other replacement thermostats I should be considering that I have missed?
  2. Does dual/single pole actually matter in this comparison for any practical reason?
  3. Am I overlooking any big pros/cons of either setup?
  4. Is the monitoring of the floor temp a big deal? It would seem that if it was, it would be a feature on all radiant heat thermostats?
  5. If you recommend an in wall switch solution, what switch? The current thermostat is rated to 4000 watts @ 240v. I do not know the specifications of the actual heating elements in the floor.

Thanks to anyone who has managed read all the way to the end. Any thoughts or help you can offer is appreciated.

(Dale C) #2

This is not a replacement for your application directly. Yours is using a remote sensor embedded in the floor presumably whereas the Stelpro is using a room sensor inside the wall mounted unit itself. So you would have to find a replacement that is compatible with whatever remote sensor you have which makes it even harder. So it might work but not based on the floor temp (which is the more ideal from a control perspective) but the room temp.

The best I can tell is your option two is the more likely solution that will be available for you.

FYI: just for clarity you do not have a dual pole thermostat currently but a single pole.

(Ray) #3

I am currently using the Sinope electric floor heat thermostat and quite happy with it.

It’s important to use the floor Temp sensor especially if you live in a cold climate for controlling the heating wire from overheating. There are a couple of protections in the thermostat for this but the long run is better to use this.
This thermostat does have double pole and there is integration with ST but with an API which is way better due to ST unreliability. Only problem is you will have to buy a hub in order to do this.
Most in floor thermostat will be double pole due to the Ground fault circuit interrupter (GFCI).

(Kevin) #4

Thanks for the reply. I’m leaning towards the in wall switch if my electrician friend can help me figure out how to fit it all into the box. Any recommendations on a specific in wall switch for this application? In searching around it doesn’t look like there is a huge selection that can handle 4000 watts @ 240v.

As far as thermostat type, I thought the 4 wire installation was indicative of a dual pole, which allows the actual “off switch” it has, versus just turning the temperature way down, which is what you would have with a single pole.

(Kevin) #5

It certainly looks like the Sinope would work great, but would be cost prohibitive I think. I have a lot of other smart devices to buy to get my home up and running like I want. The wife is already going to be less than pleased when I buy several hundred dollars worth of smart light switches.

(Dale C) #6

This Sinope product looks like an excellent alternative for your application @kkennedy22 but verify what your floor heater actually is because this one is 3600 W @ 240 Vac / 15 A The installation manual shows it requires a step down transformer to supply 24vac to the thermostat but that doesn’t make sense the way the specification is listed because it says that aux output is optional? The advantage is it can do the proper local control with the added ability to “talk” to SmartThings as @Navat604 can talk to.

The wall switch would be fine as well. I am not aware of an exact product that fits your spec but you have the ideal that you are looking for is 240v power supply and 4000W resistive rating. That is a pretty tall order but maybe @JDRoberts is aware of something?

It is not ideal but I am thinking you will need to have your electrician friend put in another box next to your thermostat that can house something like a 240V version of the Remotec 15 Amp Dry Contact Module (ZFM-80) that controls power to the floor heater. I couldn’t find one so we will still need to have 120V available to power the switch and relay so hopefully there is a source nearby the electrician can pull from.

edit update: The specs on the ZFM-80 imply this product could work for you on the 240V. So that is good but you still need the 120V for supply to the device and then I would recommend a simply plain switch on the box cover that gives local override of the ZFM.

•100% Z-Wave compliance.
•Manual or Z-Wave controlled on/off for broad variety of appliance.
•Isolated Relay Switch for loading up to 250VAC 15A / 30VDC 15A.
•Small form factor easily fit in to wall gang box.
•Able to trigger by external rocker paddle or button.
•Zero-cross sync control technology to greatly extend the switch life span.
•Operation Voltage: 120VAC
•Input Frequency: 60Hz
•Output Load: 250VAC 15A / 30VDC 15A
•Connection: Live, Neutral, 2-pin Relay Contact, 2-pin EXT Key
•RF operating distance: Up to 100ft outdoor line of sight, in unobstructed environment

(Ray) #7

Here is another option. Aeon labs heavy duty appliance module. It’s 40 A or around 9000 watts with energy monitor.
You can get your electrician to verify your floor heat wire for wattage. If you know the manufacturer of the heater. You can measure the resistance and ask them for more detail. 4000 watts of floor heat is massive.
As for single or double pole. You are correct about the 2 pole you have but I believe most in floor controller out there will be 2 pole and controlling by turning on and off with a relay and triac so it’s very similar to 2 pole except way more efficient. This of course is for in floor heat controller only. Your picture shows you have double pole.

(Dale C) #8

@kkennedy22 This is a GREAT product choice and I would say is the way to go!

@Navat604 has a great find and is indeed correct that the wiring is two pole. My mistake! I relooked at the picture and the way the wiring diagram showed it on the back of the controller wasn’t an industry standard method and I read it wrong. And you MUST use a double pole relay/switch. You have two phase power which is common for higher loads and makes perfect sense for electric floor heat. The typical max load on a single phase circuit in a house is 1500 watts for a 15amp wall plug. That is just to say your floor heating has more heating capacity than a typical single phase circuit can handle.

The specs on the ZW078 are more than you need but it will absolutely handle the load you currently have. The ZW078 is a beast! It can handle 40Amps which is the equivalent of an electric stove or clothes dryer. Your current controller is rated at 4000 Watts at 240VAC, that doesn’t necessary mean your actual floor heating is that much and in fact most likely isn’t. The engineer would size the floor heating appropriately and the controller just needs to be able to handle the load. The ZW078 is over twice the existing controller rating so you know you are safe with a resistive load rating of 9600 Watts at 240VAC. The other nice feature is it will automatically keep track of the power usage for you.

Physically the size of this is going to be relatively large (compared to the thermostat ) and you still keep your existing thermostat for local control as is but wire this in the circuit as well. You wouldn’t want this exposed in a bathroom not only because of its size but it doesn’t look rated for high moisture. You could have this installed possibly back near your breaker panel which is hopefully in the garage where the ZW078 would be hidden. The circuit for the floor heating is going to be two breakers located side by side, one for each phase of power. You want an electrician involved to install this at the panel.

(Kevin) #9

Gents, thanks for the replies and options you’ve given. I’m definitely going to get my electrician friend involved at this point and try to find out from the builder the exact specs on the floor wire. I’ll update once I decide on something.