Hi there, I am trying to install a new, more precise thermostat with my underfloor heat, here is an brief explanation of my system:

I'll try and explain this as best i can. I am trying to hook a digital thermostat--Honeywell TH1110DV1009--into my underfloor heating system. There are two parts/areas/zones to the system--one going to my garage, which cycles constantly, and calls for hot water on demand (with zone control)--the other zone only pumps when the thermostat calls for it (thermostat activates the pump). With my old t-stat, when the system would call for heat, the pump would kick on, just as it should. However, with my new t-stat, the minute the wires are connected, the system pumps constantly, whether it is calling for heat or not. I played with it a bit, the minute the faceplate is placed on the wall plate, the system begins pumping, as though it is constantly providing power and calling for heat, when it is not. I can't figure this out and it's driving me crazy. I have my old analog (not sure of correct terminology--the lever, non-digital display style) t-stat hooked up right now, and it only kicks the pump on if the room grows cold, as it was designed...

The wiring is very simple--white wire and black wire which are hooked up for lower voltage. Again, apologies if my descriptions are poor or if I have something wrong here... I don't know a ton about this stuff and I'm learning about my system as I go...

Thanks in advance
Any suggestions?

PS..I will post a picture of my setup later and the way my system is routed, if it helps

 

You are only using this for a simple heat connection. What terminals are you using.

R & w with the jumper left in place between R & RC according to what I'm looking at with the DIP switches set to the proper place for hot water system.

It sounds like what's happening is the 2 wires are being jumped just as if they were tied together to start the system.

Just follow the wiring diagram with the stat for your system.

Hope this helps a little.

 

Spott,
That's exactly what it seems like. With the older, mechanical style thermostat I have now, when I push/pull the lever to turn up the heat, the system clicks on and the pump starts pumping. However, with the digital Honeywell I'm installing, it begins to circulate the minute the faceplate is connected... despite the fact that they are both wired the same, utilizing only the R and W connectors... I really don't understand what the issue is...

 

That stat uses a C connection or batteries. Do you have batteries in it ?

Some of those stats that have a C connection are power stealing. That puts a small load on the R and W line which can be enough to trigger an electronic controller.

 

Does the display immediately show “HEAT ON” or “COOL ON” when you push the thermostat onto the wallplate? I think the “System Switch” should be set to OFF when you push the thermostat onto the wallplate, and then you do the setup and then set the "System Switch" to “HEAT” or “COOL”.

Maybe the “System Switch” isn’t quite pushed to the OFF position.

Just a thought.