Hi–I have an older 2-wire hydronic heating system (3 Taco Zone Valves) which has no C wire. The install instructions for the T-3000 say to put a power resistor on the Taco valve between terminals 1 and 2. I understand that this is typically done to allow for a trickle charge of the Thermostat when the circuit is open (i.e. when the heat is not on) to power the Thermostat. This system is in a second home in a cold-weather location and so I am hesitant to rely on this/battery power to keep the thermostat functional when the house is empty. I would prefer to run power to the Thermostat to know it is properly powered.
What about the in-wall option? Also, if I install one of the in-wall transistor in my basement can I run wires up to two different thermostats from the same transistor?
Jason–I’m still not having any luck with this. I connected my boiler to Rh and W and my 24VAC transformer to Rc and C. When I run the setup for the T3000 it detects the Rh, Rc and W wires but not the C. I have tested the wires from the transformer with a multimeter to confirm they are 24VAC. Some sources online suggesting splicing two wires to the Rh (so I would have Rh (with hot wires from both the Taco valve and the transformer), W (going back to Taco) and C (going back to transformer). Any thoughts on what could be wrong. Should I try splicing?
Unfortunately, the device did not power up based on being connected to the transformer alone. I had to put batteries in to get it to the point where it tried to do the automatic wire detection.
That is why it did not detect it. The thermostat should be powered up by a 24VAC transformer. Can you post a photo of the thermostat wiring, the transformer label and its wiring?
Thanks for your help Jason. See below. I included two pics showing the AC voltage running through both sets of wires. The set on the left go to the transformer (also showed—outside of electrical box to make it easier to see everything) and the set in the right go to my Taco zone valve.
I am wondering if your thermostat is currently jumped digitally between Rc and Rh and that may be causing the issue. If you shut off power to your heating system, confirm that voltage is not present on the Rh wire, then try setup without batteries in. Does that power up the Tstat and let you select the Rh and Rc setting?
Hmm, that makes little sense. Can you try disconnecting the heating system Rh wire while it is powered down, and instead connect the 24VAC transformer between Rh and C? Any difference?
I would expect capping Rh from the heater to be fine, however Alarm.com instructions indicate that as long as the thermostat has been programmed as having both Rh and Rc inputs, setting it up with the transformer on Rc C and the heater on Rh W should work.
The goal here is to power up the thermostat and on the T3000 during setup select the both Rh and Rc option when prompted. If you have done this and it doesn’t power off of Rc C let me know. I don’t see definitive confirmation that that option was selected.
Just out of curiosity, could I also just run a wire from the C to the transformer attached to my boiler? The new transformer I installed is right next to that.
