Years since I have been on the forum. I have older dumb Taco pumps for my radiant system. I have smart thermostats with a C wire adapter. I would like to axe the adapter. How would you do this. New transformer at the pump? just starting my research and this is always my place to go for my radiant system questions.

Most modern residential hydronic radiant floor hating systems these days use thermostats that have slab temp sensors, a control module located near the manifold(s), a transformer near the manifold, and actuators on the manifold circuits. The thermostat calls the associated manifold control module for heat. The control module then commands the associated circuit(s) actuator(s) to open. When the actuator(s) are open, then the control module commands the heat source and pump(s) ON.

Older electrically inefficient residential hydronic floor heating systems used pumps in lieu of actuators, but the principal was the same.

If you have a concrete slab hydronic radiant floor heating system, you should NOT use thermostat temp setback because the long delay to reheat a concrete slab will negate any benefit from doing this.

Gayle

Thanks for your response.

I have a thin slab radiant floor system on a plywood floor. 20+ years since I first installed it. No slab sensors. 2 Zones, though the bedroom zones very rarely get used. Small house with a propane Thelin that can bring the heat up in the spring and fall if needed. I have used thermostat setback with my thin slab and south facing windows with good results because I don't have a huge slab to reheat.

That however was not my question. When I installed my smart thermostats, I used an add on C wire transformer at the thermostat and now wish to run thermostat wire with enough wires for a C wire direct to the transformers I have. I was trying to figure out if I can use the same transformers or would have to install new ones. The transformers don't have information on them that I can read without taking them out of the junction box.

What are the chances that the transformer I used originally for my two Taco -06 115volt circulators could be used with more wires?

Thanks for your response.

I have a thin slab radiant floor system on a plywood floor. 20+ years since I first installed it. No slab sensors. 2 Zones, though the bedroom zones very rarely get used. Small house with a propane Thelin that can bring the heat up in the spring and fall if needed. I have used thermostat setback with my thin slab and south facing windows with good results because I don't have a huge slab to reheat.

That however was not my question. When I installed my smart thermostats, I used an add on C wire transformer at the thermostat and now wish to run thermostat wire with enough wires for a C wire direct to the transformers I have. I was trying to figure out if I can use the same transformers or would have to install new ones. The transformers don't have information on them that I can read without taking them out of the junction box.

What are the chances that the transformer I used originally for my two Taco -06 115volt circulators could be used with more wires?

I guess I don't understand your question or what you are trying to accomplish.

Normally you want the pump power source to be close to the pump(s). Normally thermostat wire is very small gauge wire and isn't typically used for anything beyond sending a micro amp signal from the thermostat to some distant control module that then turns ON the heat source and anything else required using a nearby power source to minimize the voltage drop and using proper gauge wire protected by circuit breakers and fuses. While thermostats often use a transformer to provide their power needs, their power needs are minimal making the very small gauge wire acceptable.

If you are attempting to power pumps via an existing transformer used for a thermostat via its normally very small gauge thermostat wire that is located some significant distance from the pumps, I don't have a clue if this would work without knowing all the specifics...the wire gauge, the wire length, the pump power requirements, the transformer power specifications, etc. My recommendation would be to do a more conventional approach.

Gayle

C, wire is just the common like in regular house wiring...common is more or less the ground wire...so if you can run an extra wire to the therm and ground it...preferably near the 24vac transformer that should do it, or ground it to the base of the transformers would be the best.