electricalthermostatthermostat-c-wire
I am trying to run a new c-wire for my new ecobee thermostat. When I finished running the c-wire from the thermostat it did not turn on. I tested the voltage at the boiler and it is only reading 17ac on the multimeter. Is there a way to fix this so that it powers my thermostat?
Both this document (PDF) and this document (PDF), say that one 24V-40VA transformer can only support 3 zone valves. Since you have 4 valves, you're over the recommended number of valves. Once you added the demand of the WiFi thermostat, you likely overwhelmed the transformer. The answer here, may be to install an additional transformer.
There's a diagram in the second document, that shows how to wire in an additional transformer. This document also has a good explanation of how the valve actually works, which might be worth a read.
Based on these documents, a WiFi thermostat should be wired in like this.
Based on the your description of the wiring, it sounds like it's a bit different than that of the documentation. Incorrectly wired valves might also be the problem. Based on the documentation, terminals 1 and 2 are connected through a heater, while terminals 2 and 3 are connected only when the valve is open.
When the thermostat closes (calls for heat), current flows from terminal 1, through the heater, to terminal 2. Once the valve opens, a contact allows current to flow between terminals 2 and 3. So basically energizing 1 and 2 opens the valve, and energizing 2 and 3 signals the boiler to circulate.
Install both a separate 24v transformer and an isolation relay with a 24vac coil at the boiler. Use the separate transformer to power the Ecobee3 thermostat and use the Ecobee3 to energize the new 24vac relay coil. Use the new relay to provide a set of dry contacts for switching the existing 12v controls (nominal) on the boiler whenever the Ecobee3 energizes the relay. Keep the new 24v system electrically isolated from the existing 12v system.
Best Answer
Yes you have 24vac at your boiler. Assuming you have enough conductors in the wire to your thermostat, it can be powered.
How many wires come from your thermostat to the boiler? The old thermo in the wiring diagram looks to just be a switch on the hot leg of the 24vac, you'll need the neutral side ( c-wire ) run to the thermostat as well. Where did you pull your c-wire feed from ?
It looks like you've circled something that has a ground, an aquastat, and the outgoing hot leg and incoming hot leg of the 24v.
The wire nut you've circled - I am going to assuming is your new c-wire - has a blue wire and a black wire and I can't tell where either of them go.