TACO Valves and Boiler not running

The Taco uses three wires for the zone valve. On zone 2, you show only red and white. That zone valve isn't going to open…………………..

Where is that lime green wire for the second zone going……………………

I can see a possible dangerous wiring flaw. Without the big picture I can only guess where the wires go to.

If I guess that the red white and green in this photo are going to the black wires that feed the gas valve, then that might mean there is no high limit between the power transformer and the gas valve. That is because the gas valve is no longer connected to B1 and B2. B1 is wired directly to the high limit temperature switch and the damper safety switch between that and the transformer. If you remove the burner power source from B1, or add a wire to that B1 to the burner, then you may inadvertently bypass the safety from the burner control

see the internal wiring of the L8148E with a vent damper here

The 24 VAC secondary winding in the L8148E is the source of the gas valve power, when the K1 relay pulls in, contact 1K1 makes and sends power to the high limit and when the AVD opens completely, the Closed Damper safety switch contacts make to complete the circuit to B1. When I look at the top photo I see wires that may supply power to B1 that may not go thru the safeties that are built into the L8148E.

That said I believe there are too many Low Voltage thermostat wires in that yellow oval above.

Regarding the Ecobee that is wired into zone thermostat 1 with a resister, You may not need that resister.

here is the Taco ZVC404 wiring you should look at carefully. It is basic and simple:

Connect zone 1 thermostat to the ZONE 1 THERMOSTATS terminals at the top.

Connect the zone 1 zone valve to the ZONE 1 24 VAC ZONE VALVE terminals at the bottom. Follow the same for zone 2. I have faded the line voltage wires because I believe they are correctly connected. That is because the Diagnostic Green LED is lit in your photo.

Now for the other diagnostic lights. on a call for heat from thermostat 1, the Yellow LED for zone 1 will light. after a minute or so the valve will open and the end switch will make causing the Red LED to light indicating that the zone valve is operating properly. Same diagnostic LEDs will work on all the other zones.

That brings me the the thermostat wires that are going to the L8148E. there should be only 1 thermostat wire with 2 conductors entering the L8148E nd that is the one from the X X on the top of the ZVC404 as indicated here

That is why I believe you have too many thermostat wires going to the L8148E.

Perhaps someone has been trying to use the wrong transformer to power the Ecobee. You use the C wire from where the thermostat is connected.

I hope this helps is your diagnosis of your problem. Make sure that the B1 and B2 go directly to the S8600 or other gas valve control. Get the Red White and Green wires away from the Black wires with the Blue wire nuts. They do not belong there under any circumstances.

I don't understand this statement. In the photo if the ZVC404, I see zone 2 thermostat with 2 wires as it should be and I see zone 2 valve wires with red white and green as it should be. look at the diagram of the ZVC from this instruction manual https://s3.amazonaws.com/s3.supplyhouse.com/product_files/Taco-ZVC404-4-Install-Instructions.pdf. It clearly shows three options for zone valves. 2 wire, 3 wire and 4 wire. Are you sure you know what you are talking about? @LRCCBJ

call Taco tech support at 401-942-8000 for properly wiring ZVC controller, zone called, and thermostat. If they’re power robbing thermostat, Taco tech can make some recommendations.