Wiring Sensi Touch tstat to Taco zvc403

CarpenterSof

I just bought this house a month ago. I want to remove a wall that had an old Honeywell mercury thermostat on it, so I ran a new 18/5 wire in a new place and got an Emerson Sensi touch smart thermostat. 

I shut the breaker off, swapped out the red and white wires, stuck the new blue wire in a spot that said “COM” (someone suggested that on Reddit for this model Taco), wired in the new Sensi per their instructions, and turned the power back on. I got no power at the thermostat. 

Any advice would be deeply appreciated!
before:

After:

jringel

you need to move the blue wire on the taco relay to the common on the top left of the control that goes to the transformer. I would also recommend that you check the va requirement for the thermostat and compare it to the transformer on the taco panel as some wifi thermostats will need more VA than the panel can provide. taco does have a wiring diagram for addressing this.

CarpenterSof

Thank you for replying!

The thermostat requires 24vac and that’s what the Taco panel says. 

I need to put the blue wire here in the same slot with one of these yellow wires?

I apologize for my ignorance of controls. I wish I learned this in high school instead of how to write a Shakespearian sonnet! 😂 

Mad Dog_2

No worries 👍 people are here to help...Mad Dog

HVACNUT

CarpenterSof said:

I need to put the blue wire here in the same slot with one of these yellow wires?

Yes, but you'll need to know which wire is Common. Do you have a meter?

CarpenterSof

I don’t have a meter. Is there another way or am I headed out to the store?

Jamie Hall

You need a meter -- or a test light, and know how to use it.

You mention the power supply -- yes, the board does supply the 24 VAC which that thermostat requires -- but that's not what's important. What's important is the volt-ampere rating, which will tell you how much current the thermostat draws and needs to be compared to how much current the board can supply.

HVACNUT

That should be 40 va transformer in the panel and only 2 zone valves are being used so adding the thermostat should be fine.

SteveSan

@CarpenterSof When wiring 3 wire t-stats to our older ZVC controls the R wire goes to the Right T and W wire goes to the Left T ( if only wiring a two wire t-stat it doesn't matter which T you land your R & W ).

Then take your common wire from the t-stat down to the #1 terminal at the zone valve connection.

Please see the attach wire document. The first diagram would be for our older SR ( metal cover ) control and second one is for our older ZVC ( metal cover ) control.

If you have any questions, please give Taco Technical Support a call during normal business hours Mon-Fri 8am-5pm EST 401-942-8000. Hope this helps.

CarpenterSof

@SteveSan, I followed your guidance and everything works! 

Thank you so much everyone for your help 🙏 

SteveSan

Glad I could help, have a great night!

lost11

CarpenterSof said:

@SteveSan, I followed your guidance and everything works! 

Thank you so much everyone for your help 🙏 

post a picture of your after!