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C wire hook up on the TACO box

BrokenOldBottle
Community Member

I have an existing thermostat running on two wires with batteries and I want to replace it with a nest thermostat that requires a C wire. I do have a third wire available to me I just need to know where to hook it up on the TACO Box

2 Recommended AnswerS

laurentbourg
Silver Product Expert
Silver Product Expert

There is a C connection hub, typically located on the left hand side of your Taco, it might also say 24V. What is the exact model of your Taco control module?

View Recommended Answer in original post

laurentbourg
Silver Product Expert
Silver Product Expert

First transformer is exactly like your original system, which should be red/R to zone valve and W to all white wires. The second transformer load also goes to Red/zone valve, but the common of the second transformer goes to C. Nothing goes to W from the second transformer, and nothing goes to C from the first transformer. 

View Recommended Answer in original post

130 REPLIES 130

laurentbourg
Silver Product Expert
Silver Product Expert

There is a C connection hub, typically located on the left hand side of your Taco, it might also say 24V. What is the exact model of your Taco control module?

Thank you I'll pull the cover off and check which model I have but I think that answers my question

I have an older system two wire. I have no circuit board. Has Honeywell RA832A with (3) zone valves. transformer on top of 832. I have extra wires not being used in my thermostat  & was planning on using one of the for my "C" wire. Just not sure where to connect on furnace side? wasn't sure if i should hook to transformer 

laurentbourg
Silver Product Expert
Silver Product Expert

Please upload pictures of your setup

PXL_20211206_225839471.jpg

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PXL_20211206_225812447.jpg

I called TACO in Rhode island and Steve in Tech Support walked me right thru it.

PXL_20211206_225805529.jpg

PXL_20211206_225812447.jpg

laurentbourg
Silver Product Expert
Silver Product Expert

I have reviewed your pics, and confirmed you should be able to tap the C wire on your 24v  transformer that is on top of your RA832 controller, connect it where the white wire is connected. 

Connected directly to the white wire on the transformer or follow the white wire off the transformer

laurentbourg
Silver Product Expert
Silver Product Expert

connected directly to the white wire on the transformer. It is a 24V transformer, correct?

Correct it is. Also if I add another nest thermostat for a different zone in the house can I add another wire on the white side of the transformer

PXL_20211207_001519774.jpg

 use the green as my c wire to white on transformer. The Old wire that was coming behind the thermostat that runs down to the junction box I connected to that. When I measure up at the thermostat I have 18 volts? 

laurentbourg
Silver Product Expert
Silver Product Expert

When you measure R to C at the thermostat, so red to green (I assume your R is red), you get 18v AC? how about when you measure R to W?

when I measure r to w=26

R to C =26

laurentbourg
Silver Product Expert
Silver Product Expert

Ok good, you should be all set. Go ahead and install your Nest, let me know if any issue. 

Thanks again I really appreciate the help 👍👍

laurentbourg
Silver Product Expert
Silver Product Expert

Anytime. Please mark the answer as a solution when you get a chance. 

Very weird I have it wired with the proper voltage but the nest display still says c wire not getting enough power

Depending on the age of your TACo box it may be required to reverse your red and white leads inside the switch coming from your thermostat. red has to go to the right lead even though they're both marked T

Yea I'm at a total Lost. At thermostat R to w =26v

R to C =26v

Nest says lost voltage on c🤔

laurentbourg
Silver Product Expert
Silver Product Expert

Check your wiring diagram in the settings on the Nest, everything looks good and matches physical config?

I will double check I have R.W and C hooked up on the thermostat. I will double check settings

laurentbourg
Silver Product Expert
Silver Product Expert

Ok let us know, sometimes the Nest gets confused and physical does not match software, so important to always make sure. Also you can look at the power section in the settings -> equipment -> tech section and also check other info to make sure it all looks good. 

laurentbourg
Silver Product Expert
Silver Product Expert

How is it looking?

One more reason I always want to kick myself in the tail when I go to The Big box store and not the supply house. Hooked up the new transformer.... Yep no power on the load side.. double check all my wiring. To find out the transformer out of the box was dead.. great way to start the weekend

Call TACO, they are really helpful

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 second picture to follow

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 hey sorry to bother you again. I hope that the new transformer from The Big box store and had no power coming from it. Hook the old one up had power coming on the load side. So I decided to try the nest power connect. Went to the junction box where thermostat wires meet with his own valve. It seemed pretty straightforward unless I missed something. But Nest screen still says no power and will not let me advance. Thanks again for your help I really do appreciate it

laurentbourg
Silver Product Expert
Silver Product Expert

What happens if you go on your thermostat to settings->power connector->power test? Also verify your wiring from the google home app. 

I was trying to upload a picture but unfortunately the photo icon disappeared. When I reviewed the wire settings in the Google app. It has selected R and W.  I was attempting to install it at the junction box where the thermostat wires and zone valve wires meet

Screenshot_20211212-121715.png

 

PXL_20211211_191221730.jpg

 I have to hook everything back up again. I replaced the new transformer from The Big box store, had zero volts coming out. Double checked wiring all of good. Installed old transformer had my 24 volts. Also had Nest power connect hooked up. White wire from thermostat should go to see on power connect? 

laurentbourg
Silver Product Expert
Silver Product Expert

Yes the white wire from thermostat goes to where you have it in your diagram. Did you check as previously mentioned on the thermostat device the settings->power connector->power test? 

PXL_20211211_191221730.jpg

 i will re-hook up everything tomorrow and look at power test. Just to confirm. "C" wire from power nest goes to spare thermostat wire? Whick would then be connected to c on back of thermostat? Or do I take "C' from nest Power & hook to white wire on transformer? 

laurentbourg
Silver Product Expert
Silver Product Expert

The C wire is from the transformer, not the spare thermostat wire. The purpose of the Nest power connector is to provide a solution to people that don’t have extra wires to their thermostats. 

Understood. So I can take white from transformer to C on nest power. I'll let you know tomorrow how I make out. 

Thanks,

Chris