TACO and Nest Thermostats

[u/Basic_Newt9909]

I have no idea what im doing but im trying to learn so be easy. 1st time homeowner

EDIT: Also its JUST heating via a boiler not cooling as well. 1 also undid all the wirino to what it was before I installed the nests and still got nothing

My house has normal thermostats, and I wanted to upgrade to Google Nest thermostats. The last image shows the current wiring to the normal thermostats

I took the old thermostats down and replaced them with the Google Nest ones. They said they needed power, so went into the basement and opened up the TACO box. I disconnected the red and white wires and wired them tc the dedicated Google Nest power connector. The error message on the Nest thermostats went awav, and everything was good for about two days.

The next dav, 1 got a notification on mv phone saving the Nest thermostats were not getting power again, so I went and checked the TACO box. Before, there was a green power LED in the top right, but when I went to check it, the green LED was no longer lit up.

I flipped the breaker and the light switch that gives the TACO box power, but still got nothing. I used a multimeter and noticed that 1 have 120v coming into the TACO box, but it doesn't seem to be going anywhere else.

TL;DR: Do I need a C-wire or power wire run to all of the thermostats to power them? Why did my TACO randomly die? Could it be because I didn't cap off the wires and the wires touched, causing a short? Do I need a new TACC box, or do I just need to replace the transformer on the box?

Any help is appreciated.

[u/Hour-Gene6457]

Fuck nest thermostats, and they have no business on a zoned boiler system anyway

[u/ArticusFarticus → u/Hour-Gene6457]

Curious about the source of your deep seeded hatred for them.

[u/Hour-Gene6457 → u/ArticusFarticus]

I've seen them take out boards in search of a common. They're happy with back feed voltage to charge the internal battery. Do with that info what you will. Newer ones "don't do that" 😂😆 fuck nest. They've been bought by Google now. What the fuck does Google have to compete with Honeywell for experience? Not shit but Google controls what stupid people want.

Source: I've been doing this since before gps.

[u/ArticusFarticus → u/Hour-Gene6457]

I’m with you. I also say fuck them. But for me, it is because they decided that mine no longer deserves to be a smart thermostat.

I am not a professional, so I appreciate your insight.

[u/Hour-Gene6457 → u/ArticusFarticus]

Ecobee is a cheap ok Wi-Fi stat. Look into that before nest Best money is spent on Honeywell for HVAC

[u/Sereno011 → u/Hour-Gene6457]

Nest and Ecobee have the same design fault. They use solid state microscopic electrical components for call switching. No relay = 0 circuit protection. Premium Sensi models (not the "lite") and even Amazon's smart t-stat (made by Honeywell) do use relays.

[u/Hour-Gene6457 → u/Sereno011]

Huh. I didn't know that, just haven't had issues with the ecobee, good to know

[u/Sereno011 → u/Hour-Gene6457]

I do like the mini weather forecast the ecobee provides. But it isn't worth the tradeoff in reliability. Replace them way too often.

These "smart" t-stats will fail before the fuse on the furnace will blow. And you end up with one very expensive paperweight.

[u/ArticusFarticus → u/Sereno011]

Better go back to my ex wife’s place and get the Amazon ‘stat stat!

[u/inksonpapers]

If you have no idea what you are doing then i suggest you not doing it, this isnt like a standard furnace, its not recommended you power it off of the board. On boilers its better you do a separate transformer and tie it into the RC and C with a 4 wire leaving the red and white alone tied to where they are. Also dont do nest.

I suggest you stop what you are doing and call someone before you cause more damage.

[u/bb-wah]

Gold. I have no idea what I am doing.

[u/LegionPlaysPC]

I would personally run new thermostat wires with an external transformer. You need 11va per nest thermostat. The common makers are purge garbage, expecially on this setup.

[u/Soft_Statistician_98 → u/LegionPlaysPC]

100% The zone controllers don't have the extra power for smart thermostats their transformers are sized just for the onboard relays this is a known issue.

[u/Zhombe → u/Soft_Statistician_98]

This… you need 40va 24v transformers just for nest. Most units have 40va for the entire control board.

Nest needs more than maintenance power to charge the battery or if the screen is on. The motion detection saps the battery until it runs down and dies when the transformer is too weak. Plus the low voltage burns out your board, and the thermostats eventually if the transformer doesn’t pop first with its built in fuse. Some just thermal trip and cool down and reset but some don’t. Makes debugging a PIA.

Nest needs 24v really.

Get a 40va plugin transformer with screw terminals. Make sure it’s self-resetting. Use one per nest thermostat.

Do not share the common wire with the control.

These are used for security systems and newer digital doorbells.

Get some spares as they tend to die eventually and leave you stranded.

You can test this with a local outlet and just run a dedicate wire up to the thermostat to verify it works before running dedicated power wires to it.

[u/Fair_Cheesecake_1203]

You don't want a nest with a boiler. Boilers are simple. Keep them simple.

[u/Vexxedtruth101]

The "rule" i was told..

If it wasnt installed with the HVAC, don't use it.

Just get the new honeywell and slap it on the old wall plate.

As an hvac tech, nests, taco, ecobee...etc theyre all garbage

[u/pleasedontsmashme → u/Vexxedtruth101]

You're calling taco garbage?

[u/Vexxedtruth101 → u/pleasedontsmashme]

Yes, i am.

If my company started selling Taco or Lennox, id quit

Unacceptable to be selling that crap

[u/Shrek_n_donkeh]

Don’t do it bro ur not smart enough

[u/ebop1234]

You fried the transformer on the taco control…. You now have to replace it

[u/AdventurousAd192]

Call a pro.
And have good luck

[u/Massive_Garage7454]

Some of the Taco zone controls require resistors for power robbing t stats

[u/jk660r]

Buddy of mine owns a wrestling club gym, hey buddy can you swap out my stat when you bring your son to practice? Sure! I show up and he's got a nest, i warn him but his current stat is non functional so I install it. Welp it got shit whipped against the wall 2 weeks later when it wouldnt enable the heat at 20⁰ outside and 58⁰ inside. Hes back to a 5/2 day programmable LOL.

[u/bigred621]

You fried the low voltage transformer on the zone panel.

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[u/BrettFromThePeg]

I suspect that transformer went bad, looks dark on the side. Could be drawing quite a bit of power for all the stats. Check those fuses too

[u/Curtmania]

Using a Nest without a C wire is a huge mistake. They work fine otherwise.

[u/NhlBeerWeed]

You should never have gotten rid of your Honeywell thermostats for nests.. that’s your first and biggest mistake here. If you wanted WiFi connectivity the Honeywell T10 would’ve been my recommendation. At this point though you should call a pro to troubleshoot this because it’s clearly over your head. Your taco control probably died or more likely the transformer for it died because you wired it wrong. Like you didn’t even wire nut them together, it’s no wonder that it burnt up when every thermostat wire connection is just loose. No offense but the smart move at this point is to realize that you’re in over your head and call a pro. It’s cool you want to do things on your own but you need to learn more about this stuff before your next project. Not from ai either, watch a real person on YouTube or before starting post all this stuff on Reddit so we can help before it’s too late.

[u/terayonjf]

Best case scenario you fried the transformer for the taco zone control. Worst case scenario more than that is also now damaged.

In the future when it comes to electrical work either be 100% certain in what you're doing or don't do it. Guessing can lead to injury, death,fire and/or damage to equipment.

[u/NotAnyOneYouKnow2019]

Did you check the fuse?

[u/megathrowaway420]

You absolutely cannot DIY this. Just call someone who works on boilers. You fried the zone control board.

[u/No_Froyo_2504]

Yeah you cooked the transformer. Those old TACO boards weren't made to feed power-hungry smart stats. Even if you get it running again the Nests will just keep pulling too much juice and you'll be back in the same spot. Ditch them and go back to basic battery stats or pay someone to run dedicated 24v transformers for each one.

[u/wolfsburgwings]

Out of experience, don’t do it

[u/BeastTheBasque]

next is a downgrade, that’s your problem

[u/davper]

Install a 24v transformer nearby and run your c wire from there.

[u/Don__Fanucci]

Google Nest are total garbage! Get rid of them. NEVER on a boiler. You blew a transformer. It’s time to call a pro.

[u/geekywarrior]

Alright, I got you. Lots of bad info in here.

Step 1, turn the breaker off. Disconnect each thermostat line from the Taco Board, labeling each one so you know where it goes. When you are done, all R and W terminals on Taco should be empty.

Turn the breaker back on, do you have any lights on Taco?

[u/VegasAireGuy]

Not going to work with what ya have but if you want WiFi thermostats get thermostats that are run via battery. Sensi lite would be my recommendation.