Long story short, I’m attempting to tap into the 27v on our boiler via the Taco zone valve controller. I’m using a wifi t-stat to control our pellet stove. The new model I purchased is not compatible with a transformer and needs a C wire. I have 27v across the two terminals where the yellow wires come in from the transformer. I put the blue wire on one side. Then after running the wire and hooking it up, I realized that no power on one terminal; it’s across two. I was hopeful the “COM” terminal on zone 4 could be used, but it doesn’t seem that has constant power. Any thoughts on where I could tap into power on this thing? I need a constant 24/27v to run the wifi on the t-stat.
So you can't just tie into the 24V right from the existing transformer? (the 2 yellow wires) Not sure why...that gives you 24V...
That’s what I tried to do. If you zoom in on the top pic, the blue wire I tapped into one of the terminals with the yellow wires entering from the transformer. I get 27v if I put my multimeter across those two terminals (where the yellow wires are).
If you have one wire hooked to each side (of the yellow wires from the transformer) and you have 24V at the new tstat, and it doesn't work, something wrong with it. If you have 24V at the yellows, and don't have 24V at the new tstat, the newly installed wire is bad? I had that happen one time...ran a new wire and as soon as I hooked it up the heat came on, no matter the state of the tstat...after a very frustrating hour or two, I figured out that I had drove a staple right between the red and white wires...shorted them out, just like the tstat was calling for heat!
Something I didn’t think of….I’m currently using one wire. Maybe I need two wires; one in each terminal. Then place both of those wires in the “C” connector on the t-stat. Will that cause a short though?
Yes, you need 2 wires...a complete circuit. Look at the diagram I put up in post #3...you have 1 "hot wire" and then 3 "neutrals" coming back, 1 each for the "heat, 1 for the AC, and 1 for "fan only", the tstat completes the circuit between the hot/neutral and makes that device run...there is no short because the contactor coil for each respective circuit provides a "load", just like a light bulb does, hot in one side, neutral in the other, bam, light...but take the light bulb out and you have a direct short. (I just reread your response...yes, both wires on the C terminal will cause a short!) If its easier just buy a 24V transformer from Supply House and use it for the power source for this tstat/stove (furnace?) https://www.supplyhouse.com/24V-Transformers-35570000
Thank you! That’s very helpful. No go if that’ll cause a short. This unit is the “Lite” version (Sensi) of their wireless t-stat. I went with that because it’s for our pellet stove and not used half the year. Unfortunately, this unit is not compatible with a transformer. My former Wyze t-stat worked with a transformer, but it’s a bit clunky with the pellet stove. I could always go with a regular Seni Touch. It’s more expensive, but that version will work with an external transformer.
What stove do you have? Looking at the manual for that tstat I guess I'm not seeing where the issue is? It says 24VAC from HVAC system...that's what you are putting to it...what's not working, the tstat, or the stove? You know that tstat uses batteries to run, right?
It’s a Hampton GC-I60 pellet insert. It runs off a milivolt t-stat. With a wifi unit, it needs contestant power for the wifi radio. The batteries will only power it for a short period of time on their own. I for some reason can’t get 24v from the Taco unit, through one wire to the t-stat. If I did, it would be powered through the c-terminal on the actual t-stat and keep the unit powered up and connected to wifi.
I was starting to wonder if you weren't dealing with a millivolt situation. So you can't get power to the tstat through 1 wire...yes, that is correct, for power to flow you need a complete circuit, that always requires 2 wires, a power side (+) and a ground (with DC) or neutral (with AC) side for the (-). So in looking up the tstat wiring for this stove I stumbled across the thread over on the other site where it appears you were hooking up your existing tstat...looks likes lots of good info there from guys that are more familiar with your exact setup than I am...and I have no problem trying to help here, but if these guys already have done the homework on this, I have no problem cheating off their paper, so to speak Its this thread, and then the one that is linked a few posts down too. https://www.google.com/url?sa=t&sou...wQFnoECBEQAQ&usg=AOvVaw32GlVMwX-lBLyqM3pdYVTw
Yep! That’s the one! I had it working with two previous wifi t-stats via a transformer. One of those t-stats dropped cloud support recently after 10 years. Not bad for a connected device! The Wyze unit I used still works, just not ideal from how you run the stove. I have a regular Sensi running our HVAC system and that works fine off just a singular C wire coming from our air handler in the attic. Unfortunately, I can’t get just a single power C wire from the boiler which is very close to the pellet stove thermostat. At this point, I may just put the Wyze unit back into service and see if I can get it to run better. You have to turn the t-stat “off” to get the pellet stove to shut down. For some reason, lowering the set point is not effective.
Thanks for your help with this brenndatomu I put the Wyze t-stat back up with the transformer for power. Below is a pic of the wiring; black and white are from the stove; the two white wires are from the transformer. My hunch is that having a fan setting in the app to “on” was keeping the stove on, even when the heat was below the set point. Will test that out later and report back. Hope this wiring pic helps someone along the way if using a Wi-Fi thermostat with an external transformer.
