Welcome! Here are the website rules, as well as some tips for using this forum.
If you've found help here, check back in to let us know how everything worked out.
It's a great way to thank those who helped you.
My Home was build in 2013. I have an oil boiler that has a honeywell transformer at72d That leads to 3 honey well zone valves. Behind current thermostats i have free wires not being used so I’m hopping one of those can be used to tap into a 24v source and use it as a c wire for my 2 nest thermostats.
The following picture shows how my boiler is wired. I’m hopping to tap into the secondary transformer white wire that’s connected to all the yellow wires. Would these transformer be overwhelmed by connecting this 2 thermostats to it ? Or even 3 thermostat.