Thermostat suggestions for boiler

I currently have a Nest thermostat. I am still on the Nest app and I am not planning on migrating. My current system has a boiler and cast iron radiators. There is no fans or ac on the system. There is no c wire. I am in the USA.

The problem:
The Nest thermostat does not give an accurate reading of the temperature and it doesn't seem to update fast enough when the radiators are warming up. For example, the Nest reads 70, however, 4 feet away, with three different temp sensors, I get readings of 66-67. When the temp is turned up to 75 for example, it keeps heating until the room reads 78-80 degrees on my sensors and Nest reads 75. Then as the room cools down, it takes forever for it to get the temp right. I did try the sensors next to the Nest and I got the same disparity.

I need a thermostat that is very reactive or has/can use reactive sensors. I was looking at the Ecobee premium. I don't know if that is the right Thermostat for what I need. I don't mind adding a C wire but it has to be for the right thermostat. I want to integrate it into the HE. I need to set-up a notification to know when the boiler has run out of water (i.e. the boiler doesn't respond to thermostat). I also need to be able to set offsets to the temp if needed.


Are you using radiators? You could use TRV's if so. Or look at Sinope. You can use that with as many temp sensors as you want with the thermostat controller app in hubitat.

I have cast iron radiators. I looked at TRV's but I decided against them. There are radiator covers and changing temp would be a pita. I am in CT with varying temps.

Is Sinope responsive to temp changes?

Very. But you can aggregate the trv's through hubitat and using multiple temp sensors. For instance you could use a temp sensor in the middle of the room to control the trv for a more accurate temp. This would also allow you to have varying temps for rooms, especially for bedrooms. For instance if someone likes it warmer when they sleep they can have it warmer in the room vs someone in another bedroom that prefers it cooler.

There is only one TRV that is on the compatibility list. That was another reason that I stopped going down that route. Are there others that work well with HE?

Pretty much any z-wave or zigbee trv will work. Take a look at the MOES. Very reliable... And of course you can set offsets to make them even more accurate.

Doesn't your system have to be piped for TRV, like in parallel vs serial?
Perhaps with your cast iron radiator system, it is piped that way, like you can turn a valve on the radiator and no other radiators are affected.
On my tube and fin emitter system, it's serially piped on each floor, so not possible to vary temp by room.

Perhaps there's a setting on your Nest that isn't configured correctly for your high mass boiler system, with its greater anticipation needs, hysteresis, indoor reset, blah blah blah. (I really don't know what I'm talking about.)

Or, maybe you should just buy a new cold climate heat pump like my (NY) governor wants us all to do. :slight_smile:

Nest adjustments are minimal. It's the reporting that is off. It thinks its 70 degrees and three other sensors say 64-65. It's the accuracy that is a mess. I think it's time to come up with a better solution.

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That's what the trv's with additional temp sensors with Hubitat's built in Thermostat controller will accomplish... With that combination you can balance everything accurately

Could there be a pipe in the wall, or something else warm?
Could you temporarily disconnect it from the wall and put it on a table along with your other temp sensors to compare?

There is nothing behind the wall that would affect the temperature. I did place the sensors next to the Nest. Same issue of different temps.