Automation scenario Nest & Sonoff TRVs


I am planning to setup a Nest v3 thermostat to my OpenTherm boiler, but want to control the temperature with individual zones and not centrally just on the one nest thermostat itself.

I’ve looked at other systems but due to support with another vendor I require, the Nest seems to be the best option. The issue for me is taking the control away from the Nest but using Zigbee based Smart TRVs iin each zone to call for heating and activate the boiler via the Nest as needed.

I want to use SmartThings to setup the integrations and have it so that if a TRV is increased within set limits it will automatically increase the Nest - is this possible?

I am testing Sonoff TRVs at the moment and hope to integrate with Smartthings - not sure if they can be integrated directly with Smartthings or needs a hub - anyone done this or used another brand that works well in this scenario?

Many thanks!

The Actions for a Routine with the Nest thermostat are quite limited. You can set the cooling temp, set the heating temp, change the thermostat mode (Auto/Cool/Eco/Heat/Off), and change the fan mode. Given these limitations, the easiest way would probably be to have a Routine(s) that cycles from off to heating when the temp dips below a measurement on one (or more) of the TRVs. You then have another Routine that cycles from heating to off when the desired temperature is measured at the TRV(s).

The Sonoff TRV Model TRVZB is supported by the Edge driver zigbee-thermostat-stock-mc from @Mariano_Colmenarejo and you can subscribe to his channel and install the driver from here.

I don’t know if you’ve considered using an Ecobee Thermostat or not, but it has separate temperature sensors that can be deployed into different locations and then used by the primary thermostat to maintain the set temperature for that location based on occupancy and comfort mode settings (like Home/Away/Sleep/etc). That way each sensor location can trigger the heating without having to use ST Routines.

Hi, thanks for sharing this - the ecobee solution does look like something that I would be after, however I do not think it is available widely in the UK and seems very pricey in respect to other solutions.

I am keen to get a solution where I have OpenTherm support with a combination boiler with the thernmostat, that acts as just an on/off - a Nest is probably overkill for this but if it works so be it.

Then with the TRVs be able to turn down the heating in each zone based on occupancy across the entire building, when a window is opened etc.

As this will be a holiday home / airbnb - happy with a master set temperature for the house when they are there, and an eco temperature at night, but also want this to go to eco if they leave the house. I’d like ideally for them to press a button on the tablet as they leave and say when they want the heating to come back on if they say go our for the day.

I’m also keen to set up a max temperature, so say 21 degress is as high as it can be set throughout, and if this is higher than the programme it will effectively boost it for 1 or two hours and then revery back to the scheduled program.

I was planning to use Sonoff or Aqara TRVs but have a presence and temperature sensor in each room to use for more accurate data and temperatures to help with configuring the routines.

Any ideas if this is possible, or with another system with the least amount of configuration possible? :o)

Hi, I have a very similar challenge. I am running a Holiday Let, equipped with an old Samsung heatpump that is slightly undersized for the property (was installed before I bought the house). The low flow temps (around 48 degrees centigrade), lack of headroom in the heatpump and poor design of house pipework means I have to avoid specific rooms being too greedy and pulling the heat away from the core of the house where the Nest controller is. The ground floor Nest is fine since it is all underfloor and works brilliantly, once up to temp.

I have purchased Sonoff TRVs for the rooms with rads in and would like to have those TRVs mirroring the temperature setting of the Nest so that the house heats up evenly.

Possible or not, do we think?

Not sure what you mean by “mirroring the temperature setting of the Nest”. Do you want the heating set point temperature on the Nest to be the heating set point temperature for the TRVs so that they shut off the flow to the rads when that temperature is reached? And are you wanting changes to the heating set point on the Nest to be reflected on the TRVs so that as the set point changes on the Nest, your TRV set point follows?

Or are you looking for the TRVs measured temperature to somehow have an influence on when the heatpump system is operating? If that is the situation, your challenge is going to be wrestling control away from the Nest and manually creating Routines to control the heatpump cycles or you may have to raise the Nest heating temperature set point so that the temperature in that location doesn’t cause the heatpump to shut off prior to the rooms with the TRVs hitting their heating set point(s). Which may have the unwanted effect of causing the downstairs area to be too warm.

If the first scenario is what you are looking for, I’ve seen examples of using the Rules API to copy a thermostat’s measured temperature to another device (virutal or otherwise) using the command for setting the destination device’s heating set point. For example, the command for a Nest is “main.thermostatHeatingSetpoint.setHeatingSetPoint”. There are examples in this topic. You could also use the 3rd party rules engine Sharptools which might be a little more user friendly than the Rules API but would run in their cloud and might require their paid tier.

Bruce, thanks very much for the reply - the first scenario is the one I’m trying to achieve. One consistent temperature throughout the house, governed by the nest(s) with each room shutting down flow as it reaches the Nest’s temperature, rather than the TRV remaining endlessly open to achieve an unattainable temperature that a guest might have set (‘5’ is 28C which is way beyond the capability of the system).

I will look into the links you suggest - this is promising…

Google Nest is not available to SharpTools through the ST integration. Google Nest limits access.

Oh yeah, I forgot that they don’t allow access to their APIs :frowning: