Hi all,
I want to replace the classic TRV’s on my radiators in the bedrooms and the bathroom, with something smarter. First I was looking at the (shelly) smart TRV’s.
However there are 3 issues that I think can be a nuissance :
They are not silent (annoying when the kids are studying in their room)
Their temperature sensor is way too close to the radiator itself. So non optimal temperature regulation.
They use batteries.
and fourth : they are not cheap.
Then I learned about thermal actuators. They are a lot cheaper, work on mains, and are silent. I can install a separate temperature sensor in each room and control the temperature to this sensor, so more accurate.
However there is one thing I am worried about (if I understand the actuators correctly) : If I use the software generic thermostat from HA, and use its digital output signal to control a relay or smart plug that switches the actuator on and off, I can do on-off regulating to the required setpoint.
So I would be continuously (but slow) opening and closing the actuator completely. What would be the overshoot in temperature that the room would continuously have? 1°C?
Because with ‘normal TRV’s’, they are always in the same position, which would result in a ‘stable’ temperature. And I would continuously be switching between 0 and 100%.
Will this also result in a ‘comfortable’ situation?
An important thing to consider that would hold me back from using this: If HA is down, you would have really lousy temperature control over your home. Also, with normal use you would likely not have “normal” override control over temperature the way guest would expect and understand. And you’d need some solid knowledge on how heating systems work.
That is why I went for a smart thermostat solution that works independently, but is connected to HA so can be influenced to be even smarter. I use external thermometers to periodically calibrate the internal ones, but that does eat more batteries though. The system supports external ones too, but they are way too pricey.
As for on-off control: it can be done. Most likely you’ll be wearing the actuators out sooner than expected though - I do not think they are meant to be used that way. E.g. floor heating is slow, so involves little switching. Are you sure they are silent and controllable from HA? That would invalve a (clicking) relay I’d suspect? And how will it work if you power it and some one manually closes it? HA won’t know I guess?
Instead of the generic thermostat I’d look for a PID controller that supports on/off control if you want it to be anywhere near what a good thermostat can do to prevent overshoot. Overshoot depends on multiple factors, so controlling it is an art - it is what PID’s are designed for. Ideally you’d have a self calibrating one. I know there are PID controller integrations for HA, I know some mention on/off control, but I do not know if they actually went so far to implement and test it properly though.
If you also intend to replace the central thermostat, you’d also need something to control the burner. The heating system needs to know when any room requires heat. (This is where good smart thermostats with connected TVR’s are at their best, by implemting true zone heating, where other rooms can be heated even if the central room does not need heating). If your central heating system also provides warm water, you might also lose control over that compared to a smart thermostat. Not a huge problem, but so you know.
You will also will need to install an bypass valve if you do not already have one. Because without that it can never be the case that all actuators are closed at the same time. You could try to automate that on HA side, but you probably cannot prevent people from actually closing the actuator, or one failing to listen to your command for some reason. Having then all closed at once will ruin the pump, which needs to run periodically.
I second what @Edwin_D says. If HA is down, crashes, hardware fails or your automation malfunctions, you may have an out of control heating situation (either no heat or too much). While that may not be a big deal when you are home, if you are gone for several weeks that would be problematic.
You are also dealing with water and pipes that are under constant thermal stress. Whatever you install in here needs to work, be designed for this application and be installed correctly. It ain’t cheaper if it floods your home when you are gone.
All that said, smart thermostats have many benefits - including a local display for adjustments and autonomous operation when HA is down and most have “learning” capability that learns how your space responds to heat. Then you use HA to manipulate the setpoints.
When it comes to heating your home, keeping great comfort while saving on energy is difficult to do right. Companies like Honeywell have done it for decades. So while e.g. a Honeywell Evohome system might be expensive, the cost is earned back over time many times over. It is an investment worth making. What Home Assistant can add to it it geofencing (per room if you want), open window control, etc.
There are other similar good systems too that are cheaper, and also can do well. Some, like Tado, are depending on cloud more than you may like though. It is some time since I did the research, so I would not be comfortable advising a specific brand (including Honeywell, it is just an example of a brand I know that knows their business, but I am not sure how well it connects to HA).
I need to heat my daughters bedroom because her room is above the garage but I don’t want the entire house getting hot because I cant cope with it being too hot. This has been a great addition to my smart home.
