(2025) Smart and/or programable TRVs that function as a flow rate valve and not a thermostat

rossn · September 23

Are there any smart and/or progamable TRVs that exist, work well, and actually adjust flow rate? Ideally both for mounting directly at the radiator and also for wall mounted controls that can control a remote, inline valve. My valves are Danfoss.

I have a two pipe setup with a combination of radiators and radiant floor (think 9 zones + some rads). Cast iron boiler.

I have looked around for smart or programmable TRVs, but keep finding they are typically a step function, working as on/off like a thermostat. Not adjusting flow rate. Ideally I would have a way to control multiple TRVs at once, such that if, for instance, we open the windows, I'm not adjusting 4 things in the master suite or even the whole house.

pecmsg · September 23

they do make pumps that operate off water temperature

Jamie Hall · September 23

Theoretically, of course, of course, it's quite possible. In practice, there are some rather interesting difficulties. They lie both in the control logic which is to be followed and in the physical construction of the valve.

Not to say it can't be done. I just don't know of any which do.

hot_rod · September 23

Is this a hot water, or steam application ?

Caleffi has a product with adjustable Cv, in the European market. Not for steam however

https://www.caleffi.com/sites/default/files/media/external-file/01330_EN.pdf

https://m.youtube.com/watch?v=bQLlu5FUOHM

Kaos · September 24

0-10V zone actuator with 0-10V thermostat. If you are into smart home, there is a lot of 0-10v output devices as they are used for dimmers, combined with a room sensor and a bit of coding, you can do your own controls.

https://www.caleffi.com/en-us/thermo-electric-control-valve-actuator-24v-source-0-10v-prop-actuation-nc-6565-caleffi-656524

rossn · September 24

Hi All, thanks for your insight - really appreciated.

To begin with, I think I made a terminology mistake with '2 pipe'. The radiators I have each have a home run off of the manifold.

@pecmsg - That is good to know. Based on the construction of my system, I probably can't leverage that effectively.

@Jamie Hall - I was hopeful someone had commercially figured that out already and had a tested product available.

@hot_rod - I'm based in the US. It is a hot water system that has two temps - med and low). I can see how the adjustable Cv of Dynamacal would be helpful. Is its primary use case when running a two pipe system with multiple radiators on a set of supply/return lines? Does Caleffi offer any digital / smart control of the valves, such that they can be grouped and controlled together?

@Kaos - While technically, I could produce my own software and control system, I think that would become very fiddly. No one has a packaged solution using 0-10v valves and a corresponding control system already?

It does make me wonder if I should run some 4 conductor wire to each radiator, while accessible.

All -

Ultimate goal: I was hoping for a TRV control system where I could adjust a group of emitters without running around to hit each one independently.

For instance, windows get opened for a few hours in one area of the house (we can be 20F over-night, and 60F during the day), or I've been away on vacation for a week with temps set lower, and bring them up half a day before we arrive home (I realize some more modern boilers may help address the later need).

I see a lot of smart TRVs, but just seems like they act like a traditional thermostat. I can keep searching and will report back my findings.

hot_rod · September 24

you have a homerun system from a manifold where each radiator has its own supply and return?

rossn · September 24

@hot_rod - that's correct

Jamie Hall · September 24

So it would seem that the hardware exists — the modulating valves (0 to 10 volt). Excellent. And, of course, the sensors, also 0 to 10 volt thermistors.

Which leaves the problem… the software and control integration. Whether you need to run a separate cable to each radiator or not is somewhat debatable; I would at least look into the possibility of a single 4 or more wire (probably Cat 5 or better) cable capable of feeding a digital command and feedback signal to a central processor but also capable of feeding the required power and ground to each unit. I suspect the computing power available in a Raspberry Pi of some flavour would be quite adequate.

The Raspbeerry Pi community is open source — and has extraordinarily wide interests, so it is entirely possible that there may be some code bits which would be usable as part of the programming.

Kaos · September 24

You don't need to do your own controls. 0-10V thermostats are common in commercial space ie:

https://buildings.honeywell.com/us/en/products/by-category/building-management/field-devices/thermostats/zonepro-tb6980-floating-and-tb7980-modulating-digital-thermostats

rossn · September 24

@Jamie Hall and @Kaos - thanks for the brainstorming on this one. I like the idea of the 0-10v actuator, if I could find a developed interface. Kaos - I will look into that and some of the commercial thermostats; however, my concern is that it may read temps at a single location, but perhaps thermocouples can be added. I do prefer a system that is also simple, from the perspective of not having to a lot of tune and tweak to it, and this might lead me away from that.

I see Danfoss also has a 0-10v actuator compatible with my RA2000 valves. I also notice they have an adaptor ring to attach them to the Uponor Manifold zones. So, that is encouraging, but will have to dig deeper to see if that adaptor fits the stainless manifolds.

I am very curious if this Shelly BLU TRV operates on/off or variable flow. The marketing statement: "Boost modeFor a fast warm-up of the room." leads me to believe, that would indicate it doesn't operate as on/off, but I will have to reach out to see. Downside is this would not cover the majority of the house (radiant floor).

(2025) Smart and/or programable TRVs that function as a flow rate valve and not a thermostat

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