Hi,
what is in your opinion the best TRV?
my requirements:
- ZigBee
- integrated via zha
- should expose, at least, current temperature, desired temperature, valve position, battery status
- max 50$ each
Thank you!
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Did you manage to identify any candidates? I’m on the hunt. I got some yesterday that were allegedly zigbee. Alas. Today I return them. 
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Hi @Bergals,
in the end, I did my setup with Beca BRT-100 TRV: Beca Thermostatic Radiator Valve BRT-100 Zigbee compatibility
It’s tuya and it seems to work quite well.
In ZHA it is integrated using this custom quirk: [Device Support Request] Improving "TS0601" "_TZE200_b6wax7g0" TRV thermostatic radiator valve · Issue #1123 · zigpy/zha-device-handlers · GitHub
It fulfills almost all the requirements: it does not report accurate valve position and current tempertature, as these values are not updated in realtime (instead valve open/close is fully accurate)
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What is the behaviuor of them when the lose power / comms? I presume they stay on whatever their last state was when the lost power / comms? Or do they fail to fully open / closed?
What do you mean with “comms”?
If they run out of battery power, I presume they stay in the last state. They would not have power to change the valve position
Upon reflection comms isn’t really a valid question as they can work in isolation and have a display so please ignore that part of the question.
That was my thinking on the power side of things. Obviously traditional TRV’s are a mechanical device so only a mechanical failure would render them inoperational. But with a smart TRV when the power is lost you could get an undesirable temperate as the valve wouldn’t be able to close once the desired temp is reached.
I wasn’t sure if they maybe used a combination of electrical and mechanical, so that if you set the valve to say 20c, it would always aim for 20c regardless of whether it had power or not.
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Smart TRV do not work without power at all.
You need to replace batteries as soon as possible, I’ll setup alerts when power level is low.
I don’t know how the mentioned TRV is handling it, but most smart TRVs open the valve when the register low bettery automatically. They call it antifreeze function. SOme open the valve to 100%, others to 30% only. However, that is the reason why I was going back to my old mechanical TRV.
Imagine you are on vacations for a few days and the battery is getting low and the valve opens to 100%.
You would constantly heat on maximum and depending on your energy prices you can cancel your next vacations because you have to pay a super large heating cost bill.
Personally I would prefer a valve which gives me the option to just close the valve, but this behaviour is usally hard coded inside the valve. Also I think it’s disappointing that you can not set a percentage value on how much the valve should be opened.
I think the best smart TRV would be a combination of mechanical TRV and smart ones. Like setting the mechanical one to specific levels, which represent a target temperature. This would safe a lot battery as the mechanical mechanism would handle the gradually closing/opening of the valve and would even ensure basic functionality and anti freeze protection when the battery is empty.
How do you manage controlling the % of the valve opening? I see that it’s a read-only value, not a controllable thing
Exactly, it is a read-only value and it not a reliable value as it is not updated in realtime. I use the valve state attribute (open/close) as it is always updated by the valve.