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Comment by simonbarker87 | Hacker News Reader

> Install Smart TRVs. This doesn’t actually address the initial problem at all. Smart TRV can’t heat a room if the boiler has been switched off by a central thermostat.

A valid point but the way round this is to set the main thermostat to the highest temp you would ever want the house to be and have the schedule to 24 hours or just the primary heating hours of the day.

I say this so those in rented accommodation don’t think they miss out on this fun. You can swap TRVs out with no plumbing skills and you don’t need to worry about what primary thermostat you have.

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There are Smart TRVs that can wirelessly trigger a contact closure that will turn on a zone for the boiler. You could also listen to the (usually Zigbee) protocol messages and close a relay yourself if you have a home automation setup (either directly from Zigbee, or by gatewaying the Zigbee to MQTT and then responding to the MQTT traffic).

The problem with running a call for heat to the boiler (nearly) full-time is that that will run the circulator pump for the zone and, if there's nowhere for that water to go (because all TRVs are closed and there's no "loopback" pipe), the circulator is going to draw a lot of power and eventually fail from being deadheaded.

> The problem with running a call for heat to the boiler (nearly) full-time is that that will run the circulator pump for the zone and, if there's nowhere for that water to go (because all TRVs are closed and there's no "loopback" pipe), the circulator is going to draw a lot of power and eventually fail from being deadheaded.

It's common to leave a single radiator without TRV for that reason - typically the bathroom.

I've found the TRV-less radiator is usually in the hallway as that's historically where a thermostat would live (ground floor, no windows, cool) and you don't want them to battle each other. You also want it to be sufficiently far from the boiler so the return water cools enough and you stay in/near the sweet spot for a modern condensing boiler.

TRVs are often avoided in bathrooms since those rooms have another source of heating (bath/shower) that will screw up what it's trying to do. Also, some smart TRVs don't have sufficient IP rating for such a moist environment. That said, you could install one in a bathroom and people do. Not sure why though, maybe they get carried away with their smart setup.

It depends on the circulator. If it’s the usual Taco 007, then yep it’ll fail. If it’s an ECM circulator set on delta-P like a Grundfos Alpha, then it won’t mind a bit.

I didn't understand the quoted critism from the article. Smart TRVs are supposed to be able to independently call for heat, isn't that the whole point of them.

There's nothing very smart about simply reporting they are too cold - is that really all Nest can do!?! I was under the impression that Tado, Drayton Wiser, etc handled this properly and would have solved the problem (albeit for lots more money).

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