Wall radiators have a valve that has this progression of settings: “❄ 1 2 3 4 5”. Naturally as you turn it a pin changes position which opens a mechanical valve a precise amount.
The question is what happens at “❄”? I always thought of that as zero, completely closed. But my central boiler seems to target 5°C/40°F even when off to protect pipes from freezing. So what happens if all the radiator valves are off/closed (❄) and the boiler is triggered to prevent freezing? Does each valve also have a thermostat to open at freezing?
I thought for years the snowflake just meant cold (closed). But I wonder if it actually means frost protection, where it does something smarter. There are times when it’s in that ❄ position and yet the radiator still heats up. I thought the valve was broken, but then other radiators occasionally did the same. Is that normal?
I think the trv (thermostatic radiator valves). Are wax motors. Basically they work on the thermal expansion or phase change of a wax to exert a force. With the trv set to 5, it takes a lot of expansion of the wax to push the pin to close the radiator valve. At *, only a little heat is needed for the wax to expand enough to close the valve… But the valve is a little open when cold. If the valve is set to 0, then it’s truly closed at any normal temperature.
I appreciate the explanation. Interesting to hear the term “was motor”, which I always thought of as a valve but I guess the fact that the wax moves a valve it’s sensible to call it a motor. IIUC, it’s similar to thermostatic shower mixers, but with a floor temp of 5°C.