Radiator Control Valve/flow valve

somejoke

If you take two identical rooms as reqards outside conditions, and overnight you leave one valve fully open and the other say half open, in the morning will one room be half as hot as the other.

Are the valves that effective/controllable or can only a trv do this.

Wearb

It's not as simple as that. A half open valve may still supply as much hot water throughput as the radiator can utilize. The get to where you suggest, the second radiator might need turning on at about 10% for example.

You also have to consider that the rate of heat transferred by a radiator is proportional to the difference between the temperature of the rad and the room.

somejoke

Sorry I'm not explaining this too well, I'm trying to understand if an ordinary flow valve offers any control over the heat output from a radiator.

Should it just be regarded as an on/off valve or does choosing any in-between setting have any real effect on adjusting heat output.

Say you were watching tv and the valve was fully open and you felt a bit hot, would turning the valve down a bit make any difference.

Wearb

As I said, at about 10% on it should start to affect the output that you ask about. You would need to experiment with it.