Question about thermostats on radiators

[AmberGer]

I don't know if I understand fully how they work. I mean, I know that you can turn them up, down, on, off but if your heating is on anyway, heating up the radiators that are turned on. I can't understand how turning off radiators can be of any benefit.
Surely might as well have them all on?

More radiators = more gas = more £££

I always understood that the boiler will heat up radiators more effectively/quicker if there are less of them, saving gas/money. So if you have a room in your house which you rarely use, it does make sense to turn the radiators off/put them on the frost setting (snowflake symbol) and close the door.

Remember NOT to turn down the one in the same room as the thermostat.

I watched a YouTube video last month about them and was amazed that I've been using them incorrectly. I would highly recommend searching for a video explanation but briefly...

Each valve has a coil inside it that measures the air temperature - adjusted to account for being so close to the rad. When the room heats up, the coil expands, reducing the flow of hot water to the rads.
The numbers on the valves correspond to a desired ROOM TEMPERATURE. I can't believe I didn't know this.
Number 5 = 30 degrees, 4 = 25 degrees, 3=20 degrees, 2 = 15 degrees, 1 = 10 degrees.
So if you want your rooms at 20 degrees, put the valves on number 3 - and the radiator will gradually click off as the room reaches this heat.

The biggest mistake people make is to put them on 5 thinking the room will heat quicker - it won't. If a room is 10 degrees, the room will heat just as quickly to 20 degrees if the valve is on number 3 or 5 - but if its on 5, it will keep pumping out heat on full blast long after the room is comfortable, causing higher bills.

That's very helpful @FruitPastilleNut
I did not know this!
Will be checking all my radiators today!

Thank you 🙂

This is helpful, I didn't know the numbers were equivalent to a specific room temperature either. I wonder H
how they work in conjunction with the thermostat and boiler though, as the thermostat will click the heating off anyway at a certain point.

And the boiler will only heat the water to a certain temp so presumably the room can only get to a certain temp anyway limited by the heat of the water in the radiator?

@BEAM123 I find that for bigger rooms, the numbers on the valve don't really correspond to the 10/20/30 degrees temperature in the room. It makes sense as the coil "estimates" temperature near the radiator and not in the middle/ on the other side of the room.

The boiler will turn off when the temperature in the room with the thermostat in reaches the selected level. So the rest of the radiators in the house will turn off too, regardless of what setting you selected on the valve of each radiator. So it takes some trial and error to figure out the optimal setting combo for the thermostat and all the radiators. You need to keep the radiator in the room with the thermostat on the highest setting I think for the system to work properly. You then put the thermostat on say 20 degrees and put the other radiators in the house on number 3. The heating in the entire house will turn itself off when the thermostat room reaches 20. The other rooms might not have reached 20 yet even though you selected number 3 there.

Or you could select 22 in the thermostat room. It will be more likely now that the other rooms will have enough time to reach the desired 20 degrees (setting 3). Once it happened, hot water will stop flowing to those radiators (but not the one in the thermostat room), thus reducing the amount of water needed to be heated and reducing gas usage etc. So now you will only be heating water to heat the thermostat room to the selected 22 degrees, which will use little energy (other radiators have already clicked off). Once that room is at 22, the boiler will click off. Then when the temperature drops, boiler will come on again but how long it will be on will depend on whether the other rooms are also cooler now and need heating to level 3 again, thus needing to heat more water and use more energy.

I think (but not 100% sure) this is more efficient than having all radiators at 5 but the thermostat turned down.

Hope this make sense!