Silly Q re heating and thermostat

[coolpotato]

This might be a very silly question but i'm sure someone on here can tell me the answer!

So the heating is on a timer, say to come in between 5am and 7am. If the thermostat is set at 20 degrees, am I correct that the heating will only come on (as in radiators will get hot) if the ambient temperature is less that 20 degrees? So that if you turn the thermostat down by a degree or two, then the heating will only come on at 18 or 19 degrees thereby a subtle but money saving effort.

But when the heating is on, but the ambient temp is above the thermostat setting, the radiators are not hot but I can feel that they are between cold and coolish, or I can feel faint heat. As opposed to when the heating is off, and the radiators are stone cold.

Does that then mean the heating is actually on but not being circulated? So is the water being heated up anyway so it only kicks in as soon as the ambient temperature drops below the thermostat setting (so long as the heating is set to on)

I just don't understand how you can save money if the water is being heated up anyway?

Does anyone my ramblings make sense? And can anyone explain it in layman terms. Thanks!!

[PigletJohn]

for the heating to come on, both the timer and the room thermostat need to be calling for heat.

Unless you have a frost stat which will override them in unusually cold conditions.

However, if you have a faulty valve in or near the boiler, it may sometimes allow hot water to leak into the radiator circuit when it is heating the hot water. This can happen with both a hw cylinder or a combi. Usually it will be most noticeable on the nearest radiator, at the top, or sometimes an upstairs radiator, but if you find the pipes leading to the radiators and grasp them, you will easily tell if one is hot. It is a common fault. 3-port valves with conventional boilers typically last about 20 years, diverter valves in combis less.

[PigletJohn]

you can also look at the gas meter.

In summer, if you are using round about half a cubic metre of gas a day, perhaps a metre, that is probably just the hot water.

If noticeably more, some of the radiators are probably being warmed as well.

It varies with the age of boiler, and insulation on your pipes (and cylinder, if any) and how many baths you have.

A cubic metre of gas costs about 25pence at the moment, plus about 20p standing charge. This will give you an idea of the cost of any wastage.

[StillRabbit]

Remember your radiators will still have some warmth even after the heating has gone off (either by timer or ambient temperature having been reached), Because it takes a while for the water to completely cool down.

I never actually turn my heating off, it is on timer and thermostat. Actual heating will only fire up if temperature where the thermostat is located falls below 18.5 degrees. As soon as 18.5 is reached the boiler (if it was on) turns off so no power is being used for heating.