Maybe a silly question

[keenbutconfused]

Just wondering if turning some (not all) radiators down or off actually reduces the amount of gas being burnt?

For example, my bathroom is extremely cold and I would like to leave the heating on to that bathroom for the majority of the day. However, the rest of house is fine at the moment and so I would like to not heat the other rooms. However, if this is going to cost me the same as heating the whole house then it is obviously going to be quite expensive.

 

[oilman]

It's cheaper if they're off, but the room thermostat will have to be set lower as well. Best solution is a programmable stat with optimising cntrol like Honeywell CM67, but make sure it's the optimising one. That will allow you to program the temperature to be lower during the day. However you might still have a problem trying to just heat the bathroom. You could fit a small electric towel rail which will keep the bathroom a bit warmer.

 

[stanrog]

On my CH system I have the bathroom radiator connected to the flow and return pipes of the boiler before they feed the radiators and hot water systems controlled by motorised values.. Thus when the boiler is on, eg for hot water only, the bathroom radiator becomes hot.

 

[stem]

Think about how it works. Hot water leaves the boiler at a certain temperature controlled by the boiler thermostat, it passes around the radiators loosing heat and then returns to the boiler for reheating back to the temperature it started out at.

Therefore the more heat it looses (ie the more radiators that are on) the more heat has to be put back and more gas will be used.

This is a simple answer and does not take into account boiler efficiency and other losses, but the basic idea is, the more heat that is taken out of the water, the more gas needed to replace it.

 

[keenbutconfused]

Any idea whether it is directly proportionate.

For example if you had two exact same radiators with same length of pipe to each. If they are both on do you use twice as much gas as if you have just one on.

 

[Santorium]

Makes sense that all things being equal, it should be directly proportional.

Course, if you've only got on rad turned on out of the two, it should also heat in half the time. 'tis all to do with specific heating capacity of water, if my memory for physics hasn't deserted me.

In summary a given volume of water (say 1 litre) will take a certain amount of energy to raise its temperature by one degree. If you double the volume of water then you must double the energy required.

 

[ricarbo]

I don't agree it's directly proportional. The heat lost from a radiator depends on how hot the room is, as well as how hot the radiator is. if you have two adjacent rooms, heated to the same temperature, the heat lost through the wall between them will be nil. If you then don't heat one of the rooms, the heat lost by the heated room will increase, because there is now a heat loss to the unheated room that didn't previously exist. therefore the rad in the heated room has to work harder. if you do calculations for my house, you find you need 12 kw to heat the ground floor only, 9 kw to heat the first floor only and 17 kw to heat them both!!!!!

 

[Santorium]

I did say "all things being equal" If only we lived in a vacuum eh?