Central Heating - which is more cost effective

slenderkitten

to be honest, i still dont understand the answers given. I dont know if i mis-read the most relevant answer.

i have my thermostat on 18 alot of the time, my boiler is set to half way individual radiators where i need them most is on top setting =5 - is this expensive?

By the way my boiler is more modern it was installed in 2005 has no water tank so just heats water as it is needed. i can see on the boiler it says 62 o (i assume this is degrees) when it is on.

I have the heaters on for 4 hours per day, 2 in morning 2 in evening, though it seems to go off 30 mins before it should - i'm getting it checked over.

Biggles

moneybunny123 wrote: »

Obviously a thermostat helps to keep a house at a convenient temperature, but there must be an answer to my question. Boiler/thermo high and radiators low OR boiler/thermo low and radiators high. One way MUST surely use less gas or oil than the other???

No.

Whichever of the two methods you use, if they get your rooms to the right temperature, when you want them to be, they will use the same amount of fuel.

You may, however, find that one or the other of the two methods, with your home and your heating system, will make it easier to achieve this end. None of us can know that.

closed

radiator on lowest setting is cheaper, but the house will be cold. Little point having trv's if they are turned to their highest settings

vaio

Mankysteve wrote: »

The most efficient temp on the boilers will be one that cuts out the boiler shortly after all the TRV's have cut out the water supply to the rads. In reality this is hard to determine. The additional pipework in the house won't leak a large amount of heat in compared with what your rads do and don't need much energy input to raise the water temps to tell the boiler its time to cut out. So the boiler temp won't make a huge difference if your using TRV's.

Surely the way to cut boiler firing once all TRVs have shut is to measure flow? No flow = No demand so turn the boiler off.

That how we used to install them when combis first appeared, a bypass loop to stop pump dead heading and a flow switch to control boiler. Bypass lets say 4 l/s flow all the time and flow switch fires up boiler if flow >5 l/s.

I don't understand why but current building regs mandate a room 'stat which must mean that either the 'stat ends up calling for heat when the TRVs aren't or the 'stat keeps the boiler off when the TRVs are calling for heat.

I suppose the other thing to consider is boiler losses, is it better to run it hot for a short time or cooler for a longer time, throw the variables of response times and radiator sizing into the mix and it gets even more complicated

southcoastrgi

moneybunny123 wrote: »

Boiler/thermo high and radiators low OR boiler/thermo low and radiators high

depending on the temp you like in the house prob neither way will heat the house to the temp you want

jamesd

slenderkitten wrote: »

i have my thermostat on 18 alot of the time, my boiler is set to half way individual radiators where i need them most is on top setting =5 - is this expensive?

Are the things on the radiators thermostatic valves? If they are, you're setting the desired temperature of the room to the highest possible temperature. Likely to be over 30 degrees. If your rooms don't get that hot it means that the heating isn't on long enough to get to the setting you have in place.

slenderkitten wrote: »

I have the heaters on for 4 hours per day, 2 in morning 2 in evening, though it seems to go off 30 mins before it should - i'm getting it checked over.

Try setting it an hour earlier, same end time, and seeing if the rooms get too hot. If they do, adjust the radiator thermostats down until the temperature gets comfortable the next day after having plenty of warm up time.

Once you've done that, move the start time later in five or ten minute steps until they are only just able to get to the temperature you want by the time you need it.

Then stop fiddling and ignore the rest of what I'm writing because it might do no more than confuse you.

If you had the heat on longer and were clearly able to get to the temperatures you've set it could make sense to turn down the central heating water temperature at the boiler because that's more efficient. But if it means you don't get to the desired temperature fast enough that won't make you comfortable. It's more useful for those who have the hearting on for longer times, like most of the day and evening at weekends.

The pump speed on the boiler also makes a difference. Higher speeds can increase the average temperature of the water in the radiators and also the amount of electricity used in pumping the water around. This higher water temperature in the radiators means that they can get the room to the temperature they are set to faster. But this is a bad idea because it increases the temperature of the water when it gets back to the boiler, reducing the efficiency of a condensing boiler. The lowest pump speed that does the job is probably best if the heating is on a lot but you might need a higher setting to get the temperature high enough in the time you're giving it. A central heating engineer would correctly tell you that the system should be set up to get a particular water temperature drop between the outbound hot water from the boiler and the inbound cooler water, and that the radiators should have their flow restricting valves - not their thermostats - set to do the same. I'm just describing how a change to a faster pump speed might get you to your set temperature more quickly - but it may cost you more money than taking longer to do it because of the reduced efficiency.

roddydogs

Not this old chesnut again

jamesd

It's inevitable because there is no one perfect answer. It depends in part on how the system is used and whether it's set up properly, whether it has correctly sized boiler and radiators and whether the user understands the controls and uses them well.

27col

ariba10 wrote: »

What ever way you look at it, it takes X amount of heat to get Y temperature.

The hotter and bigger the the heat source the quicker it will get there.

Exactly my thoughts.

jamesd

True, but will that be cheapest? Just set the pump so it has a one degree or lower temperature drop through the system at its highest possible water temperature setting with massive radiators and see if that ends up being the cheapest way of doing it. It'll be fastest but not necessarily cheapest. For short periods it might be. For all day, something that'll let a condensing boiler do some condensing would end up cheaper.