high setting or low setting on boiler?

[johnjones323]

I have an old Ideal Elan boiler, which is around 15-20 years old. This might be a silly question I don't know, but here goes.

Is it cheaper to run on Low or High setting, Low takes longer before heat reaches required temp because less heat. High reaches temp quicker as radiators are much warmer?

My question comes from, if you drive a car 80mph you might get 40mpg, If you drive at 40mpg you might get 7ompg.

Is it the same for my boiler?

 

[ChrisR]

Yes, in a word, though not as big a difference as with a petrol engine!

 

[MickyP10]

Guess you want it on the lowest setting which warms the rads enough to get the temp up - ie, if you can't feel the rads making any difference, clearly it's set too low! In a week or so's time, you'll probably have to dial in a bit more heat, as chillier weather's on its way.

 

[TicklyT]

With a lower input it takes longer to warm the house up, so you end up starting the boiler earlier to achieve your desired temperature, so the heat losses through the fabric of the house continue for longer.

If the reduced output means the room temperature never quite reaches the temperature set on the room 'stat, the heating will be running constantly, trying to get it there. With a higher output, when it does reach the set temperature, the room stat will only need to fire the boiler for short periods to maintain that temperature.

To use your car analogy, consider driving up a steep hill. A low powered car may slowly struggle up the hill in second gear where a higher powered one will easily take the hill in 4th gear..... Now which car uses the most fuel climbing that hill....

 

[ajrobb]

If the boiler heats a hot water cylinder and you don't have fancy dual controls, you'll be stuck with a boiler feed temperature of about 70°C to get the hot water up to the legal minimum of 60°C.

 

[johnjones323]

So from the info im getting, it's cheaper to run it on high?

 

[ajrobb]

If it's not a condensing boiler then it won't be so sensitive to output temperature. Modern condensing boilers run cheaper when cooler as they get up to 15% of their energy from condensing and this works better with cooler return temperatures.

 

[MickyP10]

I'm no plumber and I share your interest. From personal experience it seems to me getting the buggers as hot as possible within the shortest time is good, then there's a fair chance it'll hit the dialled-in thermostat temp and shut-off. If you have to wait a couple of hours to feel the warmth, well, don't bother. The downside is, if you have a wife like mine, she'll be so impressed that she'll keep raising the thermostat, so it's dearer but for the wrong reasons!

** Don't think anyone knows!