Query on heating 24/7 vs off and on

joeyboy

Hi folks,

So I've read the arguments before about heating the home 24hr hours vs just when you're back from work etc. Generally the advice is its a myth heating 24/7 is most efficient.

However last night I accidentally left the heating on, but the data from hive makes me confused as to why this wouldn't work out better... 

So I've been at home all week this week due to illness. I manually turn my heating on at 15-16c when I wake up (around 8) and turn it off around 9pm. 

During the night the heat has reduced from ~15.5c to 11.8-13.3c (obviously outside temp is a big factor here).

When turning the heating on, hive records it has taken 2hr 40- 3hr 50 minutes to get the heating up to 15-16c.

However last night 00:00- 08:37 when left on at 15c, the boiler only fired 4 times for ~15 minutes a time(about 2 hrs apart). For a total of 1hr 8 mins.

My confusion now then is if the boiler took 3hr 50 minutes to get up to temp on one day, and fired for around 5hrs total that day. Wouldn't it have made more sense for the boiler just to be heating all the time if it's going to only need 1hr of heating each 8 hours to keep it at 15c?

Only thing I can think of and perhaps someone can explain. Is it that each 15 minutes it fired on full power (it's 28kw boiler). Where as hives 3hr 50 minutes is worse than it looks because the boiler isn't really heating all that time as water in the rads is at the temp? 

For reference my flow temp is 60c, I turned it down after reading 75c isn't good for a new combi as it can't condense. I know turning it up would make it heat faster but I'm not too concerned if it's more efficient to be lower. 

[Deleted User]

Hive doesn't show when your boiler was actually running, nor does it show what power your boiler was running at.

Olly_J

joeyboy said:

However last night 00:00- 08:37 when left on at 15c, the boiler only fired 4 times for ~15 minutes a time(about 2 hrs apart). For a total of 1hr 8 mins.

Only thing I can think of and perhaps someone can explain. Is it that each 15 minutes it fired on full power (it's 28kw boiler). Where as hives 3hr 50 minutes is worse than it looks because the boiler isn't really heating all that time as water in the rads is at the temp?

Most boilers will fire up at near to their set max power for around 30 seconds, and then IF the return temperature is within ~10c of the flow will modulate down to an output that tries to maintain that, so its unlikely your boiler will have been running at full power for those 15 mins, given it was coming every couple of hours, hence the water in the rads was likely still somewhat warm to start with. Obviously that depends on the size of your heating system and heat-loss, so there's no way to know for sure.

Each house is different, and the best way to check is to try each method for 3 days, reading your meter at 12pm on day 1 and 12pm on day 3, so as to capture the recovery energy required in the morning when using On/Off method, and then compare the units/KW used for each method over those days. Ideally you want several days where the outside temp is roughly the same too.

My own experience is that leaving one temp set 24/7 is more expensive, but using a setback overnight of 1-2c works well