JohnG Useful heat from kero

Wearb

"My 3 bedroom (+ attic conversion) semi with oil fired (SE boiler) heating on for 15 hours/day uses ~ 7 litres Kero/day=3.95Kw/hr useful heat to rads/hot water. The boiler stat is set at 75C and room stat at 21C."


I don't want to take other post -that I cut above from- off topic, so I will ask here; Can you explain the calculation above please. I understand that there are losses from the litre of kerosene, but I didn't expect it to be almost half.

John.G

Wearb wrote: »

"My 3 bedroom (+ attic conversion) semi with oil fired (SE boiler) heating on for 15 hours/day uses ~ 7 litres Kero/day=3.95Kw/hr useful heat to rads/hot water. The boiler stat is set at 75C and room stat at 21C."


I don't want to take other post -that I cut above from- off topic, so I will ask here; Can you explain the calculation above please. I understand that there are losses from the litre of kerosene, but I didn't expect it to be almost half.

The 15 hour day might be a bit confusing..
So, I assume kero as having a Gross (HHV) of 10.55 Kwh/Litre and I am assuming my SE Firebird efficiency at 80% so using 7 Litres/day is 7*10.55, 73.9 Kwh/day, consumption per hour (15 hour day in my case) is 73.9/15 is 4.93 Kwh, at 80% efficiency net (useful heat) to rads is 4.93*80% or 3.944Kw.

Wearb

I am still confused. But from reading your answer, I calculate that you are getting 8.4Kw of useful heat from each litre of kerosene.
Taking your answer a bit further, if you were getting 20 hours out of your 7 litres (more efficient (not referring to boiler efficiency)), it would bring your useful heat down to 3.7Kw per litre.

What am I missing here?
Probably confusing apples with oranges in my reading .

agusta

John.G wrote: »

The 15 hour day might be a bit confusing..
So, I assume kero as having a Gross (HHV) of 10.55 Kwh/Litre and I am assuming my SE Firebird efficiency at 80% so using 7 Litres/day is 7*10.55, 73.9 Kwh/day, consumption per hour (15 hour day in my case) is 73.9/15 is 4.93 Kwh, at 80% efficiency net (useful heat) to rads is 4.93*80% or 3.944Kw.

John,im a little confused here too.How many hours/minutes would the burner in the boiler be actually be on during the 15 hour period
My calculations for a 0.60usg 80H nozzle with the pump at 8 bar pressure.with heating on for 15 hours,the run time of the burner is 3.1 hours if the usage was 7 litres

John.G

Wearb wrote: »

I am still confused. But from reading your answer, I calculate that you are getting 8.4Kw of useful heat from each litre of kerosene.
Taking your answer a bit further, if you were getting 20 hours out of your 7 litres (more efficient (not referring to boiler efficiency)), it would bring your useful heat down to 3.7Kw per litre.

What am I missing here?
Probably confusing apples with oranges in my reading .

OK and to Agusta too I hope, what I am saying is that I am requesting my heating system to be on for a total of 15 hrs/day via a Flash programmer; programmed to be on/off at various times during the day (to a total of 15 hours)
during this time the boiler will fire on/off on its own thermostat depending on the heat demand influenced by ambient temps etc and also the room stat and on "average" will consume approx 7 litres for this 15 hour day, obviously on very very cold days
the consumption may be 9/10 Litres and as spring approaches might only be 3 or 4 litres per (15 hour) day.
IF the oil consumption is 7 litres then based on my reckoning of nozzle output of 2.5 litres/hr then the boiler has actually fired for, 7/2.5, 2.8 hours in that 15 hour period. It is very easy to measure my oil consumption from the storage tank as 1 mm is exactly 1 litre of kero.....I take a reading every 10 days or so (maybe).
Or to put it another way, if my programmer is timed to come on for 15 hours/day but if I turn the room stat down to 10C then the boiler will consume no fuel as it wont fire up at all!.
Remember I am only calculating the AVERAGE rad/heating input per hour (not per litre) based on the programmed heating demand time and the actual boiler fuel consumed over that same time period.

jimf

15 hour day so john is only a timed period on the clock only

if room stats etc are set at 10c then of course you will have no heat requirement

so based on this such a low oil usage of course is achievable

Wearb

John.G wrote: »

OK and to Agusta too I hope, what I am saying is that I am requesting my heating system to be on for a total of 15 hrs/day via a Flash programmer; programmed to be on/off at various times during the day (to a total of 15 hours)
during this time the boiler will fire on/off on its own thermostat depending on the heat demand influenced by ambient temps etc and also the room stat and on "average" will consume approx 7 litres for this 15 hour day, obviously on very very cold days
the consumption may be 9/10 Litres and as spring approaches might only be 3 or 4 litres per (15 hour) day.
IF the oil consumption is 7 litres then based on my reckoning of nozzle output of 2.5 litres/hr then the boiler has actually fired for, 7/2.5, 2.8 hours in that 15 hour period. It is very easy to measure my oil consumption from the storage tank as 1 mm is exactly 1 litre of kero.....I take a reading every 10 days or so (maybe).
Or to put it another way, if my programmer is timed to come on for 15 hours/day but if I turn the room stat down to 10C then the boiler will consume no fuel as it wont fire up at all!.
Remember I am only calculating the AVERAGE rad/heating input per hour (not per litre) based on the programmed heating demand time and the actual boiler fuel consumed over that same time period.

Ok I've got it now, thanks. Originally I thought that you were suggesting that only about half the calorific value of the kerosene was turned into useful heat.

Wearb

jimf wrote: »

15 hour day so john is only a timed period on the clock only

if room stats etc are set at 10c then of course you will have no heat requirement

so based on this such a low oil usage of course is achievable

https://www.youtube.com/watch?v=qpDzNQNPzG0


Jim, The above 2 minute clip explains it all perfectly.

agusta

John.G wrote: »

OK and to Agusta too I hope, what I am saying is that I am requesting my heating system to be on for a total of 15 hrs/day via a Flash programmer; programmed to be on/off at various times during the day (to a total of 15 hours)
during this time the boiler will fire on/off on its own thermostat depending on the heat demand influenced by ambient temps etc and also the room stat and on "average" will consume approx 7 litres for this 15 hour day, obviously on very very cold days
the consumption may be 9/10 Litres and as spring approaches might only be 3 or 4 litres per (15 hour) day.
IF the oil consumption is 7 litres then based on my reckoning of nozzle output of 2.5 litres/hr then the boiler has actually fired for, 7/2.5, 2.8 hours in that 15 hour period. It is very easy to measure my oil consumption from the storage tank as 1 mm is exactly 1 litre of kero.....I take a reading every 10 days or so (maybe).
Or to put it another way, if my programmer is timed to come on for 15 hours/day but if I turn the room stat down to 10C then the boiler will consume no fuel as it wont fire up at all!.
Remember I am only calculating the AVERAGE rad/heating input per hour (not per litre) based on the programmed heating demand time and the actual boiler fuel consumed over that same time period.

Thanks John.I thought you had the boiler on constant for the 15 hours,controlled by the stats only.I was going to ask you where you got your insulation with the low oil consumption:)

John.G

agusta wrote: »

Thanks John.I thought you had the boiler on constant for the 15 hours,controlled by the stats only.I was going to ask you where you got your insulation with the low oil consumption:)

For info only, my average daily consumption for November was 7.43 litres/day or ~ 78.4 Kwh/day.

Sleeper12

Wearb wrote:

Jim, The above 2 minute clip explains it all perfectly.

Priceless