Efficiency of boiler rating calculation

[alto]

[FONT=&quot]i all hope someone can help[/FONT]

[FONT=&quot]I have an [/FONT][FONT=&quot]150L hot water cylinder[/FONT][FONT=&quot] with an immersion element after 1 hour it has consumed [/FONT][FONT=&quot]2.69kW of electric[/FONT][FONT=&quot] (im not too sure but I suspect the starting temperature was approx 42.9 degrees and reached 60 degrees).[/FONT]

[FONT=&quot]Now when I use my boiler i measure the water temperature and its 42.9 degrees. After [/FONT][FONT=&quot]1 hour of boost[/FONT][FONT=&quot] on the control panel the water temperature has increase to 55.8 degrees so the temperature increase is [/FONT][FONT=&quot]12.9 degrees[/FONT][FONT=&quot]. According to a digital meter I have consumed 7kW however the digital meter does not show a decimal point so I ought to deduct one unit so the usage was at least [/FONT][FONT=&quot]6kW[/FONT][FONT=&quot] to heat my hot water tank.[/FONT]

[FONT=&quot]From that data is it possible to calculate the efficiency rating of my boiler in comparison to using electric?[/FONT]

[FONT=&quot]Also would there be a massive energy loss between the boiler and cylinder (the pipe is about 2 metres to the cylinder and return length approx the same) - its fully lagged.

[/FONT]I suspect I should use the formula:

Size of tank X 4 X temp difference / 3421 = Kw rating

150 X 4 X 12.9 / 3421 = 2.26

100 / 6kW X 2.26 = 37.6% efficiency rating

Does that make sense? it that the correct method?

[FONT=&quot]Thanks in advance[/FONT]

 

[king of pipes]

FM ATLO we are plumbers not mathematicians

 

[Last Plumber]

Gas and electricity do not cost the same amount per Kw you know ?

 

[Chalked]

Gas per kw is about half the cost of electricity. Per kW of water heated. But you must have a very poor system to take 1 hour to heat up!
Modern systems take about 25 to 30mins from cold!

 

[joni os]

Water in litres X rise in Temp C X 4, gives close approximation in BTU.
By definition 150 X 17.1 X 4 = 10260 BTUs which equates to 3Kw. Something is wrong with the methodology that gave you 2.69Kw. The 2nd calculation appears equally amiss.
Temperature of water in cylinder should be taken at various levels to allow for stratification and information as to how energy usage of 6Kw was calculated is needed.

 

[Ray Stafford]

As per chalked's post, if its taking you an hour to get from 43 degrees to 56 degrees there is something wrong with either the controls or the system design.

 

[PlumbBobBob]

I think you have too much time on your hands :smiley2: