How long to heat 150 Litres of water

[ukplumber400]

I have a Premiier plus Economy 7 electric hot water tank. Model PP150E


At the moment it is on for something like 9 hours at night which seems excessive.


How long do you need the economy 7 hot water heating on for to heat 150 litres of water?



Or does it stop heating once it dectects the water is at 90c?

INFO
Model PP150E
Serial 1233
Capacity - 150L
Electric rating: 2 x 3Kw at 240Vac
2 x 2.7kw at 230Vac

HORTZMAN economy 7 Quartz timer

 

[Best]

Usually only one of the immersion elements are on the Economy 7 (the lower element so entire cylinder can be heated). So it will take a long while to heat cylinder.
The higher element usually is for when you need to heat some water in middle of day.
The immersion stat will control temperature which will normally be well under boiling point - so 65 degrees or so, depending on what it is set at.
Your immersion could be slightly faulty, or be covered with scale in some hard water areas

 

[colshaws]

http://www.ianbgas.co.uk/Heating water.pdf

 

[chris watkins]

4.2 x 150 x 55 x 100 = 3,465,000
2.7 x 90

then 3465000 = 3.9609 or call it 4 hours
....... 3600

4.2 = SHC water, 150 L, 55 dec C temp rise (10 to 65)
2.7 kW heater at 90% efficiency
3600 sec in an hour

immersion thermostat shuts off power when water reaches set temp (& it will never be 90).

 

[townfanjon]

I get asked this all the time, the timer / controller could be on for 5,6,7 hours but that doesnt mean its cost 5,6,7 hours of electricity .
Between the timer and the immersion heater is a thermostat , that switches either on or off , if its off the electricity stops flowing and obviously doesnt cost you anything .
So 5,6,7 hours of the timer may only cost you 1 or 2 hours of electricity.

 

[jtsplumbing]

Something wrong if temp is getting to 90c.

 

[joni os]

4.2 x 150 x 55 x 100 = 3,465,000
2.7 x 90

then 3465000 = 3.9609 or call it 4 hours
....... 3600

4.2 = SHC water, 150 L, 55 dec C temp rise (10 to 65)
2.7 kW heater at 90% efficiency
3600 sec in an hour

immersion thermostat shuts off power when water reaches set temp (& it will never be 90).

According to my slide rule the figure of 3465000 should be 14,259

14,259 divided by 3600 gives 3.968 or approx. 4 hours . The answer is right but
3465000. seems to be erroneous .

 

[chris watkins]

According to my slide rule the figure of 3465000 should be 14,259

14,259 divided by 3600 gives 3.968 or approx. 4 hours . The answer is right but
3465000. seems to be erroneous .

Oops should have been 3465000 = 14,259 (3465000/243)
......................................243
Then as above i.e. divided by 3600,

Thanks joni os

 

[joni os]

I went through the calculation to educate brain to think in 21st century Kw rather than 20th century BTUs. Chris's posts are always knowledgeable and informative . My examination of the detail reflects the esteem and regard I have for his contributions.

 

[chris watkins]

I went through the calculation to educate brain to think in 21st century Kw rather than 20th century BTUs. Chris's posts are always knowledgeable and informative . My examination of the detail reflects the esteem and regard I have for his contributions.

Stop it :blush5:

But we all need to be checked cos if there is one thing I have learnt over the years we all make mistakes it is what makes us human.

For me it is the mark of a man as to how he deals with those that he makes. I like to stick me hand straight up & say sorry mate (& try not to make the same one again).

 

[joni os]

I've always learnt more when I learnt I was wrong than I learnt when I thought I was right.

 

[Masood]

Oops should have been 3465000 = 14,259 (3465000/243)
......................................243
Then as above i.e. divided by 3600,

Thanks joni os

What's the division by 243 Chris? I assume a conversion from BTU to KW?

 

[chris watkins]

What's the division by 243 Chris? I assume a conversion from BTU to KW?

No no conversion Mas, you have to go back to my first wrong post - it is the 2.7 kW heater times 90% efficiency = 243

 

[Masood]

No no conversion Mas, you have to go back to my first wrong post - it is the 2.7 kW heater times 90% efficiency = 243

Cheers Chris. I was taught a slightly different formula.