Hot Water Tank Size???
- Thread starter jonny v
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It depends on your water usage patterns, though you'll typically be recommended to go no smaller than 170 litres. If you have teenagers there's no cylinder big enough, they'll still stay in the shower until it goes cold. 
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But don't forget the extra heatloss from a larger cylinder its not insignificant and additional floor strenghtening.
Check the spec and do the maths.
We've managed with 115 litre cylinders for years - for some reason everyones pushing massive sized cyclinders even though the calorifiers are more efficient than ever and hence the re-heat times quicker than ever.
Average shower at 10 litres/minute X 4 minutes = 40 litres
Assume a 60/40 hot to cold ratio
Therfore shower consumes 24 litres of hot
300 litre cylinder gives 12 showers one after another (excluding re-heat from boiler) - do you really need this?
Most showers will be taken during the timeclock hot water on period so the boiler will be replenishiing the cylinder during showering. And for the odd occasional bath just hit the +1 or boost button.
Go for a 125 or 150 litre.
Check the spec and do the maths.
We've managed with 115 litre cylinders for years - for some reason everyones pushing massive sized cyclinders even though the calorifiers are more efficient than ever and hence the re-heat times quicker than ever.
Average shower at 10 litres/minute X 4 minutes = 40 litres
Assume a 60/40 hot to cold ratio
Therfore shower consumes 24 litres of hot
300 litre cylinder gives 12 showers one after another (excluding re-heat from boiler) - do you really need this?
Most showers will be taken during the timeclock hot water on period so the boiler will be replenishiing the cylinder during showering. And for the odd occasional bath just hit the +1 or boost button.
Go for a 125 or 150 litre.
Thank you for these thoughts. What is your view on another approach which is to ues an Alpha CD50 - although having only a 52 ltr integral unvented pressurised tank it supplies hot water at 18ltrs per/min and can reheat the whole tank apparently in 3/4 minutes beginning as soon as you begin to draw off hot water. Or the Ideal 'istor' with an 80 or 120 ltr integral tank and 34 lts/min flow rate, but quite expensive!? Are these systems clever or a bit of a let-down in practice?
Once the thermal store/integral tank is run down the boiler will drop down to a normal rate of perhaps 12-15 litres/minute raised by only 35 degrees.
These boilers have more unreliable parts to go wrong and you have no immersion backup.
These boilers have more unreliable parts to go wrong and you have no immersion backup.
The Alpha CD50 is a combi with integral store which I would discount straight away for your property.
The Istor is a system boiler and unvented cylinder linked together and also has an immersion heater, limited only by the size of the cylinder.
The Istor is a system boiler and unvented cylinder linked together and also has an immersion heater, limited only by the size of the cylinder.
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