On a recent training course, he was informed that, to conform to G3, you must heat your hot water cylinder to 60 deg C or more every day to prevent legionella. I'm not belittling this advice; legionella prevention is very important, but every day? Really?
In the past we have always done this once a week.
In almost all cases where a heat pump is used, this means heating the water from the normal operating storage temperature of 50 deg C to 60 deg C with an electric immersion heater. This is very inefficient and unnecessarily costly.
Here's the maths - to heat 300 litres of water by 10 degr C electrically takes 3.5kWhr of electricity which costs 50p using full price electricity. To do this every day would cost £180 a year.
Is this advice really true or has my customer been sold a pup?
Our units, much like most others, have the facility to heat the water every day for legionella if required, but is it really a good idea?