Adjust your system regular boiler flow temperature for increased efficiency

Adjusting the flow temperature for a system boiler or regular boiler is different to a combi boiler. When you have a hot water cylinder, normally you set your cylinder stat 60 °C, to prevent legionella formation. When you set to these temps, the boiler flow temp must be higher by at least 5 degrees, in order to heat the cylinder and satisfy the cylinder stat, otherwise the boiler would not stop firing until the timer turns it off and the cylinder would never reach it’s intended temperature.

It is therefore suggested to change to a flow temp of 65 °C at the boiler in order to maintain a minimum difference of of 5°C . If the difference is smaller, the time taken to reheat the water is longer and may not satisfy hot water requirements. A higher flow temp of 70°C would mean that the hot water would warm up faster, but you would lose some efficiency.

If you have advanced controls these can automatically use a high flow temperature for the cylinder and a lower, condensing flow for heating. That setup is priority domestic hot water (PDHW). Now select your boiler below to see how to adjust the flow temperature.