Have just got a new vailant system boiler that gives a digital readout of the water temperature. The plumber has set it at 60 degrees as well as the stat on the hot water cylinder at 60 degrees.

Surely for the hot water cylinder to reach 60 degrees in a reasnoble time the boiler should be set at a higher temperature as it needs a temperature difference to transfere its heat to the coil.

I also have read that a boiler is most efficient running flat out for the shortest possible time.

I would put the boiler temp up to at least 70 degrees but that seems pretty hot to be running through the radiators when they are needed.

Any advice greatly received.

Cheers bigsurfer.

I'm not sure it reaches the temperature you want any quicker by setting it higher than you need it to be.

I imagine the hot water cylinder would have been designed with 82 degC water in mind. That is the normal standard pre-condensing boilers. Again, radiators will be rated with 82 degC flow temps. But this is only when you want the full heat output, ie cold weather. More modern systems will alter the flow temperature to the radiators depending on the outside air temperature, only reaching 82 when it is 0degC outside. at 20degC outside (if you needed heating!) 40degC would be normal.

60C will be fine… the boiler will still run flat out to get its maximum efficiency, but simply pump a higher volume of water around the system. As long as a temperature gradient exists between the tank and the coil, it'll heat up.

Overall energy use will be less (obviously) with tank set at 60C – in addition, there's a much reduced risk of scalding with a tank at 60C instead of 70 or 80. Try it for a few weeks and see if the hot water is hot enough for you.