Glow-Worm 15HKI Boiler (Gas usage)

[Peter C]

A month ago I had a new boiler fitter, The heat settings go up to 82 degrees. I have mine set mid way and the temperature is shown at about

60/62 degrees. The radiators heat up very quickly and the water in the hot tap is very hot. A bit improvement on the last boiler and I am pleased about this I am just a bit concerned about the gas usage. The 'green'light on the boiler seems to be on almost constant. Just wondered if I am using the right setting or is this the norn with this type of boiler.? I am told I will save on fuel as there is no pilot light (like the last one)but this one seems to be on 'green' and using gas far more that the previous one. ( Ok I can read the meter,) but would appreciate any views.re usage and settings please ( the hand book does not assist) Peter,

[John Rumm]

Which (counter intuitively perhaps) is what you want. Chances are the boiler you replaced had a fixed rate burner - so it was either off or full on. Hence once the house was near to your desired temperature it needs to run in short cycles, burning for a bit to get the house over the set temp, then going off and waiting for it to fall again etc.

Modern boilers have modulating burners and more sophisticated control systems. They will examine the temperature of the water as it returns to the boiler from the rads. As the house warms up, and some of the thermostatic rad valves begin to close down, this return water will get hotter (as the heating system is absorbing less of the heat from the flow water). The boiler will respond by turning down its burner and thus adding less heat to the water. This means that it will tend to run for longer but at much reduced power (and gas consumption). The result is the house temperature will remain more even with less overshooting and cooling cycles. Also, since the boiler cycles less there is less heat dumped out of the flue each time it turns off and allows the heat exchanger to cool. Finally a condensing boiler will work more efficiently with lower temperature water - hence being able to reduce the boiler power when it is not all required helps here as well.

[Peter C]