Short firing -- how short is short?

[Ian Chard]

Hi,

Once an unvented central heating system is up to temperature, how often would one expect the boiler to fire, and for how long?

Mine seems to go on and off in fairly quick cycles, although I haven't actually sat down and measured them (it would involve sitting on the toilet, as its inaudible from most of the house).

Thanks for any advice

- Ian

[rusty]

Depends on the outside temperature in relation to thermostat settings. My geriatric system goes off and on about twice per minute at -10deg C outside and thermostats set to maximum (>20c) inside. Under less onerous conditions it might be only once in ten minutes or even less.

rusty

[Andrew Gabriel]

This really is a "how long is a piece of string" question.

If it's a non-modulating boiler, then it is designed to switch on and off in order to reduce the heat output to match what the radiators can dissipate.

If it is doing this when the house isn't up to the thermostat temperature, then you will improve things by turning up the water temperature, as this will increase the power output from the radiators, and they will do a better job of keeping up with the boiler output. When the house is up to temperature, you can then knock the boiler temperature down a bit for more efficient operation.

You might get more useful advice if you gave the boiler model and power output.