Worcester Bosch Burner Indicator Question

[dschlenz]

Hi All

I have a Worcester Bosch 40CDi and I'm a bit worried its not working as designed. I have set my thermostat to 20 degrees on a timer and as expected when the temperature goes below 20 degrees in the correct time slot the Burner Indicator comes on and the radiators start to warm up. The weird thing is that the Burner Indicator goes off before the thermostat reaches 20 degrees? If I watch the boiler for 10 minutes or so then the Burner Indicator will come on again and then go off again a few minutes later, this will continue and the thermostat will rarely get to the desired temperature of 20 degrees.

Is this normal?

Should the Burner Indicator be on constantly until until the desired temperature is reached?

Thanks, Daniel

 

[mikeyd]

The boiler cycling is normal.

The boiler will stop firing when the radiators are hot. It then has to wait for the radiators to cool down a bit as they heat the room, then it will fire again. The process will repeat until the room is up to temperature.

That doesn't explain why your system never gets up to temperature though.

Do you have a thermostatic radiator valve in the room with the wall stat?

 

[ianniann]

It is normal. It is called cycling. Your boiler is (almost certainly) well over-sized compared to your heating needs so the boiler has to turn off occasionally to avoid overheating.

Do the radiators stay warm while the boiler is turning on and off? Do they reach the temperature you have set on the boiler? 40CDi doesn't have the actual temperature but the range is from almost cold to moderately hot. It does tell you the temperature the flow is at, on the LED display. For a conventional radiator heating system you'll need a temperature of 60C (in cold weather), maybe more, which means the dial at least to 4 and probably 5.

The lower settings are only useful for systems like underfloor heating, fan-assisted radiators, or very over-sized radiators that can heat properly at 30C or 40C. In warmer weather you'll be able to heat at a lower setting but the boiler may cycle on and off more often. Very large combi boilers in not-so-very-large houses often benefit from the maximum power being turned down to avoid them just beating themselves to death.

 

[dschlenz]

Thanks for the swift replies!

In answer to the first question I dont' have any thermostatic radiator valves at all.

Also the radiators do stay hot when the burner indicator is off. I've currently got it set to 4 which shows a max of about 55 on the LED, do you recommend I increase to 5 so I get the display to show 60ish?

I only moved into this house recently and my first quarterly gas bill was £750 so I reduced the dial from the max setting to 3 thinking that might help. Obviously need to find the balance between heating the house (1700 square feet) and not breaking the bank.

Thanks, Daniel