Biasi 24S problem

[mox]

Biasi will not fire at all. I have checked power supply, green light is on, red light is not on. pressure is ok. I Bled top rad which has a small amount of air in it then used the reset button and everything fine but for how long? The boiler has been ok for 7 years but in the last year has had 4 problems including a diaphragm and gas valve replacement.

Any ideas as to the cause of the problem? Am I better off considering a replacement to regain reliability?

thanks

 

[ismellgas]

does it work for hot water? then only coming on on for central heating for a matter of seconds?

 

[Agile]

What reset button have you used?

Since the boiler is apparently working OK now there do not seem to be any further issues unless it happens again.

Tony

 

[mox]

Reset button is immediately to right of the red light on the main panel behind a black cap which screws off with a flat blade screwdriver

 

[Agile]

That is a manually reset overheat thermostat.

Did you allow the boiler to run with insufficient water pressure, perhaps below 0.5 Bar?

Tony

 

[mox]

Looking at the pressure gauge, it never showed less than one bar.

thanks

 

[Agile]

In that case the boiler has overheated.

There will be a reason but without engineers tests on the boiler the actual cause will now difficult to determine.

What was the boiler being used for when it tripped?

Tony

 

[mox]

On the first occasion, the heating was on then the boiler went off and would not fire up.

After resetting, the problem has happened again today whilst moving from continuous heating to timed heating. The system originally had an onboard timer but was later fitted with an external, wired timer which has worked fine since its installation

thanks
Andrew

 

[Agile]

If it happens when the boiler is on CH and the rads get very hot then the CH thermistor sensor may be open circuit or high resistance.

You can measure the resistance with the boiler completely cold but can do an easier test. Just turn the CH temp knob down slowly when the rads are hot and see if the flame reduces in size as it should.

Even with the CH knob on maximum ( which it should not be! ) the CH temperature should not exceed about 84°.

It may just be that you are operating the CH with the knob too high.

Letting the o/h stat trip repeatedly will cause it to operate at a lower and lower temperature! Thast about 20 trips!

Tony

 

[mox]

will look into it

thanks very much
Andrew