I have recently taken on the ownership of a somewhat aged (and troublesome) Biasi 24s (Year 2000).
Shortly after getting to know each other the boiler started overheating and tripping the safety thermostat on the DHW side while blowing steam out the top like a whale. This was rectified by replacing the DHW heat exchanger, which was very clogged with black debris.
Having solved this first problem, we appear to have revealed a second issue, this being that the safety thermostat now trips on the CH side after c. 1 hr of operation. Can restart CH after boiler has cooled and safety thermostat can be reset.
At the point that it trips, the radiators are very hot to the touch. Suprisingly hot to me, as they each have a TRV, which I would have presumed would have shut them down before they got so hot. A few other points that may help in diagnosis are that
- I have checked the resistance of the primary NTC - when boiler was cool resistance was c. 14k (its chilly here today) and just after the safety tripped it was c. 800 rising rapidly above 1000.
- lowering the CH temperature regulator dial when CH is on leads to a reduction in the flame height; and
- the main circuit flow switch shaft does not protrude out perhaps as far as it could but slight adjustment of the microswitch cantilever against which it pushes seems to have addressed this, by reducing distance shaft needs to travel to trigger microswitch.
Hope the above is helpful in assessing what might be going awry. Having just been given a quote for c. £5k plus VAT for new boiler, gas piping and powerflush, spending a bit to rectify the issue(s), could be attractive.
Thanks in advance
Shortly after getting to know each other the boiler started overheating and tripping the safety thermostat on the DHW side while blowing steam out the top like a whale. This was rectified by replacing the DHW heat exchanger, which was very clogged with black debris.
Having solved this first problem, we appear to have revealed a second issue, this being that the safety thermostat now trips on the CH side after c. 1 hr of operation. Can restart CH after boiler has cooled and safety thermostat can be reset.
At the point that it trips, the radiators are very hot to the touch. Suprisingly hot to me, as they each have a TRV, which I would have presumed would have shut them down before they got so hot. A few other points that may help in diagnosis are that
- I have checked the resistance of the primary NTC - when boiler was cool resistance was c. 14k (its chilly here today) and just after the safety tripped it was c. 800 rising rapidly above 1000.
- lowering the CH temperature regulator dial when CH is on leads to a reduction in the flame height; and
- the main circuit flow switch shaft does not protrude out perhaps as far as it could but slight adjustment of the microswitch cantilever against which it pushes seems to have addressed this, by reducing distance shaft needs to travel to trigger microswitch.
Hope the above is helpful in assessing what might be going awry. Having just been given a quote for c. £5k plus VAT for new boiler, gas piping and powerflush, spending a bit to rectify the issue(s), could be attractive.
Thanks in advance