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Plumberpro, Mechanical Engineer
Category: HVAC
Satisfied Customers: 634
Experience:  Over 20 years experience in plumbing heating and gas
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HiI have a Flexicom 24HX boiler with a strange fault. Sometimes

Customer Question

I have a Flexicom 24HX boiler with a strange fault. Sometimes it will start OK but most of the time it will fail, normally on code F25 but sometimes F22. It's had the thermistors replaced and also the PCB and pump. Once started it will continue to heat for a variable amount of time. Sometimes all day, tonight about 10 minutes. Funny bit, when it goes into fault mode, a simple reset will not restart the boiler. Well it does but only for about 5 seconds and trips out. However, if you reset and then reset again during the full fire, after the delay it will then fire up and run. The problem has got progressively worse during the winter.
As a semi retired electronics engineer I suspect dodgy firmware but have no way of testing it. How does the controller decide so quickly if there is a fault when the only information it gets is from the thermistors?
The engineer who fitted it can't make any sense of it, help please.
Submitted: 3 years ago.
Category: HVAC
Expert:  Plumberpro replied 3 years ago.

Hi, your system could be sludged causing a slow flow through the boiler, or the pump could be on its way out causing the same. The pump can be tested on ohms to test the motor condition. Also recommend a flush through


Its not always an electrical fault but often mechanical