baxi 80e ongoing problems

[jrchas777]

I would appreciate any advice on this subject,the details are - I have a Baxi 80e approx 4yrs old serviced yearly by a corgi engineer.initially over the past few months it has run perfectly for perhaps a week then switched off (the flame and flue fault lights flashing)and will not reset for perhaps a dozen attempts although works perfectly ok in hot water only mode.during this period it may run for several minutes but then switches itself off or may not reset at all.it may be of interest to know that sometimes just running the hot tap is enough to kick everything back to normal without a reset.However things recently took a turn for the worse,now when the boiler seems to run normally it is switching off showing a heating overtemp fault light and will not reset until allowed to cool,other times i have seen the boiler cycle between overtemp and normal running every couple of minutes.between these two faults I am spending more time with the boiler than my family.additional details are,the boiler is in a well ventilated cupboard under the stairs with the flue directly through the outside wall,each radiator in the house has a thermostatic valve with no wall thermostat in the system(not my idea) and I have over the past few months replaced for various problems - the diaphragm in the hot side of the 3 way valve(leaking),the prv (bypassing & dumping pressure), and have checked the pcb for poor connections and dry solder joints.I suspect I may have more than one problem here,but would appreciate any help before I call in the very expensive gas board even if it is to minimise the cost by having just one thing going wrong ! cheers jrchas

 

[zimmers]

It could be the pump as it seems to be overheating due to lack of circulation, it may be sludged up and need a powerflush but if it seems to reset after a certain time then the boiler could be to hot and needs the time to cool down and then start up again.

 

[zimmers]

whats your pressure on

 

[jrchas777]

Zimmers,after replacing the prv a couple of months ago I have been keeping a close eye on the pressure and can confirm it fluctuates between 1.0 & 2.0 bar depending on how long the boiler has been operating,according to the manual I have this is within the normal limits,is there any other detail that may help?
jrchas

 

[baxpoti]

Probable possibilities

Low gas too low

Sensors are inaccurate

System contaminated

 

[bengasman]

Have had several of these with a duff board, and several with a problematic diverter, sometimes diaphragm and sometimes the spindle sticky due to limescale and corrosion build up.
I would start with the diverter as that can be verified to be clean and functioning.
Also worth checking that phase to neutral and phase to earth have the same reading.

 

[ChrisR]

cycle between overtemp and normal running every couple of minutes.

But is it REALLY getting too hot? An intermittent ch sensor or connection would look like high temperature.

 

[jrchas777]

Many thanks for suggestions,found calcified c.h.temp sensor - replaced and overheat problem stopped.now I am just left with original problem of flue and flame warning lights coming on for no particular reason and wont reset for more than a few minutes,after 6-10 tries, resets and runs normally for days then starts all over again.
have changed or cleaned everything else would a new pcb help?