Baxi condenser boiler cutting in and out

[impreza280]

I have a Baxi Barcelona condenser boiler (yes it's 21 years old and yes this model has issues). Mine has been largely reliable and had a new pump in 2020; it is not leaking and holds pressure and we always have hot water for taps and heating.

It's currently going through phases where the on/off switch is clicking and it's deciding not to fire up. If I turn it off and on at the mains then it fires up but then only for 30 seconds or so.
The PCB is original - is it likely to be this that needs replacing?

 

[martygturner]

That sort of points to the ignition failing...spark...got that as it fires, fuel air - got that as its burns, so we are left with flame detection and then the sensors, flow and temp. As its only 30 seconds the first thing is flame detection, boilers have a sparker two bits of rod that produce an arc to light the boiler and a single rod that detects the flame.

The flame detector can go faulty for a number of reasons, faulty PCB , detector faulty or it condensate drain fouled and shutting the system down - there is a float switch on yours )

You can check the condensate drain yourself, just follow the drain pipe into the boiler and see if its gunged up and full....

However i would get the boiler serviced by a competent gas engineer, its working so all the main bits are playing...the issue is finding a good engineer.

 

[impreza280]

Many thanks - sounds logical and will call the person who fitted the last parts (and didn't simply write off the whole boiler, though it's days are clearly numbered)

 

[impreza280]

Worth adding that when the (underfloor) heating is on (and there is presumably considerable water flow), it fires up and keeps going. Maybe this rules out the condensate drain?
So the times when this is occurring is when it's sitting there just ensuring the megaflo is full of hot water. Logic tells me it's an "electrical" part i.e. PCB, sensor or flame detector.

 

[ianmcd]

Logic tells me it's an "electrical" part i.e. PCB, sensor or flame detector.

What logic is that do these components not work when the boiler is only heating the HW ? do you not think you should be looking at a flow problem ?

 

[martygturner]

Err so it turns off when the tank is full of hot water ? or when its set to hot water and it goes off then ? If its firing up and running the flame detector is working then...so the pcb is ok, the spark is ok, ...so you are left with what...flow and temp ?
try https://www.manualslib.com/manual/945294/Baxi-Barcelona.html?page=6#manual it sort of tells you the issue....see which one you have
5.
Anti-cycle: When all the TRVs shut down during
Burner On or Pump Overrun finishes and flow
temperature is greater than set point then Anti-cycle
occurs. The pump, fan, spark generator and gas valve
are switched off.
6.
Ignition Lockout: When 5 ignition attempts have been
made without a flame being detected then Ignition
Lockout occurs. The pump, fan, spark generator and
gas valve are switched off. The lockout light flashes
once a second. The boiler can only be reset manually
using the thermostat knob.
7.
No Water Flow: When there is No Water Flow through
the boiler (indicated by the flow switch) then a
continuous cycle of Pump Overrun and Anti-cycle
occurs