Aggro with Baxi Combi 80e - burner intermittently cuts out

[jagofalltrades]

Please help !!!

I have just moved in and have a Baxi Combi 80e.
After re-fitting the rads I was able to start the boiler no probs.

(I had to drain the system when taking the rads off and I didn't have a key to bleed the rads after re-fill).

I noticed that two rads (front upstairs and front downstairs) were not warming up at all, even from pipes. All rad values and RTV's are open.

Later, Next day I bought a rad key and bled the air from all of the rads.

Now my problem is, when I try to start the boiler.
The burner fires up (with the burner light lit amber on the boiler panel) then after a second it cuts out. This cycle is repeated. I get no red lights on panel.

Things that I have already tried since...
------------------------------------
I've reset the timer and boiler
I've drained the system
The Auto Air Vent bleed screw was already open on the pump, which I've checked/closed.

Your thoughts please ?

 

[bengasman]

Airvent cap must be open.
Is the one second a matter of speaking, or literally?

 

[Slugbabydotcom]

We can take bets on the possibilities here.

Temp sensor 8/11
Flame sensing 11/8
APS 2/1
Flue 3/1
Fan 8/1
PCB 16/1 bar

 

[jagofalltrades]

Thanks for the comments guys.

I've just had a boiler engineer inspect my boiler last night.

Tests that he carried out
----------------------------

He checked both the air pressure valve and gas pressure valve which he said seemed fine. He told me that he bypassed the components (sorry don't what ones) to try to isolate the problem but to no avail.

He also tested the APS (he saw him sucking on the sensing tubes and pinching them during that test) which seems sound.
The flue was inspected and is clear.
The electrodes (flame sensing & spark i think) in the boiler was also brushed clean.

Afterwards he said that he is 95% certain that the PCB has gone on the boiler.

I'll you infomed whether the change of PCB does the trick.

(p.s. - the boiler airvent cap was already open .)

 

[namsag]

If its not the pcb it is the sensor by the plate heat exchanger which SLUG wenT for as favourite as i would have to, one of those faults that being in front of boiler you would go for straight away depending how fast it is going on and off then for the board

 

[fitz1]

your wires are not making proper contact on the earth or neutral.try to re do the boiler live,neutral,earth before you start buying parts.just a hunch.its to do with the flame sensing.

 

[jagofalltrades]

The wiring checked out ok.

A fault with the flame sensor seemed ok because the burner was switching on then clicking off every second or so, consistently.

PCB was then replaced. After swapping the PCB, it took approx. 1 hour for the boiler to run reliability. I guess that the boiler had to reach its operating temperature.

Thanks for your suggestions. It's always nice to have a an alternative opinion on my boiler problem.

Note - the original PCB board for the Baxi Combi 80e GC: 47-075-06 has been superseded with GC: 47-075-18.

The PCB cost me £92.18

Merry Xmas and Happy New Year to all !