Don't you just love intermittent faults?

[Dannypipe]

Got called yesterday, then customer called back and said don't worry the boilers working again.

(Transpired he had taken it apart and cleaned the flame rec probe the numpty).

Then I get called today, the boilers done it again.

I get there and the boilers working totally fine.

It’s a Main Combi 24 HE.

It's running fine for me, but customer says it goes to "Burner Failure" sometimes when running water.

I checked amongst other things,
the gas inlet and burner pressures (max/min)
The condensate trap and pipe work.
The micro amps on the flame rec probe (5 micro amps)
The thermistor was about 9K
Both inlet filters on the cold main
The fan's coil (310 ohms).
The diverter and pump proving microswitch.

I didn't check the venturi, and I have a suspicion that there may be a blockage in the plate HEX as there was a rattly sound as hot water was drawn off.

Really weird one though. It worked fine for me, I ran the hot tap for about 10 mins solid and no issue..

Anyone got anything to add to this list. I'm going to pop back tomorrow and take another look.

Hard to repair a working boiler!

Having a bit of a frustrating time with combi's this last few days. This is the second one that's left me scratching the head. Not good.

 

[mfgs]

It is really frustrating. Nothing worse than turning and not being able to get it to recreate the fault.

I normally tell the customer after a visit like that to monitor when it fails/locks out etc over the course of a few days to see if there is a pattern so we can recreate those conditions when I am infront of the boiler.

 

[AMGasServices]

Which LEDs are flashing when the boiler locks out that could give you some indication.

 

[Dannypipe]

Yeah, I've basically said something along those lines.

Its so frustrating. I ran the bath for at least ten mins, maybe longer while I tested things and listened and watched. The hot wATer was lovely and hot, and kept coming. No issue at all.

You can bet your life, I left and the boiler locked out and I got called a useless !!!

 

[Dannypipe]

Which LEDs are flashing when the boiler locks out that could give you some indication.

Burner failure is flashing in orange, and power on is steady. Doesn't give much away!!

 

[Dotty]

Moved to the private forum.

 

[AMGasServices]

According to mi the boiler is overheating then locking out. I've attached an image from the manual.

 

[iain85]

Working pressure ok? If its a old reg on meter get it changed.

 

[Dannypipe]

Yeah working pressure ok.

about 10mb max and about 2mb on min.

I've just left a message with them to ask whether the boiler played up again after I left. Be interesting if it didn't!

I didn't check the over heat stat. As it was firing ok I assumed no problem. Surely if the over heat stat was closed circuit the boiler wouldn't fire at all?

I checked the thermistor and that was OK.

Anyway, I'll wait to hear back from them, if it's not right I'll be back round there to try again.

Quite often when I get these head scratching, on/off internittant faults. It's the PCB, but I don't like to jump to expensive conclusions!!

 

[diamondgas]

Danny pop one of the leads off the condensate trap and leave it on test. I've had a good few intermittent faults with this design and that's one of the tests I do to eliminate the trap as a cause

 

[Dannypipe]

Thanks very much. I will look at this.

So if the lead goes closed circuit, the PCB will then the trap is full/blocked. Is this what you test for?

Spoke to customer. The boiler worked last night, and now it's just locked out again. Something is def' not right with it.

I offered to go round, but she said the woodburner was keeping the house warm, wait until tomorrow.

 

[iain85]

Not burner pressure, working pressure @ p1 (21 +- 2) sometimes if this is low it can cause intermittent lock out faults.

 

[Dannypipe]

Sorry mate, missed that! Yeah, I checked working pressure and it was 20mb at appliance - so that's not the cause of this issue sadly

I didn't bother checking working pressure at meter, as if I've got 20mb at the boiler, I'm assuming I've got around 21/22 working pressure at the meter.

 

[buckley plumb]

aps are prone on these boilers same as baxi 105

 

[Leo21]

I had this or similar, flame rectification lead. Just needed bending over the top of the flame on the burner. And if he's had it out himself that could be it.