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.

 

[Dannypipe]

aps are prone on these boilers same as baxi 105

Funny you should mention that.

Firstly I have an issue with a Baxi 105 that's about five mins away (but I don't think it's the APS on that one).

Secondly I also had my concerns about the APS.

It's tucked away right at the back, top left of the boiler, and tracing the cables was a pain in the backside, and I was pushed for time.

I do heavily suspect a dodgy APS, as I was already suspicious, and you if you say they're prone to faliure of the APS then thats enough for me. I'm gonna have to test it.

Thanks.

I will of course conclude this once I know what it is, for others to use in the future.

 

[Dannypipe]

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.

I put the multimeter inline on the flame rec probe. It was pulling 5 micro amps. The display actually read -5.

I didn't think too much of the - symbol. Should I have!!?

 

[Leo21]

I put the multimeter inline on the flame rec probe. It was pulling 5 micro amps. The display actually read -5.

I didn't think too much of the - symbol. Should I have!!?

Its not the continuity of the lead, it's the position. They can be miss aligned with the flame, so won't detect the flame. Bit like a bad pilot and a thermocouple. Aps are week, and can be knocked out on hw due to increased bp.

 

[Billy Bob Bob]

aps is failing change it fault cured

 

[Dannypipe]

I love you fellas, (in a straight, man love sort of way of course).

I will change the APS tomorrow. I will change the flame rec probe too simply because its a cheap part and the customer has been messing with it.

 

[Billy Bob Bob]

I love you fellas, (in a straight, man love sort of way of course).

I will change the APS tomorrow. I will change the flame rec probe too simply because its a cheap part and the customer has been messing with it.

to date with this fault,with exactly the same symptoms i have replaced around 80 aps,not one rec probe but if they been fiddling i would share your views danny

 

[Dannypipe]

Wow!

Well thanks very much for this insight. I wish I did more on the breakdown side. Some months I'll have loads, other times, it's all installs. My work is nothing if not varied!!

I will change the probe just simply as it's a cheap component, and like I say, I have no idea what he's been doing to it. The blokes a vet, so has no place inside a combustion chamber. He may have bent it, and I don't want to risk having another call out in a month or so if it also fails after I've done the APS.

Thanks very much to everyone. I will change it tomorrow evening (gonna be a late one for me as I have a mental day booked as is!)

 

[Leo21]

As I posted earlier I've had his fault with the probe, the most embarrassing bit is it was me who left it miss aligned after servicing it. Popped it back in line and hey presto. As you say though it's rare and only happened to me once.

 

[Billy Bob Bob]

Wow!

Well thanks very much for this insight. I wish I did more on the breakdown side. Some months I'll have loads, other times, it's all installs. My work is nothing if not varied!!

I will change the probe just simply as it's a cheap component, and like I say, I have no idea what he's been doing to it. The blokes a vet, so has no place inside a combustion chamber. He may have bent it, and I don't want to risk having another call out in a month or so if it also fails after I've done the APS.

Thanks very much to everyone. I will change it tomorrow evening (gonna be a late one for me as I have a mental day booked as is!)

when you fit the modified aps aim the tubing connections towards the fan so make sure the brackets in the right place

 

[Dannypipe]

Cheers all.

I'll let you know how I fare!

 

[wazzer]

ON INTERMITTENT PROBLEMS LIKE THIS i CHANGE THE THERMISTERS THEY CAN READ CORRECTLY ONE DAY/TEMP BUT NOT ON ANOTHER.....You look up and caps lock is on !!!

 

[diamondgas]

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?

Yeh that's the idea to stop the condensate backing up to far! I've noticed condensation on the insides of the traps and wondered if it in anyway effected the trip? Can recollect replacing a couple of traps and the fault not returning even though the condensate pipe wasn't blocked/frozen! Since then it's one of the tests I'll carry out.

 

[Dannypipe]

Well I've ordered an APS. The original model has been discontinued and replaced with another Honeywell one. (I've had this same thing with a Baxi combi a few years back. This it's the same APS).

Anyway, I'll pick it up tomorrow and go stick it in.

I really need to get another thermistor test lead I miss it.

Done a couple more repairs today. Seem to be having a glut of break downs this week.

 

[Billy Bob Bob]

Well I've ordered an APS. The original model has been discontinued and replaced with another Honeywell one. (I've had this same thing with a Baxi combi a few years back. This it's the same APS).

Anyway, I'll pick it up tomorrow and go stick it in.

I really need to get another thermistor test lead I miss it.



Done a couple more repairs today. Seem to be having a glut of break downs this week.

replacement should be the white round type,not honeywell

 

[Dannypipe]

Ah right, I was looking at the merchants screen, must have been looking at the discontinued one. Thanks Mark.

 

[Leo21]

The white round ones a pig to fit. It catches on the fan, and the looms barely long enough.

 

[Dannypipe]

Oh brilliant!! Looking forward to that then.

 

[Billy Bob Bob]

The white round ones a pig to fit. It catches on the fan, and the looms barely long enough.

you have to aim the tubing ports towards the fan,chuck the tubing behind it,not had a issue with the loom TBH

 

[Leo21]

Are you using the vertical or horizontal one?

 

[Billy Bob Bob]

Are you using the vertical or horizontal one?

cant see the difference aps is in the same place

 

[Leo21]

The ones I get supplied from curzons are vertical with an adaptor securing clip. In the instructions it specifies if its for vertical or horizontal application. There's no clip supplied with the horizontal one. On vertical one the connections foul the plastic cooling fan on the top of the fan spindle. The ones on euro parts are the original Honeywell ones.

 

[Leo21]

Oh brilliant!! Looking forward to that then.

Let us know how you get on, and take some pics when you've got it in. I'm missing something when I fit them. I find them a right cow.

 

[Dannypipe]

Will do. Thanks to everyone.

 

[Dannypipe]

Fitted the APS today. I have taken photos and will upload later. Just this minute got home and thought I'd check my emails while I had a bowl of soup. Which inevitably means I then go on here after!

The APS I was supplied wasn't a Honeywell. The instructions were god awful. After about five minutes of head scratching I figured out how the thing clips in place.

I found that the wiring was very tight, infact I had to cut the cable tie securing the fan and APS wires and then pull some slack just to make the leads fit.

As for it touching the fan, no it didn't, it's close (I guess about 15mm) away, but secure and not touching it.

I'll try to get on later to upload the photos. The APS did have a fault on it, but not one that should have been effecting the boiler. Will explain later, basically it's a 3 wire APS and the boiler uses two of the circuits. The one playing up wasn't the one wired. Hope that makes sense.

Got to go now. Soups getting cold.

 

[Leo21]

It's not just me then, I have to do the same to the wiring loom.

 

[buckley plumb]

the problem i have is when fitting the wiring i keep pushing it off the clip - quite easy with the side panel off though

 

[Dannypipe]

Yeah I took the side panel off. No way I could do it without. I'll get the pics loaded up now.

 

[buckley plumb]

Yeah I took the side panel off. No way I could do it without. I'll get the pics loaded up now.

as mark will tell you if you ever do a diverter remove the pcb - it caught me out covered drop down panel with 2 tea cloths and then wrapped in a plastic bag and taped up and the pcb still got wet and blew - the water tracts down the cables into the pcb.

 

[Dannypipe]

Well I promised you photo's so here you go!!

 

[Billy Bob Bob]

as mark will tell you if you ever do a diverter remove the pcb - it caught me out covered drop down panel with 2 tea cloths and then wrapped in a plastic bag and taped up and the pcb still got wet and blew - the water tracts down the cables into the pcb.

agree 100%

 

[Billy Bob Bob]

View attachment 11447View attachment 11448View attachment 11449View attachment 11450View attachment 11451View attachment 11452

Well I promised you photo's so here you go!!

easy to do LOL done so many can do them blindfolded,problem fixed now?

 

[Leo21]

That's a mains boiler, the baxi,s have two sensing tubes and three aps wires. A tip if your stuck for room at the side to take panel off, take the fan out.

 

[Billy Bob Bob]

That's a mains boiler, the baxi,s have two sensing tubes and three aps wires. A tip if your stuck for room at the side to take panel off, take the fan out.

2 tubes on all variants 24kw has 2 wires 30 has 3 wires be it baxi,potterton or main

 

[Leo21]

There's only one tube Going into the Venturi, where does the other one go?

 

[Dannypipe]

I would have taken the fan out if I'd had to, luckilly with the side panel off it was very straight forward.

Whether the problem is fixed, we shall have to wait and see. Boiler was working when I arrived, and had been ok that day.

I tested the old APS.

The C to NC wasn't working when I blew into it, or it may have been the C to NO wasn't breaking. Anyway it had an issue, but not one that I can see would have affected the boiler, as it was the wrong terminal (if that makes sense!!!!)