Potterton 24 eco HE - can't work out whats wrong

[pyxyuk]

Hello,
My first post and I'm straight into a problem! I have checked the focums but couldn't find an answer so I will try and give as much detail here inthe hope someone can help!

I have a sort of creeping death in the boiler :

Boiler had been working fine, then the hot water would sometimes not heat up, then over a day or so the HW stopped working and the flame failure light was flashing (twice per second). After a short while longer the CH also stopped heating.

My initial investigation was to check of loose wires etc and performing a reset saw the CH come on for very short periods - such as 10 seconds before the boiler cut out and flame failure flashed. In this state the start sequence for CH was working to the point that the flue fan started and air pressure switch could be heard to operate but then boiler went to flame failure with no ignition - I could not confirm if there had been any spark at the electrode.

The flashing light indicates 'blocked flue or internal failure'. At this point I got an engineer out however neither him nor me have got to the bottom of the problem. In fact, when the engineer came out the next day after boiler had been off all night both the flame on and flame failure lights were slow flashing - a different error - indicating some over temp problem and now, right now, the boiler doesn't even get as far as starting the fan.

So what we have now is:
Demand CH -> pump starts -> hydraulic switch moves and makes on microswitch. Power light is on and both other lights are flashing at a slow rate. A reset does nothing. Boiler doesn't start the fan and no attempt to ignite.

Troubleshooting to date:

The following sensors/switches have been checked:
The microswitch on the hydraulic unit, the flow sensor, the temp sensor - these appear okay although the engineer has questioned the microswitch so he is replacing that tonight.

As a second test on the circuit board connector M2, these switches/sensors have been by-passed in turn (and together) which in theory means if the mircoswitch was faulty then it has been by-passed. However doing this has made no difference the boiler still fails and doesn't start the fan.

The engineer previously thought it was the circuit board and replaced this but again no difference in the error or progress of the start sequence.

There is no difference if HW is demanded (apart from connection across the three way microswitch). Again, no change if the first microswitch/sensors are by-passed.

Final test, perhaps meaningless - the electro-mechanical timer was disconnected from the circuit board and the mircoswitch was by-passed. This resulted in the flame failure light slow flashing - seemingly this is a pump failure - however suspect this is because the timer was disconnected.

The engineer has also checked the flue temp sensor - there is no reset button on this sensor as the manual suggested but a check with the meter suggests this is okay.

The flue is not blocked, the wiring to the fan is correct, the air switch can be heard working and seems okay (but then we are not getting that far now).

Sorry for the long post but trying to give the information that might help. What has been missed, needs looking at etc. The engineer is back tonight to replace the microswitch but I suspect that since by-passing the switch made no difference I am at a loss how replacing that switch will help and the engineer is seriously scratching his head now

Gas pressure I guess hasn't been checked - engineer has said that the boiler isn't getting far enough for that to be part of this initial problem.

Any advice/suggestions etc?

.....we are approaching a week with no boiler......

 

[newbie1]

you nreed an engineer who knows what he is doing not a replace a part at a time numpty and he should have more clue than this

 

[pyxyuk]

Thanks The engineer isn't charging me for the parts that don't fix the issue or his time - he will charge for the part and the time to replace the faulty part when identified so thats not so bad in that respect (but yes I agree this is not ideal)

I would really appreciate some troubleshooting advice or suggestions if anyone has come across this sort of problem before...?

 

[pyxyuk]

Okay - got someone who is recommended by the manufacturer.

10 mins in and he says the PCB is the problem. He says that the sensors/microswitch are fine but that there is no voltage going to the flue fan, therefore the start up sequence cannot complete.

He has also said another clue is that the reset is not working i.e. you turn to reset and the warning lights and things don't reset in the way that might be expected.

Unfortunately it was about the only part he did not have however will be back early next week to sort it out.

 

[Dave]

Thanks for the update.....at least you got it sorted..

 

[Puddle]

Thought you had replaced pcb already

'The engineer previously thought it was the circuit board and replaced this but again no difference in the error or progress of the start sequence.'

Thought was pointing towards air presure switch or faulty thermistor

 

[gakmonkey]

Thought was pointing towards air presure switch or faulty thermistor

90% of time with a potterton it is the pressure switch but check both. And i still don't know why many engineers do not use a multi meter to its full potential, if something sounds like its working it does not take long to check supply at terminals to confirm this, instead of blowing tapping and all of te other traits that make us look like car mechanics.... followed by sucking air over the teeth " it's knackered mate."

 

[pyxyuk]

Yea the PCB had been 'replaced' but I didn't see the chap do this and then he decided that since the 'new' PCB made no difference he was going to put the old one back in and then continue checking components - that doesn't seem right to me surely check all the components 'off' the PCB is the starting point? Anyway, there was no checking that there was any voltage to the flue fan which is one of the tests the second guy did (and in fact is in the user fault finding charts!) I would have done it if I could have found my own multi-meter but its currently hiding out in the garage.

Now, it may be that the PCB is not the only thing however at least this new fella is checking the connections, sensors etc using his multi-meter, following the diagnostics and didn't ask me if I had a manual and got out his 'how to fix boilers 101 notes'. Sorry, the fist engineer *may* have been on the right tracks however lack of confidence, lack of customer service skills, lack of knowledge about Potterton boilers etc all added up.

So that saga continues - engineer will be back this afternoon so we'll see what happens. I am hoping that I will have a warm house to go home to after work!

I'll keep you posted!

 

[machiavelli]

Hi pyxyuk

You never said whether you finally managed to nail this fault - I am trying to sort out my sons Potterton 24 with almost exactly the same symptoms!

As it hadn't been serviced for some time, I thought that this might kill two birds with one stone - how wrong can you be! After completing the service with no effect on the fault, the engineer from the first company (found from Which? Local) replaced the Condensing trap (which WAS leaking) and the Hw Diaphram and packing gland - again with no improvement. When I contacted them the following day, they said that they would look into it, but then stopped answering my calls.

I then followed my wifes advice and found a highly 'recommended' company from Checkatrade. He came round the next day and, after a considerable amount of time looking at the problem (no multi-meter, though), said that he thought it must be the PCB. Not knowing anything about boilers, and thinking that a PCB would be expensive, I obtained his re-assurance that he would at least check all the sensors before replacing the PCB.

Desperate to get the boiler working again, I agreed to his stipulation over the phone, prior to his attendance the following day, that I would have to pay for the PCB if it was removed from its packing prior to being used.

Unfortunately, I was unable to be present and, attended by my wife, he claimed that the problem was sorted after replacing the PCB and the air pressure switch (in that order). All this cost me £300 for this second company. Analysing his procedure, I was very unhappy that he had replaced the more expensive item first (PCB), especially under his stipulated conditions, and even more incensed when I discovered that the PCB and switch, for which he charged £225, could be bought off the internet from the first company I came across for £97 (I expect some mark-up but this was a staggering 132%!).

Finally, we returned the following week to find that the boiler still didn't work, with exactly the same symptoms as at the start!!!!! I am currently trying to decide whether to press on with this company or find yet another one! If the latter, I will certainly do what we should have done first, and which was suggested above - a company recommended by the manufacturer.