Potterton Kingfisher MF - problem

[TWJ]

I have a Potterton Kingfisher MF about three years old.

It has recently been cutting out at regular intervals on start up.

The flue fan operates when heating and/or hot water is demanded by the programmer, and the pilot light, then main burner ignite, but after a few seconds, it trips out, then resets, every few seconds or minutes. It rarely fires up and continues for longer that five minutes.

The heating engineer thought the system needed a power flush and did this, but the problem remains.

Is this likely to be a fuaulty PCB, gas control valve, flame failure devise or what?

Help please

TWJ

 

[Agile]

I am sorry but you have either has a very incompetent or a money grabbing engineer. I recommend you find a competent or honest one.

The problem you describe is most likely to be caused by the pilot flame being drawn off the burner and causing a flame detection failure.

You can probably see it happening through the viewing window. Rather oddly on this model it usually still does it the same if the front cover is removed.

A similar effect can also occur if the PCB or the APS are not operating correctly.

The solution would be to replace or clean/adjust the pilot flame assembly.

Tony

 

[TWJ]

Thanks for the advice, I'll ask my heating engineeer to try what you suggest.

As for the flushing out, the system is much older than the boiler, and I do not think it was flushed when the boiler was replaced, so lots of muck came out and it has probably improved the circulation.

TWJ

 

[corgigazza]

With this boiler the aps or ignition side does not cause lock out only the over stat / ttb does so this may be faulty or the system over heating due to lack of circulation, also the pump has to be wired to the bioler to give pump over run. try running on lower temperature. over heat stat or thermistor may be faulty also if open flued the flue thermosta (tttb) may be operating.

 

[Agile]

The flue fan operates when heating and/or hot water is demanded by the programmer, and the pilot light, then main burner ignite, but after a few seconds, it trips out, then resets, every few seconds or minutes. It rarely fires up and continues for longer that five minutes.
TWJ

I did not interpret that as meaning that its going to lockout.

Tony

 

[corgigazza]

For some reason with this boiler lockout is only o/h, had it before disconnected asp run for ages, disconnect main gas soleniod runs for ages no lockout.
Caught me out first as lockout normally means start up problems. If you read instructions it says reset locket (red neon), check over heat stat, replace pcb

 

[TWJ]

Hello gentlemen, thanks for the advice.

For your information, boiler does not continually lock out, but ignites runs for a short while, goes out, then re-ignites with this forming a continuous lighting, going out sequence, hence it never runs continuously for long.

 

[Agile]

For your information, boiler does not continually lock out.

I appreciate that you will not know the significance of the words you have used but they can confuse a boiler engineer.

To "lock out" means that the boiler switches itself off and stays off until its manually reset. Usually this is acompanied by a lockout light being illuminated.

Its not possible for a "lockout" to be anything other than permanent ( until reset ).

Your boiler is failing to ignite or stay ignited and carries on cycling through the attempts until someone intervenes and turns it off.

Its probably one of the things that I have listed above.

Tony

 

[Gamekeeper]

My problem is rather similar to one posted before, but not entirely. When a call for heat comes and the water pump switches on, the boiler lights and burns for one or two minutes, then stops. You hear a repeated clicking for a further (say) 20 secs, then silence. Pump continues to run, and after a while (typically 10 minutes) the burner comes on again. And so on, until the HW tank thermostat trips and switches off the call for heat.

This may sound as if it's working, but there are two problems. First the HW tank takes quite a while to reach the setpoint, presum because the boiler is only burning for a minute or two in every 10 minute cycle. Second, there have been a few times lately when the boiler overheating cut-out has tripped, disabling it entirely and needing a reset.

Following Tony's suggestion I wondered whether the burner flame is blowing out the pilot - but if that were so, why doesn't the boiler keep trying to re-light the pilot until it ignites? Why does it just click a few times and then give up? And why the overheating cutouts?

It's a mystery. Circuit board failure?

 

[AlanE]

It's a mystery. Circuit board failure?

Why is everything a circuit board failure? Your description would indicate a classic case of poor/no water circulation.

Boiler tuns for couple of mins or so, heats up the heat-exchanger and stat turns off burner until it cools a bit. 10 mins later again runs for short while.

Check HE is indeed hot if so and pipes leading from boiler are not. If so check causes of poor circulation.

 

[Gamekeeper]

[Why is everything a circuit board failure?]
Good question. I suppose it's because the circuit board controls everything, so almost any fault *could* be the circuit board - or so you'd think if you did what I did and followed the fault-finding flow diagram in the Potterton service manual. Of course, that diagram doesn't suggest external (system) causes of failure, just boiler failures.


[Your description would indicate a classic case of poor/no water circulation.
Boiler tuns for couple of mins or so, heats up the heat-exchanger and stat turns off burner until it cools a bit. 10 mins later again runs for short while.
Check HE is indeed hot if so and pipes leading from boiler are not. If so check causes of poor circulation.]

Many thanks Alan - sounds like a good suggestion. I have only had my circulation pump turned up to middle setting during the summer - so putting it on high might do the trick. Also the system probably needs flushed, that hasn't been done since the boiler was installed four years ago.

Maybe the original poster's first engineer wasn't so far out after all when he suggested a reverse flush.

 

[AlanE]

If the system had been PROPERLY flushed when the boiler was fitted 4 years ago NO WAY would it need doing again 4 years later.

 

[spacethegas]

there is no need to reduce pump speed when system is in h/w mode.

 

[Agile]

It would help you if you were able to measure the temperatures on the flow and return at the boiler and at the cylinder.

I call that a thermal survey! It will show up any circulatory faults. But it does need to be done with the cylinder cold otherwise you would get confused by the results you obtain.

Whats the make and model of pump?

Tony

 

[Gamekeeper]

Alan: "If the system had been PROPERLY flushed when the boiler was fitted 4 years ago NO WAY would it need doing again 4 years later."
GK: Well maybe it doesn't. Just guessing. I think the guy who put the boiler in was competent enough. Maybe it's the pump.

Space: "there is no need to reduce pump speed when system is in h/w mode."
GK: I suppose not, I was just trying to reduce wear on the pump and save some juice. Call me Scrooge.

Tony: It would help you if you were able to measure the temperatures on the flow and return at the boiler and at the cylinder. I call that a thermal survey! It will show up any circulatory faults. But it does need to be done with the cylinder cold otherwise you would get confused by the results you obtain.
GK: Is it OK just to measure the external pipe temp? I can't easily get at the water itself.

Tony: Whats the make and model of pump?
GK: Good old Grundfos UPS 15/50. It's been in for nearly 20 years. Or at least the mechanical part has; the electrical bit blew a couple of years ago and I swapped a new module in, leaving the mechanics in place. Maybe time to replace the mechanical bit now.

Thanks all.