Potterton Prima F fails to ignite.

[nherriot]

Hi, just joined the site due to a boiler problem:

I have a Potterton F 50 boiler which fails to ignite. The external pump is running. The Fan runs for about 15 seconds, stops, then the cycle starts over again.
I've checked the pressure switch which I think is working. Hence no blockage on the pipes. By removing one of the silicon pipes I can fool the boiler into keeping the fan running for a minute before starting the cycle again.

Is there an easy way to determine if the pressure switch is functioning?

I hear no electronic 'click' to tell me the boiler is attempting to spark. The High tension lead goes straight on to the Electronic boiler control, does anyone know if this indicates a fault with the electronic boiler control? I guess this could be correct if I was sure that the sequence was not to open the gas solenoid first? Does anyone know where I could get the ignition sequence for this boiler on line?

Regards, Nicholas

 

[Agile]

If the APS is working then it sounds as if the PCB is faulty.

You are trying to be too clever! Most people who fix boilers dont get involved in timing sequences ( although they are easy to observe and note ).

Tony

 

[nherriot]

Hi Tony,

thanks for the quick reply! I normally diagnose computer problems, hence my over analysis. ....

OK my PCB is removed. Got any good recommendations of where to buy a new one from? Part number is 407677. I take it there is some form of 'sponsor' links on this site but it's not obvious for boiler controls!?

By the way looking at the electronic boiler control visually it looks very much like resister Z3 is perished. Do you know where I could get the circuit diagram for this PCB? (Sorry about my curiosity, was originally trained as an Elec Engineer many years ago!).

Thanks again for your help. If you ever have problems connecting a Linux Netbook pc to mobile internet I'll give you top priority on our Forum at betavine.net ! ....

Kind regards, Nicholas.

 

[Agile]

These PCBs are available from all the boiler spares merchants.

I dont think your electronics engineering training could have gone very far as Z3 is a zener! They often run rather hot so it is probably normal.

You dont get circuit diagrams for boiler PCBs unless you can trace them out yourself which would be feasible with this one but rather tedious and might take about two hours even if you do it often.

If you wanted to try to repair it then first replace the electrolytics and if that does not solve the problem change the relays.

Tony

 

[nherriot]

Hi to Tony and anyone reading this thread.

Just like to say:
1) Big thanks to the help on this forum (Tony) which helped me in quickly fixing a problem.
2) A brilliant shop on ebay who sell reconditioned units, which I found at adlink .

I got my part (PCB) for £37. So far it still works!

And anyone who has to fault find on this unit:

Firing Sequence
------------------
1) Pump on
2) Fan on
3) Air flow detector OK
4) Gas flow on for pilot.
5) Electronic ignition fire.
6) Flame on OK
7) Gas flow main on.
8) Burner ignite.

The air flow and thermocouples are constantly monitored once the main gas ignites. If air flow stops, or temp on exit pipe gets to hot while room stat is still asking for heat the boiler (as you would expect) shuts down.


Things to note
----------------
The replacement PCB does not have the legs on, so make sure you keep them from the old one.

The High Tension lead will need to be soldered on. So you will need a good solder iron, and solder sucker to remove from the old board. Be careful when soldering the lead not to damage other parts of the circuit board with excess heat. I used a mini clamp.

To reply to Tony's note. My Electrical Engineering only went to Hons Degree level. Maybe they teach Zener Diodes as part of the masters or PHD? However as anyone can vouch that's done this type of degree, we are great at fourier analysis, laplas, double integrals, bla bla bla.... And he is correct, it did not go far as I repaired it myself rather than paying someone else to do it. Note to anyone wanting to do engineering, don't do it, do finance and management. You can then replace the whole boiler if it breaks down! ....

Kind regards, Nicholas.

 

[Agile]

I am watching the X-Factor so no time to read all that yet!

And I am supporting Alexandra!

Tony

 

[swbjackson]

I'm supporting Alexandra as well.

Mike

 

[twgas]

The High Tension lead will need to be soldered on.

replaced hundreds of these PCBs and never soldered a lead onto one yet

 

[Agile]

I think he is in the wrong place!

 

[Agile]

I always like to back a winner!

Did anyonw recognise the live shots from her supporters from ALEXANDRA PALACE ?

We are going to see a lot more from this lady just like Leona Lewis!

Tony